PROBE FAQ - 1993-1997 GT (2.5L V6)

1.1 KL-03 - 2.5L V6 U.S. Engine

1.1.1 Specifications


Bore	3.33 inches
Stroke	2.92 inches
Displacement	152.2ci / 2496cc


1.1.2 Is it an "Interference engine"?

No. What is an interference engine? An interference design is such that the timing is just right to allow the valves to open into the cylinder where they share space with the piston. The valves must be closed in order for the piston to peak; the piston must be below peak in order for the valves to open. Interference engines may offer higher compression for this ability to bring the piston right to the top of the head. Conversely, if the timing belt ever goes on an interference engine while running, the valves will all be shot from being mangled by the pistons still in motion. Non-interference engines are less costly to repair in this event.


1.1.3 Are adjustable cams available?

No. simply for the reason that you would have to remove valve covers and the intake manifold any time you wanted to adjust them, defeating the notion of convenient adjustability.


1.1.4 "Solid" engine mounts

Highly NOT recommended. Slightly stiffer mounts are proving to be effective for reducing engine rocking motion, transferring more power to the wheels, faster (albeit with a bit of added vibrations at idle). Stiffer mounts are being accomplished in a number of ways: Mazdaspeed mount upgrades, solid polyurethane substitutions, even construction grade polyurethane sealants filling in the gaps of the OEM mounts. Actual SOLID mounts have been proven to be destructive in terms of transferring engine torque to the other mounts and breaking things (such as the tranny mount - several have learned this the hard way. So, stiffen the mounts: okay. Solid mounts: bad.


1.1.5 Underdrive Crank/Accessory Pulley (UDP)

There is an underdrive pulley available for this engine. The UDP regains some lost engine performance by way of reducing rotational weight over stock on the crankshaft (where rotational weight matters most) and by increasing the pulley ratio from the crank to the accessories in order to spin them slower, thus relieving some stress. There are some snafus: first is during installation you will be required to grind away some material surrounding the crank case in order to make clearance for the new pulley since, being smaller, it is not able to sit over the edge of a lip designed to block dust from nearing the crank seal. Some material is also removed from the plastic timing belt covers where they come near the pulley. Both can be done easily with a rotary tool and a cutoff wheel (rather than a grinding bit). Last is once installed you have to face the annoyance of the reduction in alternator output which manifests itself through dimming headlights at idle during nighttime driving. Some circumvent this by increasing the idle rate. Others have suggested a higher output alternator. Most just deal with it as is, revelling in newfound power.


1.1.6 At what RPM do the VRIS plates open and close?

RPM 0000 - 3250 > both closed
RPM 3250 - 4250 > #1 open, #2 closed
RPM 4250 - 6250 > both open
RPM 6250 - 7500 > both closed


1.1.7 3 and 5 angle valve jobs

This has to do with grinding the sealing faces of the valve and the seat in order to to both improve the seal and make the shape closer to a "curve" which allows the air to move through the opened valve more efficiently. The valve opening is the single-most restrictive point in the intake/exhaust airflow, so even subtle changes here have the potential for significant impact on performance. Results do tend to vary between vehicles though and it may not have the dramaic effects he hopes for on this engine.

While there is room for airflow improvement on KLDE heads in the way of port and polish work, the KLZE heads really have very little room for gain. A 3 or 5 angle valve job and 1mm over-sized valves might yield a fractional improvement in airflow, but with the cost of these modifications, they are generally considered unreasonable on this platform.




1.2 KL-ZE - 2.5L V6 Japan Engine


1.3 Eunos 800 (Miller Cycle)

2.1 Fuel

2.1.1 What is the "banjo bolt mod"?

A banjo bolt is a specially designed hollow bolt that allows fluid or air to pass through it. The fuel lines on this car use banjo bolts to connect to the fuel rails which supply injectors with fuel at the top of the engine. Curiously, of the three banjo bolts on the fuel rails, only one of them, the supply line, has a lateral hole through it that is smaller in diameter than the lengthwise bore. The "banjo bolt mod" entails removing this supply line bolt and CREFULLY using a drill/drillpress to increase the diameter of the lateral hole to match the lengthwise bore. Please exercise caution working with extremely flammable fuel and pressurized fuel lines! This modification tends to result in slight increases in fuel pressure. Don't expect horsepower out of it - you won't see any. It is mainly intended for those who are fine tuning their fuel delivery system.


2.1.2 How much horsepower will a high pressure fuel pump give me?

Little, if any. A high pressure fuel pump increases the potential for fuel pressure delivered to the fuel injectors, but while some have occaisionally noted a slight fuel pressure increase from the addition of such a pump, usually pressure will remain the same. It takes an adjustable fuel pressure regulator to actually change the pressure. It should be noted that the stock fuel pump's output is sufficient to fuel a 250HP engine, so unless you're making some awesome power under boost or Nitrous Oxide, a high pressure fuel ppump is probably not going to do much for you.




2.2 Intake

2.2.1 Variable Resonance Induction System (VRIS)

What is VRIS? This is a unique configuration of electromechanical gadgetry controlled by the Engine Control Unit (ECU) designed to optimize the airflow characteristics of the intake manifold at various engine RPM's, resulting in a smoother overall power output curve than a static intake manifold configuration would offer. The VRIS system opens and closes each of two solenoids as needed to actuate either of two sets of butterfly valves located within the intake manifold itself. The two valves offer 4 possible airflow configurations within a single manifold, each of which is "tuned" to be optimal for airflow at specific RPMs. As engine RPM changes the ECU changes the VRIS solenoids to reflect the optimal intake manifold configuration. The use of "resonance" refers to airflow characteristics that physically resonate through the intake routing into the cylinders. With increased velocity (from higher RPM), the optimal resonance changes; the VRIS is intended to adapt to these resonance changes. In some cases, such as forced induction or nitrous oxide applications, the VRIS butterflys are considered obstacles to the flow of air more than they are beneficial. In other cases various normally asperated engine modifications make the ECU's stock VRIS switching points no longer optimal for the modified engine's new airflow resonance characteristics. In either of these cases, many people opt to simply have the VRIS butterflies removed from the intake manifold so as not to obstruct airflow. A couple of experimenters are working on independent subsystems capable of altering the VRIS switching points from the stock ECU in order to "fine tune" their cars, but this is largely looked upon as somewhat futile since true "fine tuning" of such a system would prove to be a significant challenge, even with free dyno time. Unmodified or lightly modified normally aspirated engines respond to removal of the VRIS plates with interesting power output spikes at those RPMs where the VRIS system would normally have altered configuration, but generally does not result in any loss of power; such power spikes however are responsible for a somewhat less-smooth ride, certainly something that grandma might not appreciate - remember: this IS a passenger vehicle, not a race car.


