It has happened to me when downshifting a little too quickly and not blipping the throttle.
Down shift to fast and car accelerates
Thread Starter
Pro
Joined: Apr 2004
Posts: 591
Likes: 0
From: Long Island New York
Down shift to fast and car accelerates
I have noticed that when I down shift a little two aggressively and cause the engine drag light to come on that the car will accelerate hard for a split second.
I'm sure it has to do with the tune that was done and was wondering if anyone knows where to start looking.
Other then that the car runs like an animal
I forgot to mention that its an M6
I'm sure it has to do with the tune that was done and was wondering if anyone knows where to start looking. Other then that the car runs like an animal
I forgot to mention that its an M6
Last edited by C6Coupe; Jan 5, 2008 at 09:10 PM.
Moderator
Joined: Dec 2002
Posts: 40,897
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From: Lakewood Ranch, FL
I have noticed that when I down shift a little two aggressively and cause the engine drag light to come on that the car will accelerate hard for a split second I'm sure it has to do with the tune that was done and was wondering if anyone knows where to start looking. Other then that the car runs like an anamal
I'm sure it has to do with the tune that was done and was wondering if anyone knows where to start looking. Other then that the car runs like an anamal
Pro
Joined: Mar 2006
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From: Pa
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Le Mans Master
Joined: Sep 2004
Posts: 5,707
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From: Los Angeles
You don't even have to blip the throttle. You're probably just shifting too early or at least a lot earlier than necessary. It won't do it if you don't try to down shift to a lower gear while still going too fast. Stay in the higher gear and let the drivetrain drag slow you down, then shift down just before you need to accelerate. It's a much better habit for roadracing too even if you know how to heel-toe shift.
Moderator
Joined: Dec 2002
Posts: 40,897
Likes: 4,350
From: Lakewood Ranch, FL
With a 6 speed - May be. I can downshift mine whenever I want to - you CAN overrev if you aren't careful/don't know what you are doing. Computer will protect you from overrev going up but not down.
Safety Car
Joined: Jul 2001
Posts: 4,456
Likes: 6
From: Spicewood, Texas, USA TX-Texas
Someone here is confused...either the poster for saying the CAR accelerates after a downshift (assuming no addition accelerator depression), or others for thinking the engine speed is mismatched. Or, maybe I'm confused because I don't understand how any of this ties together.
A. If the CAR is accelerating after a downshift, and you're not depressing the acclerator, then you may have a problem (poltergeists?). To my knowledge, factory MN6 cars have no way to control engine overspeed (kaboom!) due to shifting into too low a gear...maybe your tune did add a new dimension here, and it's danged complicated.
B. If the ENGINE is accelerating to higher rpm without additional accelerator input after downshifting, then that's what happens when you shift a manual transmission into a lower gear...happens every time. If you shift with mismatched RPM, you will get a distinct SLOWING lurch until the engine is brought back up to speed...the engine goes to idle during the shift unless you're holding the accelerator positon.
A. If the CAR is accelerating after a downshift, and you're not depressing the acclerator, then you may have a problem (poltergeists?). To my knowledge, factory MN6 cars have no way to control engine overspeed (kaboom!) due to shifting into too low a gear...maybe your tune did add a new dimension here, and it's danged complicated.
B. If the ENGINE is accelerating to higher rpm without additional accelerator input after downshifting, then that's what happens when you shift a manual transmission into a lower gear...happens every time. If you shift with mismatched RPM, you will get a distinct SLOWING lurch until the engine is brought back up to speed...the engine goes to idle during the shift unless you're holding the accelerator positon.
Racer
Joined: Jun 2006
Posts: 327
Likes: 12
From: Carlsbad California
I have noticed that when I down shift a little two aggressively and cause the engine drag light to come on that the car will accelerate hard for a split second. I'm sure it has to do with the tune that was done and was wondering if anyone knows where to start looking.
