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Old 22nd July 2008, 16:22   #16
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Its nothing but the revvlimiter cutting off fuel. In some cars, it cuts in early when the car is stationary. I have noticed this in almost all Mercedes-Benz'.
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Old 22nd July 2008, 16:30   #17
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Originally Posted by GTO View Post
Its nothing but the revvlimiter cutting off fuel. In some cars, it cuts in early when the car is stationary. I have noticed this in almost all Mercedes-Benz'.
yes the engine behaves very much like the fuel supply has been cut off. and due to this i observe a big jerk to make the car shake even on stationary.
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Old 23rd July 2008, 10:38   #18
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amit_mechengg,

Give us an exact RPM figure where this happens.
Does it happen only if you revv suddenly or even if you raise the RPM slowly?

Also, ive been told (i cant give a confirmed reason why) that taking a car to redline without load on the engine is not reccomended.

cya
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Old 23rd July 2008, 11:42   #19
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hi rehaan, i cannot tell u at what exact RPM does this happen because i dont have a rpm meter. but yes i think its a revvlimiter. and this happens i all altos as well as santro.

yesterday i checked with 2 more altos and one santro all MPFIs. i can conclude that this happens in all mpfi engines.

and yes it is 100% true that it is not recommended to revv the MPFI engines to high rpms without loads, it damages the catalytic converter and might be other components too.
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Old 23rd July 2008, 11:46   #20
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Just curious, why does load on engine affect catalytic converter?
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Old 23rd July 2008, 11:48   #21
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Guys,

What I do not understand is the need to rev to high RPMs in neutral and when stationary? Why would one want to do it ?

Cheers,

Rajan
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Old 23rd July 2008, 11:54   #22
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Guys,

What I do not understand is the need to rev to high RPMs in neutral and when stationary? Why would one want to do it ?

Cheers,

Rajan
there is absolutely no need to revv high in neutral. it happened just by coincidence first time in my life that someone sitting in the car revved high in my parking and i was standing behind the car and noticed that the exhaust jerks. so as a worry i tried it many times and found that the engine jerks too.

went to the service station and there he engineer told me that all MPFI jerk and you should never revv in idling.

during idling the car runs on a rich mixture where the carbon and other gases content is more. this affects the catalytic converter.

but during running condition the engine runs on a leaner mixture and thus the gases get filtered easily.
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