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E90/E92/E93 M3 (2008 - 2014)
4th generation E90 M3 sedan, E92 M3 coupe and E93 M3 convertible. The last of the naturally aspirated M3s, powered by a 4.0 liter V8 making 414hp and 295 lb-ft of torque.

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  #1  
Old 06-03-2012, 03:30 PM
JDL92 JDL92 is offline
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Mein Auto: 2008 M3 vert
lunges in 1st gear

Hello everyone,

I am looking for an explanation why a 2008 M3 manual transmission car would lurch when in 1st gear when driving the car hard.

Thanks
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  #2  
Old 06-03-2012, 03:58 PM
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MMME30W MMME30W is online now
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Mein Auto: 2009 W906
Can you elaborate on "lurch" and "hard"?
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  #3  
Old 06-03-2012, 06:09 PM
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dynosor dynosor is offline
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JDL

The M3 has an electronic throttle and I think this is at the heart of the problem. My 2003 330i has one too and it is the car's most annoying feature. For smooth launches you absolutely have to roll into the throttle smoothly or you will be rewarded by a hesitation followed by a jerk. Often a first gear jerk is strong enough to lift ones foot off the throttle a little and an oscillation can be set up. If that happens the solution is to lift completely for a second or to floor it completely.

At 50, I have only owned manual transmission cars and my 330i is much harder to drive hard and smooth than my brother's '96 M3, despite the latter being more powerful - the E36 M3 has a cable operated butterfly that is smooth and hesitation free. Your M3 has the added problem of a Sport setting that increases throttle response, or propensity for jerkiness if you want to nit pick.

The electronic throttle would be OK if it emulated a good "manual" throttle. Instead the fly-by-wire system uses not only throttle displacement in its computation, but speed of application. To ensure that you really meant it when you whack the throttle partway open there is a short delay. This is followed by the throttle servo opening the throttle faster than you would without any consideration for "taking up the slack" in the engine mounts, drive train or your neck.

My 330i is also blessed with a clutch that takes high and was very abrupt when new. It took me a long time to learn how to drive it smoothly and at first I never tried to pull away hard in first - instead, I would make a gentle pull-away and then step into it from second onward. I have added a clutch stop that reduces the pedal travel and that seemed to make the car easier to drive. Many have removed or disabled a valve in the clutch that limits how quickly it can be let out and swear by that making clutch engagement more predictable.

I get a brisk but smooth pull-aways by first raising the revs to about 1500 RPM before letting the clutch out. Then at the clutch engagement point I floor the throttle quickly but smoothly by rolling into it, while at the same time letting the clutch out just as quickly and smoothly to prevent the revs from building or bogging while the clutch slipping.

When shifting to second, you first need to back out of the throttle to reach a point of almost neutral torque. To do this smoothly again take a lot of concentration on being smooth. When re-engaging the clutch in second you need to have you revs match to avoid lurches. If you time it right you can let the clutch out quickly and almost completely without opening the throttle; otherwise you may need to blip the throttle a little just before engaging the clutch. You need to be on the power again immediately after the shift or it will seem like a lurch due to engine breaking - in practice you can start to open the throttle before your left foot is fully off the clutch, but if you add too much too soon you will slip the clutch under power - not good. As soon as the clutch is fully locked up you can increase the throttle to full in a smooth movement; again by rolling into the throttle.

You should avoid opening the throttle quickly and then backing out of it as this confuses the computer. That said, this is exactly what a throttle blip is, but the system seems to recognize a blip with the clutch depressed, while a blip with the clutch engaged causes jerking – perhaps it is only following orders.

Last edited by dynosor; 06-03-2012 at 06:13 PM.
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  #4  
Old 06-17-2012, 05:20 PM
JDL92 JDL92 is offline
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Location: New Jersey
 
Join Date: Mar 2007
Posts: 33
Mein Auto: 2008 M3 vert
Thank you for your information and for your time responding. I have been trying to repeat the lurching but haven't been successful repeating the problem which is a good thing. I am having so much fun driving this car.

Thanks again
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  #5  
Old 07-11-2012, 04:40 PM
SunnyandRich SunnyandRich is offline
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Quote:
Originally Posted by dynosor View Post
JDL

The M3 has an electronic throttle and I think this is at the heart of the problem. My 2003 330i has one too and it is the car's most annoying feature. For smooth launches you absolutely have to roll into the throttle smoothly or you will be rewarded by a hesitation followed by a jerk. Often a first gear jerk is strong enough to lift ones foot off the throttle a little and an oscillation can be set up. If that happens the solution is to lift completely for a second or to floor it completely.

At 50, I have only owned manual transmission cars and my 330i is much harder to drive hard and smooth than my brother's '96 M3, despite the latter being more powerful - the E36 M3 has a cable operated butterfly that is smooth and hesitation free. Your M3 has the added problem of a Sport setting that increases throttle response, or propensity for jerkiness if you want to nit pick.

The electronic throttle would be OK if it emulated a good "manual" throttle. Instead the fly-by-wire system uses not only throttle displacement in its computation, but speed of application. To ensure that you really meant it when you whack the throttle partway open there is a short delay. This is followed by the throttle servo opening the throttle faster than you would without any consideration for "taking up the slack" in the engine mounts, drive train or your neck.

My 330i is also blessed with a clutch that takes high and was very abrupt when new. It took me a long time to learn how to drive it smoothly and at first I never tried to pull away hard in first - instead, I would make a gentle pull-away and then step into it from second onward. I have added a clutch stop that reduces the pedal travel and that seemed to make the car easier to drive. Many have removed or disabled a valve in the clutch that limits how quickly it can be let out and swear by that making clutch engagement more predictable.

I get a brisk but smooth pull-aways by first raising the revs to about 1500 RPM before letting the clutch out. Then at the clutch engagement point I floor the throttle quickly but smoothly by rolling into it, while at the same time letting the clutch out just as quickly and smoothly to prevent the revs from building or bogging while the clutch slipping.

When shifting to second, you first need to back out of the throttle to reach a point of almost neutral torque. To do this smoothly again take a lot of concentration on being smooth. When re-engaging the clutch in second you need to have you revs match to avoid lurches. If you time it right you can let the clutch out quickly and almost completely without opening the throttle; otherwise you may need to blip the throttle a little just before engaging the clutch. You need to be on the power again immediately after the shift or it will seem like a lurch due to engine breaking - in practice you can start to open the throttle before your left foot is fully off the clutch, but if you add too much too soon you will slip the clutch under power - not good. As soon as the clutch is fully locked up you can increase the throttle to full in a smooth movement; again by rolling into the throttle.

You should avoid opening the throttle quickly and then backing out of it as this confuses the computer. That said, this is exactly what a throttle blip is, but the system seems to recognize a blip with the clutch depressed, while a blip with the clutch engaged causes jerking – perhaps it is only following orders.
Excellent post.
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