Other then that the car runs like an animal
I forgot to mention that its an M6
I'm sure it has to do with the tune that was done and was wondering if anyone knows where to start looking. Other then that the car runs like an animal
I forgot to mention that its an M6
Le Mans Master
Joined: Sep 2004
Posts: 5,707
Likes: 4
From: Los Angeles
Since Corvettes have throttle by wire, they are able to do lots of amazing things not possible before. When you down shift too early, the engine creates excessive drag on the rear wheels. Depending on how badly, this could be a dangerous situation in slippery conditions. The computer senses tire slip, just like traction control, and boosts the throttle to the engine just enough to put traction back in all 4 wheels. Normally this gives a message in the DIC that it has done so.
Down shifting to second from 3500 to 4000 rpm in third and letting the clutch out suddenly can easily cause rear tire slippage and very high engine revs. This system just helps keep these kinds of mistakes from being dangerous. It of course will not help if you down shift from 5,000 causing a physical over rev condition which could mechanically damage the engine. There's no safety net for idiotic.
Down shifting to second from 3500 to 4000 rpm in third and letting the clutch out suddenly can easily cause rear tire slippage and very high engine revs. This system just helps keep these kinds of mistakes from being dangerous. It of course will not help if you down shift from 5,000 causing a physical over rev condition which could mechanically damage the engine. There's no safety net for idiotic.
Drifting
Joined: Sep 2004
Posts: 1,551
Likes: 4
From: Livingston Texas
My guess is your TM settings are too high. I have enclosed a quote from a SAE paper on how the engine drag control system works.
Torque Subtraction Term - In addition, there is a torque
subtraction term applied to the PID result. This is an
additional safety measure that slowly decays the engine
torque to ensure that EDC control exits after a certain
period of time
.
Originally Posted by Enhanced Vehicle Stability with
Engine Drag Control
Keith Beyer, Eric Krueger and Mark Sonnenberg
Delphi Automotive Systems
Engine Drag Control
Keith Beyer, Eric Krueger and Mark Sonnenberg
Delphi Automotive Systems
Torque Subtraction Term - In addition, there is a torque
subtraction term applied to the PID result. This is an
additional safety measure that slowly decays the engine
torque to ensure that EDC control exits after a certain
period of time
Drifting
Joined: Sep 2004
Posts: 1,551
Likes: 4
From: Livingston Texas
Someone here is confused...either the poster for saying the CAR accelerates after a downshift (assuming no addition accelerator depression), or others for thinking the engine speed is mismatched. Or, maybe I'm confused because I don't understand how any of this ties together.
A. If the CAR is accelerating after a downshift, and you're not depressing the acclerator, then you may have a problem (poltergeists?). To my knowledge, factory MN6 cars have no way to control engine overspeed (kaboom!) due to shifting into too low a gear...maybe your tune did add a new dimension here, and it's danged complicated.
B. If the ENGINE is accelerating to higher rpm without additional accelerator input after downshifting, then that's what happens when you shift a manual transmission into a lower gear...happens every time. If you shift with mismatched RPM, you will get a distinct SLOWING lurch until the engine is brought back up to speed...the engine goes to idle during the shift unless you're holding the accelerator positon.
A. If the CAR is accelerating after a downshift, and you're not depressing the acclerator, then you may have a problem (poltergeists?). To my knowledge, factory MN6 cars have no way to control engine overspeed (kaboom!) due to shifting into too low a gear...maybe your tune did add a new dimension here, and it's danged complicated.
B. If the ENGINE is accelerating to higher rpm without additional accelerator input after downshifting, then that's what happens when you shift a manual transmission into a lower gear...happens every time. If you shift with mismatched RPM, you will get a distinct SLOWING lurch until the engine is brought back up to speed...the engine goes to idle during the shift unless you're holding the accelerator positon.
Safety Car
Joined: Jul 2001
Posts: 4,456
Likes: 6
From: Spicewood, Texas, USA TX-Texas
I can't imagine a situation where adding throttle automatically without the driver's participation would be a good idea...The driver might be trying to get the vehicle stopped using every means at their disposal...antilock brakes, engine drag, dragging their sneaker.
If Thelma and Louise had been driving a Corvette, and changed their minds at the last moment, they might have gotten a little extra boost at the end to keep the tires from skidding.