2.2.2 Throttlebody modifications

There are a couple interesting things you can do with your throttlebody:

1) You can bore it out to a larger, straight-through diameter. Taking yout throttlebody to a machine shop, you can have them bore it out to 65mm. A few people have gone 1-2mm larger, but 65mm seems to be the safe maximum concensus. In fact testing has shown that 64mm may actually make better airflow through the TB than 65mm - bigger is not necessarily better, as with any porting work. Make sure that the shop you select to perform this understands what is involved with boring out a TB as they should also be commissioned to fashion a new throttle plate for it since the old one will be too small after the bore. The throttle plate must be made perfectly so as not to leak air when installed. If it leaks, it'll play havoc with your idle. A throttleplate is NOT a simple circle; It is a crossection of a cyllinder (an elipse). The OEM throttleplate screws are stamped into place, ensuring that they won't come free. either have the machine shop do the same for the new screws, or find some alternative method of securing them (such as thread lock) - a screw coming loose from here could have devastating consequences. A bored throttlebody is designed to increase air volume ientering the intake manifold.

2) You can cone it. The OEM throttlebody's inner diameter has a stepped reduction between the inlet opening and the throttle plate. Coning is the process of reducing the step and nearby surfaces to a smoooth, cone-shaped surface tapering neatly down to the plate from the opening. This coning procedure can be accomplished with a simple handheld rotary tool, grinding & sanding bits and sandpaper. This coning process is expected to increase air velocity entering the intake manifold, but has not been dyno proven to generate useful results.

3) You can bypass the coolant lines. Are you perturbed by the engine coolant lines going to your throttlebody? If so, you're not alone. It is possible to simply detach these two lines and connect them to eachother with an elbow-shaped pipe fitting and a couple hose clamps. This eliminates hot engine coolant from heating up your throttlebody (and therefor intake air charge) that has been working so hard to defeat the cold air intake you installed. Beware, however, that the lines are installed this way from the factory for a reason: the engine coolant heats up the throttlebody as the engine comes up to normal operating temperature. The heat in the throttlebody melts thermowax in a sealed chamber within the idle air controller (IAC), thus changing the behavior of the IAC. The IAC allows the ECU to alter the idle rate of the engine based on accessory load (such as electrical draw, air conditioning, etc). By bypassing these coolant lines you will render your car's IAC ineffective - or at least less effective. It turns out that in most cases the TB still reachs sufficient operating temperature, though not quite as high as with the coolant running through, to melt the wax and leave the IAC operational, however it takes a bit longer to reach this temperature. If this doesn't bother you, then proceed!

So is volume or velocity better? It's your call, it has yet to be back-to-back dyno proven. Coning is a Do-It-Yourselfer job, whereas boring always requires the assistance of a machine shop.


2.2.3 How do I remove the VRIS plates?

First be clear that you NEED to remove them. Unless you are running a significantly modified engine or with Forced Induction/Nitrous Oxide, you needn't remove them at all; moreover, removal will probably result in detriment to the performance of your car. If you know better than this already, well alrighty then! For VRIS #1 simply remove the 3 bolts on the U-Tube, then pull the tube off; for #2 you'll have to remove the throttlebody. For both, take a grinder and grind down the bottoms of the screws as far as you can without damaging the spindles. The screws are pressure-stamped to where they flare out, holding them tightly in place. If you cannot remove the screws with a screwdriver, then they'll have to be drilled out completely with a power drill and bit. Once the screws are out, either grab the plates with pliers and slide them out, or tap them out with a hammer. The rest of the procedure is a snap from here. If you have any intention of replacing the plates, make sure that your method of affixing them back to the shafts absolutely will not release hardware that could enter into your valves and/or cylinders. This means using threadlock on screws, etc.


2.2.4 How do I remove the intake manifold?

1) For the obvious, pull out your ignition wires and intake ducting up to the throttlebody.

2) Unbolt the VRIS solenoid bracket and the hose bracket below it from the back of the manifold - leaving this all in the engine bay minimizes the number of things you have to disconnect.

3) Detach all the vacuume hoses you see connecting to it and mark each hose & connector with tape & a number/something so you know where each one goes when you put it back together. At the back of the manifold, there should be one for each of the two VRIS actuators, one tiny one on the passenger side for the climate control system, a bigger one near the center for the brake booster and one final small one on a downward-facing elbow near the throttlebody. On the driver's side there will be two or three vacuume connectors (depending on IM model), two on runner #6 and sometimes one on #5.

4) Depressurize the fuel system (read up) and disconnect supply & return fuel lines

5) Remove 8 bolts and 4 nuts from the intake manifold's flanges and one tricky bolt (aka "THE BOLT") located way at the back near the VRIS #2 actuator (it's completely out of sight nestled behind some vac tubes & junk - you'll have to feel around for it.

6) Disconnect the two coolant lines going to the throttle body & remove electrical connectors going to the TPS and the IAC (both conencted to the TB)

7) Begin lifting the manifold out, but stop a couple inches up and remove the blasted vac line that is connected beneath it before you pull to far and break the damn plastic connectors off the VRIS vac cannisters mounted beneath the IM (I detest this configuration!). Then you can finish removing it - don't go yanking it out like a babboon though - there might be things still attached to it that you didn't notice and you don't want to rip them off the engine - remove anyting you overlooked before pulling it completely.




