chase-rx8auto

i have a question about the lower redline of the auto rx8s. is the redline difference because of the different motor? i read that the six speeds had a six port and the auto had a four port engine. or is it because of something else in the drivetrain? would there be any performance gains in raising the rev limiter on an auto and if so how would i go about doing so? any help or info you can give me would be very appreciated.

Brettus

iTrader: (2)

the 04 -05 4spd ATs have 4 port motors - the 6 spd AT has a 6 port .

See the AT forum for "interceptor" and you will find your answers

N rider89

the lower redline stems from the torque converter. it cant handle the higher revs. you could go custom for a better converter

also the 04-05s had a 4 port motor.

tajabaho1

what about 07s? I would really like to mod my car to be as fast as the manuals

toxin440

well sorry to say you need to just trade your car back in for a manual then. The money you'd spend trying to catch up to a stock RX8 - is wayyy more then the loss you'd take on just trading in.

Justinrx8

Not really.. the only thing a manual has on the autos (6 spd anyway..) is like 1500 - 2000 more rpm's on the tach. Other than that, the autos are making more power to the redline.

From what I understand, torque converters are the very last thing you add if you are going to mod your car, you have to get all your other stuff in before it like the forced induction system and whatnot.

I am curious though to see what is affected by the redline.. like overall what do you have to reinforce and upgrade to be able to take a higher redline on both models? I'd love to see an Rx-8 with a double digit redline that will run longer than an hour..

TurboEight

iTrader: (1)

the difference is not JUST the 2 k more RL........

maxxdamigz

iTrader: (1)

Off the top of my head, redline in piston engines is controlled by 3 things: Quality of the balance, max speed of the piston, and value train. On a lot of engines, the valve train winds up being the limiting factor. The value springs are unable to return the valves fast enough and you get valve float, broken stems, bad things. There can also be choke velocity in the intake, but that is easier to work around. Now, in a rotary, you have no valve train so that limit is removed. I'm pretty sure the design of the engine does not approach any kind of rotor tip speed maximum, but that may exist. Balance of the engine can be a factor. I think, mostly, the geometry of the intake/exhaust and the tune gave the 6-port manual a power curve and it peaked before 9k. There was no need, then, to go to 10k. A manual transmission, being mechanical links, handles the high speed motor output shaft fairly easily. The automatic transmission has to work with the limitations of the fluid mechanics that exist in the torque converter. Being the only rotary car on the market currently and probably possessing the highest redline of any reasonably price automatic (does an S2k come with a 9k auto redline?), the impetus to design a higher performance torque converter is probably not very high. The auto, then, is retuned for a lower redline and produces more torque. This leads to higher power at the listed RPMs. The power that makes its way to the wheels, however, is significantly less. When the auto peaks and hits redline, the manual continues to make and increase in power. It is fairly tough to argue that the 4 port engine is actually faster or stronger than the 6 port in stock trim. It is, however, tuned for better torque in the RPM range it does use.

I'm not familiar with the strength of the auto Mazda is using in the RX-8, either in the 5 spd or 6 spd, but autos traditionally suffer when subjected to higher than stock power levels. They develop more heat and can be overworked faster than the manuals. Then again, if you drive a manual poorly, you can destroy a trans pretty quick at stock power. Traditional auto trans mods include secondary filters for increased debris removal, trans oil coolers to help dissapate the increased heat, shift kits, and high stall/performance torque converters. The nice thing about autos in the performance environment is the shift speed and shift consistency are tough to match. In handicap bracket racing, autos fair well.

In closing, paddle shifters are pretty cool!

Mendossa

The AT6 is putting 212hp@7500rpm vs 232hp@8500rpm for the MT6 (source is Mazda Canada website). AT is not "making more power to the redline" whatever that means.

maxxdamigz

iTrader: (1)

I think what he is saying is the AT6 makes 212hp@7500 rpm and the MT makes less than 212 @7500 RPM which I think is true. You could counter by saying the MT is making 232@8500 and the AT6 is making strange noises at 8500.

WaitingforFI

iTrader: (1)

The major limiting factor of the auto is the torque converter, at those revolutions you would start seeing cavitations like in a boat, and thus ruin the fluid inside.

