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Car Stutters Big, Changing At High Rpm

123456

By 123456,
in Engines & Forced Induction

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Cubes Grand Master

Cubes

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Posted
when you change gears quickly the bov doesn't have much time to dump air, so there isn't much of a pressure loss in the piping.

i'd possible point the finger at the boost controller. the air between the controller and the wastegate isn't able to escape fast enough, so the wastegate is still partly open when you get on the gas again, so you have less boost until the wastegate is fully shut.

My thoughts also.

When I was fiddling around making my own bleeders a few years back I came across this issue, but boost didn't come on with a jolt it was a smooth slow spooling laggy gutless feel.

IF the bov is venting to atmosphere you can experience a 'lag' of sorts between gear changes that feels like a jolt as the motor floods. The reason for this is between gear changes the ecu has metered an amount of air that has entered the ic and its piping, when shutting the throttle partially for a gear change the bov opens and dumps this air. So the mixture is going to be pig rich.

There's a couple of ways around this... Recirc bov or no bov at all.

For almost none of that slight 'lag' when you jump back on the throttle after a slow/mediocre speed gear change run no bov as the turbo doesn't have to do any work to 're pressurise' the ic and its piping. You get back on the throttle and the turbo torque is just simply there. ;) The total opposite of what many believe. The bov in fact increases slow/mediocre gear change lag.

A fast slapping change.. well bov or no bov there's no real difference.

In your case... I would start by blocking the bov off. See if it makes a difference. If there's no difference you know the issue is some where else.

  • 3 weeks later...
123456 Proficient

123456

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Oh by the way i finally got around to blocking my bov off and it's fixed the surging problem on gear changes, and seems to have more go after changes as well (+ i just got hi flo panel so i dont get any flutterz) so give it a shot and post results here if any one can be bothered

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