2.3 Exhaust

2.3.1 Test pipes / "race catalytic converters"

Test pipes are straight-through exhaust plumbing with flanges on the ends to insert in place of the catalytic converter, a larger chamber section of exhaust stuffed with a reactive material designed to reduce environmentally harmful emissions. In most states it is unlawful to render emissions control device ineffective on emission-controlled vehicles. Race-only (off road) vehicles are NOT emission controlled vehicles. It is also not lawful to replace a catalytic converter before it has been in use for at least 50,000 miles. This is because the converter contains hazardous materials which if regularly removed prematurely, would add up to more hazardous waste than necessary. A legal alternative to a test pipe is a higher flowing catalytic converter. The test pipe will permit exhaust gasses to escape more freely through the system than a catalytic converter, also reducing back-pressure on the forward exhaust components. A test pipe will also affect the sound of the exhaust system - whether for better or worse is purely opinion - the tone change is subject also to the effects of the other exhaust components (muffler, headers/manifolds, turbo, pipe diameter & type).

3.1 Clutch & Flywheel

3.1.1 Why resurface a used flywheel?

The clutch uses a pressure plate that clamps a friction disc between the plate and the flywheel. The surface of the flywheel is thereby a clamping surface. Whenever the clutch is changed and/or the flywheel is out of the car is the perfect time to have the flywheel resurfaced to ensure that it is the best clamping surface possible. As a friction device, a clutch requires good friction to be useful. If a flywheel's clamping surface has been glazed over from use, resurfacing tidy's things back up for a nice friction clamping surface again.


3.1.2 Rotational Weight Reduction

As a general rule of thumb, for every 1lb of rotational mass removed from the crank/flywheel/pulley system (everything that spins at a 1:1 ratio with the crank shaft) there is a 2HP performance improvement in 1st gear. By reducing the weight of these items, you reduce parasitic power losses associated with the power needed to get that mass moving and keep it moving. So if we turn our attention to rotational weight reduction, these are some of the things we might find ourselves looking at:


• Flywheel - Not only are there lightweight alternative flywheels available pre-fabricated and new in a box, but you can even modify your stock flywheel for weight reduction. Aftermarket flywheels tend to be made from billet aluminum with a bolt-on steel pressure ring (the surface that the clutch disc clamps onto) and a steel ring gear for the teeth to engage the starter motor. These flywheels tend to weigh in at 7 to 11 lbs - quite the savings over the heavy weight stock champion @ 22lbs! It should be noted though that flywheel weight of all these items, being the most significant single point of weight savings, is also most responsible for associated 'behavioral changes'. This refers to the reduced rotational weight allowing the engine to respond much more quickly to changes in rotational speed.. thus RPMs rise and fall much faster the lighter you get. At 7.5lbs, most tend to regard the engine as being much too sensitive for normal driving and that even 9lbs can be pretty challenging. So you have to choose your target weight carefully; an alternative to going the billet aluminum flywheel route is milling down a stocker. You can take your sstock PGT flywheel and cut out about 2-5 lbs fairly readily, perhaps a bit more, but probably not much before weakening the wheel to where it cannot dissipate heat properly (as a frictional component of the clutch system, yes heat is a BIG factor!) and may warp under stress. You can also seek out the flywheel from a ~1992 Maxda MX3 1.8L V6 engine which fits our car perfectly and starts out lower weight already (16-18lbs) and leave it that way, or have it machined as low as 12-13lbs! Often this is a significantly less expensive alternative to the aluminum aftermarket wheels. Of course, as with any machine work, only a professional machinist experienced in this type of work should be milling your flywheels. It must be properly weight balanced and the work should be guaranteed. And off-balance flywheel at 7000 RPM could cause unspeakable damage, possibly even personal injury. There are takes of flywheels destroying their mounting hardware and those steel teeth eating straight through the tranny bell housing , firewall and driver's leg at 7,000RPM. No joke. Don't play unsafely, kids.

• Clutch - While the clutch disc and pressure plate are typically selected for their clamping force properties, they also add a component of mass to the 1:1 rotational parts. If you have a specific target weight in mind for your clutch/flywheel combo, then it would be best to take the weight of the clutch into consideration, especially if looking at killing down a flywheel to desired weight.

• Crank Pulley - Though there are not a lot of aftermarket options here, another item for consideration is the crankshaft pulley. The stock pulley represents a set of pulley ratios driving belts to external accessories (alternator, power steering, etc) as well as a a high speed lump of steel with a pretty significant mass. Billet aluminum alternatives both weight less and reducde the crank-side pulley size, thus "under-driving" the attached accessories, conserving power that would normally be used to spin them faster. One disadvantage is that aftermarket pulleys ten to do away with the harmonic dampener which absorbos irregular vibrations along the driveline and smooths them out. There are stories on the Internet of such vibrations being left unchecked by and aftermarket pulley destroying an engine by damaging the oil pump, but there has been no evidence of such catastrophe with the KL03/DE V6 engine. Further, the harmonic dampener on the stock pulley is made from a pppor grade of rubber which tends to dry, harden, crack and eventually decompose completely over an extended lifetime - even this has not caused oil pump damage. So it would seem that there is no cause for alarm here.

• Crank Shaft - The crank shaft itself is often left alone. Truth be told, it is a bullet-proof design: forged and double-nitrited for impressive strength. Though it is a VERY heavy part of the engine's rotational assembly, some have said to leave it alone as modifying it will only weaken its design and that any significant power-adders would more than make up for the minimal amount of weight savings that might be had from it. Still, for discussion purposes, it should be noted that there should be ample material on the crank to lighten it by several pounds. It is possible, however, that it would be more trouble than value, especially given the increased difficulty that comes along with balancing one lightened.

• Rods & pistons - Funny that some components that don't rotate should be considered to be part of the rotational assembly, but they are in fact tied directly to it. The KL03/DE rods & pistons are often considered a weak point in the engine design when it comes to increased power handling. In truth, the stock rods once shot-peened should hold up to most applications, but for significant power (350+ HP) increases, a strong argument can be made for replacing them with aftermarket rods. Match them to aftermarket pistons and use some aluminum/titanium alloys and you can reduce their weight. Use floating wrist pins and you can reduce their stress. Balance the entire assembly and you can make them last indefinitely. But the real beauty of custom rods/pistons from from custom compression ratios - reduce or increase as applicable to your performance goals.


There are even slight performance savings in weight reduction of rotational parts that are not 1:1 with the crank shaft such as wheels (tires & rims), brake rotors and axles, but gains here will be significantly less obvious. More important out of those items is wheel & tire size than wieght.





