Rev the engine while in park/neutral
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Joined: Dec 2007
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From: Corona, CA
03 g35 coupe...........02 c32 Sold
yes, its a feature to protect the engine. The ecu disables my sc and keeps the rev's to 4k if i'm in park or neutral. If your jump starting someone, 4k should be more then enough to jump start most cars. Our batteries are pretty robust.
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From: Diamond Bar, CA
W206 PHEV AMG
do not rev the car if you are trying to jump start another car, unless you want to destroy someone's electronics. just turn the car on and let the battery in the other car charge before you attempt to start that car.
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Joined: Dec 2007
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From: Corona, CA
03 g35 coupe...........02 c32 Sold
i always thought it was just our weak electronic german cars. I jumped started a bunch of hondas that way without problems. They wouldn't start unless i revved the car.
MBworld Guru
Joined: Apr 2002
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From: Diamond Bar, CA
W206 PHEV AMG
that's never the right way. the point of jump start a car is to use the car that is working to charge the battery of the drained car. It's not to force the drained car to start right away. I never had to rev any car to jump start another car.
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From: Atlanta Metro
Current: C217 V12TT AMG Previously: C55 AMG, SL65 AMG
To the OP, yes most automatic's have a safety feature that only lets it rev to 4k. You shouldn't be revving like that in park/neutral, and it also protects you from doing a neutral drop at high RPM and messing up your transmission (not that a 4k neutral drop is safe either).
As for the revving the engine while jumping, I was always of the train of thought that you need to rev and hold your engine (let's say in the 2-3k range) to get the alternator spinning. Alternators don't produce as much amperage when they're at idle speed.
As for the revving the engine while jumping, I was always of the train of thought that you need to rev and hold your engine (let's say in the 2-3k range) to get the alternator spinning. Alternators don't produce as much amperage when they're at idle speed.
MBWorld Fanatic!
Joined: Dec 2007
Posts: 5,034
Likes: 6
From: Corona, CA
03 g35 coupe...........02 c32 Sold
To the OP, yes most automatic's have a safety feature that only lets it rev to 4k. You shouldn't be revving like that in park/neutral, and it also protects you from doing a neutral drop at high RPM and messing up your transmission (not that a 4k neutral drop is safe either).
As for the revving the engine while jumping, I was always of the train of thought that you need to rev and hold your engine (let's say in the 2-3k range) to get the alternator spinning. Alternators don't produce as much amperage when they're at idle speed.
As for the revving the engine while jumping, I was always of the train of thought that you need to rev and hold your engine (let's say in the 2-3k range) to get the alternator spinning. Alternators don't produce as much amperage when they're at idle speed.
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Senior Member
Joined: Sep 2009
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From: Middle of IL in a corn field
2006 C55 AMG White/Ash
It doesn't hurt anything because there is a voltage regulator in place. If it would hurt the car being jumped, it would also hurt the car making the juice.
Back to the original post, all modern cars have a rev limiter built into the computers. It's not healthy to have no load on an engine with high rpms.
Back to the original post, all modern cars have a rev limiter built into the computers. It's not healthy to have no load on an engine with high rpms.
