Quote:
Originally Posted by LS1Formulation
This is what I came up with:
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Final Gear Ratio : 3.91
Tire Size : 315-35-20
Max Power RPM : 6420
Limit RPM : 7100
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Gear Ratio Compound
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1 3.010 11.769
2 2.070 8.094
3 1.430 5.591
4 1.000 3.910
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Gear MPH/1000 MPH @6420 MPH @7100
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1 7.25 47 51
2 10.55 68 75
3 15.27 98 108
4 21.83 140 155
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Gear Change RPM drop (change @6420) RPM drop (change @7100)
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1->2 -2005 (To 4415) -2217 (To 4883)
2->3 -1985 (To 4435) -2195 (To 4905)
3->4 -1930 (To 4490) -2135 (To 4965)
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From what I'm seeing, I may very well want to lower my shifts. My power peak is at 6420, and my torque has kind of a double peak from 4600-5200. If I go by where it crests 400 lb. ft. ( peaks at 407 lb. ft. ), it's from about 4400-5600 RPM. That's a pretty wide torque plateau, and as it stands, I'm falling right into the center of it. However, with my gear ratios, when I shift from 3-4 @ 7100, my RPM drops to 4965. I'm trapping so slow for my ET ( anywhere from 108-112 ) that by the time I reach the stripe, I'm spinning roughly 5000 RPM or so. So 4th gear is almost useless, as I'm shifting to it around 100 feet before the end of the track, and barely gaining any RPM whatsoever. But if I lower my 3-4 shift to 6600, it will drop me right at the start of the torque plateau and I'll have a little more time under power... What do you think? Am I on the right track with my thinking here?
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I think you may be thinking this through wrong. First, forget about where peak torque happens - horsepower is the actual measurement of how much work an engine is capable of. What you want to do is maximize the average horsepower throughout the run. This means using a shift point after the power peak, but before or at where the power level past the peak matches the power at the shift recovery point in the next gear.
This post covers that really well:
https://www.camaro5.com/forums/showp...72&postcount=6
I'll re-share it for those that don't wanna click the link:
I have a good visual to share on this to help you think about maximizing average power through each gear. This chart shows where you going to land with shift recovery on a 3-4 shift in a regular TR6060-M10 combo. Yellow is shifted at peak hp (6500rpm), green is shifted at about 700rpm beyond that, 7200rpm. It's not hard to see why shifting at peak power is leaving significant performance on the table, you're going to be buried on shift recovery much further down in the RPMs, where the car develops less power.
This is why I get so frustrated at dyno operators and tuners that run the car out to where-ever it peaks and then quit. That doesn't tell the whole story, and that 500-1000rpm beyond the peak is crucial for determining where the best shift point is gonna lay. Given the choice, I pull the car out as far as I trust the motor to routinely go - because that's your real potential operating range, and will help dictate what the best shift-point will be.
Another thing to keep in mind for this discussion is stick-shift vs. auto. Auto guys are faster for a lot of reasons, and shift recovery is one of them. The torque converter will reduce how far back down the rpms drop after a shift. This in turn means the car doesn't need to be pulled as far past the peak. Depending on what the curve looks like, you could very well shift 2-300rpm beyond the peak and not be giving up much. On the other hand, stick shift cars have zero slip once they make the gear change, and drop rpms much lower. So, they must be pulled MUCH deeper beyond the peak to make the best average power through the gear - like as shown in my graphic.
I hope that helps.