LSA blow off valve sound

[Jarvo505]

Hi, recently purchased a VF GTS and have noticed under hard acceleration around 5,000rpm there is a choof noise that sounds like a blow off valve.

Is this normal or possibly a bypass valve issue?

Thanks.

 

[Deuce]

I cannot say I know the LSA well enough, but it should have a bypass valve which will open when you are off the throttle.
Possibly after you lift after a squirt on the gas, manifold pressure may release backwards through the bypass towards the airbox.

But as I said, I don't know an LSA so cannot confirm.

 

[Jarvo505]

Turns out this seems to be the bi-modal exhaust valve closing, then opening again at higher rpm.

 

[Deuce]

Turns out this seems to be the bi-modal exhaust valve closing, then opening again at higher rpm.

Good to know. Cheers.

 

[Jarvo505]

Just removed the bi-modal valve relay and went for a squirt. No more choof noise, so this confirms 100% that is it!