Noob: Proper Manual Shifting Questions

[TazioNYC]

Originally Posted by penny

Tom, you're awesome. Is there a math to this? What if I want to downshift at 2k rpm? Thanks bud.



Tazio, downshifting at 4-6k rpm would bring rpm to 5-7 rpm, correct? Hehe, that's a bit scary for now. Car hasn't been broken into yet. The gap difference between the gears you mentioned is pretty much on the dot from my learning experience. Thanks for the info.

Question: When downshifting, should I boot the rpm up and catch it while it goes down, or catch it while it is going up?

Whoops! Late night typo...I meant NOT to downshift :-) Sorry.

[jasonite]

When I'm approaching a stop and am only in 4th gear to begin with, I'll normally just coast til the rpms are low enough that the engine's going to begin spluttering, then I'll clutch-in, shift to neutral, and clutch out and break to a stop.

When in 5th or 6th and/or traffic is slowing down ahead of a stop, then I'll usually coast til 3rd gear is appropriate for a downshift.

My advice would be to not downshift through all the gears - and certainly don't ever downshift to 1st unless you're moving so slowly that the engine is about to splutter but you intend to keep moving very slowly, like in stop-n-go traffic that's literally just creeping. But usually 2nd gear will do for these situations anyway.

If you get in the habit of never downshifting into 1st, you decrease the risk of sometime accidentally downshifting into 1st when you're going 20mph+. Which would be bad

[Tom K.]

Originally Posted by penny

Tom, you're awesome. Is there a math to this? What if I want to downshift at 2k rpm? Thanks bud.

Thanks for your kind words.
From the BMWUSA web site, the gear ratios for your 135i are:
1st: 4.06 to 1, 2nd: 2.40; 3rd: 1.58; 4th: 1.19;
5th: 1.00 (Direct Drive) and 6th: 0.87 (OverDrive)

So 1,000 rpm in 6th times the 5th ratio of 1.00 divided by the 6th ratio of 0.87 = 1149 RPM

1,000 rpm in 5th times the 4th ratio of 1.19 divided by the 5th ratio of 1.00 = 1190 RPM

1,000 rpm in 4th times the 3rd ratio of 1.58 divided by the 5th ratio of 1.19 = 1328 RPM

etc., etc. These figures are different than the one's I posted earlier as the gearing for the 135i is slightly different from my 128i.

For calculating the rpm difference @2,000, simply double the figures - so 2,000 in 6th = 2,300 in 5th. 3,000 in 6th = 3,450, etc.

Have fun!
Tom