!#5: Aftermarket Exhaust On Line: January 2012

!±8± Faq on Modifying the Toyota Supra

What does Bpu(Tm) stand for? (Bpu(Tm) is a trademark of SupraStore.com)

Basic operation Upgrades. These modifications are: A full length three inch down-pipe (with or with-out high flow cats), 3" (75mm) or bigger cat-back exhaust system, raised boost (18psi), and the required boost cut eliminator (Greddy Bcc) needed to accomplish that boost without activating the facility fuel cut-off at 14-15psi. These are the modifications that have proven to contribute the best Hp-to-$$$ ratio.

What does the + mean when someone says Bpu(Tm)+? And what is Apu?

That stands for any supplementary power producing modifications other than the basic Bpu(Tm) modifications. One "+" refers to Adj. Cam Gears and under-drive pulleys, the second "+" refers to a Fuel controller, Ecu upgrade, etc. For instance, a Supra with the Bpu(Tm) modifications, plus a front-mount intercooler, would be called Bpu(Tm)+. If you added cam gears to that, it would be Bpu(Tm)++, and so on. The "Bpu(Tm)" term is used until you have an upgraded turbo(s). Then it is referred to as Apu, developed operation upgrades. This designation pretty much covers every modification that can be performed.

What are the first engine modifications I should perform?

I suggest beginning with raising the boost of the stock turbos to practically 18psi. This will require a ability boost gauge and a boost cut eliminator (Greddy Bcc). You will accomplish 15 or so Psi with the stock Down Pipe in place. This will contribute an increasing of practically 30rwhp. After those modifications are completed, it would be a logical next step to setup the Down Pipe and Cat-Back Exhaust at the same time. You will now be at full Bpu(Tm).

What do all the varied "Free Mods" do?

There are many dissimilar "free mods" for the Supra Tt. I will cover just a few of them here. The ones I will cover fall into three categories, boost control, Egr disabling, and Ttc or True Twin Conversion.

Three of the boost control mods are: Bleeder-T Mod, Clamp Mod, and the Vsv Bypass Mod. Each of these modifications raise boost levels without the use of a boost controller. But you have to keep a close eye on your boost gauge, and make sure they are not allowing the turbos to boost too high (18psi is a safe level).

The next mods, are the true twin conversion mods (or Ttc). This modification disables the Sequential twin turbo operation, and causes the turbos to run constantly in parallel (both on at the same time). This is supposed to allow for slightly great mid-range power (before the secondary turbo would usually come online) and allows for a smoother power band, without the abrupt boost increase caused by the transition from original to secondary operation. However, this does noticeably decrease low-end power, and increases exhaust noise levels, and therefore may not be desirable on the street. Two types of the Ttc mod are, the original Ttc mod which includes 2 methods, wiring the actuators, or installing a one way valve, and the Electronic Ttc mod (Ettc).

The last mod I will discuss is the Egr mod. This disables the Exhaust Gas Recirculation system, which is meant for emissions, and therefore, this modification is for off-road use only. This mod is supposed to prevent the super heating of the estimate 5 and 6 cylinders, which may cause burnt valves.

How much power will my car make at Bpu(Tm)?

It varies from car-to-car, and the conditions as well as tuning. Most Bpu(Tm)-only Supra Twin Turbos, dyno between 370 and 410 horsepower at the rear wheels. This is usually achieved with moderate temperatures, a reset Ecu (to erase whatever bad the Ecu may have learned), and often a little bit of high-octane un-leaded race fuel. On the street, power will be reduced, especially in poor weather, but at least 90 percent of the power should be retained.

What kind of 1/4 mile Ets and trap speeds should I run at Bpu(Tm)-only?

It varies Widely depending on driver skill. As well as track conditions, elevation above sea level, ambient temperatures, humidity, and pre-race preparation. But most fall between 12.3 to 12.9 ets with 112 to 119mph trap speeds on street tires. Times can drop well into the 11s with drag radials, a good driver, and good conditions, as well as allowable pre-race preparation.

