Quote:
Originally Posted by NISFAN
When I get a chance, I will set up autotest2000 with a full dyno plot of manual and auto versions, with a range of BMW diff ratios.
Autotest also has an 'optimum parameter' function, so you can set a test up and it will graph what diff ratio will run the quickest times.
But as you say, it doesn't always follow that a higher ratio gives more acceleration. When I picked up my 240, I immediately started looking for a spare diff to convert to LSD. I couldn't find any 140/240 diffs on eBay, but came across plenty of 3.08 versions. I quickly ran the numbers in autotest, thinking that the shorter gearing would be a plus. Turns out the figures were worse.
As you mentioned, 1st gear on an auto is already a high ratio, making it higher would almost make it useless for traction and real forward progress. If you have to short shift to get out of it, then all the good work is undone.
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Did you ever get a chance to run this simulation/plot?