Simon
|
| posted on 30/9/07 at 10:15 PM |
|
|
New diff
Peeps,
Following on from Bearingkits post t'other day, thought I'd look into BMW diffs.
Just bought one from Germany with a ratio of..........wait for it......
2.28:1.
Bit low perhaps Done some calcs and come up with:
in 5th - 70mph at 1954rpm,
- " - 50mph at <1400rpm
At 5500rpm in
1st 50
2nd 79
3rd 118
4th 165
5th 197
I know the last two are fairly irrelevant, but given the fact my turbos are quite small, I reckon the ratios should allow me to make the most of the
expected "power band" and make haste without having to thrash the motor. I'll also benefit massively in the fuel economy department
- I reckon at constant 50ish, I'll better 50mpg
Standard E46 330D produces 330lb ft, so I should be safe!
Comments please (nice ones only)
ATB
Simon
[Edited on 30/9/07 by Simon]
|
|
|
|
|
Paul TigerB6
|
| posted on 30/9/07 at 11:47 PM |
|
|
Slightly overgeared me thinks - cant see a se7en pulling 4th, never mind 5th with those ratios, no matter what the power.
These cars are about acceleration and handling surely - sod the fuel economy!!! Sorry, cant be nicer
[Edited on 30/9/07 by Paul TigerB6]
|
|
|
Simon
|
| posted on 1/10/07 at 12:20 AM |
|
|
I'm not expecting much out of the top one, but at least I'll have ability to use all cogs
I never used 1st, always started in 2nd - look at the speeds in 2nd (with 3.92 diff) compare with 2.28 diff in 1st.
ATB
Simon
|
|
|
smart51
|
| posted on 1/10/07 at 07:05 AM |
|
|
1400 RPM is too low an engine speed, even if your engine is torquey and your car light. Labouring an engine at such a speed is not good for it. Nor
will it be good for performance or economy. An engines best Brake Spcific Fuel Economy is usually around 2500 or 3000 RPM. At 1400 it will be less
than poor.
The institute for advanced driving recomends keeping revs between 2000 and 3000 for constant speed driving meaning you won't ever use 5th
legally. 
You may have chosen the wrong ratio. Its a bit low even for my BEC. I recon 7 MPH / 1000 revs in 1st = 82 MPH in 1st and then 16.3 MPH / 1000 revs
in 6th = 4290 RPM at 70, 164 MPH at peak power and 191 MPH at the red line.
Good luck with it anyway.
|
|
|
02GF74
|
| posted on 1/10/07 at 01:45 PM |
|
|
0-60 in 15 seconds?!!! seems a strange choice; let us know how you get on shuld you fit it.
|
|
|
wilkingj
|
| posted on 1/10/07 at 03:00 PM |
|
|
quote:
Originally posted by Paul TigerB6
These cars are about acceleration and handling surely - sod the fuel economy!!! Sorry, cant be nicer
[Edited on 30/9/07 by Paul TigerB6]
Couldnt agree more... and a nice v8 burble
Mind you... I get 26mpg on the motorway at 70/80mph.
Thrash it about town / back roads, and its somwhat less mpg
However, the GF is huge (Grin Factor)
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
|
|
|