What is a Bpu(Tm)'d Supra Tt's top speed?

Speeds in the mid-high 180mph range should be achievable. Once the speed-limiter is disabled, by pulling the "Trac" fuse of course.

Will the life of my engine and Drivetrain be adversely affected with the Bpu(Tm) mods?

Yes, but not by a significant amount. If the car is maintained properly, and the car is treated with some respect for the components, you should say much of the power train's life. Which inspecting the fact that the Supra is by far one of the most trustworthy and durable sports cars, it will last longer than most well maintained Stock sports cars. The only Drivetrain components that will see a significantly shortened life will be the stock clutch. It will more than likely not last much longer than 8-10k miles once at Bpu(Tm). This especially holds true if the car is development repeated high speed runs using 5th and 6th gear at wide open throttle. If your stock clutch has high mileage on it, or is already beginning to slip, you will need to plan on a new high-performance clutch. Also the stock turbos will be branch to a somewhat shortened life span (how short will depend on how you drive and say the car, as well as how much boost you will run)

What's the reliability of a 600hp Supra Turbo?

Chassis, electrical, and suspension components should see little effect on reliability on street driven Supras. The stock 2Jz-Gte engine should hold up pretty well to this power level. Just how long depends on maintenance, and how hard you drive it, and how often. But typically Supras can go for years at this power level. The transmission reliability will depend on either it's an automatic or Manual. A stock automatic will not hold this much power, a built transmission will be required, and it's reliability will depend on it's found and construction. The 6spd by hand should hold up just fine, as well as the rear differential and axles.

The only real reliability concerns at these low power levels would surround the actual modifications you perform. Excluding facility short-comings, the components utilized, even very high ability ones, may fall short of facility component reliability, as the built in compromises that exist in everything, would lean more towards the side of extreme performance, than of extreme reliability (Keep in mind we are talking about a Toyota here, whose reliabilty standards are exceptionally high) This may comprise fuel ideas components, turbo components, and especialy electronic wizardry. Basically a set-up that is either Very well concieved, or utilizes Oe components as much as possible, without over burdening them, would posses *near* stock reliability. And tuning of the components, and component selection, and matching, would play a Huge role in this.

What are the power limits of the varied facility components (Differential, Transmission, Motor, etc.)?

There have certainly not been sufficient failures to certainly pin point a limit for the varied power-train components. The motor could fail at facility power levels if it was running dangerously lean. But when well tuned, the motors internals (Pistons, Rods, Crank, Head Gasket etc) are trustworthy to 700rwhp. But of procedure at these power levels, if the engine is not set-up and tuned properly, it is certainly a bomb waiting to go off, any way this would be just as true with a built motor. Some owners have pushed their stock internals to the limit and have well exceeded 800rwhp, and even approached 900rwhp. I still don't understand how such an over built motor made it past the bean counters at Toyota Corporate.

The 6-speed Getrag is ridiculously strong for an Oe transmission. Its limit's will be affected greatly by driving technique, such as launching, and either or not power shifting is used. Even driven hard, the Getrag should hold up reasonably well with 700Rwhp. If you treat it with some respect, it should be able to cope around 800Rwhp or more, although great care and respect will need to be practiced at those levels.

Differential, axle, Cv Joint, and drive shaft failures are a Very rare occurrence. So I don't have much info on their failure limits. On street tires, it would be practically impossible to break any of these components at Any power level. The tires would spin before they would put the driveline under that kind of strain. The tires act sort of like a circuit breaker. If you run drag slicks, this does not hold true of course, yet they have proven themselves to be 10 and even 9 second capable.

Will drivability, interior noise levels, and low-end power be adversely affected with the Bpu(Tm) mods?

