5.1 fd on the track?


morevtec

morevtec

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hi lads,
currently have a s80 4.4 for b18c4 sir dc2 in my race car.
I was looking to put a 98 spec s80 n3e in it but I have since found a 5.1 fd I was wondering would the gears be too short with a 5.1 in my standard 4.4 box? its only for track use!
 
Those ratios are the same as the EK4/EK9 right?

Should be good for around 125mph, I'd say it'd be fine.
 
I know the 4th and 5th are shorter than the 98 spec.
im just afraid that it might be too short and end up constantly changing up and down every few mins
 
Put this together for you to see how it compares to stock:

5.1 vs 4.4 FD on B18C

Hit start and scroll down the page for the comparison, hopefully it'll make sense. :nice:
 
For mondello id say a 5.1 would give too short gearing. A 4.7 fd seems to be ideal for mondello. Most of the corners are 2nd and 3rd gear with the 4.4 but ur not getting to use the full potential of the gearbox as the 4.4 is to long so id go somewhere in the middle.
 
I thought 4.9 would suit it better than 4.7

I thought the 5.1 might be ok because when people buy race gear sets they're quite short.
 
I have a 98 spec S80 (4.7FD) + Vti 4th & 5th gears and max speed is 220 - 225 on gauge with a 8300RPM rev limiter.
 
morevtec said:
thanks for that kozy usefull info but complicated to know how exactly it would fair out on the track.
Click to expand...

Yes I know where you are coming from, unfortunately short of diving in and just spending the money, there's no other way to really describe how it changes things.
 
Kozy said:
Yes I know where you are coming from, unfortunately short of diving in and just spending the money, there's no other way to really describe how it changes things.
Click to expand...

yea it really is the best way and what suits one track wont another.
wonder is it much grief to change the fd.
 
I reckon it's probably a 'Haynes 5 spanner' job.

If you can get the box in and out, and are careful with a few fiddly springs and getting the shims right, it should be fairly straightforward.

I think I'd rather do that, than try and change the clutch on my ATR again though. :nono:
 
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morevtec said:
yea it really is the best way and what suits one track wont another.
wonder is it much grief to change the fd.
Click to expand...

Give me a few weeks and I'll tell you what is it like to do it for the first time with no previous experience... Removing it is easy, I can tell you that! :D
 
its a tricky one this its hard to know if the short fd on standard gears will give a close ratio gear feel or be a diseaster.
 
Put it this way, if you shortened the FD enough, you could effectively turn 5th gear into the original 4th, 4th into 3rd, so on. Basically each ratio just becomes one lower, and 1st becomes totally unusable. If you did this, it would be a disaster as you would have achieved nothing except losing 5th gear!

It is certainly not the same as a close ratio kit, but moderate changes just give the effect of having slightly more torque. Just be aware it will not change the drop between the gears at all.
 
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Shorter final drive will definitely not give you the same feel as gear set. In fact, we should really be fitting gear set first and then play with the FD depending on where the car is used! I have gone for 4.9, hopefully that will mean that I will be able to use 4th and 5th a bit more.
 
i have a 4.4FD, but ATS close gear set. HUGE difference. corner exits are really incredible. i had a '98 spec itr tranny before this, corner exits were lacking. the car really came alive with this gear set. BTW, top speed is about 120-125mph.
 
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