Backpressure Data from track rental

M

murphster

Well-Known Member
Joined
Feb 15, 2003
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).
 
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This is an example what a run log looked like with just manifold and backpressure psi turned on. Boost and backpressure is pretty steady at the end of the run. Manifold boost is in green and backpressure is blue (not to scale).

image.jpg
 
Very nice, do you feel your combo has more to give?
Looks real good to me, Thanks for sharing.

How much co2 and what size spring and gate?
 
murphster said:
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).
Click to expand...

Nice data. Drive pressure doesn't look very high. Would have been nice to see pre-cooler pressure.
AG.
 
fastblackracing said:
Very nice, do you feel your combo has more to give?
Looks real good to me, Thanks for sharing.

How much co2 and what size spring and gate?
Click to expand...

It started getting hot and muggy in the afternoon or there would have been better gains with the higher boost. I definitely think there is more in it, and the data shows that the backpressure ratio is not increasing yet.

I wonder what the difference would be with an open dump vs through the exhaust?

I am running a Turbonetics Racegate (44mm?) off the header with a 9lb spring. I run pretty high CO2 pressure, probably 50psi or so but I need to verify the exact #.
 
turbobitt said:
Nice data. Drive pressure doesn't look very high. Would have been nice to see pre-cooler pressure.
AG.
Click to expand...

I wanted that data too, I thought it was the same sensor as the backpressure sensor so I put in the same settings. I'll figure it out and will get some data at higher boost. Won't be able to get as much as I could have at the rental though unfortunately.

I also got some good data from my accelerometer with different shifts points, I'll post that up in another forum when I get a chance.
 
murphster said:
I also got some good data from my accelerometer with different shifts points, I'll post that up in another forum when I get a chance.
Click to expand...

Accelerometer data is really useful when combined with DS speed. I find it correlates very well if you have any wheel spin.
AG.
 
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