Drivability is not adversely affected. Interior noise level depends on the exhaust ideas you choose. Some will make it far louder; some will certainly make it quieter. But most are just a little bit louder than stock. But the added dBs are also combined with a Much sweeter exhaust note, so it's without fail worth it. And the interior of the Supra is pretty quiet anyway, so on the highway, it will be Very livable. As far as low-end power goes, the down-pipe will greatly decrease Turbo Lag. So low-end power and response is much improved over stock.

Will emissions be adversely affected by the Bpu(Tm) mods?

As long as a high-flow cat is used, emissions should not be effected, and you should still pass visual inspection. If you run without catalytic converters, you are doing so at your own risk, and you would not pass visual or emissions testing.

Will fuel mileage be adversely affected by the Bpu(Tm) mods?

If driven calmly, as in light throttle, mileage should not be significantly affected. Mileage will greatly decrease while however, if you drive "vigorously", more power equals more burned fuel I am afraid.

Should I setup an "Intake" (Open Element Filter)?

This is a bit of a yes and no answer. The stock filter assembly is a flow restriction, and an open element intake would increase possible flow. However, it will also draw in more heated engine compartment air, which can hurt performance. My advice is to either modify the stock filter box, or setup a cool air induction box, like the Max Air. An added bonus of the open element filters, is that they allow you to certainly hear the original turbo and by-pass valve.

What about the stock intercooler?

The stock intercooler does a decent job up till about 17psi on the stock turbos, after that you would probably consideration a significant gain, especially in warmer temperatures, with a nice front mount intercooler. However, keep in mind it will block some of the airflow to the radiator, as well as decreasing response slightly.

Should I replace the facility rubber Intercooler hoses with aftermarket metal hoses?

It wouldn't hurt. But it won't help a lot either. At the most you may slightly increase throttle response, but at least it will look nicer.

What about the fuel system, are the stock injectors and fuel pump large sufficient for Bpu(Tm)?

Yes, the stock fuel ideas is very safe and trustworthy to 450Rwhp, although I would suggest a fuel pulsation damper bypass. whatever over that, and I would very suggest having the car dyno'd, and using a wide-band O2 sensor (not a cheap A/F gauge related to the stock O2) to check the fuel ratio at your high boost setting. 11.5:1 would be a safe fuel ratio.

What are the stock injectors rated at?

540cc/min

Would the Supra advantage from a fuel controller?

Bpu(Tm)'d Supras run a little on the rich side as far as fuel ratios go. This hurts power. What it does do is contribute a protection margin that makes engine damage through detonation unlikely. If you get a fuel controller, and tune it properly (on a dyno, with an literal, Egt gauge, and a high band O2 (The Stock O2 sensors are not accurate), then you should be able to gain a noticeable estimate of power. One of the most beloved electronic fuel controllers is the A'Pexi S-Afc. The Fields Sfc is good too.

What should I use to increase my boost level, an Electronic Boost Controller, or a by hand Bc?

Using an Ebc is the safest way to raise boost, it will prevent spiking and over-boosting. But it certainly comes down to your budget. If you can afford an Ebc, get one. If you can't, go with a Mbc. And always keep an eye on that boost gauge. And whatever you are using to control boost, remember to not get carried away, I don't suggest going usually over 18psi.

What is the best Electronic Boost Controller?

There certainly is no Best. Although the A'Pexi Avc-R is a nice unit, it provides much more control over boost than other Ebcs, but it is also more involved to install, and tune. The new Blitz unit is also nice. Most of the large manufacturers make decent units. Just avoid fuzzy-logic adequate models if you still have the sequential stock turbos, they will become "confused" by the unnatural behavior of the sequential system.

When installing my Ebc, do I connect it to both of the Turbo's Wastegates?

The original Turbo is the only one with a wastegate. When in full twin turbo mode, the boost of both Turbos is regulated by the original turbo's wastegate. So, only connect it to the Primary's.

Some citizen say I need to replace my Ecu with a reprogrammed one, instead of just using a boost controller. Do I?

