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      01-19-2014, 10:56 AM   #1
Stock4Evr
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RPM's Shifting

I'm from the old school and would shift when I heard the sound, I liked, coming from the engine. At what rpm's would you take a 2012 135i, w/DCT, to when shifting. Normally I do it around 3-3.5k. Is there an rpm point where you are not gaining any more speed/power?
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      01-19-2014, 12:51 PM   #2
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Quote:
Originally Posted by WebViewer View Post
I'm from the old school and would shift when I heard the sound, I liked, coming from the engine. At what rpm's would you take a 2012 135i, w/DCT, to when shifting. Normally I do it around 3-3.5k. Is there an rpm point where you are not gaining any more speed/power?
The engine has a flat torque curve, the pull seems to be the same in nearly any gear, but shifting at just over 5k will yield best results for around town sporty driving.

(If you are trying to drag, optimally you will nearly ring it out.)
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      01-20-2014, 05:26 AM   #3
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Quote:
Originally Posted by w3rkn View Post
The engine has a flat torque curve, the pull seems to be the same in nearly any gear, but shifting at just over 5k will yield best results for around town sporty driving.

(If you are trying to drag, optimally you will nearly ring it out.)
Thank you, that is what I was looking for.
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      01-20-2014, 07:51 AM   #4
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IIRC

the hp curve maxs out circa 6k rpm so somewhere around there would be optimal.
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      01-20-2014, 08:11 AM   #5
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For maximum acceleration, shifting at 3-3.5k is far too low. You want to be close to the rev limiter (7k) but not at it, suggest around 6.5krpm. However with DCT and such a wide torque band, you can afford to shift a little earlier.

For economy, you'd want to be as low as possible obviously, without the engine struggling too much. So usually <2krpm would suffice to get around town.
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      01-20-2014, 10:21 AM   #6
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Checkout a dyno graph. You want to maximize the "horsepower under the curve". I.e. the shaded area below the max horsepower line along the RPM axis. You want to straddle the largest bump in the horsepower curve.

It is important to understand you do NOT want to straddle or maximize torque. If that were true, the fastest N54 on the drag strip would be shifting around 5000rpm, and it would still be much slower than the I6 turbo diesel.

For a tuned N54/N55 I think the optimal shift point ends up being somewhere around 6200-6500. Horsepower starts to fall quickly after 6000, but shifting lower puts you at a point on the curve before horsepower peaks.

For a stock car, I think it may be slightly higher, maybe more like 6300-6700. Tuning adds slightly more more midrange than it does top end due to huge peak boost numbers that taper faster at high RPM than the stock tune. This adds more horsepower from 5000-5500 than it adds from 6500-7000.
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Last edited by Freon; 01-20-2014 at 10:29 AM..
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      01-20-2014, 01:52 PM   #7
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Optimal power range is from 3.3-4.3k for my tune engine. I normally shit at very low 6k before the PSI tapper dives.
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      01-20-2014, 03:19 PM   #8
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Quote:
Originally Posted by Tommeh View Post
...I normally shit at very low 6k before the PSI tapper dives.
Ok. But when do you shift?

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      01-21-2014, 07:23 AM   #9
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I love this site. So much useful information. Thanks guys.
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      01-21-2014, 07:04 PM   #10
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Quote:
Originally Posted by WebViewer View Post
I'm from the old school and would shift when I heard the sound, I liked, coming from the engine. At what rpm's would you take a 2012 135i, w/DCT, to when shifting. Normally I do it around 3-3.5k. Is there an rpm point where you are not gaining any more speed/power?
If I hear a boom I know it's too late.
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