I was at a track rental yesterday and got some backpressure data on a lot of runs. I just installed a sensor on the turbo outlet for pre intercooler pressure but unfortunately something was hooked up wrong, probably needed 12V instead of 5V. So I only have manifold pressure to compare to after the intercooler. I'm guessing it could be a 2-3 psi drop at the lower power levels and up to a 4psi drop across the IC at higher boost. So the backpressure ratios would be better if comparing to the pre IC pressure at the turbo.
The pressure is in psi and the numbers are pulled from the end of each run in third for consistency and the boost was very steady (CO2 controlled). The ratio is just backpressure/manifold.
manifold...backpress...ratio......timeslip
18.4.................23.5...........1.28.....10.25@131.5
20.2.................27.0...........1.34.......9.99@134.6
24.0.................32.4...........1.35.....10.02@136.6
25.6.................35.3...........1.38.......9.86@139.3
26.1.................36.8...........1.41.......9.45@143.3
27.4.................38.7...........1.41.......9.44@143.4
27.6.................38.2...........1.38.......9.32@145.1
Combo is a 3bolt 71hpq turbo, Cottons FMIC, unported GN1 heads, 224 cam, TA race headers, 3.5" external dowpipe, ATR dual 3" exhaust with turndowns after pitbull mufflers. Runs were through the exhaust, no dump. Pump gas (93 octane) with Alcohol injection (VP M1 methanol).
The pressure is in psi and the numbers are pulled from the end of each run in third for consistency and the boost was very steady (CO2 controlled). The ratio is just backpressure/manifold.
manifold...backpress...ratio......timeslip
18.4.................23.5...........1.28.....10.25@131.5
20.2.................27.0...........1.34.......9.99@134.6
24.0.................32.4...........1.35.....10.02@136.6
25.6.................35.3...........1.38.......9.86@139.3
26.1.................36.8...........1.41.......9.45@143.3
27.4.................38.7...........1.41.......9.44@143.4
27.6.................38.2...........1.38.......9.32@145.1
Combo is a 3bolt 71hpq turbo, Cottons FMIC, unported GN1 heads, 224 cam, TA race headers, 3.5" external dowpipe, ATR dual 3" exhaust with turndowns after pitbull mufflers. Runs were through the exhaust, no dump. Pump gas (93 octane) with Alcohol injection (VP M1 methanol).
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