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View Full Version : Lets talk final drive ratios!


Bruce Leroy
05-14-2008, 09:32 AM
I'm specing out a semi transmission build for my em2 civic and I need some help from people with experience...

The car is going to be an all around performer. mostly spirited mountain driving, maybe some 1/4 mile runs with a little autocrossing thrown in, but mostly a fun street car. I will be using a smallish turbo, hopefully making around 220 whp.

Right now i have the stock ex trans, i've purchased a lsd, but before I put it in, I would like to know if its worth it to switch out to longer fd ratio. Or just keep what I have.

Here is a plot of the stock ratios

http://img.photobucket.com/albums/v602/2blu/Exratios.jpg


here is the hx 3.842 fd and 5th gear.

http://img.photobucket.com/albums/v602/2blu/Hybridratios.jpg


Would the fd benefit me performance wise, or would it do the exact opposite.

I figure I could stay in boost longer, less wheel spin, only have to shift twice in the quarter, and would drop my rpm at 80mph fro 4000 to 3200 in 5th (which should give me better mpg).

Plus if i ever do decide to build the motor for bigger power, I think the shorter gears would be a hindrance, especially on street tires.


Anyone have any input???
Thighs
05-14-2008, 10:31 AM
i would DEFINITELY go with the 3.8. the 4.4 is way too high for a boosted car and you will end up not staying in boost and spinning tires alot.

plus gas mileage would go wayyy up.
Bruce Leroy
05-14-2008, 10:39 AM
i would DEFINITELY go with the 3.8. the 4.4 is way too high for a boosted car and you will end up not staying in boost and spinning tires alot.

plus gas mileage would go wayyy up.


thanks for the imput

+ reps
RWD164
05-14-2008, 05:04 PM
4.41 is way wrong for what you are trying to do. The 3.8 is the way to go for reliability as well. The 4.41 will have a lot more stress because of more rapid acceleration. Is there any thing shorter available (3.63?) This would be even better.

MA
redrumracer
05-15-2008, 07:42 PM
what program shows you that
RWD164
05-15-2008, 09:29 PM
what program shows you that

Program?
Bruce Leroy
05-15-2008, 09:36 PM
4.41 is way wrong for what you are trying to do. The 3.8 is the way to go for reliability as well. The 4.41 will have a lot more stress because of more rapid acceleration. Is there any thing shorter available (3.63?) This would be even better.

MA

There might be a longer one, but I going with what i know will fit in my transmission. Plus i'm not going to have crazy hp... even IF i build my internals/head, I doubt i'll be making crazy power. Maybe 275 ~ 300 at the wheels.


what program shows you that

http://www.geocities.com/z_design_studio/transmission_z28_6.html