would 3.9 gearing be too aggressive for FI later? I'm NA at the moment. How much work and $$ would it be to go down to 3.7 from 3.9 or later.

 

Don't bother with it. There are countless threads in the FI forum on this, you should take a look at them.

 

oh yeah.. forgot to mention I have 5AT and badly need some mid range pull.

 

I went to the 3.5 FD in my Vortech'd 5AT setup. I know sentry65 is running the 3.9s with his Vortech'd setup.

 

depends on how much power youre pulling...it can be easily be too aggressive for most FI kits, but possibly doable if you're staying <~350whp

 

IMO the AT needs 550 whp plus to not have to touch the rear gearing. As bad as it is that are 5 gears have to match the 6 speed gearing we have 3.3 's in the final drive. That’s what makes the AT seem so slow because are gears r harder to go through since the are longer and we have a longer final drive.

Its as simple as the gears in the bicycle when you want to pick up speed quick or your going up a mountain you go down to the smaller gears as the are easier to pedal them. Now if you put the bigger gear in the bicycle you will find that it take way more power to pedal it. So as a result this is the same thing in cars.

But yes if your around 350 rwhp or to 450rwhp go for it but don’t go higher then the 3.5's. I got beat by a rsx type S with turbo on 10 pounds they make around 330 to the wheels but their final drive is a 4.7 if im not wrong and gears are slightly less aggressive then the 6speed manual Z. We started in 2nd and it was even when I went into 3rd he started pulling I lost by 1 car 1/2 not much but shouldn’t have lost to it.