Reprogrammed Ecus for the Supra Tt are Very $$$. They are in the 00 range. And they have not been proven to contribute a significant increase in operation or protection on Bpu(Tm) level cars. Their merit shows itself on cars with upgraded Turbo(s). Just be sure you buy your Ecu, or have it reprogrammed by a reputable shop that knows what they are doing. And have it tailored to your singular car (Driving habits, and Mods). And I would also suggest taking a look at the Aem Programmable system.

What is a safe boost level to run at Bpu(Tm)?

The general consensus is 17-18psi. Some citizen have taken it higher, but I don't suggest it if you don't have the money for a turbo replacement/upgrade.

Which Down-Pipe is recommended?

The Rmm (or Rod Millen Motorsports) Cat-less Downpipe is the most ordinarily used. any way many other brands exist. Some down-pipes, such as the Random Technology Dp, feature an emissions legal high-flow catalytic converter.

Will a high-flow cat hurt performance?

It will have some effect on power output, but not a lot. Its exact effect on Hp is not clear, but it probably costs a few hp at the most, maybe 5-15hp at Bpu(Tm) power levels.

What is a Down-Pipe?

It is the section of the exhaust ideas that connects the outlet of the Turbocharger's Turbine section to the "Cat-Back" exhaust system. The Downpipe is also where the two catalytic converters are located, as well as the O2 sensor (or sensors in Obd-Ii cars).

I have an Obd2 car. Can I still setup a Down-Pipe?

Yes. But unless the Dp has a Catalyst and a second location for an O2 sensor, you will trip your check engine light, unless you get one of those O2 "black boxes".

Which Exhausts are the loudest?

The Tanabe Racing Medallion, and Hks Hiper Titanium seem to be the two loudest systems.

Which Exhausts are the quietest?

The Tanabe Hyper Medallion, the discontinued Tanabe G-Power Medallion and the Greddy (Sp) street operation seem to be the quietest. At whatever less than full throttle, they are no louder than stock. But at full throttle they seem to "wake up" a bit.

What are some recommended exhaust systems?

It depends on your personal preferences. Below I will break down some of my recommendations based on safe bet combinations of preferences.

Subtle Styling / Very Low Cost:

-Random Technology (75mm, full stainless steel)

Subtle Styling / Low Sound Level / Moderate Cost:

-Greddy street operation (80mm)

-Tanabe Super Hyper Medallion (80mm, full stainless steel, 50-state legal)

Subtle Styling / Moderate Sound Level / Moderate Cost:

-Atr (75mm, full stainless steel)

Tasteful Styling / Low-Moderate Sound Level / Low Cost:

-Hks Dragger Ii (85mm)

Tasteful Styling / Low-Moderate Sound Level / Moderate Cost:

-Greddy Power extreme (80-94mm)

-Hks Super Dragger (95mm)

Tasteful Appearance / Moderate Sound Level / High Cost / Super Light:

-Veilside Tear Drop Titanium (90mm, full titanium)

Tasteful-Wild Styling / Low Sound Level / Moderate Cost:

-Trd 2nd gen.

Wild Styling / Moderate Sound Level / Low Cost:

-A'Pexi N1

-Hks Hiper (75mm)

Wild Styling / Moderate Sound Level / Moderate Cost:

-A'Pexi Gt Spec (95mm, full stainless steel)

-Blitz Nur Spec (80mm, full stainless steel)

-Hks Hiper Carbon/Titanium (75mm, Cf wrapped muffler, titanium tip)

Wild Styling / High Sound Level / Moderate Cost:

-Tanabe Racing Medallion (80mm, 50 state legal)

Wild Styling / High Sound Level / High Cost / High Flow:

-Hks Hiper Titanium (104mm, titanium muffler)

What is the cheapest route to replacing the Dp and Cat-Back?

