SBD turbo surge??

[shif7i7down]

So should i remove the turbo and readjust the Wastegate preload along with the bov and spring r&r just to rule out Any possibilities?
What else can i do to find out the root cause?

Also want to add that it doesn't do it while in neutral or in any other gear lower then 4th gear. I can go wot all the way to redline in 1st 2nd and 3rd without the issue.

Also noticed that it happens at 6.5krpm in 4th gear, 4.5krpm in 5th gear and 3.5krpm in 6th gear.
So it should have something to do with load right?

[Fizz]

I've read about this before on another forum, where the guy experienced a similar issue. I've found a video which I believe shows the exact same symptom:

[ame="http://www.youtube.com/watch?v=nCj6Spwl1CU"]True Compressor Surge - YouTube[/ame]


According to Garrett turbos, compressor surge is:

The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side. Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself. Common conditions that result in compressor surge on turbocharger gasoline engines are:

-A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body
-The outlet plumbing for the bypass valve is too small or restrictive
-The turbo is too big for the application

My advice is that you shouldn't touch or adjust anything on your car if you're not 110% certain what you're doing. Take it to an expert immediately.

[mike the snake]

I would leave things as-is and take it to an expert. That is not a normal sound.

[Poodles]

The only bad sound is that terrible racket I hear after you let off that gas which means it's not related to the turbo (no load = no boost)


Seems speed related to the chassis, not the engine, so maybe one of the undershields is loose?

[shif7i7down]

Originally Posted by Poodles

The only bad sound is that terrible racket I hear after you let off that gas which means it's not related to the turbo (no load = no boost)


Seems speed related to the chassis, not the engine, so maybe one of the undershields is loose?

That's a possibility but what's weird is that it happens at the same 6.5krpm in 4th gear, 4.5krpm in 5th gear and 3.5krpm~ish on 6th gear.

[Poodles]

Originally Posted by shif7i7down

That's a possibility but what's weird is that it happens at the same 6.5krpm in 4th gear, 4.5krpm in 5th gear and 3.5krpm~ish on 6th gear.

IIRC, that's all essentially the same speed.


Push the clutch in and coast, if the noise is still there, it's nothing to do with the engine.

[shif7i7down]

I'll test that out

[woode]

Originally Posted by Poodles

IIRC, that's all essentially the same speed.


Push the clutch in and coast, if the noise is still there, it's nothing to do with the engine.

+1

[MAPerformance]

Sounds like one of the plastic shrouds under the car is catching air and dragging onto the ground. (number 3 in the pic) Happened to me when I forgot to install one of the bolts under the front of the drivers door. Only made noise above 55 MPH in my case.

Originally Posted by shif7i7down

here's a video of what i'm talking about.. sounds weird

[King Tut]

Can you take a picture of where exactly you tapped into the brake booster line for the vacuum/boost source running to your BOV? Try removing and plugging that line to the BOV and drive the car to see if it makes any difference.

[shif7i7down]

I'll take a picture when i get home from school, and post it up,

as far as the plastic under the car, i'll still have 1,2 and 4. i didn't install 3. but it could be the peice labled 4 that could also be draging, i'll check it tomorrow when there's daylight.

One thing that did bother me a bit is that the 50mm tail bov came with an extra spring. Is the extra spring and the one pre-installed in the bov the same pressure spring?

[Mike&Ike]

Originally Posted by shif7i7down

I'll take a picture when i get home from school, and post it up,

as far as the plastic under the car, i'll still have 1,2 and 4. i didn't install 3. but it could be the peice labled 4 that could also be draging, i'll check it tomorrow when there's daylight.

One thing that did bother me a bit is that the 50mm tail bov came with an extra spring. Is the extra spring and the one pre-installed in the bov the same pressure spring?

You are supposed to replace the spring that is in the BOV with the extra one that it came with.

[Fizz]

Originally Posted by shif7i7down

One thing that did bother me a bit is that the 50mm tail bov came with an extra spring. Is the extra spring and the one pre-installed in the bov the same pressure spring?

Umm....you didn't just place both springs together in the bov did you (if that's even physically possible lol)?

[Boofneenee]

Does that sound occur at that rpm in every gear?