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Forge Cbv Flutter/compression Surge

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Two months ago and after some pulls with the WG line disconnected (to verify a boost issue) I immediately started to get a lot of flutter/compression surge when I left off my foot of the gas. During those pulls/tests I didn’t achieve too much of high boost (20psi max maybe) but I knew immediately something was not ok.

I checked all the vaccum lines and replaced the line that goes from the intake mani to the CBV. No changes, same flutter etc.

At that point I was almost sure my stock CBV diagram was dead and I confirmed that when I took it out for inspection. It had a small hole on it.

So I made some research (in the forum and other sources) and I concluded the best way would be to replace the CBV with the Forge one (instead of the IPD one or the stock one) and so I did it.

I started with the yellow spring (the 2nd weakest one) and the flutter/compression surge was reduced significantly however I was still getting a considerable level of fluttering/compression surge at low/medium boost levels when I left off the gas (sometimes even when in vaccum if I recall correctly).

Then I replaced the spring with the green one (weakest one) and 1 shim and once again the flutter/compression surge was reduced a bit but it was not completely gone!

I can try to put only the green spring without the shim but I suspect that will not make the flutter/compression surge to go away completely.

Has anyone experienced the same flutter/compression surge with the forge CBV, even with the green spring fitted on it?

Last resort could be try to put the stock spring (which I think I still have) in the CBV housing and see what it does.


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