Have a institution operation exhaust shop found a faultless 3" exhaust ideas (Turbo-to-Tip). It should cost well less that 0. And then you can use the muffler and exhaust tip of your choice.

Which Fuel Cut Eliminator is recommended?

The Greddy Bcc (Boost Cut Controller) is very recommended.

What does the Fuel Cut Eliminator do?

The facility Ecu is programmed to inaugurate a fuel cut if the multiple pressure exceeds 14-15psi. It does this as a protection measure to prevent what the Ecu sees as over boosting. The Fuel Cut Eliminator effectively eliminates, or at least raises the cut to a higher pressure. A reprogrammed Ecu can also eliminate this function.

Which boost gauge is recommended?

Any high ability boost gauge will work well. Accuracy is the prominent feature to look for. Autometer gauges are a good value. The Japanese gauges, A'Pexi, Greddy, Hks, etc., have more features, but at a much higher price.

Where can the boost gauge be installed in the interior?

If you want to mount it in the dash, the two most beloved places are the Clock location (which holds a 52mm gauge), and the Air Vent beside it (which holds a 60mm gauge). You can also use an A-Pillar gauge pod.

What is the stock boost pressure?

11-12psi

Are Cam Gears a good modification for the Supra Tt?

Yes, they have been shown to contribute a 5-15rwhp gain on a Bpu(Tm)'d car. But to excerpt their potential, you must have them tuned, by a knowledgeable tuner, on a dyno. And most of the power gains will be seen on the exhaust side. I also suggest buying cam gears which feature 5-bolts.

Are Under Drive Pulley(s) a good modification for the Supra Tt?

Most of the crank-shaft under-drive pulleys require the dismissal of the facility torsional damper.

This is from Mkiv.com :"this is Not an external (harmonic) balancer, as the crankshaft is fully balanced, rather it dampens both the axial twisting couples produced by the firing pulses, and the radial bending occasion from the accessory drive belt."

Basically this gadget provides crutial isolation between the engine driven accessories, and the crankshaft. However, dismissal of this can contribute a 10-15rwhp gain, but at a cost for long term use.

Do I need to upgrade the ignition when upgrading to Bpu(Tm)?

The stock ignition ideas is Very capable of supplying sufficient fire for a Bpu(Tm)'d car. The stock ignition ideas uses 6 large coils, one for each cylinder. So the ideas is capable of supporting Very impressive Hp levels. You may need to change to a colder range plug with a tighter gap (see below).

What about the spark plugs, which are recommended at Bpu(Tm) or higher level?

Basically you want similar plugs as stock, but a cooler heat range and a smaller gap. The stock plugs are Ngk Bkr6Ep-11 (2978) and are platinum tipped and have a .044 (1.1mm) gap. The ideal Ngk change for a modified Supra would be the Bkr7E (6097). It is one range cooler (the '7'), is non-platinum tipped (the lack of the 'p') and has a smaller .0315 gap (lack of the '-11'). This plug is also called the Ngk 6097 and they are fairly inexpensive. Platinum tipped plugs are not desired for high power applications, Iridium plugs are more prefered. Unfortunately their doesn't seem to be a Bkr8E which might be great for high-Hp Supras.

Another good plug to try is the Denso Iridium Ik22 or Ik24. These plugs may last longer than the above mentioned Ngks, but are also 6 times as expensive. The stock change plug would be the Ik20, the Ik22 is one step cooler, and the Ik24 is two steps cooler than stock. The Ik22 would be good for ~400rwhp to ~600rwhp. The Ik24 would probably be a good option above that. Two other plugs ordinarily used are the Ngk 3330 (Bcpr7Es) which differ much more from the specifications of the stock plugs than Ngk 6097. Also the Rapid Fire #5 used to be very popular, but are more expensive, don't last as long, and have fallin out of favor. Both of those plugs have been known to cause little stumbling at idle. Plugs on Supras do not live long, usually around 5,000-10,000 miles. So I suggest replacing them with every other oil change.

