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FAQ Section:  These are short answers to many repeated questions I have seen on the BBS sections.  Some of these are purely my own opinions and others may differ but I have just listed some quick answers to help reduce repeated posts.  I also would like to thank all those with helpful knowledge who have continued to answer many key topics presented by visitors.

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[toggle_item title="LSD - OEM and Aftermarket Limited Slip Differentials" active="true"]

Are OEM (Optional Equipment) Limited Slip Differentials any good?  The answer is yes they are perfectly good and it is wrong to say they are not.  However, almost all of the factory equipped LSD have not been overhauled since it was shipped from the factory.  Since LSD are just like clutches and brake rotors, and wear significantly over time and abuse, that I cannot say they are in very good condition.  Yes, with the use of very poor tires, or in slippery surfaces, they are still very effective at 100,000 and beyond, but in most cases the factory LSD has had thousands of miles of use and have degraded to nothing much than that.  Since overhauling an LSD costs a lot of money and lots of skill and time for a weekend mechanic, this is where the consideration of the aftermarket units comes into consideration.  Replacement or rebuild of LSD requires similar amount of work as most of the labor is charged on the disassembly and assembly of the rear differential (transmission on FWD and MR2's).  The cost of the parts alone is a smaller chunk of the bill compared to most other repairs.  Since OEM LSD has small clutches and are of two-pinion mechanical unit, the wear is much greater when exposed to performance application.  They are also limited in it's ability to handle high torque situations such as using today's newer radial and semi-slick tires. Aftermarket units such as KAAZ, Cusco, ATS, and newer TRD types use up to six plates that are both larger and stronger than the OEM.  The devices also use 4-pinion designs which makes the LSD more responsive as well as more positive when engaging.

The rebuild kit from Toyota for an OEM LSD cost around $400 (AE86) in parts while a new aftermarket ones range from $650-$900.  Though looking at the parts-only cost, the differences seem significant, however when you consider that install and rebuild costs about $500-$1000 in labor charges, it makes reasonable sense to spring for the aftermarket unit which generally has longer service life, and cheaper replacement parts.  more on LSD

Can I put aftermarket LSD in a AE86 that didn't come with factory LSD? Do I have to do some modification?

OK, the 7mm difference is due to some production suppliers having different specs. Both axles were used and on AE86 throughout the production cycle. Aftermarket supplier LSD (KAAZ and Cusco) will accept both and is built with enough clearance to cover for pinion offset differences as well. Interestingly enough, OEM (race version) TRD 4 pinion units did not clear the longer axles. The axles should be shaved about 5 mm in this case to fit correctly. Aside from this problem, the only difference would be between 1984-85 axles being smaller than 1986-87 differentials. So buy the proper LSD for your year and you are all set.

One more thing... The rear end could have been swapped in whole between late and early models in the 15 years the cars been around by previous owner so you should check the actual axle version you have by inspection, and not trust the model year of the car.

Here are some photos from another web page in Japan. (Taka8's AE86 and 4AG in Japanese Language)

Early (1984-85 AE86) and Late (1986-87 AE86) Axles, you can see the difference in number of teeth and diameters.

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[toggle_item title="TVIS -  Keep it or Remove it?"]

There have been many, arguments on the issue of TVIS on early model 16 valve 4A-GE.  The TVIS creates higher velocity intake charge at the engine's lower operating range by closing off one intake runner of the pair on each cylinder.  Now, this is a highly effective method of making usable torque curves while retaining higher volume flow at high operating range.  In most near normal applications, generally meaning light bolt-on tuning, the TVIS continues to function very well. Thus keeping it is a very good idea.   However, heavier modifications including ECU, Carburetion, highly aggressive valve train/cam and internal work all present effects which create difficulty in controlling these items.  For example, the triggers for the TVIS will be eliminated for carbureted applications, and it's variable induction, even if it was operational presents more complex challenge to jetting your carburetors.  Heavily modified engine which greatly alters maximum rev range and shifts the power band in either direction will present similar challenges to an ECU programmer as well.  In those cases it is easier to remove the TVIS and use the capabilities of the ECU tuning or carburetor jets to match your desired torque range.  In short, for most basic performance upgrades, the TVIS should be kept and maintained to give nicer overall torque curve which does NOT inhibit power in any significant way.

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[toggle_item title="4A-GZE or 20V?  What's better?"]

