Rev Limit for Torque Converter
 

Howdy!

I understand the 7.5K rev limit is necessary due to the Torque converter limitation.

Some questions:

1) Exactly what is the converter limitation? (suspect trans fluid cavitation or centrifical force)

2) Will an aftermarket converter raise the potential limiting RPM?

3) Any recommended method of raising the redline without having to replace the ECM?

Thanks!

^Thank you sir - you just saved me some homework time :)

wait i just have a quick question. Cobb Accessport only works with MT model not the AT model? even though 6 port AT model is the same with 6 port MT model?

Cobb Accessport is more like a device that allows you to reprogram your ECU.

So as soon as it has support for our car, it does not matter if its AT or MT, u just need the correct *flash* and u're set.

Yeah, the ECU programming is different.

My understanding was that they weren't releasing it for the AT initially because they didn't have a development car to work with.

Personally, for the 4-port I don't get my hopes up about any computer-related upgrades until they are released. We are a very limited market compared to the 6-ports.

And we do appreciate your consideration of the AT market! Glad somebody does :)
But I understand that MT products are going to sell a lot better.

Plus you just like us ATs because of your drag racing days :)

But in 30 years my car will be a lot more rare, and I'll be able to get 1 miiillioooon dollars for it. Especially if I threaten potential buyers with my giant "laser".

Yeah, I never understood some people's disdain for cars that are different from their own preferences. I personally just like cars, and I appreciate that some have different wants and needs than I do.

Although I don't think I'll ever understand things like the bone stock old toyota camry I saw a few months ago. Bone stock except for a HUGE park bench GT wing :) Ah, the follies of youth... :)

The 7.5K rev limit you are talking about is controlled by ECU. It can be removed and I had mine removed. The problem is that only Japanese Pro-Tuners were doing it. With the Cobb, Hymee, EFIDude reflashers out or coming out, you should be able to use those.

It is suggested to raise the rev limit to just 8,500 rpm. There is not much power to be found above this unless you have a twinscrew Supercharger. Otherwise, there is no need to go past 8,500. Also, above that, puts your auto transmission in danger exponentionally and can cause more wear.

If you remove the rev limit, make sure to have an automatic transmission cooler and high performance/high temp automatic transmission fluid (like from Redline). Also, if you go to the high end of the rev band a lot, than think about replacing your automatic transmission fluid once a year. Like motor oil in extreme conditions, automatic transmission fluid can break down and become less effective. However, this depends on how hard you are on your car and transmission.

The torque converter limits you at dead stop "brake launches" (holding brake with one foot, revving with other foot, then letting go the brake). The Auto RX-8 will only rev around 2,500 rpm or so. By comparison a manual RX-8 could launch at 6,000 rpm if it wanted to (however your clutch would be in danger).

Modifiying the torque converter requires it to be rebuilt or you are looking into a new transmission. BHR/CRH is looking into a solution for this on MT and Auto.

My transmission was burnt so i took it to level ten and to rebuild it would have cost 3200 and the performance upgrade went for 4400 so i decided to go with there performance upgrade. All the parts are custom built even the torque converter. The transmission now can handle 1000hp and take a beating. I know i will never hit the 1000hp mark but its nice to know it can. Also got a 3yr 50k mile warranty on it. Level Ten is located in Hamburg NJ 07419 www.levelten.com

the stall speed was raised but i dont know to what though. I like it

Couldn't he test the stall limit by doing a brake torque launch? Just hold the brake, step on the gas, and see what rpm you can get it to?

I think it may be around 2800 to 3000. The torque converter is built to level ten's specs for each car

Now if i had a supercharger on my car i could show what this tranny can handle. But not enough money

OK, I have the s/c so what's the hold up? My punch list never seems to get smaller.:) Now that I will have the flash on Monday you will need to do some serious thinking about the trans. I know that the 4 port trans will handle 9000 RPM but refuses to shift until you reduce the rpms to below 8500. With the new BHR inner-cooler and BHR radiator it does not even get into the overheating range. Lets see what happens after Jeff is done with the flash.

