Technical > Turbochargers

KO3 turbo - no boost. Why?

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runforrestrun:
So I'm helping RyanC get his engine started today - fully rebuilt 1341cc g40.

It's running but there is no boost. The actuator doesn't move, and the boost gauge is just reporting vacuum.

We are both tired so any suggestions welcome about what silly things it could be.

Turbo is a brand new refurbished item from CR turbos.

The dump valve is a used item made by forge motorsport. We can't feel any air escaping from it under any condition.

Cheers in advance

Jim and Ryan

GR40:
State of the blow off? Also turbos only boost under load! If you are reving the engine in neutral you ll see no boost!

runforrestrun:


Is that so? Why is that - we expected to see some boost when revving the engine even in neutral.

The dump valve looks in brand new condition and we were told it was a working item

GR40:
I ll try and explain it as simply as possible without being 100% right but making as much sense as possible. The engine can flow more air though it than the turbo can push when there is no load. You need the resistance from the road to slow down the engine revving to it's limiter in order to create pressure in the manifold.

runforrestrun:
That makes sense! I see what you are saying now.

We found the problem - the adjustable dump valve was set wrong and was open all the time.

It works now :) :)

G smiles for miles

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