Schuyler

iTrader: (1)

So, my car is daily driven, and will be used for 4 Autox a year or so, and HPDE like twice a year. 5-speed, and guestimated final numbers should be a round ~225ft-lb, 235hp.

I'm considering swapping my 4.30 to a 3.90 to have a little longer in each gear. I have an offer to trade my diff flat out, though mine has 72k on it, and the mileage on the 3.90 is unknown. Otherwise, his asking price is $500 without the carrier. Looking to hear from people on both sides, as most people I've asked their opinions are running a 4.10.

My fear is, as far as enjoying the turbo DD, I'll lose some of that *back of your seat* feeling at this power level. I expected fuel economy gains on the highway, but in reality, I will only be going from 4080rpm@80mph to 3709rpm. So, not really all that much of a change.

AutoX I think will be benefited by having a higher top speed in 2nd gear.

I can't speak for HPDE, as my first event is in May.

So, Tl;Dr: What is your ideal final drive for a T25/2554 setup with a 5 speed, that will be daily driven, with bimonthly autocross time, and semiannual HPDE?

aidandj

iTrader: (5)

I'm about to pull the trigger on a 3.9 r&p for like $90. Its no 3.63 but I think it will help with dding.

18psi

iTrader: (76)

I'd switch the 4.30 for a 3.90 if it was straight across that's for sure.

aidandj

iTrader: (5)

True. That's a steal.

Schuyler

iTrader: (1)

Is it? From what I'd heard with the 4.30 becoming Spec Miata legal they were going up in price.

18psi

iTrader: (76)

maybe.
but the 3.90 is better.
so who cares lol

concealer404

iTrader: (3)

I liked the 4.10 with the 5spd in my similarly/slightly more powered 95. Doubt a 3.9 would ruin the car at all.

18psi

iTrader: (76)

thing is, when you turn the boost up, and you will turn the boost up, and break the 5sp, and you will break the 5sp, and get a 6sp, you'll be so much happier with the 3.9

bbundy

For autocross 5speed +turbo power plus DD and a few hpde not too ridiculously high RPM limit you want the 3.909. with the rev limit turned up above ~8000 rpm the 410 would be faster and better use of the power band.

Schuyler

iTrader: (1)

See the problem is, as I know you personally have made evident, stock rods and 5-speed are good friends. lol.