Check valve as boost control

[Guest Anonymous]

I have a VNT turbo making too much boost so I need an external waste gate. Got me thinking (always dangerous) why not use the blow off valve or a check valve to limit boost. That is to "waste" the air on the compressor side as opposed to the exhaust side. Is there a reason this is never done? At least I have never seen it done. Anyone have any insite?

Thanks

[Cody 82 ZXT]

If you did this it would be compressing to much air which would lead to a air intake charge that would be to hot. Not a great idea. It wuld work but, is not a performance option.

 

I would find out why you are making to much boost with a VNT turbo. Aren't they supposed to have an internal regulator to control the vanes in the turbine housing? Also is this on a L-28? I thought they didn't make a VNT that was big enough for the Z engines?

[Guest Anonymous]

That make sence. Yes the VNT has vanes to control adjust the A/R . What I have read is that the original vehicles these turbos were on had a very restrictive exhaust system that limited boost. With my 2.5 pipe the thing is up to 20psi in nothing flat. Very interesting turbo virtually no lag. Its on an L-20

[SleeperZ]

The VATN controller should be able to limit boost almost completely with any reasonably sized motor. It would not be particularly difficult to add an external wastegate though, if you can verify the controller is working properly. But it sounds to me like your controller has a problem with opening the vanes enough to limit the boost. Dumping intake is not the right solution to control boost, but you could recirculate it with a weak compressor bypass valve.

[TimZ]

The VATN controller should be able to limit boost almost completely with any reasonably sized motor.

 

Not necessarily - the VATNs that I have seen are generally intended for moderate power levels (<300hp) on smaller displacement motors (<~2 liters). They have a range of adjustment, but if the displacement is still too large, they can be overpowered. From what I have seen, the L-series in any semi-serious state of tune should be big enough to overpower the VATN.

 

If you recall their use in the Maximum Boost book, two of the larger VATNs were required on the turbo NSX project, and that was just to get it to a little under 400hp at the flywheel.

 

Oops - just noticed that the post was referring to an L-20, which should be suitably small, although it is still possible that you are on the borderline. It would be a good idea to check the function of the vanes and their control mechanism.

 

For a 2.8 I still think it would be too small, though.