[Mk2] [Turbo] Taller final drive modification to Mk2 Turbo Gearbox - Results

[Scott Barton]

Following the exceptional service i received from Century Motorsport and my newly fitted modified gearbox i thought i would post up the findings.

Now this test was not an exact science and simply involved a Tom Tom sat nav to record the speed as best i could, and my car rev counter. The important bit is that the exact same method of measurement was used, and the same strip of M26 motorway (Albeit in opposite directions)

The following results were taken:

Existing Rev 3 LSD Gearbox
60mph - 2750rpm
70mph - 3000rpm


Modified Rev 3 LSD Gearbox with taller final drive
60mph - 2500rpm
70mph - 2750rpm


Clearly see a considerable rev count reduction throughout the speed ranges.
Another observation made on the fuel consumption on my drive up there compared to the journey back. I used just over 3/4 tank there, and just over 1/2 back. The speed and journey times were variable though so not sure how much i can read into that.

On the whole, very satisfied!

More info here:
http://www.imoc.co.uk/forums/viewtopic.php?t=135158

And trader feedback thread here:
http://www.imoc.co.uk/forums/viewtopic.php?t=135423

[RyanRs]

Scott, i know this is a hard one to explain, but how differently does it pull now? I would imagine with the whole gear ratio now being slightly lower, the car will require more power to move, which would 'technically' cause a reduction in initial acceleration, however the increased initial load on the engine would cause an increase in exhaust velocity and therefore a decrease in turbo spool time and as a result; Increase the initial acceleration.... ?

So put simply, Does it accelerate faster! lol

[ashley]

Looks like a really worthwhile mod- very very tempted: cheers for sharing Scott

[Marf]

How much are the bits to do this?

[Century Motorsport]

Just to clear up the confusion, Scott had the longer final drive fitted - all the gears are std.

The final drive mod consists of a Crown wheel, pinion & oil pump gear. This will effectively lengthen each gear - Ryan's terms of the crank gear being on a push bike being the final drive and the gears on the rear wheel being the gears is a good way to think about it

[Scott Barton]

Thanks mate.....

[mr2toby]

Hi Scott

Glad the kit went to good use. If you like i can work out your maximum speed in each gear before and after the final drive mod.

Just need your rpm limit, wheel size, rear tire width and sidewall profile.

[Kongaroo]

If I were to make what I considered a perfect gear ratio I would want a considerably taller than stock 1st and 5th gear.

Has anyone come up with a way to make just the 1st and 5th gears taller but leave all the other gears as they are?

[Johnny G]

I think the cars gearing is great for <350bhp. For more than that you need longer gears to make the engine sing a bit IMO.

[Scott Barton]

Hi Scott

Glad the kit went to good use. If you like i can work out your maximum speed in each gear before and after the final drive mod.

Just need your rpm limit, wheel size, rear tire width and sidewall profile.

Hi mate, yep the parts were certainly put to good use.
Car drives like new now!