3.2 Transmission

3.2.1 Limited Slip Differential (LSD)

A limited slip differential has restricted ability to rotate one of the drive axles faster than the other compared to the OEM differential. This translates to being better able to power through cornering and eliminate "one-legged" take-offs (where one wheel gets all the power, losing traction while the other ust sits doing nothing) when drag racing. Presently the only "real" limited slip differential available is produced by Quaife and is exclusively distributed through Mazda dealerships. An emerging alternative is a device called "Phantom Grip" - it consists of a pair of metal blocks with various load-rated springs between them. The parts are assembled into the OEM differential housing and work to reduce slip by exerting outward pressure (as rated by the springs) on the rotational assembly. There are some concerns that this is somewhat of a "kludgey" method of reducing slip and that it migh increase the wear on the OEM differentials parts. Still others have announced success with use of the Phantom Grip and stand by it.


3.2.2 What is the IAT Mod?

This is a fun little trick for the ATX (Automatic transaxle) folks out there. In short, this modification allows your car to perform better by powering through shifts due to disabling the fuel cutoff between shifts. This result is accomplished in a rather abstract way: by splicing a toggle switch (with wires running to the cabin) between the wires of the IAT (Intake Air Temperature) sensor on the VAF (Volumetric Air Flow) meter you can temporarily disable the ECU's (Engine Control Unit) ability to properly monitor air flow into the intake. Rather than shutting down operation of the engine, the ECU seems to default to a sort of fail-safe operational mode which bypasses the fuel cutoffs normally associated with ATX gear shifting for reduced transmission stress and smoother shifting. The effective result is a powerful shift (often breaking tire traction) that allows significantly faster accelleration. The CEL (Check Engine Light" is expected to turn on whenever the IAT is bypassed. Only recommended for brief usage - use it like you would nitrous oxide. A transmission fluid cooler is recommended to be in place prior to using this technique - be good to your ATX and it will be good to you. Consult a wiring diagram to find which of the VAF wires to interrupt with a toggle switch (The sensor is on the black/yellow and green/white wires in the VAF harness - the black/yellow is the common ground, shared with several other components and is probably the best candidate).




3.3 Axles

3.3.1 Aftermarket axles

Well, the bad news is that there aren't any. The good news is that you can have some made. If it's really worth it to you to have some titanium alloy half-shaft and intermediate shaft axles made up to handle your torque-monster engine, then go for it. It should be noted, however, that with that kind of power, you're building on the wrong platform and a FWD car will just let you down on the strip when it comes to traction. For power levels requiring custom axles, you should be well into RWD conversion territory and in which case you would need a drive shaft, not an axle. Just food for thought..

4.1 Belts

4.1.1 What size alternator-A/C belt do I use?

With an OEM crank pulley:
WITH A/C:
WITHOUT A/C: Dayco part # 340K5, 34" 5 ribbed belt.
With an Unorthodox Racing Under Drive Pulley (U.R. UDP):
WITH A/C:
WITHOUT A/C: Dayco part # 315K5, 31.5" 5 ribbed belt.




4.2 A/C removal

Removal of the air conditioning system is a fairly straight-forward job. There are those who question the reasoning behind it, and those who "get it". Let me try to explain in as few words possible: weight and parasitic loss reduction and space savings. The A/C system components add up to about 50lbs of dead weight - that is if you don't give a crap about A/C creature comforts. Even with the A/C disabled, the engine still has to turn a belt & pulley on the A/C unit which is not huge, but is eliminated nonetheless. The components also happen to take up useful space in the engine bay and in front of the radiator. These are spaces that could be used for more useful things such as intercoolers, fans, superchargers, etc. So here's what you do:


1. You can start by getting an accessory belt that is appropriately sized for the same engine without A/C and install it! Fortunately for the design of our pulleys and such, you can bypass the A/C pulley and still properly tension the belt without interference from teh A/C still being installed. This way you can minimize the downtime on your car while you struggle with removal of the useless gear.
2. Now go have your A/C system discharged by a professional. It only costs $25 and you'll be doing the environment a favor. Why make a mess unneccesarily? Someone has to start caring about this planet and it may as well be you. Yeah yeah, I know. The other method, God forgive you, is to try and isolate a hose with rubber gloves and rags and the works and crack it open and let it vent all the pressure to the atmosphere. Don't get any on you.. nasty stuff. And dont let anyone see you because it's EPA-regulated. Theres some pretty nasty oily goup inside the system too, resumably for closed lubrication of the moving parts. Harmless to touch, but I wouldn't let it soak into my skin.
3. The rest of the work is just disconnection and removal of all the parts. Some of them are tricky and intertwined and difficult to manipulate, etc. It'll all come out, from the condenser all the way back to the evaporator. Typically the part on the inside of the cabin is left in place since it is small, very little weight comparatively, and a royal pain to remove. There is a bracket that holds the compressor to the engine block that can be removed as well. By that point you should be seeing a lovely spot to attempt a super-charger install.
4. Now you can cleam the grime from your parts, buff them up and put the system up for sale. Those A/C compressors go for something around $400 new, so a working used one is of decent value to someone with damaged goods. You get the picture, I'm sure..

4.3 Engine Cooling

It's rather amusing that a lot of people spend quite a bit of time fussing about cooling their engine more than necessary. They try thermostat tricks (replacing it with a lower temperature version, boring passages through it, or eliminating it altogether) they try pulley tricks (small pully make pump spin more faster, ja!) they try to find bigger radiators - but all to no avail. The KL03/DE cooling system is just fine folks. If you want to improve its efficiency, replace the stock radiator fan with a higher CFM fan (2400+ CFM) and you'll never have a problem. Remember: engine cooling and under-hood temperatures are two different things. If you have high under-hood temperatures, don't blame the engine cooling system. Look into things like hood vents or cowl, air routing through the engine bay, exhaust/header wrap, etc. And remember: the of the two stock fans on the radiator, only the driver side one is intended for engine cooling; the smaller passenger side one is for the A/C system.

