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4:10 diff


Woppum
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Thought some of you with E46 M3/CSL's would be intrested in a new diff i have installed. Basically what it does is shorten each gear by 10-12%. What this means is the car is now geared from 210 to 185mph. The conversion costs around £1000 and can advise on the following:

1) it is grating on the motorway as soon as you get passed 100. On the bright side you get to the 100 much quicker.

2) It is like making each gear 40% shorter. 2nd gear is like 1.5 of old, 3rd is 2.5 etc. 3rd gear is simply stunning, like a 430 at full chat. Acceleration is simply stunning and you fly through the gears.

3) With the sport button on or off - in the wet, with cups, you better have quick reactions. The car will snap in fourth gear let alone anything below.

4) Fuel economy is worse but not terrible. I drove from London to Sheffield today and back which at about 350 miles is the longest drive I have done with the new diff. Went through 1.5 tanks.

5) The car is noisier and twitchier at speed. Becasue you are at such high rpm, even at 120 (cool down lap:) ) any bump in the road will make you bunny hop. You have to concentrate 100% of the time and keep both hands and penis on the wheel.

6) On track this should mean much better results? I have only done Silverstone so far and as that track has expensive memories for me I cant really say if it is faster - but it bloody well should be! Shim when are we next at Donny?

Kindly a mate has made the below chart to show the current ratio compared to the new. Let me know if you have any questions, happy to advise.

newratio.jpg

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This post reminds me of when we used to mess with the sprocket sizes on our bikes... used to make them feel so much quicker, but gear changes became much more frequent.

So this is why they had your exhaust off at Christmas then, to get at the diff.

You'd seriously not want to do this on a manual car...

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Depends what you want the car for and how far you would go for the extra performance. The car is faster, really faster - not talking about sillly remaps, cats, zorsts, air filters etc. The car is simply much more accelerate. Even at Silverstone GP (a power circuit) the 7GT3 boys were impressed about how fast the car was (still not nearly as fast as them though!).

In this game its about compromises. It is harder to drive as it kangeroos in 3rd gear. You have to change more frequently which is fun for me but others may find annoying, it is noisier and uses a fair amount more fuel. You dont get something for nothing.

You make your choice really. Im just stating the pros and the cons. It seems to suit me but i might build a spare diff with normal ratios for road use too?

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