Compressor Surge Issues
 

So, just to give everyone a visual on my setup...

The initial setup was a greddy turbo kit, with a synapse blow off valve, and a vacuum block.

The Synapse BOV has three ports, two on the back, which are connected to a boost/vacuum source (the vacuum block) and the one on the side is a boost only source, which was directly connected to the actuator.

The car boosted fine, to 8psi or so, and vacuum was anywhere from 15-30psi (negative) depending on throttle position, speed, etc, according to my autometer boost gauge. During boost, there was not an ounce of surge. The BOV, like advertised, slammed shut.

Today, I installed my AEM trueboost boost controller, replacing my Autometer gauge. Now, the boost line from the gauge is connected to my vacuum block. The solenoid has three ports on it. One for the actuator (port 2) one for the vacuum block (port 3) and port 1 has no use, so I used the provided AEM breather on it. Now, for the boost only nipple on the BOV, I T'd into the line between the solenoid and the actuator, trying to get the same input as before the boost controller. The "boost controller" part of the gauge is OFF until I get it tuned. I am using it just as a gauge for now.

Now that you have the scenario, here are the problems....

1)I assume the gauge from factory is set for PSI, not BAR or anything else. The gauge reads a MAX of -11 for vacuum, usually 10. My autometer on the highway in 6th@55 with very light throttle would read damn near 30. The trueboost reads -11.

2)I have compressor surge everywhere, even when I am not boosting at all. If I rev to 3-4K or so, and let of the trottle, you get the squirrel mincer sound.

Hopefully, I explained everything in detail, and someone can provide some insight. I appreciate any help into seeing what I did wrong. Thanks again guys.

WOW you saw -30 vacuum before in highway crusing? Thats weird..
The most I see is -24 and thats around 4.5K with my foot fully off the gas. With my foot on the gas at all (even just trying to keep speed) the lowest my vacuum is maybe -15.


What is this "provided AEM breather"? You shouldn't have a breather in a vacuum system. :thinker:

[QUOTE=TRBOKEV,Apr 21 2008, 02:08 PM] WOW you saw -30 vacuum before in highway crusing?

OK I see, its just for the boost solenoid.

My greddy EBC only reads a max of -9.9psi but my apexi analog gauge reads as low as ~-100 Kpa or approximatly -15psi. I think it just might be the design of electronic boost controllers (can't read high vacuum)


Is you car boosting normally aside from the compressor surge?

Your AEM is probably reading vacuum in PSI. -11 psi is about -20 in/hg.

It sounds to me like the BOV is not seeing any vacuum at all to open.

You need to get the boost only signal to the BOV tee'd in between the compressor housing and the solenoid.

There should be no vacuum going to the solenoid at all. Only a boost-only source. It also sounds like you've got the vac block, plumbed to the solenoid's normally open side of the circuit.

Sounds like the Autometer shows vacuum in inches of mercury (in/Hg) and the AEM in gauge PSI.

The conversion is 1 PSI is approximately 2.04 inches of mercury. This explains the much higher readings on the Autometer.

[QUOTE=synapse,Apr 21 2008, 03:19 PM] Your AEM is probably reading vacuum in PSI.

Here is a little diagram I drew up at work...it's crude, but this is how my current setup looks...this is the one that has the surge problem. Before this, the side nipple on the BOV was directly connected to the red circle (actuator) and the boost solenoid was not there at all.


Before the boost controller with just an autometer gauge...everything was perfect.....no surge. (Note, in this picture, the truboost was actually an autometer gauge, I forgot to edit the picture)
http://i19.photobucket.com/albums/b1...oostBefore.jpg

After....surge everywhere.
http://i19.photobucket.com/albums/b1...BoostAfter.jpg

AEM's diagram on how it should be wired to an internally wastegated turbo...
http://i19.photobucket.com/albums/b1...EMSolenoid.jpg

The black ports on the vacuum block that have no lines on them are plugged off and not used.

How does the actuator get a boost signal to open the wastegate? Is it internally controlled? I ask this because in your first picture there is no source going to the actuator. I just want to understand it before I start throwing stuff out on the table.