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1994 Toyota Supra Turbo 6spd
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Discussion Starter #1 (Edited)
i know not many supra guys have experiement with gearing ratio except the 3.27 one for the 6spd. but i know the auto tt rear and NA rear is a lot lower than the 3.13 and 3.27

they are around 4.27 and 3.77 (auto tt) to be exact. i know it helped spool up the turbo of a t04r (t67) to give him 500 whp at 4500 RPM with a 6spd in 4th gear!
this was with an AUTO rear end.. with an NA he quoted he had 500whp at 4000 rpm! lol

compared to other smaller to similar size turbos that is making 350-450whp at 4500 rpm. i'm not sure how much lower the horsepower figures are if you swap out to the auto TT rear end (i'm sure it's less than a normal 6spd) but torque seems to be a bit higher at an earlier rate as well. i know there are other factors in this but 50whp SOONER at least is a big difference.

a few down sides to it is obviously A HUGE drop in mph and top end in each gear. you'll be shifting likea madman a lot more and a lot faster.
the RPM will FLY up almost way too fast in the bigger turbos? not enough time in boost. tires will probably be spinning a lot more? there will be less load in each gear.
 

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sure your RPM would go up faster with the shorter gear. and you will have the same power level at the same RPM. you will just have the high power earlier, cuz of your RPM goes up earlier.
 

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Discussion Starter #3
YaosAuto said:
sure your RPM would go up faster with the shorter gear. and you will have the same power level at the same RPM. you will just have the high power earlier, cuz of your RPM goes up earlier.

so technically, the only difference is the RPM would go up faster? spool up and rwhp/rwtq would stay the same at the same RPM?

i've been asking around and a few people said they were experiencing faster spool up, but that might just be the "feeling?"
 

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I'm skeptical about faster spooling of the turbo but I'm not sure.

Exhaust airflow that spools the turbo is not just rpm related, it's engine load related. So I'm "theorizing" that with the much lower rear, under the same conditions the load on the engine is actually less at any rpm so it pumps less air and it may not spool as readily at the same rpm.
 

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Nick 95 6sp said:
I'm skeptical about faster spooling of the turbo but I'm not sure.

Exhaust airflow that spools the turbo is not just rpm related, it's engine load related. So I'm "theorizing" that with the much lower rear, under the same conditions the load on the engine is actually less at any rpm so it pumps less air and it may not spool as readily at the same rpm.

its more RPM, more pumps of the air, less MPH. the shorter rear end would have higher RPM at the same MPH. more RPM more exhaust air.
 

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YaosAuto said:
its more RPM, more pumps of the air, less MPH. the shorter rear end would have higher RPM at the same MPH. more RPM more exhaust air.

Are you just speculating? Because I would have to agree with Nick, that there is a lot more load with longer gears which will help spool up. Shorter gears will rev faster but there is a lot less load on the motor. This is why in 1st gear it is harder to boost than it would be in 5th gear.

I think load has a bigger factor than rpm to a certain extent.
 

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cwtt said:
Are you just speculating? Because I would have to agree with Nick, that there is a lot more load with longer gears which will help spool up. Shorter gears will rev faster but there is a lot less load on the motor. This is why in 1st gear it is harder to boost than it would be in 5th gear.

I think load has a bigger factor than rpm to a certain extent.

yes, i am just speculating. and isnot the RPM the load of the engine?
 

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Discussion Starter #8
nick is right, the longer gears do give more load. that is why the turbo spools up so much faster in higher gears than lower. that's one example.

i'm not sure with the RPM based spool up.. i'm sure that contributes to the spool up but i think load definetly will play a bigger role.

1st, 2nd and 3rd gear is pretty much useless though (in my car) with street tires. with slicks, 2nd gear is somewhat useable.. lol
 

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YaosAuto said:
yes, i am just speculating. and isnot the RPM the load of the engine?
Not at all, as shown by the examples mentioned above. Another useful example is brake boosting; in the same gear at the same road speed, rpm's can be the same but boost could be very different.
 

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interesting post, can someone with experience in using the N/A rear end with the TT auto trans give us some feedback with their performance??
 

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you guys are right, more load can make more boost. more RPM can make more boost too. i don't know how to calculate them both. but at the same time more RPM can make full boost earlier. so i think the shorter gear makes better boost.
 

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My NA-T feels like it spools quick because the RPM's NEVER drop lol so like you were sayin earlier maybe its the "feeling"

WOT seems to be all waste gate all the time through the entire RPM range :rofl: .

Also like you said earlier, top end is .. different .. i say get 1 of each rear end and some drive shafts and use a dif. one for each track. depending on straight away length...

don't know if that helps, but thought i'd chime in
 

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english is not my first language, i don't know how to explain it to you guys. but if you put 2 same car in the race, the shorter rear end gear one will go faster if it doesnot run out of gear. i think the load boost you are talking about can make better boost only when the car can't make full boost at the gear.
 

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YaosAuto said:
english is not my first language, i don't know how to explain it to you guys. but if you put 2 same car in the race, the shorter rear end gear one will go faster if it doesnot run out of gear. i think the load boost you are talking about can make better boost only when the car can't make full boost at the gear.

thats not true,

it depends on the engine characteristics, power and torque curves and much more things,
in some engine setups like the BMW 3.5 turbo the car needs a long rear end gear to go fast because then it can use his big torque advantage,
the longer he stays in a gear the faster is the acceleration.

Hope my english is not too bad:)
 

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Discussion Starter #16
the topic kind of got strayed off by the spooling topic between you guys. but i'd like to really hear more about the possible benefitial gains of going with auto gearing or something similar (for the 6spd) and or hear that is not effective for our cars because of too short of a gearing or etc..

are there no one using this set up for road racing? just curious, it definitely might be too short of a gearing for our close ratio 6spd. only brought this up because i saw a few japanese road racing cars use high final drive ratios such as the skyline, nsx and rx7. all over 4.0 final ratio
 
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