DelSlow

iTrader: (2)

Im building my motor now, and I want to be be able to rev to 8500 if the power is still there. I know the S5 gears are not hardened, but Ive read that the FD gears are. Are the FD and FC gears interchangable? I figure the S5 T2s 7k redline is there for a reason, so I want to upgrade. Mazdatrix wants 160 apeice for FC gears, but over 300 for FD's.

RotaryEvolution

iTrader: (30)

i thought the redline was more to keep the apex seal from getting tossed out the exhaust port than for breaking the stationary gear but i don't know of many people who rev past that point daily so i couldn't specify just that i hear of apex seals tossed alot more than stationary gear problems.

DelSlow

iTrader: (2)

Ive heard that stationary gear deformation is what can cause the seal damage

Funkspectrum

iTrader: (5)

I'm not really sure if you can swap rotors....I know that the RX-8 rotors can be used but there is no real gain in power or performance.....

At least....that's what I have heard.

RETed

Kouki FC turbo stat gears are hardened.
If you going to change over to FD stat gears, you need to change out all the crap in the front, cause the design is different - you need at least the FD spacer, pair 'o thrust bearings, and some other small bits.

Unless you spinning way up high or running over 400hp, getting hardened stat gears is a waste of money.

I don't think you're making power up to 8,500RPM unless you're running a big port engine?
This basically means you need a BP or larger.

I don't understand why people want to rev the engines so high?
Is this a bragging thing?


-Ted

Dan H

Ted, are the S5 NA stationary gears hardened too? Thanks in advance.

RETed

No, as far as I know, only the turbo ones are.


-Ted

drago86

S5 NA stat gears are hardend,.. infact all gears from 89 up are.

RETed

Oops, drago86 is right.
All S5 stat gears are ion-nitrided.
The Kouki turbo rotor gears are ion-nitrided also; the Kouki NA rotor gears are not.

http://www.thecarricos.com/ACRE/New-tech90-7-12.pdf


-Ted

pengarufoo

I disagree here Ted.

http://kahren.net/cars/2/DSC00047.JPG

That dyno is from a somewhat radical, but STOCK PORT NA - this shows you even the tiny stock NA ports can flow well enough for a 6500-7000RPM torque peak. I'm pretty surprised by this actually, considering my thumb barely fits in the NA primary intake port

I tend to shift @ 8500 on my street port NA, it's still making GREAT power and I look forward to dragging it out longer in the future. I have not dyno'd yet but judging by the fuel map the torque peak is around 7000-8000 rpm. I have my rev limit set to 8600 and occasionally hit it on accident especially in 1st, after I get a scatter shield installed I will likely raise the limit to over 9. My setup is simlar to what put down the numbers in the dyno graph, cept mine is ported and some other details like hardened rb stat gears etc.

Revving that high, for my setup at least, results in more torque @ the rear wheels at that road speed than there would be in the next gear up, it also lands the motor closer to the torque peak when I finally shift to the next gear, usually anyways. If you're even just street ported and have done other supporting mods appropriately, 9k is reasonable IMHO.


115mph in 3rd is good times. ~150 in 4th, vrewm. 1st is too short and 2nd too tall on the NA box though, 5th is pointless. I can't tell you how many races I've been even with someone through 3rd til around 7000rpm, then pull on them til rev limit while they shift and suddenly lost a significant fraction of their rear wheel torque after the shift.

You just have to make the engine breathe up high, lose the stock intake manifolds and go speed/density, open up the exhaust, and as long as you replace the intake manifolds with something that flows really well it will work nicely, at the very least at high rpm.

DelSlow

iTrader: (2)

Im going with a large street port(a VERY large SP, from what Ive seen on other motors), and hoping to put down over 400. Its just that all the dyno sheets Ive seen with similar mods the power just keeps climbing past 7k, 8k, etc...

RETed

Uh, that's cheating. :P

Most of the NA dynp graphs I've seen "lose steam" at around 7,500RPM.
If you want to wind it up there all the time, you're degrading longevity to be able to run up that high?
That's something you, as an owner, need to make a decision on...


-Ted

brent clement

One reason for the rev limiter is because when you start getting up around 8500 plus you're ecc. shaft starts to flex and the sides of the rotors start to contact the intermediate housings. At least that's what I've read.