Compressor Surge

[JohnDodge]

I am getting some turbo bark and I am trying to figure out how to resolve the issue. I have the 48RE transmission and most times under partial throttle climbing an on ramp, the turbo barks once the TC locks up. It doesn't do it, if I put the hammer down unless I jump out of the pedal quick (which I try not to do).



I can't really understand why it surges under the load of the truck alone, at partial throttle. Is the boost elbow causing it? Is the wastegate not operating freely? Is there anything I can do to stop it from surging at low load partial throttle?



I know the turbo has some side to side play. I was going to measure the play this weekend to see how soon the turbo will need to be replaced. I don't think there is much in and out play. The truck only has 160,000 miles.

 

[Prairie Dog]

This doesn't help much but bone stock, my 03 barks the turbo if I gear down (man trans) under heavy throttle/load on a hill. I learned the only way to keep it from happening was to set the cruise and then when I want to shift down, I push the clutch in (cruise still on). The eng will flare slightly before dropping the cruise and keep the bark from happening.

 

[cerberusiam]

Is the boost elbow causing it?

Yep, thats exactly what is causing it along with the extra fuel from the EJ\A. The results of cranking the boost up and adding fuel with a small exhaust housing manifests in a tendency to bark worse. The rpm drop on lockup defuels so much the exhaust flow can't support what the comp wheel is pulling for air and you get a compressor stall until boost drops to a supportable range.



At WOT you don't get the defuel because the ECU is playing catch up with the fueling so there is no flow drop to cause the stall. You just have to learn to drive around it as much as possible. The boxes that don't allow adjustment of the low\no boost fueling seem to be worse because of the lack of fuel at lower throttle opening. They still bark but not as often or as bad.

 

[JohnDodge]

I was considering pulling the turbo off this weekend and making sure the wastegate was operating properly. I was also just gonna do a quick verification of the seals and overall shaft play.

What is different about the boost elbow? Could I replace it with a standard farm store adapter with a full flow opening? I assume the boost elbow just restricts flow to the wastegate.

 

[cerberusiam]

The fact th eturbo is barking is a pretty good indication its all right. You can check to make sure your end play and side play is still good to be sure.



If you replace the boost elbow with a full flow fitting then you loose the extra boost and all the EJ\A will do is melt things. The boost elbow is restricting the boost signal the the WG to allow the turbo to build more boost. IIRC, somewhere around 20-22 psi is stock boost. With the extra fuel you have you should be maxing it out around 30-32 psi for best effect.



The boost elbow should have a set screw on it to allow you to adjust max boost. If you back the screw out it lets more boost to the WG actuator and will open the WG sooner. The WG doesn't open from too much boost in the system or defueling or anything other than the signal coming from the elbow. It could be sticky and not opening correctly but you would see that on your boost gauge at WOT.