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Dyno & Tuning Question
My engine was just dyno'ed today and the engine builder told me the following:
"We leaned it out to get an extra 20hp to 12.5 A/F ratio. If you want, I can rejet back to 11.8 A/F ratio, but 12.5 is fine too!!" My engine is a 482, Shelby block, Edelbrock heads with bigger valves, Holley 850, Shelby dual plane intake, Crower hydraulic roller cam (112 LSA, 244/252, .618/.638). From what little information that I've supplied, what are your thoughts? Thank you. |
Re-tune it once it's in the car on a chassis dyno. It doesn't matter what it does on an engine dyno, as long as it comes off there with a safe A/F as a baseline so you know you won't hurt it once it's in the car.
Once you get it on a chassis dyno, have the carb adjusted for about 12.6-12.8 A/F. This would be for 93 octane pump gas. You can actually run it about 13.0-13.2 on 93 octane, but with more and more gas across the country going oxygenated, 12.8 or so would be a nice safe A/F that shouldn't cost you power. |
How much power did it make?
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Sal, I need to tune it for 91 octane gas here in CA. Would you still keep it that lean? |
12.5 ain't too lean...
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Further details, the A/F was around 11.8 up to about 5000 rpm, then it rose to around 12.5. The original A/F with stock jetting was around 11.6 to 11.9. If put back to stock jetting, the motor made 580HP. Peak HP was at 5500 rpm. peak torque at 4500.
Thus, if I keep the modified jetting at 12.5 A/F, at least until I get to a chassis dyno, then the engine in theory should run fine on 91 octane CA gas? |
Does the dyno guy know what he is doing??
Rodknock You are paying this guy for his PROFESSIONAL KNOWLEDGE and tuning your motor. He is asking you what you THINK???:eek: 12.5-12.8 A/F is where the most power will come from your motor under full WOT. Is your motor broken in??? If not,IMO I would go back to running a little richer at a 12.0-12.2 A/F. What exhaust exhaust is on the motor?? The car pipes or the dyno pipes? with or without mufflers. This all makes a big differents with tuning the motor. The motor dyno will get your setup in the ball park. To get the most power and performance out of your car you need to go to a chassic dyno. To twick the motor at the end a LM 1 tester will tell you at any rpm what the A/F readings are. What gas is the dyno shop running??? This will effect the numbers also. Take the motor and install it in the car. TOW it back to the dyno shop and have the A/F checked out with the exhaust on your car hooked up. This will save some money in the long run. An EGT reading also would not hurt. You want to talk call me 732-254-3536 in the evenings after 8:00pm est time. Rick L.
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The engine was just broken in yesterday and then dyno'ed. They used 91 octane pump gas and dyno pipes. I will hopefully get the engine by this weekend and then install it over the next several weeks (uh, months?) and then get it to a chassis tuning place here in Northern California. I think for now, whether it's 11.8 or 12.5, it will be close enough as you say.
Thank you. |
Rodney,
601 HP will be enough to get your adrenaline pumping! What was the old driver's ed tip...hit the gas like there's an egg under your foot. :LOL: |
Rodknock where in northern calif are u?
If close to sacramento give SVS dyno a whirl. They do great work. |
Ed, I would really like find a dyno shop in the SF-Oakland-San Jose-Fremont area, but I appreciate the recommendation.
Doug, I don't think they teach that little morsel of wisdom to the youngsters anymore, so I think you made me feel old (or older). |
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Here's a pic of my new engine. I haven't figured out how to upload pics to the gallery yet.
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Rodnock,
I talked to these guys at WSCB last year. They seem to really know their stuff. I plan on taking my car to them for dyno tuning one day in the future. They're located in Tracy. Speed Freaks Inc Chris |
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