There is no definite answers to such question as both engines are quite different and is just a matter of what your needs are and what you really enjoy in an engine. The 4A-GZE in general, like most forced induction engines, provide very deep torque range from low to mid rpm, and provides the driver a similar feeling as larger displacement engines. The power output is provided low in the rpm range. By contrast the 20V and modified 16V engines, being naturally aspirated, requires much higher revs to get similar output and torque curve is steep and narrow at the top. The more aggressively you tune them the more this is apparent. The 20V with it's VVT operating, provides more stable higher torque output than the 16V but is vastly lower than that of the 4A-GZE. Novice drivers will definitely be faster with the 4A-GZE while more experienced drivers will find very rewarding challenge from the 20V while showered with the concert of individual throttles all singing like the best of racing motors. All this however is provided that you had installed and tuned the engine well, which seems to be more of a problem for beginners. In any case, never budget your project short, or cut corners on parts needed, or else your project will just be that...a compromise, even when just installing it using OEM specs. more on 4A-GE

added: 4-10-2010

4A-GZE - Forced Induction (Supercharger)
A forced induction engine, especially that like the 4A-GZE which uses Roots-Supercharger, will have very low torque availability. This means much of the horsepower is available at the lower to mid rpm range just as if you had a larger displacement engine. The principle is just that, to force more air and gasoline mixture into the chamber than normal atmospheric pressure allows, and burn that much more fuel within a limited cylinder space of the small engine.

Having said that, the heat generated from the engine is quite a bit more in need of attention. Despite the power being created at lower engine friction state, the sheer combustive heat and pressures generate a lot of heat. Therefore, the engine is stressed, needing a much more robust and heavier internals. The 4A-GZE does have a forged piston, and reinforced skirt area as well as it being based on a later model 4A-GE connecting rods and bearing system. It is durable engine when properly operated with factory ECU with all the sensors properly connected or with professional aftermarket ECU integration. However, like any forced induction engine, it is very susceptible to failure from bad installations, calibrations, etc, since the forces are that much greater for each combustion cycle. Also massive heat generated requires a much more robust cooling system for oil and water, and still has issues if the engine is used for very long duration under heavy loads, (such as in sustained hours in spirited open road driving, or large number of laps in a closed race track.)

16V-20V NA engine:

Naturally aspirated engines in contrast, are much simpler in actual design and parts list. It is a design where extra air and fuel is burned more rapidly by spinning an engine capable of sustaining very high RPM. The torque curve is narrow and it takes a skilled driver to maintain a high power range consistently, the more busy and variable the race conditions get. Some find this a rewarding trait (I do) but others prefer easy, consistent power of a forced induction method as in supercharging or turbocharging. The benefits of a high rpm NA engine is instant response. The engine will respond quickly to throttle and a more experienced driver will find such merit a definite must when driving on a track that involve braking and turning. As side bonus, the wailing sounds of a properly tuned high-rpm engine is what dreams are made of for enthusiasts who enjoy a fine calibrated engine in a car or a bike.

However this is not to say the installation or care taken in installation is any less complicated. It has to sustain rather high internal forces from higher rpm operation, and careful assembly becomes much more critical in such engines than in a low-rpm forced induction engine. Spinning an engine efficiently at over 6000rpm is a very precise business and it most often is a very expensive proposition with work becoming much more reserved for experienced tuners to achieve good results. Simply slapping pats together from a catalog will most often never achieve the intended result. And every gram of fat and every 1/100ths of a gram of balance will affect significant amount of power.
20V and modified 16V naturally aspirated 4A-GE engines are much simpler in electronic control and regulation. However it still needs precise timing and delivery and slightly higher electrical needs at higher RPM. Sustaining high rpm requires a very good ignition system. This is because the high rpm engine will require the spark plugs to fire more frequently and more precisely. If the engine is spinning at 8000rpm, the plugs must fire 4000 times per minute. The time it takes to recharge a coil for a spark is greatly reduced the higher rpm we must go. The problem in modern ignition system is not so much the timing control as computers are much faster than 4000X per second in processing. However the great electrical draw required to charge the coils are sometimes lacking in home-brew projects based on a 1986 Corolla specification alternator and supply. Many reduce the size of the battery to save weight, adding to more issues at times.

Case Point:

In both designs though, Toyota did quite a good job of putting together a nice reliable EFI and ignition system. However there are many small parts and sensors that all need to work together to work as a whole.
99% of the time I see people having engines not operating well or being destroyed on track are due to haphazard installations, mis-tuned ECU parameters, missing sensors, or worn out electrical systems of connectors and harnesses and faulty sensors.

