Compressor surge

[promisedland]

Hello all, I want to pick your smarts and learn more about compressor surge,
While towing a 15000#~~ trailer i was in 3rd TC locked,[48re with 33" tires] up a grade about 45-50 mph so around 2000rpms, i was at 60-70% throttle position and doing fine. Then, 'because i could' i opened her up more. at close to wot i heard what i'm told is comp. surge. Like an aggressive rev limiter. Clearly from the turbo.
I was running my 350~~rwhp tow tune, my boost was 26~# I have run at wot when towing before, maybe at higher rpms though... max boost that i have seen other times is 32~#.

 

[EDankievitch]

What can happen is the Compressor wheel can cavatate loose it's bite when it does you'll get a barking sound as the charge air blow back through the turbo. Too much boost pressure, un smooth air flow into the turbo or just over speeding the turbo all can cause this to happen. It will destroy the turbo if you continue to let it happen. I've witnessed this happening on a two stroke 645 EMD diesel. It'll scare the hell out of you when you see the air filters come out of the housing and it barks.

 

[Tuesdak]

You do have a turbo that is known to surge and bark. This sounds like it would be surge. Absolutely you don't want whatever condition to keep going on due to clear indications from your truck it don't like it. Did the condition reoccur in a lower gear at higher RPM with the TCC locked?

Couple thoughts. Running out of fuel or air perhaps from filters, lugging the engine/turbo combo, and slipping the TCC or transmission.

Slight differences between our setups being I have a cam, NV5600 that would be like the TCC locked, and a stage 3 that's supposed to be worse with surge/bark.

From my experience going "large turbo" I find that they like higher RPM's. The BB Garrett has surprised me by spooling up at lower RPM's than antique V8's hot rod diesels I mess around with. (It lights off below 2000 RPM!? Yay!) Regardless running higher RPM may be the easy cure as it gives the turbo more airflow to work with. IMO the cam I have made a world of difference as I have not yet surged/barked the turbo even shifting - cutting full power. I am also rev happy and still have to get used to the lower RPM grunt of the 5.9. So I may be at a higher RPM anyway. I am not clear why you can go WOT and have the auto stay in gear with the TCC locked. Most auto's I have would do their best to pin the tach at redline when my foot hits the pan.

When I attempted to lug my V8 with the TCC locked at 35 MPH (45 MPH is where GM would lock it up) I found that I could slip it badly on a grade and then the ECM would unlock the TCC and then lock it back up - made quite the hunting for a gear feel as it did this 5 times in 10 sec... A better aftermarket converter is able to hold. Just saying trans/TCC slip is something you may have ruled out. FWIW To keep the smoke down from a larger turbo on the hot rod GM I also reprogrammed the shift points to downshift sooner under load.

Someone with more turbo expertise than I can explain how you flirt with surge on the compressor map:

 

[promisedland]

Thanks, and I tend to lug instead of Rev when I tow.
I talked to turbo resource about it & was told to run higher rpms.
Only happened once, I don't want to hear it again!
Fuel & air should be good. Filter minder was fine.

Someday I'll have a cam

 

[cerberusiam]

That is not enough boost to surge or bark the turbo without a shift point. The HE351 is pretty solid with good exhaust flow so as long as that was steady should be no problem. Not sure what you mean by rev limiter but the only time have heard anything like that is when the rail drained. The other thing is you may have a problem with the WG actuator being set to light id that is all the boost you made. That should be at 35-37 psi for best effect.

 

[Bob4x4]

That is not enough boost to surge or bark the turbo without a shift point. The HE351 is pretty solid with good exhaust flow so as long as that was steady should be no problem. Not sure what you mean by rev limiter but the only time have heard anything like that is when the rail drained. The other thing is you may have a problem with the WG actuator being set to light id that is all the boost you made. That should be at 35-37 psi for best effect.

He is not running an he351

 

[Bob4x4]

The bigger turbos are fun when not towing,with paddle shift capabilities they would be more user friendly.I tried a big turbo on my 05 just not worth it,I tow enough to pass up the big fun turbo to be able to tow without having to do high rpm lifestyle

 

[promisedland]

62-64 garrett gt3782r turbo with a .89 AR.
I ment that it sounded like a Rev limiter...