I think the trick with a reflasher and map editor is to adjust the rev limit right up to that "locking point". It is hard to say, because the tach is not perfectly accurate. But maybe to 8,200 RPM.

Mine "locks" too, but I don't have to ease off the gas. It hits 8,500 and there seems to be a delay from the ECU as oppose to when I do it before it locks. I don't let off the gas, so the ECU is doing something, but whatever it does, it creates a small delay.

It is tricky, and it's like a timing thing for me in 0-60 or 1/4 mile runs. Usually, I shift before it locks (around 8,000 rpm), and at a high enough point to get some advantage. But, sometimes I don't make it and it "locks" until 8,500 rpm or more and the ECU limits it/holds it, after a delay. It seems I can shift to 2nd gear, but if I do it after a certain point, it seems to go to 8,500+ by itself and stay there briefly before the ECU shifts it.

However, in just open road conditions, not shifting from say 1st to 2nd gear it does not seem to be an issue. So I think the problem may be isolated to that particular gear. If possible, you are looking at reducing the "shift point" from 1st to 2nd gear to 8,200RPM or so and that would be for 0-60 and 1/4 mile a 4AT.

I never posted the results of the Cobb AP flash with Jeff's maps on this thread.

Before the flash, I was about to write off my a/t as toast. It was acting as if the power was too much for it. Ray and I had plans on what was to be done but figured we'd wait for a few additional weeks.

I can not say too much for the Cobb AP flash and Jeff's maps. My idle has returned to stock like in it's smoothness and most important it "fixed" my trans. Currently my 4port a/t trans with a s/c motor shifts better than it did stock. Much smoother, quick response, sure shifts and all the way to 8500 rpm. Over 8500 rpm is still refuses to shift until I reduce to below 8500 rpm but I think I can live with that for the foreseeable future. The flash uncovered some other faults such as a bypass valve that only wanted to work occasionally and the fact that Jeff needed more information (released) from Cobb.

With Ray's a/t radiator the trans fluid not seems to not get over ambient temperature. On his next visit we will add a full time trans temp gauge to really track it. We will get more technical as we get further into it. Presently it seems to be not as important as it was although still a concern as we continually do little mods.

You are correct - I did not mention that here cuz we were into transmissions but BHR has a new offering for an upgraded bypass valve for the Pettit s/c. I was having some mysterious boost problems where the boost would just drop out all of a sudden. I
Ray tested the boost numbers and determined it was the bypass valve. He pull his magic again and came up with a new billet aluminum by pass valve that is working like a charm.

I'll let him tell you more about it.

I'm still waiting for the other reflashers and editors, EFIDude and Hymee, before making a choice.

Luckily, I have the advantage of a modified Re-Amemiya flash already. I'm thinking once I decide on a reflasher and map/editor, I will backup the Re-Amemiya flash and get the lastest Mazda flash. I will put both flashes on a computer, do things like compare them, and minor things like the rev limit and fans would be the 1st thing I tackle.

Wouldn't you want your trans temp warmer than ambient for optimal fluid performance? Of course you do live in the desert, so maybe ambient is just fine :)

^^^^ he said it the way I meant it.

ah, gotcha - thanks for the clarification!

Allthough I still think ambient Las Vegas temp is probably warm enough :) I was there in October once and sweated my family jewels off :)

It's down right cold in October at least 90 F. I have to wear a jacket:) .

Just posting to see if anyone has definitively determined why the rev limit was set at 7500. I'm going to change my fluid to Amsoil, so if the limit is trans fluid temp I think I would feel safe raising my rev limit to 8000. However, if it is some other issue I think I will leave it at 7500.

Thanks!

According to my chat with Mr. kanai (knightsports, Tokyo) in this june, he said raising the rev limit above 8000rpm carried no meanings because the buterfly valve in the intake was fully open below 8000rpm.