5.1 Chassis

There are a few aftermarket solutions available for bolt-in roll cages & roll bars. They are generally constructed to minimize materials usage while maximizing strength - and at the same time eliminat hazards to vehicle occupants in the event of structural failures. This is why roll cages are left to professionals who really know what they are doing. Can you imagine your displeasure of being impacted from the rear and having a tube from your home-built roll cage thrust through your torso? What may seem like a great idea and seem to be the epitomy of strength to you by hand and as a weak human (compared to the forces involves with massive bodies in motion) may turn into a lethal weapon when subjected to forces beyond your control - Don't risk your life by performing amatuer work on your chassis! If you want a custom cage or roll bar, take it to someone who specializes in designing these things according to standards and have them make you something that you can count on - and that won't get you banned from the track.

5.2 Suspension

5.2.1 Springs, Struts and Substitutes

Spring and strut combinations can have positive or negatives effects the handling of the vehicle. There are various considerations for each type, but in general, there are only a few types to consider:

5.2.1.1 Springs

You've got your normal springs, your coilover springs to consider. Normal springs are most like the stock/OEM springs that come with the vehicle. They tend to sit in the same "perches" that the stock springs sit in, but have various heights and spring rates that affect the ride height of the car, thus the center of gravity, thus the handling. Aside from affecting ride height, the spring rate also has an influence on handling as it relates to the car pitching from side to side and its response.

Coilover springs are significantly smaller radius springs that ride on specially formed seats designed to be adjustable in position allowing arbitrary lowering or raising of the car's ride height at each wheel. These types of springs offer tremendous flexibility, but because they are so small tend to be significantly stiffer than regular springs in order to hold the same weight under reduced travel. They also don't require the use of the stock spring perches which allows them to be cut away leaving onlt the perch welds for the special coilover perches to rest upon. This is not vital, but is a commenly chosen route that may allow the use of larger than normal wheels. They happen to weigh less than full sized springs & perches too!



5.2.1.2 Struts

There are basically only two types of struts available: adjustable and non-adjustable. Non adjustable struts are like your stockers: fixed response properties. Adjustable types, like the Tokico Illuminas, have an adjustable response. In either case, the struts should be made the properties of the springs you have them paired with, and which, in turn, should reflect the requirements of the vehicle's handling (e.g. tight rear, loose front, vehicle weight considered, etc). The spring rate and the strut's rating should be closely paired. It may be possible to also have custom fixed-rate struts produced where stock struts are cut open and internally modified to have the desired characteristics.


5.2.1.3 Substitutes

Last are the fully adjustable suspension types: airbags & air rods. These are not performance items, folks. They will harm handling more than help. These are an aesthetic modification only for extreme lowering and ride height adjustment where needed. Typically air bags are a substitute for a spring where an air rod may be a replacement for spring and/or strut.




5.2.2 Links, Mounts & Bushings

5.2.2.1 Rear sway bar end links

Looking for rear sway bar end links for your OEM sway bar? Try the 1995 Nissan Altima end links as a cheap alternative.


5.2.2.2 Strut mounts

There are some aftermarket strut mounts available that are stiffer than the stock mounts and thus reduce flxing in the suspension to tighten it up. The strut mounts are bolted to the top of the strut where it mounts to the chassis.




5.2.3 Strut Bars and Sway Bars

There are a wide variety of strut tower bars available for these cars. Strut tower bars are bars that stretch the width of the car between brackets mounted atop each strut. The part of the chassis where the strut mounts to the vehicle is called the "strut tower", hence the name. By tying together the towers, you reduce/eliminate the chassis' flexing ability to bring the towers together or apart in response to driving conditions thus, again, stiffening up the suspension handling. The rear strut tower bar makes a significant difference where the one from the front is only slight. this is because the front one is not far from the firewall which itself somewhat braces the chassis in this manner (though not completely. The rear, on the other hand, is entirely defenseless as has been the case for every hatchback ever manufactured. Strut tower bars tend to be more or less effective depending on their design/manufacturing qualities. Some are more rigid than others, more or less adjustable, etc. So not all are made equal and you'll have to do some homework and/or experimentation to decide which is right for you. If you are a home-fabricator type, then this is a fairly safe, and simple project to tackle and have very good results with using steel bracing. It should be noted that because a bar resists both tensile and compressive loads between the towers, generally a tubular shaped bar, and particularly round over square, has the best structural qualities to battle these forces and make a solid difference. Remember also that, as Buckminster Fuller discovered, the triangle is the strongest structural shape in the known universe, so take that into consideration when creating your bracing - there are some fairly simple methods of incorporating one or two triangles into a design that would significantly improve performance.




5.3 Brakes

Why is it that performance newbies always want to go real fast, but don't care if they can stop real fast? Stopping ain't no fun! Perhaps not, but it's an often-overlooked piece of the performance puzzle that must be fit into place before the picture can be completed. There are a variety of brake upgrades available for our veehicles rangine from improved rotors/pads capable of greater wear, heat dissipation and stopping power to full brake kits with larger rotors, more powerful calipers and accompanying brake lines. It's not beyond the serious hobbyist to identify brale parts that are desired and have them adapted to fit. There are Probes running with RX7 brake calipers made possible by special adapter plates. There are cars running completely custom rigs too. It just goes to show where all-out commitment to doing the job right can land you: safely stopped at the side of the road rather than over the embankment and down the cliff face.


5.4 Steering

There's not a lot to be said about the steering system on our cars. The power steering subsystem appears to be fairly efficient and even performs acceptably when under-driven by a crank pulley. Some racers have decided that power steering is for wussies and they'd rather not subject their engine to further parasitic losses and so have the system removed. Yes, it can be done, but you have to do a couple tricks. The first trick involves customizing an pulley appropriately to drive the water pump off the A/C / alternator belt rather than the power steering belt since, without the power steering pump in place, the P/S tensioner pulley will not be able to tension a belt to drive the water pump. This results in a requirement for a pulley to match the position of the A/C / alternator track and a longer belt to loop over it. The one tensioner will suffice to drive all these devices. The new pulley could be custom fabricated readily enough, or if you're really resourceful you can see about adapting the waterpump pully from a 2.0L engine to bolt on to the 2.5 since, when flipped in orientation, the 2.0 pulley lines up perfectly with the target track on the 2.5. That taken care of you would be free to drain and remove the power steering pump and reservior and associated tubing, etc. and cap off the valve bodies on the steering wheel shaft. Some have said that the steering wheel shaft may be too weak to handle the stress placed on it from the wheels/rack & pinion without the aid of hydraulic pressure which it is designed to operate with. Others have driven their car in this manner for years without incident. Decide for yourself. Perhaps a custom intermediate shaft could be produced to replace the valve bodies with a straight shaft. Perhaps it's no big deal at all and that the hydraulics really don't alleviate any stress from the shaft. Make note also that with the power steering gear installed and the engine off, it is considerably more difficult to turn the wheel by hand than with the hydraulics disconnected since when they are not pressurized in your favor, they actually resist your motion - it won't be that difficult to turn once removed.. it'd be like any other car without power steering.

