Shifting from 1st to 2nd
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Racer
Joined: Jun 2005
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Shifting from 1st to 2nd
What is the optimal point to my shift Z51 C6 from 1st to 2nd to get maximum speed. Seems I am doing it wrong as I have initially been jumped by an 05 Mustang and an automatic C5 until I get to 2nd?
Supporting Vendor
Joined: Oct 2004
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Originally Posted by TOPGON
What is the optimal point to my shift Z51 C6 from 1st to 2nd to get maximum speed. Seems I am doing it wrong as I have initially been jumped by an 05 Mustang and an automatic C5 until I get to 2nd?
Melting Slicks
Joined: Jul 2001
Posts: 3,284
Likes: 3
From: Southwest Florida
You'll always be faster taking each gear to redline (6500). No matter when you shift to second, your acceleration will always be greater in 1st gear and will drop when you put it in 2nd.
Mike
Mike
Racer
Joined: Nov 2004
Posts: 298
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Mike is right, take it to redline....though that may not always be the case.
For Corvette:
Max torque=400 ft-lbs
1st = 2.97
second = 2.07
To roughly determine the best shift point:
The most torque you could get going to rear axle in second would be 2.07*400 = 828 ft-lbs. If you divide this by 1st ratio it will give you the equal engine torque for 1st gear, 828/2.97=279 ft-lb.
Therefore, you should shift to second at redline or when the engine torque drops to 279 ft-lb. Since the engine torque is still over 300 at redline, you should shift at redline. A table for all the gears is below:
Gear | Ratio | Max Torque | Shift Torque | Optimal Shift
1 | 2.97 | 1188 | N/A | N/A
2 | 2.07 | 828 | 279 | Redline
3 | 1.43 | 572 | 276 | Redline
4 | 1.00 | 400 | 280 | Redline
5 | 0.84 | 336 | 336 | 6150
6 | 0.57 | 228 | 271 | N/A
Also, since peak torque is at 4400 RPM, that would be ideal starting RPM for each gear if possible.
For Corvette:
Max torque=400 ft-lbs
1st = 2.97
second = 2.07
To roughly determine the best shift point:
The most torque you could get going to rear axle in second would be 2.07*400 = 828 ft-lbs. If you divide this by 1st ratio it will give you the equal engine torque for 1st gear, 828/2.97=279 ft-lb.
Therefore, you should shift to second at redline or when the engine torque drops to 279 ft-lb. Since the engine torque is still over 300 at redline, you should shift at redline. A table for all the gears is below:
Gear | Ratio | Max Torque | Shift Torque | Optimal Shift
1 | 2.97 | 1188 | N/A | N/A
2 | 2.07 | 828 | 279 | Redline
3 | 1.43 | 572 | 276 | Redline
4 | 1.00 | 400 | 280 | Redline
5 | 0.84 | 336 | 336 | 6150
6 | 0.57 | 228 | 271 | N/A
Also, since peak torque is at 4400 RPM, that would be ideal starting RPM for each gear if possible.
Last edited by OttoNP; Jun 29, 2005 at 09:43 AM.
Le Mans Master
Joined: Dec 1999
Posts: 6,338
Likes: 2
From: Somewhere Texas
Originally Posted by OttoNP
Mike is right, take it to redline....though that may not always be the case.
For Corvette:
Max torque=400 ft-lbs
1st = 2.97
second = 2.07
To roughly determine the best shift point:
The most torque you could get going to rear axle in second would be 2.07*400 = 828 ft-lbs. If you divide this by 1st ratio it will give you the equal engine torque for 1st gear, 828/2.97=279 ft-lb.
Therefore, you should shift to second at redline or when the engine torque drops to 279 ft-lb. Since the engine torque is still over 300 at redline, you should shift at redline. A table for all the gears is below:
Gear | Ratio | Max Torque | Shift Torque | Optimal Shift
1 | 2.97 | 1188 | N/A | N/A
2 | 2.07 | 828 | 279 | Redline
3 | 1.43 | 572 | 276 | Redline
4 | 1.00 | 400 | 280 | Redline
5 | 0.84 | 336 | 336 | 6150
6 | 0.57 | 228 | 271 | N/A
Also, since peak torque is at 4400 RPM, that would be ideal starting RPM for each gear if possible.
For Corvette:
Max torque=400 ft-lbs
1st = 2.97
second = 2.07
To roughly determine the best shift point:
The most torque you could get going to rear axle in second would be 2.07*400 = 828 ft-lbs. If you divide this by 1st ratio it will give you the equal engine torque for 1st gear, 828/2.97=279 ft-lb.
