Bespoke gearbox for boosted 9


EK9 Matt

EK9 Matt

Well-Known Member
Joined
May 24, 2015
Messages
508
Hi guys, as a few of you are aware I've recently done a few trackdays in my boosted 9, the problem I have (or think I may have) is at Cadwell I was in 5th at about 7000rpm down park straight. Now this is fine at Cadwell but I fear on a long straight I may run into the 8700rpm limiter.
Been thinking of building a box with a different 4th and 5th (with an Mfactory plate diff to boot) out of an S80 4.7FD to be specific, as they're longer, but don't want to go the other way and it be too long!
I don't want to go 4.2FD, ie an S9B as it's sooo long, so my question is has anyone done this and what's it like?

Thanks in advance,
Matt.
 
Last edited:
Tbf I thought park straight was quite long when I've seen it on video.
It looks much longer than the start/finish stretch at brands. On low boost I peak roughly 120mph so I barely reach 5th lol
 
Lol! You need a 4.7FD haha! It's the likes of Donnington and Silverstone I'm worried about.
 
Although the top speeds on either box are essentially the same.
 
A 98 spec S80 with 4.7FD has a longer 4th and 5th than a 96-98 spec S80 if I'm correct, so would give me more top speed?
 
That's correct longer 4th and 5th ratios but a shorter final brings them back down to the same (like 1mph in 5th difference) to the s4c and 4.4 s80.
I have the 4.7 s80
 
Sorry I may have been misleading there, I'm going to keep the 4.4 FD.
 
Ah and use the 4th and 5th from the 4.7s80.... Yeah that would lengthen it up.
Especially on 16s
Your top speed should be like 160 as it is.
 
That's it jesse:)). Yeah it's around that which is plenty fast enough lol. Was just thinking about not revving her out so much, it's only a thought like. Just didn't want it to be horrendous if I did do it.
 
You must log in or register to reply here.
Back
Top