The only other related topic is that of aftermarket steering wheels. There are many available and you can take your pick. Just remember a few things - first you have to make sure that they offer a hub for your vehicle to adapt the wheel to your car. Second you'll have to do some toying around with wiring to reconnect your horn and you may be forced to re-route or entirely eliminate your cruise control functions since an aftermarket wheel surely will have no provision for these vehicle-specific items. Oh well, the price of beauty, right?

8.1 Ignition

8.1.1 Aftermarket Ignition

There are a number of general use aftermarket ignition systems out there, but by far the most popular for the Probe community is the MSD (Multiple Spark Discharge) 6A line of products. The MSD 6A devices are capable of delivering a more powerful spark across your plugs that won't get blown out prematurely and ensures positive combustion with each ignition pulse. Installing the MSd, however, requires a fundamental understanding of the electrical signals and wiring in ignition systems and typically amounts to completely butchering the OEM ignition wiring harness. There is an adapter now from MSd for 93 & 94 Probe V6 distributors which cleanly connects the MSD system without cutting any wires, but nothing for the 95+ cars which have a revised distributor.


8.1.2 Ignition Wires

A pretty basic thing to replace in your engine bay is the ignition wires, both for periodic maintenance and for performance reasons. Fortunately there is a method of measuring the wires to determine whether they need replacing, and periodic checks may allow you to avoid frustratingly poor performance from your engine. To check the wires you need a multimeter - measure the resistance of the wire from end to end. A good wire will measure from 5K ohms to 20K ohms. A bad wire will be one which reads hundreds or millions of ohms, or one which reads well under 1K ohms.

Note: This ignition system requires resistance-type ignition wires to be used. Solid core/low-resistance wires will cause problems with performance, heat up, and possible represent a fire hazard, so don't use them!

Often tuners will upgrade the wires in order to build up the ignition system with specific goals in mind such as a high compression engine, forced induction or nitrous oxide use. If your goal is in that list, then upgraded wires are for you. Otherwise, unless you just want aftermarket wires strictly for aesthetic purposes, there's no reason to pay more for something that's not OEM specification (unless, of course, they cost less than OE wires, in which case, go for it!)




8.2 Other Electrical & Wiring

8.2.1 Connecting an Air/Fuel Gauge

There are a number of options for this task. The wire you connect to is dependent on which engine you have (OBD vs/ OBD2).

Some installers simply run the meter's sense wire to the black wire of a 3-wire connection coming right off the front bank O2 sensor (the other two wires are white). There is a 4th connection, but it's not a wire and that is the manifold itself as a GND.

To avoid running a wire all the way into the engine compartment, you can be a little smarter by tapping into the ECU harness right in the cabin. To do this however you should have a wiring diagram handy. The wiring diagrams shown in the Haynes repair book seem to be sufficient for this. Find the diagram that that matches your car's ECU connections. Located the O2 sensors on the diagram. There are two halves to each sensor. One half is a heating element (coil + resistor). The other half is the o2 sensing element (variable resistor & resistor). Follow the wiring diagram and mark the sensor halves of each - the heating half is useless for this task.

Now on each sensor half, one of the two wires goes to ground, the other is "signal" you want to tap the signal wire. Your best bet is to identify where all the grounds are and mark them. The ground is given away by either a grounding symbol or by sharing the wire with other electronic components. Each signal wire goes straight into a connection on the ECU harness. now just take your pick on which signal wire you want to use, tap it and away you go.


8.2.2 Replacing front turn indicator bulbs

First, get an 1157 and 194 bulb (per side). Stock the 1157's are orange coated, but if you replace both at once, you can put in the "clear" ones, or if you can source some you can install "hyperwhites" which appear to have a bluish coating, but shine a bright (slightly bluish) white. The 194's can be clear or hyperwhites as well.

To replace them, you have to get down under the front of the car. There is a plastic mud/rock gaurd that covers the bottom, front of the car and you'll have to undo a couple fasteners to bend it out of the way - you don't need to remove the whole thing. Peeking in the opening with a flashlight, you should be able to see the underside of the turnlamp housings. The bulbs are socketed- the big one (1157) faces upward, the small one faces forward. you have to give each a twist to pop their sockets out, then remove the bulbs from the sockets. The 1157 is a press & twist, the 194 is just a press-fit. Pop `em back in & replace the mud gaurd's connectors and you're done.


8.2.3 Replacing rear turn indicator bulbs

The rear bulbs are somewhat more troublesome than the fronts and bulb selection varies with the year. Per side, for 1993 and 1994 vehicles, you need one (1) each of 1156, 3496, 3497 and 168. For 1995 and up you need three (3) 1156 and one (1) each of 3496 and 168. You will probably have to remove the tail light assembly and inspect each of the bulbs to determine which needs replacement. Or you can simply buy all the bulbs and replace them all indiscriminant of which is blown.