I know AE86 is a way to enjoy a great car for a budget that’s rather smaller than those of modern cars or more fancy exotic automobiles. However, this is never to say that as such, the installation and building should be compromised due to resources and budget. Both NA 8500rpm engines and forced induction technology engines are by NO means mundane, and it is rather just as exotic as high end cars. Just think, a Bugatti Veyron or Porsche 996 Turbo, or just about any exotic you can think of, basically uses the same principle in a more elaborate form with more cylinders...but the base design is not much different!! All of them are combination of sophisticated EFI, forced induction and/or very high rpm engines. Toyota only made a ton of them, made it reliable and cheaper, and made them available to a more average consumer base.

So please keep in mind the requirements and gather your plans carefully. Shortcuts never save costs in these engines, and it can be much more expensive than a larger engine spinning slower, breathing normal air since they have the inherent advantage of 100+ years of simple engine principles and heft.

But as always, do it right... and you shall experience a satisfaction like no other!!

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[toggle_item title="Brake upgrades - big calipers"]

One thing most people neglect when describing braking systems deficiency is maintenance of the OEM units. True in the most grueling stages of track driving, the brakes on the Corollas in particular fails to deliver. However, in many cases and for most drivers, even those who visit the track often, overlooks the potential of the OEM units. With fresh re-build or replacement of the master cylinder and calipers, stainless lines, the AE86 in particular can stop very impressively using performance pad upgrade alone. And the feeling is night and day when the OEM units get proper maintenance. With larger modified rotor/caliper upgrades, the brakes will also require re-proportioning for the front -rear bias, as well as in some cases master cylinder upgrades. This latter step requires lots of track time and pad selection becomes key in further balancing your brakes to satisfying levels. What this presents is that you now have to deal with many sets of pads to find the right one and much track time to figure out your bugs. In any case, the brakes are what ultimately stop your car in a CONTROLLED manner. Please be very cautious and employ the skills of qualified tuner to figure on what you need to do, otherwise you'll be exposing yourself to serious danger, possibly without an once of fun factor.

So why not a BIG Caliper?

Well the question lies in the cost and amount of design work. I am not saying larger calipers are not beneficial, rather it certainly is but it has to be fitted and designed correctly to work with a specific car. Once cannot just graft on larger calipers on a car and expect it to be working in balance. larger calipers usually have much larger pistons, or multiple pistons. The master cylinder that pushes the hydraulics need to be sufficient to move the brake fluid with enough force and volume of the new calipers being fitted. The brake balancer, usually fixed on production cars, will need to be modified or replaced to accommodate the new balance settings between front and rear brakes. Finally, there is also a task of making sure that the wheels on the car will fit around the brake system, and that it can operate safely with the new forces. All in all, its a balancing act and a design process of trial and error sometimes, for fitting new calipers and disks. So having a track to test on, and tooling to modify what may need to change is a must as well. So cost and resources in concern, are you really ready to delve into the process? I won't say, since each individual has specific needs, and certainly, done correctly, a larger caliper system will have better resiliency for heat dissipation, and better control against fade and more braking power.

 

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[toggle_item title="Individual Throttle Body - 20V 4-throttle on 16V 4A-GE"]

Another popular topic these days is adapting the individual throttles from the 20V onto the 16V..."Can this be done?"  You bet!  But there are many obstacles which may hinder your attempt and here's some of them.  NO! you will not be able to use the 16V ECU to run the throttle as fuel map requirements are vastly different for the 20'v throttle unit.  The lower rpm ranges require much less fuel while in the upper ranges the throttle needs significantly more fuel.  Since the whole idea of making precise fuel maps are the key to making the difficult and sensitive 4 throttle to work well, it is not a matter of backyard tuning by simply shifting AFM or Vacuum Sensor signals or shuffling fuel pressures.  You must almost always use an aftermarket or re-computed ECU get anywhere near the operation you need...even to match the original spec of the single throttle you tossed in the garbage.  Second, since the 20V's idle is controlled not by the TPS and the throttle body, but rather a secondary port called ISCV which leaks idle air in a controlled manner aft of the fully closed throttles.  Since the 16V engines never had this, you have to figure out a way to devise a similar tactics through your own ingenious method.  The throttle in any case must be fully closed to get idle mixture control on.  The manifold will not bolt on to the 16V's intake so an adapter should be used or fabricated.  Overall, not many of the private shops have successfully made such setups perform better than what can easily be done with the single throttle, even though almost all of them have succeeded in getting a car to run decently.  That said,  there are a handful of shops that did make things work wonderfully (all in Japan that I have seen) with the 20V throttle mechanism and kits are available.  Be cautioned that they are NOT cheap and greatly exceeds the cost of swapping the entire 20V instead, because it will require a fully programmable ECU and their research results in the form of software.  For many of us, a set of side draft carburetor will be a more effective and much cheaper option than grafting the individual throttles on the 16V.

