Jerk/surge versus starting rpm of acceleration

Slidewayz · 07-31-2009, 08:12 PM

OK, so maybe this is subjective, but...

It seems like the time rate of change of acceleration (jerk/surge) is greater when acceleration starts at a higher rpm.

This isn't just spool time for the turbo...enthalpy of the exhaust gas...blah blah blah.

What I have noticed is that if I start accelerating at, say, 1500 rpm, the rate of acceleration is lower at 5000 rpm than it is if I start accelerating at 3000 rpm.

Is this an ECU thing? Not clear how it can be measured or if I'm just hallucinating, but I did a bunch of runs and it sure seems like you catch the car napping...

JayKay335i · 07-31-2009, 08:29 PM

Take a peek at the torque curve.

Slidewayz · 07-31-2009, 10:31 PM

what I'm getting at is how power delivery varies AT THE SAME RPM depending upon the initial WOT rpm.

07-31-2009, 08:12 PM	#1
Slidewayz Major 33 Rep 1,177 Posts Drives: 2007 335i Join Date: Jan 2009 Location: Oakland, CA iTrader: (5)	Jerk/surge versus starting rpm of acceleration OK, so maybe this is subjective, but... It seems like the time rate of change of acceleration (jerk/surge) is greater when acceleration starts at a higher rpm. This isn't just spool time for the turbo...enthalpy of the exhaust gas...blah blah blah. What I have noticed is that if I start accelerating at, say, 1500 rpm, the rate of acceleration is lower at 5000 rpm than it is if I start accelerating at 3000 rpm. Is this an ECU thing? Not clear how it can be measured or if I'm just hallucinating, but I did a bunch of runs and it sure seems like you catch the car napping...
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07-31-2009, 08:29 PM	#2
JayKay335i Banned 189 Rep 5,046 Posts Drives: ///M323 DCT Join Date: Apr 2009 Location: North Dakota; its best DUHHHHHH iTrader: (1)	Take a peek at the torque curve.
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07-31-2009, 10:31 PM	#3
Slidewayz Major 33 Rep 1,177 Posts Drives: 2007 335i Join Date: Jan 2009 Location: Oakland, CA iTrader: (5)	what I'm getting at is how power delivery varies AT THE SAME RPM depending upon the initial WOT rpm.
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