To remove the tail light assembly, pop and lift the rear hatch and ensure that it is well supported while you are working under it. Above each tail light, you will see a slim piece of plastic trim that covers the tops of the lamp housings. The plastic piece snaps into place and can be removed by applying slight pressure with a flat-bladed screw driver to each of the tabs indicated by the arrows on the face of the piece. Lightly pry each one out and pull the plastic piece away. The top of the lamp housing will be white in color aside from massive amounts of dust that tends to accumulate here. Remove the single, black phillips head screw that can be seen securing a tab down to the body of the car. Now here's where things get tricky. The remaining fasteners that secure the lamp housing to the vehicle are simple, plastic clips, all but one of which are sliding guides. The one which is not a sliding fastener is a snapping clip and is located on the side of the car where the tail light wraps around. The trick is to apply controlled pressure to slide the lamp housing sideways (away from the license plate or center reflector) towards that snapping clip such that the snapping clip releases and the lamp housing slides free of the vehicle. The reason this is tricky is because aging clips are sometime quite un-cooperative and take quite a bit of encouragement to get them to release. But rest assured: eventually they WILL release, so take care not to fling your entire body off into the bushes once it does. Moreover, remember that the red lense face is made from a relatively brittle clear plastic which may crack if subjected to too great a stress or sharp impact. Don't pound the thing with your fists, don't try to pry it with bars or screwdrivers - you'll only be pissed at yourself if you crack that lense and I'll warn you now: they're $100+ at the pick & pull.. you don't even want to know how much they are from a dealer. SO, STRONGLY ENCOURAGE the thing to release itself. Sometimes it is helpful to force the asssmebly to move back and forth until it decides to slip free.

Once you get the thing free, you will see a rat's nest of wiring leading to several lamp sockets. Each socket may be removed from the back of the housing by giving it a counter-clockwise twist and pull. Replace those bulbs that you need to. All the bulbs but the 168's are a press & twist socket connection. The 168's are just press-fit.

Now before you make a move to re-install the lamp housing you have to check out each of the clips. Often the clips will become mis-positioned or come off the car and hang onto the lamp housing. Each of the sliding clips along the rear gate of the car needs to be solidly pressed into place. You should not be able to wiggle them with your fingers and the sliding direction (it's not hard to figure by looking at it, I won't go into great depth explaining this) should be horizontal. Sometimes they are pretty tough to press back into proper position. Try resting the handle of a screwdriver against them and give them a shove; they pop back into place with a hearty "SNAP". Make sure there are no "cling ons" hanging onto the lamp housing and that they're all in place. This is a good time to wipe over all the components/areas with a rag that you normally don't have access to for routine cleaning. Now position the lamp housing off to the side just in line with those sliding clips. Sometimes you have to supply some forward pressure while you slide horizontally. It takes some feeling around to assure that all the slides mate up and that the side snap aligns itself. Give it a good shove from the side, not at the very tip, but more towards the middle of the side, centered over where that snapping clip is located. Some times it helps to "strongly encourage" the thing with an open palm and a bit of force, but again: no serious pounding or sharp impacts or you will break the in such a way that you will look totally uncool driving down the road. Once you get it in place, replace that single phillips head screw over the top tab and snap that plastic trim back over the top (sometimes a flat-blade screwdriver is needed here to to direct those tabs back into position) and badda-bing: you're done! Now onto the other side.

9.1 What should be checked/replaced every 3-5K, 15K, 30K, 60K miles?


3-5K	15K	30K	60K
• replace: oil  • replace: oil filter  • check: air filter  • check: radiator coolant level  • check: power steering fluid level  • check: transmission fluid level  • check: brake fluid level  • check: clutch fluid level  • check: tire tread wear	• check: spark plugs & gaps  • check: ignition wire continuity 1  • check: distributor cap & rotor	• replace: spark plugs  • replace: fuel filter  • replace: air filter  • replace: radiator coolant flush  • replace: PCV valve  • replace: transmission fluid	• replace: timing belt  • replace: water pump  • replace: accessory drive belts  • replace: valve cover gaskets  • replace: distributor cap & rotor  • replace: ignition wires  • check: cylinder compression  • check: clutch & clutch line  • check: brake lines, pads & rotors  • check: ignition timing  • check: throttle position sensor adjustment  • check: idle rate

¹ Should have 2-20K ohm resistance max - any higher should be replaced

10.1 How do I check my fuel pressure?

There are universal fuel pressure testing kits - they are basically just a typical fuel pressure gauge that comes with an assortment of tubes, hoses and fittings to facilitate adapting it to pretty much any car. You'd have to see if any local shops around you offer them for rental.


10.2 Why is revving a cold engine bad?

Because
1) On whole, your car's engine spends more time running at normal operating temperature than either too hot OR too cold. For this reason, not only by design, but through normal wear, your engine's parts have become self-accustomed to operating at this temperature. This is partly related to thermal expansion of the metal parts and other parts "giving way" to this expansion. Running the engine hotter or colder (most frequently colder since you start it every day, but rarely overheat) means that the bits and pieces are not at their "normal" heat-expanded size and thereby may have too much or too little "play" in them.. things start jiggling around, a little friction here, a little there, and badda bing: you end up with more wear & tear on your parts from operating outside of normal temperature range.

2) Equally important is your engine lubricant. There is not just concern that your engine oil is all in the pan at start-up - this much is evident. But did you ever hear about people's HLA ticking when the engine is cold and by warm-up the ticking going away? This is because engine oil ALSO has an operating temperature at which it most effectively lubricates. Sure, it does an "okay" job cold and a decent job warm, but it is best when at full temperature. And guess what - there's "too hot" for oil too - it's called "thermal viscocity breakdown" and it's a serious engine killer. This engine has a nifty "heat exchanger" on the engine block between the engine oil & coolant for the very purpose of regulating oil temperature, highlighting its importance.

Perhaps there are other aspects to the effects of cold operation wear & tear, but that is how I understand it. In terms of "what breaks first" from beating on the engine while it's cold, I've always heard that the piston rings take the brunt of the abuse - but I've never tried to find out for myself...


