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Discussion Starter #1
Ok from what I always thought was that you sensed boost from the intake manifold (after throttle body). My thoughts on it were if you let off the throttle the pressure on the intake side would drop which would drop the pressure on the top of the wastegate allowing the pressure on the bottom to overcome spring pressure. Now that I'm to the point of plumbing my WG and after some looking around the net I'm seeing that I'm wrong. :huh:

What would the difference be to have the boost sensing line come from the top of the throttle body rather than directly from the outlet of the turbo as in the picture below? If there is a difference, is it due to distance from the turbo? And what does it affect...i.e. delayed response? The reason I'm asking is I have a perfect port to connect to rather than drilling/tapping the turbo housing.
 

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Well, I believe its far better to have the boost reference off the compressor housing because you never have trouble raising boost pressure, the problem is always lowering the pressure. The lowest pressure you could ever achieve is the wastegate spring alone coupled with any boost creep your setup may have. Now If your intercooled there is a pressure drop through the cooler and thus lower on the other side. If you were then sensing on the throttle body side your minimum pressure would be higher.

If your not intercooled, it shouldn't make any difference. Just make sure that your throttle body port doesn't see vacuum as previously stated.
 

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simplyvinyl said:
I understand that....but what about boost sending on the inlet of the throttle body?
If your boost controller is a one way deal then you would be fine... My boost controller is a simple deal but its also somewhat of a check valve.

I have my signal coming from the plenum. I heard its not as strong as at the compressor housing but it seems to work fine.

BTW all draw through systems see vacuum when the throttle is closed so not sure how or why capsoval just stated to make sure the t/b port does not see vacuum on a blow through system.
The wastegate is not made to see vacuum..the boost controller can stop the vacuum signal and only allow boost pressure signal to the wastegate.
 

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Discussion Starter #6
I guess I'll just drill and tap the turbo housing if the inter-cooler is going to affect it. But now what about the boost reference for the fuel regulator. I went and bought a check valve to ensure no vacuum for that line. Can I just tee off the same line for the wastegate and forget the check valve? There should be any vacuum problems at that point.
 

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Brian Sanders said:
If your boost controller is a one way deal then you would be fine... My boost controller is a simple deal but its also somewhat of a check valve.

I have my signal coming from the plenum. I heard its not as strong as at the compressor housing but it seems to work fine.

BTW all draw through systems see vacuum when the throttle is closed so not sure how or why capsoval just stated to make sure the t/b port does not see vacuum on a blow through system.
The wastegate is not made to see vacuum..the boost controller can stop the vacuum signal and only allow boost pressure signal to the wastegate.
I often forget that there is also the draw through style, closed minded cause i've always been blow through. The bottom side of the wastegate would still see vacuum on drawthrough with the diagram above, as would the blowthrough style if allowed to see vacuum. Guess that wouldn't really matter is would just pull the wastegate closed off throttle.
 

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simplyvinyl said:
I guess I'll just drill and tap the turbo housing if the inter-cooler is going to affect it. But now what about the boost reference for the fuel regulator. I went and bought a check valve to ensure no vacuum for that line. Can I just tee off the same line for the wastegate and forget the check valve? There should be any vacuum problems at that point.
On all my blowthrough setups I have allowed my FPR to see vacuum, just like in modern vehicles.
 
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