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[toggle_item title="How do I modify the Air Flow Meter setting to gain power?"]

You don't...  If Toyota had gained power significantly without sacrificing anything, they would have set it there from the factory.   AFM and MAP sensors are monitored by the ECU to reference a precise fuel delivery, at best you may gain 2-3hp somewhere but you will lose out overall.  The only exception to this is if your car was previously tampered there already...then you need to set it back. There are much more effective ways of making power and it costs a little money.  AFM alteration seem free but you neglect what you lose in fuel economy and possible repair bills.

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[toggle_item title="MAP vs. AFM - Do Japanese spec. OEM AE86 4A-GE parts make more power?"]

Not really, the only reason the Japanese versions of the early 16V 4A-GE came equipped with MAP sensor (vacuum sensor) control is because it was much cheaper to equip, keeping the cost of the car's purchase price down.  The USA versions came with the AFM ( air flow meter) because it can monitor the intake air somewhat more accurately in that era of technology...and thus was required to meet California's smog regulations.  Both units work equally well and the only sole advantage to having map sensor controls is the fact that induction chamber modifications are somewhat easier without the bulk of the AFM unit.  The performance is in no way significantly better though as many believe.

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[toggle_item title="What are the visual Difference to GTS and SR5?"]

In the USA, AE86 and AE92 came in trims called the SR5 and GTS.  The GTS was basically the trim level which included the 4A-GE DOHC engines in both versions of the Corolla.  In the AE86, the driveline from transmission to the rear differential was different and included a lower 4.3 final gear ratio in the 5 speed transmission.  The SR5 was 4.1, as well as the few AT equipped GTS.  The GTS package also included rear disc brakes, higher grade interior trim, and body color front and rear bumper skins with front spoiler.  Cosmetically the GTS also were trimmed with larger side moldings, Twin Cam 16 decal, and rear spoiler.  SR5 versions had drum brakes and black bumpers as door moldings.  In the case of AE92, the rear wing and side skirts were standard on the GTS as well as decals. more

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[toggle_item title="Lowering your car equals a faster car?"]

If you want to get better at driving your car, don't worry about it yet. OEM springs are the best set to learn the craft of smooth, stable driving, through pitch and yaw. Some take shortcuts and go straight to sport suspensions but those make learning harder even if it makes you a faster driver temporarily. Just replace your bushing sets and get fresh shocks and go to your local autocross events or driving schools. I can guarantee that's the fastest way to better driving and learning to drift like a champ. you will figure out what to do later when you want to get faster. It'll come to you naturally when you fully understand the dynamics of sport driving later.

If on the other hand, you want to lower it for appearance, use correct reputable manufacturer spring sets to lower your car. (more on this topic)

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[toggle_item title="Carburetors or Fuel Injection? What's better?"]

It really depends on how well it's tuned for a specific stage. EFI in stock form isn't geared to pull down the 1/4, but programmable ECU operated right will give much more accurate mixtures and timing and is prone to give better results. Why go back to an old technology when EFI setups cost nearly the same as sidedraft carbs these days. I prefer EFI any day, unless it's a collector showpiece that must have original equipment, with which without it would lose it's attraction. I'm talking about older cars such as Toyota's mystical 2000GT of 1967 and TE27, Z cars...etc... also see: Carburetors for the 4A-G

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[toggle_item title="Break-In for a Freshly built 4A-GE, how and how long?"]

Yeah, for break in, you want to always use mineral based oils so you get proper break-in and clearance before a nice synthetic film is coated.

I like to use Pennzoil's plain Jane yellow bottle on engines with used parts or just to flush out old motors just acquired. It does a good job of cleaning internals without sacrificing protection for city use.

Use the oil for first 500 miles on newly built engines, then once more for another 500 miles. After this you can use synthetics like Mobil1 for another 1000. That's total of 2000 miles of limited rpm city use. Perhaps below 5000rpm should be good.

After 2000 miles, put in once again new oil and go crazy...and after that its just important to change oils as often as your budget and time allows... For me thats every event, before and after, and at least once every 2 months if no events are on the calendar.

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[toggle_item title="4A-GE/GZE Flywheel Choice...how heavy?"]

HKS makes, what I feel is best Street use flywheel. You can use the AE111 flywheel for the AE86 as well provided you use the clutch and plate from AE111 as well. HKS flywheels are great balance between response and in-town torque. It's about 6kg.

