When to shift?
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Joined: Apr 2004
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From: Savannah GA
When to shift?
I've read a couple theories on when to upshift when looking for best acceleration times, but I have not read anything specific on C5s. From what I understand, you can get the best acceleration times by shifting when the higher gear's HP equals the current gear's HP. For some 6 speeds, that is around 6,550 RPM.
So, two questions: Is this theory correct? And if it is, what's the RPM for the C5 at these shift points?
Thanks,
Dave
So, two questions: Is this theory correct? And if it is, what's the RPM for the C5 at these shift points?
Thanks,
Dave
Race Director
Joined: Aug 2000
Posts: 10,649
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From: Central Florida
Re: When to shift? (lively14)
Others can answer the theory. My view is that on the LS6 you worry about being the at the highest RPM AFTER the shift where the torque is higher.
If your profile is current, your car is a 99 coupe with M6. No info on mods, if any.
I determined the optimal shift points in my Z06s by experimentation at the drag strip.
I learned that the best times are attained by shifting at the highest possible rpm without hitting the rev-limiter.
If I kiss the limiter, it costs less than a tenth. If you slam the limited, you kill the run.
If I reduce the shift point by 200 RPMs, it costs about one .07-.10 per shift.
You need to be careful in 1st and 2d because the tach lags slightly behind the actual RPM.
Your LS1 may give different results. Only way to find out is to experiment. But my info my give you a start.
Ranger
If your profile is current, your car is a 99 coupe with M6. No info on mods, if any.
I determined the optimal shift points in my Z06s by experimentation at the drag strip.
I learned that the best times are attained by shifting at the highest possible rpm without hitting the rev-limiter.
If I kiss the limiter, it costs less than a tenth. If you slam the limited, you kill the run.
If I reduce the shift point by 200 RPMs, it costs about one .07-.10 per shift.
You need to be careful in 1st and 2d because the tach lags slightly behind the actual RPM.
Your LS1 may give different results. Only way to find out is to experiment. But my info my give you a start.
Ranger
Le Mans Master
Joined: Apr 1999
Posts: 6,129
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From: Vette
Re: When to shift? (lively14)
For best results you want to maximize the HP curve (not TQ) for the entire run.
There’re various shift-point calculators where you can plug in your dyno numbers and they’ll give you the shift points
I’ll save you the time though - for Ls1/6 you basically want to shift as close to red-line as possible (just like Ranger said)
There’re various shift-point calculators where you can plug in your dyno numbers and they’ll give you the shift points
I’ll save you the time though - for Ls1/6 you basically want to shift as close to red-line as possible (just like Ranger said)
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Joined: Apr 2004
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From: Savannah GA
Re: When to shift? (Dr.Ron)
Thanks to all for the input. Do any of you who have a HUD ever use the "SHIFT" message advice, or do you just watch the tach? It seems to go off at about 5.7-5.8k RPM, but, as mentioned earlier, the extra 4-500 RPM would seem to produce better results.
Thanks much,
Dave
P.S. The only mod I have is so far (just purchased 20 days ago) is a CORSA exhaust (now reflected in my profile).
Thanks much,
Dave
P.S. The only mod I have is so far (just purchased 20 days ago) is a CORSA exhaust (now reflected in my profile).
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From: suffield ct
Re: When to shift? (lively14)
C5'S DONT LIKE ANYTHING HIGHER THAN 6000 RPM, THE FUEL SHUT OFF IS 6200, I HIT THE SHUT OFF TRYING TO SHIFT AT 6000, SO I SHIFT AT 5900, STOCK C5 VERT 6SPEED WITH ONLY A COLD AIR INTAKE WITH STOCK RUN FLATS WENT 12.8 109 MPH SPEED SHIFTING, NO POWER SHIFTS.
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Drifting
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From: North West nj
Re: When to shift? (567521)
I 1st set my light for 500 rpm before the limiter & now it's set a little closer to the limiter , just 200 rpm before the limiter is where my light is set now.
Gradually work up to a safe shift point everyone reacts differently to the light.
Gradually work up to a safe shift point everyone reacts differently to the light.