What is the Hks Vpc and Gcc?

It is an electronic device, which electronically and physically removes the very restrictive mass airflow sensor from the intake tract. Vpc stands for Vein Pressure Converter. The Hks Gcc is a gadget that allows supplementary fine-tuning of the Vpc.

Do I need an after-market Blow off Valve?

It is not certainly required, but it is a good idea. The facility by-pass valve is prone to failure, and an aftermarket Bov is probably a wise venture for preventing turbo damaging compressor surge. And it sounds cool too. However, it must be noted that if you still have the facility mass-air flow sensor, a blow-off valve, which is vented to the atmosphere, may cause stumbling between shifts.

Can I run Nitrous Oxide on the Supra Tt, even if I am already at Bpu(Tm) power levels?

Yes. Most citizen run 50-75 shot wet multiple systems. If you want to run a higher shot than this, you might want to reconsider a well-designed direct port system. I have seen as much as a 200-shot used on one of these systems, and an upgraded fuel ideas would be a must.

450hp just isn't enough, what can I do?

Ah the possibilities Basically you are only little by your imagination, and your wallet. You know what they say, speed costs money, how fast do you want to go?

The real power lies in singular and Twin turbo upgrades, and the options are limitless. You can either build a mild motor that puts out 450 Rwhp all day long with instant boost response, or a 1000+ Rwhp monster.

Unfortunately, things start getting more difficult after uncomplicated Bpu(Tm) modifications. Modification becomes more than "bolt on Downpipe, gain 50hp". Things like tuning, parts selection, and matching combinations of parts become much more important. However, this is the case with Any high Hp car. Actually, even at exceptionally high power levels, the Supra Tt is still easier to excerpt power from than practically any other operation car. But it should be kept in mind, that it wouldn't be as uncomplicated as the Bpu(Tm) bolt-ons.

If you just want something that will toast that pesky Viper Gts. Then focus on a mild singular turbo upgrade (T04S04, T60-1, Sp57-Sp61). Along with this, you should setup a front mount intercooler, a fuel controller, fuel pulsation damper bypass and Egt gauge. This is assuming you have done all the Bpu(Tm) mods, plus Bov, Ebc, Cam Gears. With tuning, and a few odds and ends, you should be able to pull 450-500 Rwhp (490-580 crank Hp) numbers while on a stock fuel ideas (assuming it is in great condition). This would be a total venture of practically ,700-,500 in engine/electronic components (also includes the allowable gauges). If you already have the Bpu(Tm) mods or Fmic, etc., you will spend less than this. The incompatibility in prices reflects the cost of higher end parts and increasing of a Hks Vpc to replace the restrictive stock Maf.

The next level would require a completely upgraded fuel system, and operation cams would be recommended, as well as supplementary electronics (programmable engine administration such as the Aem, or Vpc/Gcc/Ecu combo, etc.). This would allow you to run much larger turbos and injectors. You can make it past the 700Rwhp range without needing to replace the internals of the motor with stronger components, even at these power levels, if properly tuned and maintained you should preserve a fair estimate of reliability while still on the stock internals, as some citizen have eclipsed the 800Rwhp level while still running stock bottom ends in their Supras. If you pick to go ahead and build up the bottom end, then the skies are the limit as far as power goes. Just make sure to have part selection, installation, and tuning done by competent and experienced persons. Although this should hold true at Any level of modification.

Should I setup a Turbo Timer?

Absolutely. Unless you don't mind sitting in your car while it idles down every singular time you need to turn the car off. A Turbo timer keeps the engine running for a preset time once you turn off the ignition. So you can remove your keys, and lock up the car and not have to worry about it, it will shut off on it's own. This is prominent for the life of the turbos. If the turbos are not given time to cool down, it can overheat the oil and cause coking which will block oil flow to the turbos and damage bearings and cook seals.

How much is the Supra's power output affected by changes in ambient temperatures?

