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If the compressor surges in the words true meaning and it was working normally at sea level, then you're in the situation where the pressure ratio is too high now at altitude, but airmass flow is too low for the comprssor = it surges.
If we look at the comprssor map, you'll see that the flow needs to pretty high in order to run high boost (pressure ratio) with out surging. The red circle indicates the possible are where the compressor can go over the surge limit.
For instance if we look at my car it does about 246g/s ~31.5lb/min of airmass flow at 5500rpm.
Now if your car runs at some what at this level you'll be very near the surge limit when running at altitude where pressure ratio is higher. With out measuring it is hard to say what the real pressure ratio in your car is, but assuming boost+ 0.1-0.2bar it cant be too far off. There for your pressure ratio is around 2.7-3.0.
What can you do?
1.Make the engine breath better = airmass flow will increase with the same level of boost = point on the map moves to the right, ie. further away from the surge limit. These changes would be modifications to head and cams.
The stock head with in the stock cam is not the best alternative in terms of flow when we speak of +350Chp engines and it will start to act as a bottle neck.
2. remove all restricting components from intake piping to lover the pressure difference over the compr. wheel
3.limit boost lower
On the other hand it might be worth measure the flow to be certain that the point goes of the map. There should be pitot type instruments which you could install to intake piping to determine the flow.
Edit. how does the car behave at sea level in terms of surge?
posted by 81.197.223...
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