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beepbeep beepbeep is offline
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Join Date: Jun 2001
Location: Sweden
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Originally posted by Lensart
Goran, I went through a ton of math (not my strong point) and came up with:
35.8 lb.min @ 7000. 31.01 lb.min @ 6000. 26.73 lb.min @ 5000. 20.85 lb.min @ 4000. 16.04 lb.min @ 3000. at and presure ratio 2.01 with a 80% volumetric efficiency. I used some charts to get some of the info (I'm lazy) so the numbers may not be exact. Do you think I'm close?

How important is the 3000 rpm point as it's pretty close to the surge line.
I'm looking at Gt30R and Gt35R maps but I'm not sure where the points should end up.
Thanks Randy
My calcs on your engine:

Volume: 3400cc
Boost: 1 bar
RPM: 6500
Efficiency: 36%
Natural capacity: 95%

Calculated power: 450hp

Calculated mass flow: 35.2lb/min

Fuel flow: 100L/h

Suited injectors (80% duty cycle + 1.2 safety factor): 420cc

Suited turbo: GT30R (just plot it on pressure ratio of 2 and mass flow of 36lb/min and you'll see that you're within 72% efficiency. Raising boost to 1.6 bar will bring you to 45lb/min and you're still on 72% island.

Remeber, you won't be driving at 6000 RPM all the time but accellerating from maybe 4000 RPM. 1 bar @ 4000 RPM means 21lb/min, which would put you quite near surge line on GT35 but will pull good on GT35.

According to my calc, you should be getting sizeable boost already at ~3000 RPM using GT30R. GT35R is optimized to build boost early so it will also build boost almost as quick as GT30R but it will then take some additional revs to bring it to max boost (see the "notch" on surge-line on GT35). GT35 will give you extra power on the top and room to grow but also worse spoolup and bad low-rev response. GT30 will give you very driveable and responsive 450hp engine without breaking a sweat.

Your headers look very good and will work well in this application. On turbocharged cars, equal length headers are of less priority compared to short/heat retaining headers.

I still believe there is power/response to be won by using modern ball-bearing turbocharger. Re-welding of flange shouldn't bee too complicated/expensive.

Good luck!
Thank you for your time,
Old 10-06-2004, 10:02 AM
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