Very noticeably, just as with most turbo cars, the Supra Twin Turbo can be very temperature sensitive. Especially with the stock turbos and intercooler. On a Bpu(Tm) car, I would not be surprised to see a 10 percent allowance between 50-60deg temperatures, and 90deg plus temperatures

Will the stock clutch hold the power levels of a Bpu(Tm) car?

It depends on the condition and wear on the stock clutch. If it is in good condition, yes, it will hold the power, pretty well in fact, although you may contact clutch slip while at full boost in high gears such as 5th and 6th. If you drive vigorously, meaning you run at high boost frequently, then the life of the stocker will be Greatly shortened. Be surprised if you see an extra 10,000 miles after Bpu(Tm).

Can I resurface my flywheel when replacing the clutch?

It is not recommended. Buy a new Toyota Flywheel.

Can I setup a lightweight flywheel?

Yes, but be aware that they can generate a lot of noise at idle, and can send more vibrations and shock to the costly Getrag transmission.

Why is pulling the Trac fuse useful over just turning it off with the switch on the town console?

Just pushing the "Trac Off" button only partially disables the Trac system. It disables the Trac throttle body and Trac funtion through the Abs ideas (on 93.5-96 only), but not the Trac system's ignition timing slow up function. Unplugging the Trac fuse eliminates both functions, as well as the 155mph speed limiter, which works through the trac system. The fuse can be found in the main fuse box on the driver's side of the engine compartment. It must be noted that removing the fuse will cause the Trac light to stay on, but you'll get used to it.

Will the Trac ideas enhance the cars performance?

No. The Trac ideas was calibrated to enhance traction in glossy conditions. It was not calibrated with operation in mind. When the Trac ideas senses a loss of traction, it comes on hard, cutting power drastically; this will do nothing but hurt performance. I also would not rely on the Trac ideas for providing stability at high speeds, if you were to loose control, it would be too slow and clumsy, and would more than likely hamper your efforts to collect control.

How can I remove the facility 155mph speed limiter?

Remove the fuse for the Trac system. The speed limiter works through the Trac throttle body.

What is the Supra Tt's top speed with the Trac fuse removed?

There is some consider on this subject. There are rumors that 180 can be achieved. But by going with the numbers, 168-172mph in stock form seems possible.

What is the Supra Tt's maximum theoretical top speed? Can it exceed 200mph with sufficient power?

Lets find out.

The Supra Tt with the 6-speed has a stock engine redline of 6800rpm, and a 6th gear ratio of .79:1, with a rear axle ratio of 3.13:1. Now we multiply our 6th gear ratio times our rear axle ratio, and we find out our final gear ratio is 2.472:1. Now we divide 6800rpm by our total gear allowance of 2.472:1 and we find out our rear axles, and therefore wheels are spinning at 2751rpm at 6800 engine rpms.

Now we need to speculate our tire circumference. The rear tires section width it 255mm, and the sidewall's aspect ratio is .40, so our sidewalls are 102mm. Now, to change this to inches, we divide this by 25.4, which equal's 4.015 inches. Now multiply this by two, since we have two sidewalls development up the total diameter, and add the wheel diameter of 17", and we see a total diameter of 25.031 inches. Now to find out our circumference, we multiply that estimate times pi (3.14), and we find out the circumference is 78.59 inches, now divide that by 12 to change to feet. And we get 6.549 feet total circumference.

Now multiply our tire's revolving speed, by the tire's exterior circumference, and we find that the tire is exterior 18,016 feet per minute, divide that by the 5280 feet in a mile, and we find we are exterior 3.412 miles per minute, now multiply that by the 60 minutes in an hour, and we find we are traveling 204.7miles per hour @ 6800rpm in 6th gear. If the engines redline is increased to 7500rpm, which it often is, because of a higher flowing turbo. Then our maximum speed would be 225.8mph, given sufficient power of course.

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