Engine bogging down with any swift throttle change

[Rotary Evolution]

the compressor outlet doesn't show vacuum, only boost positive pressure and not the same pressure at the manifold leading into the engine so it isn't a good spot for the pressure sensor line. the sensor needs to see engine vacuum and pressure that the engine sees to accurately advance timing.

move the line to either the top or bottom front port just past the throttle body off those 3. the center port iirc goes to a port before the throttle body so isn't a good MAP source.

i highly doubt this is your problem but it is a problem that should still be addressed.

[JustJeff]

Originally Posted by Rotary Evolution

the compressor outlet doesn't show vacuum, only boost positive pressure and not the same pressure at the manifold leading into the engine so it isn't a good spot for the pressure sensor line. the sensor needs to see engine vacuum and pressure that the engine sees to accurately advance timing.

move the line to either the top or bottom front port just past the throttle body off those 3. the center port iirc goes to a port before the throttle body so isn't a good MAP source.

i highly doubt this is your problem but it is a problem that should still be addressed.

Yeah, I was thinking about just that while diving home for dinner. I need to get more vacuum hose to make any changes so that will have to wait till tomorrow.

Whats your opinion of using the same nipple that's under the BAC for Pressure Sensor, BOV, and aftermarket boost gauge?

Also I tested my father's S5 N/A TPS resistances out of a growing curiousity... and found the same areas of deadspots on the narrow range where the multitester goes into OL and then picks back up for one single reading and holds. I seem to see this with every TPS I've tested.

[RETed]

Originally Posted by JustJeff

Whats your opinion of using the same nipple that's under the BAC for Pressure Sensor, BOV, and aftermarket boost gauge?

#1 priority is the BOV valve.
Always use a dedicated vacuum line for the BOV.
Do NOT "T" this line, if possible.
If the BOV doesn't get a strong enough vacuum to trigger, it fails to open efficiently.
If the BOV doesn't open properly, it'll kill the turbo due to compressor surge.
I tend to use the fitting under the BAC valve for the BOV, since we're only concerned with vacuum.
The BOV opens due to a vacuum signal - i.e. when you lift off the throttle under high RPM's.
Pulsations under other conditions doesn't mean anything to the BOV; it stays closed under anything close to "0" or positive boost pressure.
This fitting also is usually the closest to the BOV in most installs (and with the stock unit), so having a short vacuum hose helps here.

Everything else doesn't really matter.
Unless you're worried about being off a few psi, they are not important.
Stock ECU retards ignition timing under positive boost - it does not affect fuel delivery.
The stock ECU ignition maps are very conservative, does being off a few degrees won't hurt anything.
Most aftermarket boost gauges aren't accurate enough for you to worry about being off a few degrees; even if the gauge is off, it's just a display.

Killing your turbo is a different matter...


-Ted