Engine Question
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Engine Question
Hey Guys this could totally be my imagination but i dont think so.......i drove my car the other day for the first time in a couple of months and it "seemed" like when i lift off the throttle to shift gears it is taking longer than it used to for the revs to come down, like i have to wait longer between shifts (like a really heavy flywheel would keep the engine turning longer). I did notice that my throttle pedal is very sensitive and may be pulling on the cable a little to tight. Could that be the problem or is there a valve or somthing that could be causing this???
Thanks
Thanks
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From: Atlanta, GA / Lake Keowee, SC
I am so weak on the mechanicals, but a long time ago I had a problem with what i think someone called the decelerator valve? something like that atleast. It was a bronse colored circular piece - its long since gone on my car, but your issue sounds like my problem years ago. Cheap fix as I recall.
Three Wheelin'
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From: Texas
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From: Beverly Hills, Mi.
I saw Steven's reason and I'm not buying it.
He claims that the engine will go lean for an instant. Fact is, during the event, there's more fuel available than there is air so the engine goes rich for an instant.
How the recirculation valve works and what it does isn't complicated. As long as the pressure is being vented out of the intake between the metering plate and the compressor it won't matter where that air goes.
He claims that the engine will go lean for an instant. Fact is, during the event, there's more fuel available than there is air so the engine goes rich for an instant.
How the recirculation valve works and what it does isn't complicated. As long as the pressure is being vented out of the intake between the metering plate and the compressor it won't matter where that air goes.
Race Car
Joined: Sep 2005
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From: England UK
Just change the Bosch plastic recirculation valve to an aluminium type recirculation valve. Forge make them and offer different springs and shims so you can tune it how you want. Why waste fuel/energy.
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Thread Starter
Registered User
Joined: Oct 2005
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From: Not here
OK so that would be this thing here.... right? the black cylinder with the hose coming out of the top??? Is there a way to clean this thing or should i just buy a new one. Are you guys pretty sure thats what is causing this???? Can there be anything else i need to check???
Thanks Guys
Thanks Guys
Rennlist Member
Joined: Apr 2007
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From: Beverly Hills, Mi.
That's it.
Here's the replacement I recommend: http://www.forgemotorsport.com/conte...duct=FMDVSPLTR
Here's the replacement I recommend: http://www.forgemotorsport.com/conte...duct=FMDVSPLTR
Race Car
Joined: Sep 2005
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From: England UK
Jerry, it could be a number of faults causing your problem, but this is certainly one of them. The other thing that could happen is for the diaphragm to come out of that Bosch recirc valve and ruin your turbo. I intend to get an aluminium recirc valve when I put my car back together, may run the Bosch one as it's brand new for 6 months or so but not for long term as I don't want to ruin my HFS.
Thread Starter
Registered User
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From: Not here
Ok thanks guys..... i am going to buy one and well see if that fixes it. Can someone explain to me "WHY" this would keep the rpms from falling as fast as they should, im having trouble visualzing how this works.
Race Car
Joined: Sep 2005
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From: England UK
Jerry, the small hose on the valve is connected below the throttle plate so air could be sucked in through this small hose if the valve allows it. If the valve was working correctly it wouldn't allow this.
Thinking about it, if you get the problem without boost you could test it by not building any boost & clamping this hose with some mole grips (I think you guys call them vice grips in the US of A
) and see if it feels better.
Don't clamp the pipe and get the turbo spooled though
Thinking about it, if you get the problem without boost you could test it by not building any boost & clamping this hose with some mole grips (I think you guys call them vice grips in the US of A
) and see if it feels better.Don't clamp the pipe and get the turbo spooled though
Rennlist Member
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From: Beverly Hills, Mi.
The Bosch valve has a diaphragm that a vacuum signal from the engine opens to allows the high pressure air that's trapped between the metering plate and the compressor to vent into the engine, bypassing the throttle plate. This slows the deceleration of the engine which burns unspent fuel and lowers emissions.
Anecdotal evidence suggests that the Bosch valve doesn't last long. The symptoms that you describe sound more like what I was experiencing with the first Forge recirculation valve that I tried.
Problem is that it slows shifting way down and while you are waiting to shift the turbo is slowing down all the time. When you are finally able to shift the turbo is no longer developing any boost.
Anecdotal evidence suggests that the Bosch valve doesn't last long. The symptoms that you describe sound more like what I was experiencing with the first Forge recirculation valve that I tried.
Problem is that it slows shifting way down and while you are waiting to shift the turbo is slowing down all the time. When you are finally able to shift the turbo is no longer developing any boost.