10.3 How do I pull my OBD (1993-1995) MALF codes?

The codes are blinked out by the Check Engine Light (CEL) on the instrument cluster. Remove the key from the ignition, pop the hood, find the tniy black box labeled "DIAGNOSTIC" near the stock battery tray location at the driver's side fender. Pop open the lid to the box to find the following pinout in the image to the right. Connect a short jumper wire between the pins STI and GND. Now run as fast as you can and take cover. Just kidding. So now, get comfy in the driver's seat with a pencil & paper, put the key in the ignition and turn it to the "ON" position, but don't start the engine. The CEL will begin pulsing any stored malfunction (MALF) codes on the CEL light. The long pulses represent the tens column digit, the shorter pulses represent the ones column digit. Take the count of each, put them side-by-side and you'll end up with a two-dgit code which, if all goes according to plan, should be listed in the table below:



CODE	DESCRIPTION	MEMORIZED
02	'NE2' crankshaft position sensor	Yes
03	'G' camshaft position sensor	Yes
04	'NE1' camshaft/crankshaft position sensor	Yes
05	Knock sensor	Yes
08	Volume Air Flow sensor (VAF)	Yes
09	Coolant temperature sensor (CTS)	Yes
10	Intake air temperature sensor (IAT)	Yes
12	Throttle position sensor (TPS)	Yes
14	Barometric pressure sensor	Yes
15	LHO2S inactivation error	Yes
16	Exhaust gas recirculation (EGR) system	Yes
17	LHO2S inversion error	Yes
23	RHO2S inactivation error	Yes
24	RHO2S inversion error	Yes
25	Fuel pressure regulator control solenoid	Yes
26	Canister purge solenoid	No
28	EGR vacuum solenoid	No
29	EGR vent solenoid	No
34	Idle air control (IAC) solenoid	No
41	VRIS #1 solenoid	No
46	VRIS #2 solenoid	No
67	LFAN relay (1993 only)	No
69	ECTF sensor (1993 only)	Yes


10.4 How do I determine the cause of my airbag light trouble codes?

The code is blinked out by the light on the dash. Some codes are on coninuous, some are flashing continues, others are distinct sets of pulses to represent each of two digits, the higher order digit first, a short pause, then the lower order digit, then a longer pause and the sequence repeats. So if it flashes twice, then pauses, then once, then a longer pause and repeats, the code is "21" which can be looked up in this table for troubleshooting:



Code	Component/Fault Description
--	No Air Bag Lamp - Inoperative Lamp Circuit or No Ignition Voltage to Diagnostic Monitor
--	Continuous Air Bag Lamp - Diagnostic Monitor Disconnected or Inoperative
12	Low Battery Voltage
13	Air Bag Circuit or Crash Sensor Circuit - Shorted to Ground
21	Safing Sensor - Not Mounted on Vehicle Properly
22	Safing Sensor Output Circuit - Shorted to Battery Voltage
23	Safing Sensor Input Feed/Return Circuit Open
24	Open in Circuit 944B or Low Resistance in Crash Sensor(s)
32	Driver Side Air Bag/Safing Sensor Circuit - High Resistance or Open
33	Pin 7 Not Grounded at Diagnostic Monitor
34	Driver Side Air Bag/Safing Sensor Circuit - Low Resistance or Shorted
35	Low Resistance Across Pins 8 and 9 at Diagnostic Monitor
41	Crash Sensor Circuit - High Resistance or Open
44	RH Crash Sensor - Not Mounted to Vehicle Properly
45	Center Radiator Crash Sensor - Not Mounted to Vehicle Properly
46	LH Crash Sensor - Not Mounted to Vehicle Properly
51	Diagnostic Monitor Internal Thermal Fuse - Blown and Short to Ground No Longer Exists
52	Backup Power Supply - Voltage Boost Fault
53	Internal Diagnostic Monitor Fault
--	Rapid Continuous Flashing of Air Bag Lamp - All Crash Sensors Disconnected
Automatic Transaxle Codes
111	System Pass
112	Intake Air Temperature sensor or circuit
113	Intake Air Temperature sensor or circuit
116	Engine Coolant Temperature sensor or circuit
117	Engine Coolant Temperature sensor or circuit
118	Engine Coolant Temperature sensor or circuit
121	Throttle Position Sensor or circuit
122	Throttle Position Sensor or circuit
123	Throttle Position Sensor or circuit
157	Mass Airflow sensor or circuit
158	Mass Airflow sensor or circuit
159	Mass Airflow sensor or circuit
172	Heated Oxygen Sensor or circuit
173	Heated Oxygen Sensor or circuit
179	Heated Oxygen Sensor or circuit
181	Heated Oxygen Sensor or circuit
211	Ignition System
212	Ignition System
213	Ignition System
214	Camshaft Position sensor or circuit
244	Camshaft Position sensor or circuit
327	EGR function sensor or circuit
332	EGR function sensor or circuit
337	EGR function sensor or circuit
411	Idle Air Control valve or circuit
412	Idle Air Control valve or circuit
452	Vehicle Speed Sensor or circuit
511	PCM
512	PCM
513	PCM
519	Power Steering Pressure switch or circuit
521	Power Steering Pressure switch or circuit
522	Transmission Range sensor or circuit
536	Brake On/Off switch or circuit
538	Dynamic response test
539	A/C sensor or circuit
554	Pressure Regulator solenoid valve or circuit
559	A/C relay or circuit
563	Cooling fan relay or circuit (high speed)
564	Cooling fan relay or circuit (low speed)
565	Purge control solenoid valve or circuit
571	EGR solenoid valve or circuit (vent)
572	EGR solenoid valve or circuit (vacuum)
998	PCM


10.5 What causes and resolutions are there for no ignition/spark?

There is a fuse in the cabin labelled "engine" that can prevent spark. Check and replace this fuse as needed.

You will also not receive spark if your Crank Position Sensor (CPS) is dead. Check the electrical connector on that sensor (the connector is positioned near where the oil dip stick and water temp sensors are) and make sure that there is no water in it, and that the contacts look clean, no corrosion. Sometimes it also helps to give each connector spade about a 10 degree twist with needlenose pliers which will help them maintain positive contact on the receptacle end.

Earlier models (93-94) suffered from an ignition module which is sensitive to heat and burns out in relatively short order. The ignition module is a small electronic circuit within the distributor and is considered a non-servicable part: an entire distributor must be sourced to replace it. There are aftermarket solutions however if you like the idea of doing it yourself and saving a few hundred bucks. It is possible to adapt a GM ignitor module which only costs around $25 and will get your car running again! Often times people will combine the GM ignitor with a multi-spark ignition system such as an MSD 4A series which is 50-state CARB legal.

Other things to look for include extremely worn distributor cap or rotor components which should be cleaned and/or replaced as needed. It is also common to get water inside the distributor cap after hosing down the engine. You'll have to remove the cap and dry it out before it will ignite correctly again. Regular spark plug and ignition cable inspection and replacement should be performed as well. If none of these things turns up a solution, you may need to consider swapping the ECU to see if something terrible has fried your computer. It's not common, but it does happen.