compressor surge?

[topfuel]

What is compressor surge? I dont understand this term.
And also, what does a compressor map tell you?

Still learning...

 

[JDEstill]

Essentially a compressor has a minimum required flow for stable operation. If you get a turbo that is too big, and the engine can't flow the minimum amount of air for that turbo, the compressor becomes unstable, and the flow it provides jumps up and down and all over, making the car run a bit jerky.

For an explanation of compressor maps, there are several sites on the internet that explain them. One is here:
http://www.gnttype.org/techarea/turbo/turboflow.html

John

 

[Freedster]

Good general explanation here:

http://www.cleandryair.com/surge.htm

It happens in turbo cars when the throttle slams shut and a wave of pressurized air backs up to the compressor and tries to make it spin backwards. It can destroy the turbo. That's why most turbo cars built these days have blow-off valves.

- Freed

 

[JDEstill]

Freed, surge is a lot more than just what happens when the throttle is closed after going WOT. If the compressor is mismatched to the engine it is feeding, you can have surge at part throttle. There's plenty of guys running monster turbos that surge when they are at part throttle, trying to hold 10 psi or so. If their engine at 10 psi boost can't take the minimum amount of air their turbo needs to flow, surge is the result.

John

 

[topfuel]

Wow... I always sucked at math, it was the hardest subject for me to grasp in school.
But after reading both of those articles (twice), I understand compressor surge now, and I feel a bit smarter too...

Thanks guys
Mike

 

[Freedster]

Originally posted by JDEstill
Freed, surge is a lot more than just what happens when the throttle is closed after going WOT. If the compressor is mismatched to the engine it is feeding, you can have surge at part throttle. There's plenty of guys running monster turbos that surge when they are at part throttle, trying to hold 10 psi or so. If their engine at 10 psi boost can't take the minimum amount of air their turbo needs to flow, surge is the result.

John

Makes sense. Same concept, different conditions. The turbo is pushing more air than the engine can take in both cases.

Not a condition I had thought of, but one that could easily happen. Good call.

- Freed

 

[TURBOV6]

Can this surge really damage the turbo?

My 44 does this pretty often when on part throttle on the freeway and starts doing it like 10+ psi. This only started when the V4 was put in. I have a BOV and tried to losen the spring and the surge is still there.