MK4 AUTO Transition Question!! How much power can it take

[Guest chrisandreas]

I have a fully stock NA 94 MKIV and in the near future want to add turbo and whatnot to get the bhp to around 500bhp maybe 600 at 30psi

 

I'd like to know if I have to convert to manual to push big power or is it possible to push decent power on an auto?

 

Has anyone pushed over 400 on stock auto gear box?

 

Please let me know.

 

Chris

[Annabella]

Lots of varying opinions.. Stick a cooler on it should help.

 

http://www.mkivsupra.net/vbb/showthread.php?265008-N-A-Autobox&highlight=autobox+max

 

http://www.mkivsupra.net/vbb/showthread.php?64887-NA-autobox&highlight=autobox+max

 

http://www.mkivsupra.net/vbb/showthread.php?291157-NA-VS-TT-Autobox&highlight=autobox+max

 

 

And look at this:

 

http://www.mkivsupra.net/vbb/group.php?discussionid=90&do=discuss

Edited September 6, 2016 by Annabella (see edit history)

[Guest chrisandreas]

Thank you for that, So I am looking 300bhp to be safe but 600bhp is possible with a cooler. You wouldn't also know a good cooler by any chance too would you ?!:p

[Frank Bullitt]

Thank you for that, So I am looking 300bhp to be safe but 600bhp is possible with a cooler. You wouldn't also know a good cooler by any chance too would you ?!:p

 

There are loads of choices available, it all boils down to budget. If you use the search function you should be able to find many autobox cooler installs

[Swampy442]

But you'll never get that power with the original NA engine set up so really the question is irrelevant

[David P]

You clearly haven't understood the information you have been provided.

[Guest chrisandreas]

Thanks for the replies I am going to go for auto set up for now whilst I source a v160 or possibly 350z manual trans

[Action Jackson]

Today I learned that you can buy coolers for gearbox oil.

You performance junkies are mental, you know that right?

 

BUT I have only seen gearbox coolers for automagic gearboxes - is there a reason for this? Or am I just bad at online shopping?

[David P]

Today I learned that you can buy coolers for gearbox oil.

You performance junkies are mental, you know that right?

 

BUT I have only seen gearbox coolers for automagic gearboxes - is there a reason for this? Or am I just bad at online shopping?

 

The reason is........ you're not almost a doctor of gearboxes.

[ianhid]

Today I learned that you can buy coolers for gearbox oil.

You performance junkies are mental, you know that right?

 

BUT I have only seen gearbox coolers for automagic gearboxes - is there a reason for this? Or am I just bad at online shopping?

 

Short and very simple version: Auto gearboxes use torque converters instead of a clutch to transfer power off the engine into the gears. The torque converter is a fluid coupling, an impeller attached to the engine output stirs the fluid and causes a turbine attached to the gearbox input to turn (there's a stator in here as well, not necessary to understand heating). Because the two aren't connected directly, you can sit on the brakes with the engine running and a drive gear selected. Your engine then cheerily whisks your trans fluid (ATF) at ~1k RPM until you decide you want to go somewhere (yep, that'll heat it up some). This fluid coupling is lossy even when driving (ignoring lockup clutch for now), the lost energy ends up as heat in the ATF, which gets very hot if not cooled.

 

You don't want your ATF to overheat (fun fact, ATF is flammable), so you need to pump the ATF through a cooler. There is a cooler built into the standard radiators, as soon as you replace the standard rad then you need to fit an aftermarket cooler as well, hence why they're a popular item in shops. You also fit additional cooling if running more than the design power in the hopes of saving the transmission. This is not a magic bullet but it will give you a bit extra headroom. The power limits are different on the NA and TT boxes, the differences are in Annabella's links above but basically prepare yourself for a bit of reading. David P is the wizard as far as getting more out of an auto box.

 

Manual gearboxes are very different beasts. They use a heavy gear oil, don't get anything like as hot and just use air cooling within their design limits. If you get enough power into a manual trans to think you might need additional cooling, chances are you will break something else first...

[Action Jackson]

The reason is........ you're not almost a doctor of gearboxes.

 

HAH! Got me there!

 

Short and very simple version: Auto gearboxes use torque converters instead of a clutch to transfer power off the engine into the gears. The torque converter is a fluid coupling, an impeller attached to the engine output stirs the fluid and causes a turbine attached to the gearbox input to turn (there's a stator in here as well, not necessary to understand heating). Because the two aren't connected directly, you can sit on the brakes with the engine running and a drive gear selected. Your engine then cheerily whisks your trans fluid (ATF) at ~1k RPM until you decide you want to go somewhere (yep, that'll heat it up some). This fluid coupling is lossy even when driving (ignoring lockup clutch for now), the lost energy ends up as heat in the ATF, which gets very hot if not cooled.

 

You don't want your ATF to overheat (fun fact, ATF is flammable), so you need to pump the ATF through a cooler. There is a cooler built into the standard radiators, as soon as you replace the standard rad then you need to fit an aftermarket cooler as well, hence why they're a popular item in shops. You also fit additional cooling if running more than the design power in the hopes of saving the transmission. This is not a magic bullet but it will give you a bit extra headroom. The power limits are different on the NA and TT boxes, the differences are in Annabella's links above but basically prepare yourself for a bit of reading. David P is the wizard as far as getting more out of an auto box.

 

Manual gearboxes are very different beasts. They use a heavy gear oil, don't get anything like as hot and just use air cooling within their design limits. If you get enough power into a manual trans to think you might need additional cooling, chances are you will break something else first...

 

Flipping love this. Honestly learning a lot, thanks very much for the info.

Every days a school day

[Chris Wilson]

Good post ianhid, a very good explanation!

[mihai]

well... i destroyed my auto box with 450 hp and no oil cooler... a feu years ago....

 

- - - Updated - - -

 

well... i destroyed my auto box with 450 hp and no oil cooler... a feu years ago....

[Alex_GT]

tl;dr

Wouldn't changing the ATF for a higher specification solve all these problems?

[Chris Wilson]

No, part of the issue is more heat generation. With a high stall converter a HUGE amount of extra heat. But more importantly is the extra torque breaks internal mechanical parts. All the broken auto boxes of single turbo TT's I have here have failed mechanically, and not through excess heat. An N/A auto box is weaker than a TT one....

[Alex_GT]

So are coolers pretty much redundant? I mean, the power that the auto box on the Supra has to deal with is nothing compared to cars that were built even in the 60's/70's. Is the Supra auto box just poorly/cheaply built?

[Chris Wilson]

No, the Aisin-Warner box is one of the most reliable ever made, but manufacturers only build to handle the required torque rating, they don't build gearboxes with the intention of people putting them behind engines with a lot more torque. That's why the n/a box has less torque capacity than the outwardly similar TT box.