 

[cerberusiam]

Well, 88 mm compressor on a .89 AR ball bearing turbo should not do that, especially not at that much throttle opening. Compressor surge is a lack of exhaust flow to support the boost. 26 psi is not much on a turbo that will support 40 psi and that much throttle opening you would see surge BEFORE fuel was increased. Off hand I would say there is glitch in the fueling map that either caused the surge or it was popping out the exhaust. The observed numbers just don't seem to add up to compressor surge.

 

[AH64ID]

I've got over 60K miles on the same turbo at weights up to 28Klbs GCW and have never had mine surge.


Was the boost fluctuating when you heard the popping?

Did the EGT's spike?

The Stage 2 has a 61.4x82mm 6 blade wheel.


The Stage 3's with the 63.5x88.25mm compressor and .99A/R exhaust are known to surge, but the stage 2's are not. As long as it's not accidentally a Stage 3 it shouldn't surge.

 

[promisedland]

I measured the compressor wheel inducer when i got the turbo, and Jay at Turbo Resource said its a stage2.
I was told it WAS [i bought it used] a stage1 that had been upgrade to stage2. So its likely a stage2.

When it surged i immediately let off so i didnt see any fuctuation.

I will be hauling another load tue eve, same weight, same hill. I'll see if i can get a log.

One thing comes to mind, I have my wastegate disconnected,
I gained 4~ # of boost empty WOT with the street tune and i just didnt get around to checking my drive psi #ers. Why?? Because i just want to know! With the wastegate connected i see 30# of boost.

For the record; what size turbine does the stage3 have?

 

[promisedland]

duplicate post

 

[AH64ID]

IIRC all 3 stages have the same turbine wheel.

Why keep the WG disconnected?

I'm actually surprised you see more boost with the Stage 2 than your modded HE351. The Stage 2 should flow more air with less boost, at least it does in my experience as well as others I have spoken to.

 

[promisedland]

I wanted to see how the boost/drive ratio was affected. I saw higher egts while towing last summer, so i wondered if this would push more air...
Egts have been lower, but the weather is cooler as well.

Prob ill connect it again though once i get my drive checked.

I really didnt think my gate was opening before, but it seems is was. i had checked my gate with a air gauge when installing. 40psi it was opening. I have wondered how gate settings are affected with drive pushing against the puck?

 

[cerberusiam]

WG connected\disconnected should not ever affect boost or EGT's if it set high enough. If it is actually set a 40 psi you should see no difference. Boost will not drop until either the compressor starts stalling or the WG opens.

How are you reading boost, electronic or an analog gauge? If it is electronic I wonder if the ECM is just smoothing the spikes you would see when either it surges or the WG opens. The description does not sound like surge, rather, more like the WG was opening\closing really fast or it was popping out the exhaust because of weird rpm\fueling\boost combination. If it was really fast staccato burst, like a machine gun for lack of a better comparison, I would guess the WG is blowing open. Might try tightening the adjustment and loading a heavier tune to see if you can replicate the situation at higher boost conditions.

 

[promisedland]

Reading boost via my Touch.
The air tube to the waste-gate is completely disconnected at this time...
The "surge" as I'm calling it, wasn't that 'fast' , slower. Much like the Rev limiter on my 99 olds silhouette Maybe 2~3 times a second.

 

[AH64ID]

That could also be a small boost leak.

 

[Bob4x4]

Have you monitored fuel psi while under load?

 

[cerberusiam]

Disconnected doesn't really matter as the actuator spring should hold it closed until it blows open or the actuator opens it.
Did the truck accelerate and rpms rise when you went WOT with it? At 2000 rpms even with 33" tires you should have good exhaust flow to spin 26 lbs of boost out of the turbo. Surge is going to happen when the exhaust flow cannot support the boost the compressor is developing, almost always defuel will be the direct cause of that either with a lack of fuel or a shift point that drops rpm a LOT. Just going WOT throttle should add more fuel which will boost exhaust flow not drop it unless when you went WOT the ECM did not like something or you drained the rail. The 03-04 trucks had real issue with WOT and fueling curves but not seen much problem with the 600 engines. Try and see if you replicate to track boost and RP to see if you have something dropping out in just the right conditions. John may have to tweak that tune a bit for you.

 

[promisedland]

I have not checked fuel psi, I will check this on tue eve when i haul another load.

I was going uphill loaded 3rd TC locked, As i recall the boost climbed a lil and the eng started building more power till it ''surged'' & i left off.
I then kept the throttle lower till i crested the hill and all seemed well. The trans stayed in 3rd TC locked.

I will try to log the next run! Thanks guys! :thumbup: