Turbo Compressor Surge?

[JP87GN]

has anyone exerienced it and is there a fix? I recently installed a CAS V4 and Razors PAC alky kit and now I get a surge at about 15# of boost.

 

[TurboSlacker]

Here's a bunch of notes I gathered on this subject previously:

Compressor surge (or slam), its caused like someone said earlier, throttle body partially open but the turbo is trying to push more air thru than the engine can handle so the solonoid pulls boost and everything catches up with itself, and repeat....mine does it 3-5 times a second at part throttle, one thing that i have heard that can fix it possibly is electronic boost controllers but i dont know that for sure, for anyone who needs/wants more info or a better explanation call john craig at limit engineering, he will explain it to you, and btw IT IS VERY COMMON ON TE44'S like the one i have. Sounds to me like the rod on the waste gate needs to be lengthened. If you are running 25 psi by adjusting the rod, there is not enough(rod length) to open it enough when there is soo much extra capacity at low boost. Finally decided to try another MAF just for nothing better to do. Walla, problem solved. My LS1 MAF had gone belly up, and the symptoms I suffered were exactly as yours. If the wastegate rod is set at 25 psi, the wastegate should be welded shut during this whole deal. Trying to hold 8-10 psi with your foot is regulating boost on the compressor side and has nothing to do with the wastegate (turbine side). Trying to regulate turbo boost on the compressor side will cause unsteady intake flow, so the MAF readings will be whacked. If the MAF is malfunctioning, the readings will be even more whacked. This is very common. It happened to me ALOT when I had the TE44 and a FMIC. Once I went to a PT54 this problem went away. It is simply compressor surge. Probably no real need to look any further the car is not designed to see that kind of boost when the throttle blade is just cracked (cruise conditions.) and the larger the intercooler volume, the more it exacerbates the problem (more area to compress air). How tight is your wastegate rod? If you shortened it significantly it will surge/flutter at part throttle. My TA49 does this as do most larger turbos. Mine does it more the shorter the rod is. That's compressor surge and throttle body flutter. Part throttle with 5-15 psi of boost is right where this happens. The throttle blade is not designed to be partially closed while the turbo is making boost and the compressor is not designed to pump air against a closed throttle blade. Yours sounds pretty mild. With a boost controller, you can regulate the boost with the wastegate as the turbo gods intented. Us guys that set our boost to 23 psi to race, then drive home from the track, regulating our boost with the throttle foot can get surges bad enough to shake us out of the car. The part throttle is very common with the larger turbos and front mounts. You will have to tune for the top end first. The light throttle is a problem. I did not have much luck with a bov valve. It seemed to help the problem when lifting off the gas a little but made it worse down around zero-1# of boost when easing up an entry route and holding light throttle...sometimes it just goes into never-never land and starts coughing and refusing to take gas until I lift and then give it substantial pedal. Too rich will add to the flutter at part throttle, I have noticed. When backing out of the throttle, it helps to lift completely rather than easing back and catching it part way. These larger turbos want to make boost easily and when the tb butterfly is only cracked a little...it can't go anywhere and kicks back against the compressor.

 

[JP87GN]

Thanks Dan, That helps explain some things.

 

[Ormand]

The boost controll/waste gate is not really the problem. If you look at a turbo compressor "map", the left side of the diagram moves up and to the right. As flow increases, to the right, boost also increases. Surge occurs when you get too big a compressor. Your engine is only 231 cubic inches, and if you are not pulling enough air to get the compressor over to the right, past that first line in the "map", then the compressor is in an unstable condition, and will "cycle" from higher flow to higher boost. (May be a "bistable", rather than unstable.) If you lower boost just a little, the problem may go away. Or you can just ignore it. Check the section in "Maximum Boost" by Corky Bell, on turbo sizing.

 

[UNGN]

Originally posted by Ormand
The boost controll/waste gate is not really the problem. If you look at a turbo compressor "map", the left side of the diagram moves up and to the right. As flow increases, to the right, boost also increases. Surge occurs when you get too big a compressor. Your engine is only 231 cubic inches, and if you are not pulling enough air to get the compressor over to the right, past that first line in the "map", then the compressor is in an unstable condition, and will "cycle" from higher flow to higher boost. (May be a "bistable", rather than unstable.) If you lower boost just a little, the problem may go away. Or you can just ignore it. Check the section in "Maximum Boost" by Corky Bell, on turbo sizing.

That's true, but with a TA48, I'm pretty sure the compressor isn't too big.

This is more likely a part throttle flutter caused by trying to regulate the boost with the throttle instead of with the wastegate.


Moral to the story:
If you want to accellerate at 15 psi, set your wastegate at 15 psi. Don't try to use your foot to get 15 psi, and the "surge" will go away.

 

[Roc87]

Mine does this at WOT also, never did it with the 51 (part throttle maybe but not WOT) now with my 61, about half track the car falls on it face because of compressor surge (Using the RJC controller). Never did it on the street because I never did a wide open run past 100mph .

 

[turbo2nr]

That is the main reason behind the BOV. Companys install in turbo cars to improve drivability, Not to make cool sound effects.

Get a BOV. It will smooth your car right out.

 

[JP87GN]

Originally posted by turbo2nr
That is the main reason behind the BOV. Companys install in turbo cars to improve drivability, Not to make cool sound effects.

Get a BOV. It will smooth your car right out.

Where inline do most suggest to put the BOV?

 

[turbo2nr]

Pipe going to Throttle Body. Little welding is needed.

 

[turbobob924]

Flutter and MAF signal with TE44

Bob Baily has suggested that perhaps my MAF signal issue is really turbo surge/flutter at partial throttle?

Any guys out there still with a TE44 and having surge issues??

Would a bigger TB (57 or 62) help?

 

[GNVYUS 1]

A BOV will not help surging at WOT. It's being slammed shut by the boost signal from the turbo and the springs pressure. It will only open when those two are less then the pressure inside the pipe, which only happens when you are not in boost.

Are you getting it at WOT or part throttle?? Sounds like part throttle to me.

 

[TURBOELKY]

I get that flutter, but only on the highway at 56 mph, part throttle. If I put more foot to it, or let off and re-accelerate, it goes away. So basically, " go fast, or slow down biachhh",,, thats what my car tells me, sorry about that thats with a t 66, and external gate off header.
at full throttle, no problems throughout the torque curve, at least to the mph where i'm scared to go any faster

when I first had this "surge", it felt like my headgasket did before it got blown to peices my buddy told me to floor it, and it disappeared....

 

[UNGN]

If you didn't see the posts, Bruce Plecan recommended putting a 3" "Tornado" gas saver right in front of the compressor housing to smooth out the flow through the compressor.

It won't help WOT performance (or get you better gas mileage) but it may get rid of part throttle surge.

 

[87GNSteve]

If you didn't see the posts, Bruce Plecan recommended putting a 3" "Tornado" gas saver right in front of the compressor housing to smooth out the flow through the compressor.

It won't help WOT performance (or get you better gas mileage) but it may get rid of part throttle surge.

Worked for me!
Do it.