E46M3.. Short Diff Ratio For The Track..?
Discussion
Quick question..
Who's done a short diff on their E46 track car.. and what's the best ratio on a std gearbox suited to most circuits..
3.64:1 is std I believe, I'm looking into a 3.9:1, but have found a 4.1:1.. but unsure if this is too short..? I can't remember what the Mph/1000 rpm gearing is in 5/6th..!
The stock ratio is too long.. Silverstone is all 3rd/4th gear..! maybe just grab 5th if you get a good run onto the hanger straight..!
Who's done a short diff on their E46 track car.. and what's the best ratio on a std gearbox suited to most circuits..
3.64:1 is std I believe, I'm looking into a 3.9:1, but have found a 4.1:1.. but unsure if this is too short..? I can't remember what the Mph/1000 rpm gearing is in 5/6th..!
The stock ratio is too long.. Silverstone is all 3rd/4th gear..! maybe just grab 5th if you get a good run onto the hanger straight..!
Edited by RatBoy M3CSL on Tuesday 21st September 22:49
Yes E46 M3 is 3.64 as standard. I would suggest going for a 4.1, that seems to be the popular change for E46 M3 owners.
I have a E36 M3 which is 3.23 as standard, but went for a 3.64 and now sourced a 3.73 as I'll get away with slghtly shorter.
Mine made a huge difference to performance, accelerated much harder. The diff swap gave an extra 14% torque at the wheels and it revs through the gears much quicker now.
Definitely the best performance mod you can do on any M3. I think mine revs about 350rpm more at 70mph, so not a big deal really.
I have a E36 M3 which is 3.23 as standard, but went for a 3.64 and now sourced a 3.73 as I'll get away with slghtly shorter.
Mine made a huge difference to performance, accelerated much harder. The diff swap gave an extra 14% torque at the wheels and it revs through the gears much quicker now.
Definitely the best performance mod you can do on any M3. I think mine revs about 350rpm more at 70mph, so not a big deal really.
This page will work it out for you
http://www.endtuning.com/gearratios.html
Just load the E46M3 settings (see the bottom of the page), make sure you put in 19" wheels and you can edit the diff ratio and get it to tell you RPM's. I believe the E46 M3's diff is 3.62:1
Simply put though, your rpm will go up by (New diff ratio)/3.62
4.1 diff gives an rpm rise of 13.3% at any given speed (given that you in the same gear)
3.9 diff = 7.7% rise
with a 4.1 diff you will be at 4607rpm instead of the standard 4068rpm in fourth gear at 70mph etc...
http://www.endtuning.com/gearratios.html
Just load the E46M3 settings (see the bottom of the page), make sure you put in 19" wheels and you can edit the diff ratio and get it to tell you RPM's. I believe the E46 M3's diff is 3.62:1
Simply put though, your rpm will go up by (New diff ratio)/3.62
4.1 diff gives an rpm rise of 13.3% at any given speed (given that you in the same gear)
3.9 diff = 7.7% rise
with a 4.1 diff you will be at 4607rpm instead of the standard 4068rpm in fourth gear at 70mph etc...
Edited by BenGismo on Wednesday 22 September 19:13
.. You know what ... its even right.. 
.. at the end of the hanger straight.. i'm just on the rev limiter in 4th at an indicated 140mph... in my modified road M3 last year.. with 3.64 stock diff gears, with a 4.1 diff it will max out at 156mph in 5th.. which should be plenty.. still dont need 6th at Silverstone, but more get up and go to get up and get gone..!
Shimmy, let me know if your stepping out of your ready to go unit or taking the gearset out.. I will have a std sealed unit to swap with if its any good to you..!
.. at the end of the hanger straight.. i'm just on the rev limiter in 4th at an indicated 140mph... in my modified road M3 last year.. with 3.64 stock diff gears, with a 4.1 diff it will max out at 156mph in 5th.. which should be plenty.. still dont need 6th at Silverstone, but more get up and go to get up and get gone..!Shimmy, let me know if your stepping out of your ready to go unit or taking the gearset out.. I will have a std sealed unit to swap with if its any good to you..!
Edited by RatBoy M3CSL on Wednesday 22 September 21:55
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