5.1 final drives. what are your thoughts

[Touge Tom]

I'm considering changing from 4.7 to 5.1 final drive. Pros and cons anyone?

[Tai]

Are u planning to track the car often?

[nickk]

If it's for the street, your on drugs.
I've got 4.9's and it's boarder line bearable on the freeway and im very tolerant- close to 4000 rpm at 100k's.
The pull would be amazing though.

[Touge Tom]

well its for street, track and hill climbing-(touge). along with this change (when i get the fund's, half way there.), i plan to up the rev limit to say 10k+. what this argument bring's to mind is would it be better to hold out a 4.7 final drive, having to do less shift's to 10k+ and increase my top speed (which i don't see the point of). or make up this loss of top speed of using a 5.1 and revving to 10k+ making more shift's? can some body please tell me different? your harsh opinion's are welcome.

[Tegzieboi_BAR]

The 4.9FD lowers your top speed to roughly 210 kph. I can imagine that using a 5.1FD would limit it to 200 at best. I think for hill climb style events this could be somewhat beneficial but since you already have a B20 VTEC with a much lower powerband compared to something like a B16 and even B18's i honestly think 4.78FD is the way to go for you, i sure as hell wouldnt go past 4.9FD.

I have a 4.4FD JDM ITR box and manage to clock up to 190kph down the main straight at Mallala Raceway in SA with a street setup just clicking into 5th gear. I intend on upgrading to a 4.9FD and even then i think with some work to my motor i may be getting close to the limits of my 5th gear.

If u really feel like the upgrade is necessary i certianly wouldnt go past the 4.9, and if ur gna drive it on the street im sure u'll get sick of sitting on 3k rpm in 5th gear in 60 zones. Dnt think its worth it.

[GSi_PSi]

i wouldnt go 10K on a B20, hell 9K is pushing it, why do you need to rev when you have great power midrange?
4.7FD is good already but 5.1FD would be pretty sweet, great for toque but im kinda thinking were in sydney you would go about tougeing?
do you still have a VAFC tuning your setup?

[Touge Tom]

i wouldnt go 10K on a B20, hell 9K is pushing it, why do you need to rev when you have great power midrange?
4.7FD is good already but 5.1FD would be pretty sweet, great for toque but im kinda thinking were in sydney you would go about tougeing?
do you still have a VAFC tuning your setup?

Well I've done all the cam,head work and block work prepared for this 10k+ push. And from the fed back so far I'm still boarderline on which way to go. And yes im still using the shitty vafc2 set up at the moment. Im shoping round for s200/s300.

[meatball]

theres a s300 for $600 in the parts section. check it out

[TODA AU]

well its for street, track and hill climbing-(touge). along with this change (when i get the fund's, half way there.), i plan to up the rev limit to say 10k+. what this argument bring's to mind is would it be better to hold out a 4.7 final drive, having to do less shift's to 10k+ and increase my top speed (which i don't see the point of). or make up this loss of top speed of using a 5.1 and revving to 10k+ making more shift's? can some body please tell me different? your harsh opinion's are welcome.

If you're building an engine that will last @ 10K+rpm, you don't mind stumping up & doing things right.
So buy a close ratio gear set & a taller final drive.
You'll get a tall 1st gear for fast standing starts & close ratio through the rest.
Going this way is a lot faster, particularly for track & hill climb & just as anoying on the street as the 5.1 final...