Hi Dave, I have attached a T3 60 series compressor map. Based on your spreadsheet it should be a good match. A new wheel and housing is not too expensive, install and balance was around $100 last I had it done. If you would like another compressor map I could look through my collection, I have about 60 or so, though some are not the best because they were faxed to me back in the days of thermal fax machines.
The red line on the image is 30" map, blue is 35", green is 40"
Ian, You apparently know your turbochargers.
The problem with the T4 60 trim is that it is basically the same as the stock compressor, which tended to allow the turbine to overspeed and that is why I am trying something bigger.
I am starting to wonder if this is really surge. I went flying again today with the wastgate fully open and the pop-off set to full loose. I climbed out at 32" which was a real treat, letting the MAP fall with altitude. I got to the test area and let the boost creep up a little. At 9500', 27"MAP 5800 rpm (170 KTAS) it happened again. That is just not asking a lot of boost from this turbo. I am still keeping my mind open to other possibilities but just cant come up with anything that makes sense.
The problem with the turbo maps is that there are too many variables (like VE and throttle body losses and compressor efficiency) which can all have such a huge effect.
In your spreadsheet I think your pressure drop across the intercooler is too high, 2 psi for the intercooler and 0.5 psi for the throttle body might be closer, I took my laptop for a ride in my car and went for a drive to confirm this, I lose
1.2 psi across a Spearco intercooler, and 0.3 across the TB, I tried to aproximate the flow you are planning. Compressor efficiency is a bit low at 60%. VE might be a bit high. Adjusting these figures will move the lines I drew on the image to the right and down. If you decide on a stree port the map will look better still.
-- Ian
Don't forget that the throttle valve is half closed. On the ground a half closed throttle (n.a) would give about 24 MAP (all guessing here), or about a 3 psi drop. In other words, keeping that throttle closed is hurting my boost.
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