N rider89

i believe the torque converter is the same one from the FD rx7

Creto

the 07's are 6speed 4 ports. 06 was the only year that had a 6speed 6 port for the ATs (so far at least).

N rider89

im fairly sure the 07s are 6 port...

zoom44

you'd think a change like that would be mentioned in the spec deck

https://www.rx8club.com/attachment.p...chmentid=81933


or that they would note that difference on the website like they did in 2004 and 2005

http://www.mazdausa.com/MusaWeb/disp...ehicleCode=RX8


or that maybe i would have made mention of that before if it were true.

therm8

The best thing about the 6port ATs is that if you raise the rev limiter the engine breathes very well (due to the extra intake ports), so you'll see a pretty good gain in power. 8000rpm shouldn't be too hard on the TC, if it cavitates there, it's likely cavitating at 7500rpm as well. You'll only see 8k for the briefest of moments anyhow. The biggest problem is slip. At 8krpm the converter may have excessive slip, efficiency goes way down, and the extra power made at the engine is used to simply heat up the ATF. Torque converters operate much like a centrifugal pump, and thus have optimum ranges of efficient operation. My guess is that most of the extra power would get to the wheels. But don't ever expect to be as fast (straight line) as a MT. Even if you had the same redline and power curve, the 6MT is geared much more aggressive than either the 4 or 6AT. The only way to top a non-FI'd MT is a little FI for yourself.

No one has confirmed that the converter (4AT) is the same that the FD used, but since the 4AT transmission came from the FD (modified for electronics) one might assume that the converter tagged along. Level10 modifies FD converters for higher stall and better efficiency, so that'd be a good way to find out. Mine's a daily driver, and a new converter costs over a grand, so sending it off isn't an option as of right now.

Creto

Zoom, no need to be snotty.

If you go to http://www.mazdausa.com/MusaWeb/conf...modelYear=2007 and select the 6spd auto, you will notice that the description changes from 6port to 4port, regardless of the trim level. So it may be true that 07's have 6 port, but perhaps someone should tell Mazda that.

Galen Darkmoon

Well, Ya had me going. So after a quik call to the tech dept. the 07 6spd autos are indeed a 6 port engine.

tajabaho1

so basically we gotta change the torque converter to be as fast as the MT?

sosonic

I think people are mixing things up.

The torque converter issue is with how high you could rev the engine from a stop. The Auto torque converter prevents you from going past 2,500 rpm at rest. A manual could rev to 7,500 rpm and take off (of course clutch life would be very limited). A custom torque converter would allow the Auto to "brake launch" from say 4,000 rpm or a bit better.

Autos could also do a "neutral slam" at something crazy like 7,500 rpm, but expect your auto transmission life to be very limited. But in theory, an Auto could launch at the same rpm as a manual if you don't mind buying a new transmission soon or if you have taken special care of the Auto transmission (via cooler and good AT fluid) or maybe a customized torque converter.

How high you can rev while in motion, I thought was about heat. The auto needs a good tranny cooler to keep the heat down while at high revs above 7,000 rpm. Mazda went cheap on the auto and did not provide a good tranny cooler. You also need good AT fluid like Redline or Royal Purple. I bought these and have regularly gone over 8,000 rpms in my 4 speed Auto with ZERO problems. The problem though is launching at high revs (0-60 and 1/4 mile), but keeping the auto a good daily driver. Top speed though, 150 mph, is not a problem if your tires can take it and you remove the rev-limit via ECU flash.

tajabaho1

^ oh about that, sorry to be out of topic here but.........can a piggyback ecu remove the damn limiters also?

zoom44

meh- im always snotty about stuff like that. here i am trying to get the facts out ot everyone by geting ahold of speck decks and price lists and order forms etc etc and then people come along and contradict that work. i get a little snotty about it. nothing personal. i have alerted them to fix that error on the website

FlyLow

On the 05 MT how many ports are there? 4 or 6? thanks

EXILE

The 6MT always had the 6 port engine.


EXILE

N rider89

here one thread where we talked about it a little, no one has really gotten one and documented it so...

https://www.rx8club.com/series-i-specific-performance-mods-97/pros-cons-customized-torque-converter-100956/