I currently use Project Mu, flywheel, plate and cover combo. Its a bit noisy due to the multi-piece pressure plate design and holds much like a twin plate. Its a bit too light for street use and I occasionally stall the engine in traffic (^^;), but gives a crackling light response from its 3.9kg weight.

Toda also makes really nice flywheels for race fields...

In any case, as long as its reputable manufacturer and the weight is to your necessity, its fine to use just about any flywheel you feel is good. Just make sure not to get crappy ones as you can lose your tranny, your money and sometimes your feet as it can become a grenade inside your bell housing at high rpm.

I'd say about 5-7 kg is good for race/street car with crispy NA motor of 16V or 20V. Its also a fine choice for autocrosser and racers who need middle range torque to be stable.

6-9kg for a 4A-GZE equipped car to stabilize idle and to help the supercharger from stalling the engine torque. Also for front drive Corollas and MR2 where traction/torque can greatly affect handling...

3-5 kg for those who basically don't drive on the street and wind the engine at top rpm at track events, and for 4A-GE use on formula cars and other light weight contraptions.

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[toggle_item title="What's the best drift setup?"]

First of all, there isn't much reason to go through all the trouble of using Ground Control coil-over if you are to use the standard length shocks.  Without the shortened strut and short stroke, you cannot adjust the height (lower) the car more than 1.5 inch or so without encountering stroke deficiency problem.  This is the reason we convert them to use the short stroke.  With shortened suspension, you will be dropping the car from between 1.5 to 3.5 inches.  In which case, as you probably know, will require short stroke shocks at both ends as well as race height coils on all 4 ends.

Standard Ground control kit for the AE86 comes with a 350lbs Spring (front only), which are equivalent of 6.25kg/mm approximately in 8-inch length.  To match, you can use TRD race coils for the rear in 4.3, or 5.1 kg/mm springs. These are great for occasional track use while still providing balanced handling for everyday use with ordinary street tires (IE. all season high-performance tires, Dunlop SP8000, Bridgestone RE710, Falken Ziex 502 and with proper adjustable shocks, Summer ultra performance streets such as Potenza S-03 Pole Position, Falken Azenis, Dunlop W10.... but not race compounds such as Kumho V700 or Hoosier RA1, which require yet stiffer springs)

You mention drift.  The truth however is that, there is no one answers for drift setups.  It all depends on what kind of drifting and where your skill levels are...  As novice drifter, perhaps normal OEM car is the easiest to learn...  This will facilitate easier understanding of car's inputs and feedback.  Going to a faster and stiffer setups will make things more difficult to learn, though it enables a skilled drifter to gain higher speeds and stability using much higher grip tires.  (This is why, I really don't want to use the word "upgrade" to any suspension modification, as it all depends on how good the driver is...and to a novice, a race setup is hardly an upgrade as the car will be more difficult to drive and learn in)


Provided you do possess decent skills and have some track experience, I would gladly recommend the setup above.  6kg F/ 4kg R spring combination is very compliant and with proper shocks, you will notice that ride quality actually increases as the car pitches less and still tracts the road fairly well.
This combination is also very good for novice as well, as basic character of the car stays intact for the most part and is probably the next step after learning to throw the rear end around on a normal setup.

If significant race track/autocross use is in your future, and want to experiment with advanced driving and race tires, I would suggest at least 8kg front and 5.5 kg rear.  This combination is still very comfortable in
the streets too.

As for shocks, it is the shocks that mainly decide how soft or hard your suspension will feel in normal traffic, as it is responsible for controlling the suspension stroke speed.  Springs are responsible only for how far it will ultimately stroke under constant g's... that is not significant factor for bumps and irregularity in the road.

For drifting and street as well as occasional track, I would recommend Tokico HTS102.  These are available only in Japan, and not through Tokico USA.  However, Shinkai Racing (linked in my web page under links section) will be able to order them from Japan for you.  They retail about $475 for
all 4 shocks and shipped here may have slightly higher price...  It is however significantly lower priced than any TRD set you will be able to find in adjustable form.  The HTS is adjustable to accommodate from 4kg/mm springs all the way up to 12kg/mm and more.  In other words, it has the adjustment
range of 3 sets of race shocks from TRD.  I found them much better for drifting than the TRD as stability after the tire breaks loose, is excellent It is not a set to win autocross events however, as traction levels of race tires do make the HTS a bit too loose (meaning stiff compression and lack of traction and lateral grip upon driver input) in the rear, and rebound rates in the rear seems to be setup more for rear end controllability than sheer traction and grip...  Overall though HTS is recommended more than TRD if fun
factor is in your mind than clocking track record laps.

Did this help??  Or did I lose you somewhere??

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