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05-26-2009, 01:19 PM | #1 |
Scooby Specialist
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Join Date: Oct 2003
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Max PSI on 93 octane, conflicting results.
So out of a triad of tuning and theory books I've been reading, the reported max PSI on 93 octane in the higher RPMs (given still in efficiency range of turbo) is about ~20 PSI.
I did a few tests and have been running 24.5psi at 4K RPM tapering to 22.5 PSI at redline. Not smart from what I've read, but then again I always log. NO METH!! Timing is sane as well. 14.5 degrees peak torque, ~ 4K RPM 21 degrees at 6K RPM 23.5 degrees at 7.2K RPM Tests run at 90F. AFRs dip to ~ 11.0:1 at peak torque and hold about 11.3:1 tapering to 11.1:1 at redline. Knock threshold for stock ECU has been upped, and tuner pro doesn't light up. My basic modifications on my 04 STi: - EL Headers - UP Pipe - FP Green 7cm^2 2.4" - AEM CAI - APS TMIC - Catted DP - Borla Hush Granted not 90F, but representative of what I've seen. 4th gear. Code:
Time PEDAL LOAD RPM FBKC FLKC IAM KNCK LD PSI WB02 9188 17.65 0.84 2217 0 0 1 0 0 -6.3 14.65 9391 28.24 1 2285 0 0 1 0 0 -5.5 14.65 9594 54.51 1.33 2256 0 0 1 0 10 -2.6 14.7 9813 91.37 1.47 2302 0 0 1 0 10 -0.4 14.11 10016 99.22 1.51 2321 0 0 1 0 10 0.6 13.03 10219 100 1.55 2392 0 0 1 0 10 1.1 11.93 10438 100 1.61 2424 0 0 1 0 20 2.3 12.34 10641 100 1.69 2503 0 0 1 0 20 2.9 12.68 10844 100 1.77 2522 0 0 1 0 20 3.5 12.81 11047 100 1.83 2616 0 0 1 0 30 4.1 12.81 11266 100 1.91 2629 0 0 1 0 30 4.9 12.68 11469 100 2.03 2695 0 0 1 0 30 5.9 12.53 11672 100 2.13 2802 0 0 1 0 40 7 12.42 11891 100 2.3 2870 0 0 1 0 40 8 12.23 12094 100 2.43 2977 0 0 1 0 50 9.6 11.96 12297 100 2.62 3040 0 0 1 0 60 11.3 11.65 12516 100 2.85 3171 0 0 1 0 70 13.3 11.3 12719 100 3.14 3259 0 0 1 0 80 15.5 11.17 12922 100 3.46 3412 0 0 1 0 90 18 11.17 13125 100 3.82 3574 0 0 1 0 100 20.6 11.11 13344 100 4.06 3713 0 0 1 0 100 23.5 11.02 13547 100 4.06 3898 0 0 1 0 100 24.1 11.02 13750 100 3.98 4016 0 0 1 0 100 24.3 11.2 13969 100 3.94 4190 0 0 1 0 100 24.1 11.43 14172 100 3.9 4306 0 0 1 0 100 24.1 11.62 14375 100 3.88 4483 0 0 1 0 100 24.1 11.68 14594 100 3.87 4604 0 0 1 0 100 24.1 11.58 14797 100 3.82 4822 0 0 1 0 100 24.3 11.52 15000 100 3.79 4864 0 0 1 0 100 24.1 11.45 15219 100 3.73 5000 0 0 1 0 100 23.9 11.34 15422 100 3.69 5152 0 0 1 0 100 23.7 11.3 15641 100 3.67 5272 0 0 1 0 100 23.3 11.33 15859 100 3.62 5484 0 0 1 0 100 23.3 11.33 16063 100 3.59 5622 0 0 1 0 100 23.1 11.37 16266 100 3.51 5670 0 0 1 0 100 22.9 11.34 16484 100 3.45 5804 0 0 1 0 100 22.7 11.3 16703 100 3.39 5904 0 0 1 0 100 22.7 11.33 16906 99.61 3.33 6032 0 0 1 0 100 22.9 11.33 17109 98.82 3.27 6165 0 0 1 0 100 22.7 11.3 17328 98.43 3.2 6250 0 0 1 0 100 22.7 11.27 17531 98.04 3.14 6440 0 0 1 0 100 22.5 11.24 17734 97.25 3.08 6465 0 0 1 0 100 22.3 11.24
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05-26-2009, 02:03 PM | #2 |
Scooby Newbie
Member#: 12482
Join Date: Nov 2001
Location: Lakewood, Co
Vehicle:2000 RS w/ej20 & e85 94 RX-7 1/2bridge w/meth |
It's not really boost that determines it... its the air flow that does.
You can have a small turbo that pushes x amount of air at 20psi, and a big ass turbo that pushes the same x amount of air at 10 psi. The air flow is what determines if you're gonna run lean or not... not the pressure. edit: fwiw I run e85 so I can't help you much with the 93 question. |
05-26-2009, 02:14 PM | #3 | |
Scooby Specialist
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Quote:
The limit I'm talking of (and should have been more specific with) is this *magical* PSI limit that my books refer to that off the top of my head are a combination of engine compression ratio, PSI (with sane AFRs) and octane rating of fuel. Was this just an arbitrary limit for the sake of not so skilled readers or are there some physics that I need to read up on that determine max PSI for a given octane? Rule of thumb and correlation and causation issue> |
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05-26-2009, 02:42 PM | #4 |
Scooby Newbie
Member#: 12482
Join Date: Nov 2001
Location: Lakewood, Co
Vehicle:2000 RS w/ej20 & e85 94 RX-7 1/2bridge w/meth |
I think I know what you're saying. You're talking about detination do to pressure. We'll I guess you'd have to figure out what pressure causes 93 octane to spontaniously combust. Then you'd have to figure out the amount of pressure thats in the cylinder at it's max compression at atmosphere (14.7lbs). Then figure out how much more compressed pressure 20psi makes.
I'll see if I can't figure that out for yeah. |
05-28-2009, 09:55 PM | #5 |
Scooby Guru
Member#: 159682
Join Date: Sep 2007
Chapter/Region:
NESIC
Location: Maine
Vehicle:1995 WRX 2015 F150 |
I ran almost the same timing and boost on my 2.0 20G on 93 and it works fine.
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