mdw1000

Help educate me here guys. I'm wondering exactly why the AT is limited to less RPM than the manual. Is it because the tranny can't handle the power, or is it because it can't handle the RPMs? I'm wondering because there is an article in C&D about this really impressive turbo that has just come out for the manuals. Something like 390 hp. Could our ATs (I have an 05) handle a big increase in power like that as long as it was made below 7500 RPMs, or would much more power than stock mess up the tranny?

Thanks, and I apologize for my ignorance

mdw1000

I should also say I realize this turbo is for the 6 port engine, but i'm wondering if it is possible we could get some sort of decent turbo setup.

therm8

The torque converter isn't capable of handling the higher revs of the 6 port engine. The tranny is the same as the AT that the 3rd gen Rx-7 had (which was also limited to 7500rpm vice the 8000rpm for the MT for the same reason). I don't know what kind of power the FD AT owners have reached (you might check at rx7club.com), but I think I remember seeing 300rwhp at one time. Regardless, stock FD power levels should be no problem for the AT 8.

*This is for the 4spd auto, I have no idea how strong the 6spd auto is, but if I had to guess, I would say it's not as strong as it was built for much lower power vehicles.

Aznman101

*This is for the 4spd auto, I have no idea how strong the 6spd auto is, but if I had to guess, I would say it's not as strong as it was built for much lower power vehicles.



what do you mean it was build for much lower power vehicles? So is the 4spd actually better than the 6spd? if you could explain it to me that'd be awesome. i have an 05 4spd so i was hoping there was an upside to not waiting....except getting to drive it for an extra 5 months and paying 4 grand less.

mdw1000

Thanks for the info, therm8! I didn't realize it was the tranny from the 7. Wonder what the likelihood of some sort of FI is for this engine, considering it is a more limited market than even the MT 8s.

therm8

The 4spd was used in the FD, which had considerably higher horsepower and torque than either the 6port 8 or the '06 Mx-5. Given cost controls inherent in auto manufacturing, the 6speed should be weaker than the 4spd. It's irrelevant at stock power levels, and the superior gear ratios of the 6spd make it obviously better for the average person. But for modification purposes, the 4spd should be tougher, and transmission modifications (such as those performed by Level10) for the FD should also work for the 4spd 8.

Disclaimer: this is all conjecture on my part, and I could be completely wrong

Brice-RX8

I highly doubt the 6sp is weak. The tranny is made by the same company that makes S2k 6sp's, Aisan (or something like that). If you look at the side of the tranny case you will see this name. Considering there are quite a few high power S2k cars on the road, I am pretty sure they handle power very well.

therm8

We're talking about the 6spd auto.

DOMINION

Yup. I think your on to something here Therm8. Good work

Easy_E1

iTrader: (2)

It's funny , but I use to turn 10,000+ rpms in my '74 RX-4 13B 3spd AT,with no tranny problems. The car did have a stock trans cooler onit.
I dont understand why this stock torque converter can not take the RPM's.
Why would they put such a trans in a high revving application.
And why don't they put a trans cooler on the AT RX-8?
Seems to me Mazda should have thought this out a bit more.

therm8

It does have a tranny cooler, but it's the same as all modern ones...built into the radiator. Prior to adding any significant power, I'll be adding a better one, along with a 2nd oil cooler.

10k rpm on the 3spd auto is interesting. Once I have the capability of adjusting the cutoff, I'll probably test out the limits of the converter a bit. I'd like to get the converter worked by level10 as well, but the 8's my only vehicle and a new converter is kind of expensive.

Easy_E1

iTrader: (2)

ok so the cooler is in the radiator ,cool.
Yeah that trans never missed a lick.
The engine was bridge ported (big ports) ,had hardened stationary gears,
shaved the rotors 2/32nds RacingBeat highrise ,Holley 850cfm double pumper,
2 Accel super coils, 2 MSD multi spark ignition boosters, RaceingBeat headers,
dual exhaust system. 13.9 in the quarter mile. Just shifting into 3rd gear going thru the traps. On the dyno she had almost 300hp at a little over 9000 rpm.
Got about 8 miles to the gallon.

teen_living_a_dream

but wouldn't having less power but a better set up tranny be better? AT 6spd is closer ratio than manuals so you would need much more power from the 4spd - probably more than the tranny can handle- to keep up with a stock 6spd AT, right?

There is one definite advantage. 4spd should be cheaper to repair/replace than the 6spd.

therm8

Depends. The 6AT isn't that much faster than the 4AT. Besides, the guy who has Pettit's AT prototype supercharger on his car, says it's faster than a stock 6MT (it may not be, but it's definately much closer than stock vs stock). And the 6MT has even closer ratios, not to mention more power than the 6AT. Low end torque evens the field quite a bit (I believe the Pettit 4AT is 220ish tq and 190 hp to the wheels). But then, I imagine a supercharged 6AT would be a bit faster the the 4AT still.

Personally I don't need to be faster than anyone else. I just want to be faster than I am currently .

sgrenesis

btw can any one tell me the formula to work out from whp to bhp.

trying to see how much is 208whp and 220whp and 250whp converted. thanks.