Team Owner
Joined: Jul 2003
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From: [Enter Unoffensive Comment Here]
Cruise-In VI Veteran
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St. Jude Donor '06
Re: When to shift? (z-u-later)
I 1st set my light for 500 rpm before the limiter & now it's set a little closer to the limiter , just 200 rpm before the limiter is where my light is set now.
Gradually work up to a safe shift point everyone reacts differently to the light.
Gradually work up to a safe shift point everyone reacts differently to the light.
I have my light set 300rpm before redline. Although your power may be falling off the curve at max rpm in any given gear, you are usually jumping into a more powerful rpm in the next gear if you wait.
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From: Savannah GA
Re: When to shift? (lager99)
Have any of you guys ever installed anything that allows/requires you to set the fuel shut-off at a higher RPM? For instance, I'm considering installing a COMP Camshaft , FAST manifold and new valve springs, rocker arms, etc. (thanks to Chevy High Performance mag for the idea to break my bank), and your supposed to change your rev limiter. If anyone's done that (or know someone who did), what kind of stuff do you need to change it?
(Sorry, I know this is a bit off topic)
(Sorry, I know this is a bit off topic)
Melting Slicks
Joined: Oct 2000
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From: Stamford CT.
Re: When to shift? (lively14)
The "ideal" shift point can be determined if you have a dyno chart and your gear ratio's. You first figuer out what your efective torque is in the gear your in at a given rpm, by X the flywheel torque X the trans ratio. You can figuer out the rpm change after the shift by divideing the ratio your in into the ratio your shifting in to X rpm before shift. The aim is to have the most effective torque after the shift..keeping in mind the possible extra time it might take to wind the gear your in might take. You also need to take the other varriables into account. rev limiters, available traction after the shift, and type of shift(speed, or power shift) really very simple
..Ric
..Ric
Thanks to all for your help.
Intermediate
Joined: Mar 1999
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From: Naples FL
Re: When to shift? (lively14)
The optimum shift point for 1997-2000 and 2001-2004 LS1 engines are different due to a number of changes made to LS1 engines in 2001, among which includes a cam with less intake duration. The 2001-2004 LS1 engines make more horsepower and torque than 1997-2000 LS1 engines, but they do so at slighlty lower RPM.
1997-2000 LS1 engines are rated at 345 horsepower at 5600 RPM and 350 Lbs/Ft torque at 4400 RPM. Dyno tests indicate that the horsepower on these engines drops off by about only 3 horsepower by 6000 RPM. Consequently, the optimum shift point for 1997-2000 LS1's is about 6000 RPM, just shy of the 6180 RPM rev limiter.
2001-2004 LS1 engines are rated at 350 horsepower at 5200 RPM and 360 Lbs/Ft torque at 4200 RPM (A4) or 375 Lbs/Ft torque at 4400 RPM (M6). Dyno tests indicate that the horsepower on these engines drops off by about 5 horsepower by 5500 RPM, by about 7 horsepower at 5700 RPM, by about 9 horsepower at 5900 RPM and by about 11 horsepower at 6000 RPM. Consequently, the optimum shift point for 2000-2001 LS1's is about 5600 RPM.
1997-2000 LS1 engines are rated at 345 horsepower at 5600 RPM and 350 Lbs/Ft torque at 4400 RPM. Dyno tests indicate that the horsepower on these engines drops off by about only 3 horsepower by 6000 RPM. Consequently, the optimum shift point for 1997-2000 LS1's is about 6000 RPM, just shy of the 6180 RPM rev limiter.
2001-2004 LS1 engines are rated at 350 horsepower at 5200 RPM and 360 Lbs/Ft torque at 4200 RPM (A4) or 375 Lbs/Ft torque at 4400 RPM (M6). Dyno tests indicate that the horsepower on these engines drops off by about 5 horsepower by 5500 RPM, by about 7 horsepower at 5700 RPM, by about 9 horsepower at 5900 RPM and by about 11 horsepower at 6000 RPM. Consequently, the optimum shift point for 2000-2001 LS1's is about 5600 RPM.