Partial Throttle Compressor Surge?!?!?

[wannarace]

I saw this definition of Compressor Surge from a previous thread:

TurboByGarrett.com - FAQ's

"...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 "

When I lay into the throttle and build boost, no matter how much, in higher RPM's and boost stabilizes, I get a ch-ch-ch sound and causes the car to surge. This is a partial throttle pull. I get off the pedal completely, the BOV rips and problem goes away. No surge is ever experienced when throttle is completely lifted. Although I just may not be hearing it over the RFL dumping.

I'm wondering, I'm seeing constant boost by the gauge and said pressure keeps the BOV shut. Considering the compressor has built up way more pressure to keep that manifold constant. Would it seem that the partially closed throttle plate is just bouncing shockwaves back at the turbo?

The other issue is, when making WOT pulls, shifting at redline, It takes a second for the turbo to spool back up on the next gear. I do not hear any noise that would suggest surge but this should not be an issue for a HX-35 with BEP housing. Especially running a stock motor, which I am. The turbo starts spool up around 3200rpms reaching full boost about 3800.

I was thinking along the lines of improper BOV operation. I know it should react to differences in pressure between the manifold and intake piping but only seems to release under manifold vaccum. Could it just not be releasing fast enough. I am using a Turbo XS RFL with no shims.

Any input is appreciated!

Here's is a pic of my engine bay. I have since converted to a 38mm External WG setup.

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[JusMX141]

I believe the problem is stemming from your RFL. The 35's anti-surge cover hasn't been known to surge under any condition on anyone car.

 

[wannarace]

I agree. Maybe the ch-ch-ch I hear is the BOV releasing to keep boost constant. Kind of an open-close-open-close due to the spring pressure in the RFL instead of a smooth release of excess boost. The surge I get does resemble a boost leak. Still doesn't explain the stall I get between gears on a WOT run. Unless that spring pressure is allowing enough residual pressure to cause the compressor to stall?

 

[91tizzy]

sorry i dont have any input on this but I just had to comment on the state of your car and bay....very clean...nice job

 

[wannarace]

sorry i dont have any input on this but I just had to comment on the state of your car and bay....very clean...nice job

Thanks... input or comment... still appreciated!

 

[rarson]

It's not compressor surge, it's BOV flutter. The spring is shutting the BOV, which raises pressure, which causes the BOV to open. Lather, rinse, repeat, many times a second.

 

[wannarace]

It's not compressor surge, it's BOV flutter. The spring is shutting the BOV, which raises pressure, which causes the BOV to open. Lather, rinse, repeat, many times a second.

Sounds like the gremlin... Thanks.

I tried checking oil pressure to the turbo investigating the problem of stalling in between gears. I don't think I thought it through too well when hooking up the gauge so I'm not going to go by the "no oil pressure at WOT".

FYI: I used a 3/8" Tee at the turbo with 1/4" flare adapters on 2 sides for oil feed and gauge. I think I've got the "path of least resistance" working against me. I am feeding from the head. I'll put the tee higher up to have oil going through 3 1/4" flares, next chance I get, and will post back. Other than that I'm out of ideas on why my compressor stalls.

 

[1gentalonfan]

Does it go really rich when you shift? My brother bought his 1g with the stupid blow through gm maf setup already in it, had nothing but problems with sputtering, loss of power, only to replace the gm maf eventually(after tons of other work) and still have it do it. So i told him to hook the stock maf back in and power came back, no sputtering and it ran better than it ever has. afr's also stayed more consistent with the stock. When i was running a stock maf before i switched to speed density i had my bov vented and it would cause it to run rich between shifts and my turbo wouldnt spool for shit for about a second or 2 and then spool hard as #### again.