I've plotted a 7M-GTE running at a pressure ratio of 2.4 (about 20psi boost) for two rpms (5500 and 6500) on compressor maps for the 57 and 60-1 setups. The 7M data comes from figgie's spreadsheet, so look there for the assumptions. Target is 400 hp.
57: This looks like the best match to the 7M. At 5500rpm the compressor is still in its peak efficiency contour, well away from the surge line. At 6500 we are losing efficiency, but still in a reasonable range, and the 7M is losing VE here so the air flow is probably a little optimistic anyway.
60-1: To me this wheel looks a little too big for the 7M. To stay in the peak efficiency contour you need to be running less than 15psi, so at 20 psi 5500 rpm it is not very efficient and also very close to the surge line. At 6500 rpm the efficiency is better, but still not good. There is clearly more room to get more air flow than the 57, but you will be far from the efficiency sweet spot no matter what boost you are running, and at lower pressures you are really close to surge.
Now people are using the 60-1 with good results it seems, so I am interested to know where this analysis is going wrong. I'm no turbo expert by any means, so tell me the flaw in my reasoning here.
57: This looks like the best match to the 7M. At 5500rpm the compressor is still in its peak efficiency contour, well away from the surge line. At 6500 we are losing efficiency, but still in a reasonable range, and the 7M is losing VE here so the air flow is probably a little optimistic anyway.
60-1: To me this wheel looks a little too big for the 7M. To stay in the peak efficiency contour you need to be running less than 15psi, so at 20 psi 5500 rpm it is not very efficient and also very close to the surge line. At 6500 rpm the efficiency is better, but still not good. There is clearly more room to get more air flow than the 57, but you will be far from the efficiency sweet spot no matter what boost you are running, and at lower pressures you are really close to surge.
Now people are using the 60-1 with good results it seems, so I am interested to know where this analysis is going wrong. I'm no turbo expert by any means, so tell me the flaw in my reasoning here.
