Help me with my vacuum problem please!

[blackrosenova40]

A couple of days ago I installed a used 14b turbo into my car because my old one was shot. It boosts great and holds perfectly to 14 psi. Idle vaccum reads 19-20 inches and decelaration vacuum usually read 24. Just today as I left school I noticed it was pulling less vacuum during decelarating.

For example if I brought the engine up to 6000 and let go it will not pull more than 20!
But if I bring it down to say 2000 and then decelarate it will pull pretty close to 24.

Anybody have any clue whats going on? My idle is fine and im running a maft pro using a Map sensor and ait sensor.

My guess is theres a leak from the intake manifold (vaccum lines coming from the intake or throttle body gasket, or intake gasket or fuel injector seals). Or my sencond guess is an exhaust restriction.

 

[romeen]

Do a boost leak test. It will identify any vacuum leaks. If you had an exhaust restriction severe enough to affect intake vacuum then I would think that your car would barely even be running.

 

[blackrosenova40]

What size is the inlet of our turbo's?

 

[romeen]

The o.d. of the compressor inlet on a 16G is 58mm (2.28"). The 14b has a slightly smaller inlet although I forget the exact o.d. But a 2" coupler should work fine for the tester if that's what you're getting at.

 

[Dream On]

Yeah, you can always use one a little bigger. I use the stock intake ring that goes around the turbo in my boost leak tester to fill the gap.