Therefore, you should shift to second at redline or when the engine torque drops to 279 ft-lb. Since the engine torque is still over 300 at redline, you should shift at redline. A table for all the gears is below:
Gear | Ratio | Max Torque | Shift Torque | Optimal Shift
1 | 2.97 | 1188 | N/A | N/A
2 | 2.07 | 828 | 279 | Redline
3 | 1.43 | 572 | 276 | Redline
4 | 1.00 | 400 | 280 | Redline
5 | 0.84 | 336 | 336 | 6150
6 | 0.57 | 228 | 271 | N/A
Also, since peak torque is at 4400 RPM, that would be ideal starting RPM for each gear if possible.
TRR
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
All the math and the calculations don't do much in the real world. Try different shift points yourself.
My car feels much stronger on a first to second power shift if I short shift @ 5800-6000 RPM. If you try for 6500 RPM you'll run into the rev limiter and lose lots of acceleration.
My Dyno shows peak torque @ around 4500RPM and peak HP @ about 6000 RPM with both TQ and HP decreasing after 6000 RPM. Obviously modifications will change the peaks but for a mostly stock car I don't see any gains running to redline. My G-Tech shows the same results.
My car feels much stronger on a first to second power shift if I short shift @ 5800-6000 RPM. If you try for 6500 RPM you'll run into the rev limiter and lose lots of acceleration.
My Dyno shows peak torque @ around 4500RPM and peak HP @ about 6000 RPM with both TQ and HP decreasing after 6000 RPM. Obviously modifications will change the peaks but for a mostly stock car I don't see any gains running to redline. My G-Tech shows the same results.
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Melting Slicks
Joined: Jul 2001
Posts: 3,284
Likes: 3
From: Southwest Florida
Originally Posted by haljensen
My car feels much stronger on a first to second power shift if I short shift @ 5800-6000 RPM. If you try for 6500 RPM you'll run into the rev limiter and lose lots of acceleration.
Mike
Burning Brakes
Joined: Apr 2005
Posts: 944
Likes: 2
From: Greater Detroit MI
Originally Posted by mikeyc6
That depends on whether you want feels faster or is faster. If you shift at 5800-6000 RPM (cars being equal), you'll lose every time to a driver shifting at redline. You'll never bounce off the rev limiter if you know how to drive, but even if you do, you'll still be faster than short shifting. Math/physics never lie. The butt often does!
Mike
Mike
Racer
Joined: Nov 2004
Posts: 298
Likes: 0
I checked it out, you should be able to redline in 5th, car should max out in 6th around 186 MPH around 4500 RPM. That is for 6 speed with 3.42 axle.
At this speed:
You are traveling almost a football field a second....
The force pushing back on your car is around 806 lbs...
You are burning over a gallon of gas in 2 minutes....
At this speed:
You are traveling almost a football field a second....
The force pushing back on your car is around 806 lbs...
You are burning over a gallon of gas in 2 minutes....
Melting Slicks
Joined: Jul 2001
Posts: 3,284
Likes: 3
From: Southwest Florida
Originally Posted by OttoNP
I checked it out, you should be able to redline in 5th, car should max out in 6th around 186 MPH around 4500 RPM. That is for 6 speed with 3.42 axle.
At this speed:
You are traveling almost a football field a second....
The force pushing back on your car is around 806 lbs...
You are burning over a gallon of gas in 2 minutes....
At this speed:
You are traveling almost a football field a second....
The force pushing back on your car is around 806 lbs...
You are burning over a gallon of gas in 2 minutes....
Mike
Le Mans Master
Joined: Jan 2005
Posts: 5,611
Likes: 5
From: Thousand Oaks California
When you upshift, you want the RPM drop to take you to the "peak" horsepower RPM. The stock LS2 h.p. peaks at 6000 rpm. So, as mentioned above, a 6500 rpm shift is about right.
Melting Slicks
Joined: Jul 2001
Posts: 3,284
Likes: 3
From: Southwest Florida
Originally Posted by calemasters
When you upshift, you want the RPM drop to take you to the "peak" horsepower RPM. The stock LS2 h.p. peaks at 6000 rpm. So, as mentioned above, a 6500 rpm shift is about right.
T1 = torque in gear 1 at current RPM
G1 = gear 1 ratio
T2 = torque in gear 2 at RPM after the shift
G2 = gear 2 ratio
Depending on the gear ratios and the shape of the torque curve, you don't necessarily want to shift so that the RPM in the next gear is at the HP peak. On the LS2, the torque curve doesn't drop off enough to warrant a shift before max RPM. Simply put, no matter when you shift from 1-2, 2-3, 3-4, or 4-5 your acceleration will be reduced as soon as you switch to the next gear.
Mike
Le Mans Master
Joined: Dec 2003
Posts: 7,457
Likes: 144
From: NC
Last time at the track (last week), I tried different shifting RPM's to see if 6500 was in fact the proper smack point. It was. I tried a few times at 6200 instead and was slower every time. 6500 in the real world was the peak. Never bounced off the rev limiter either.
Racer
Joined: Jun 2005
Posts: 267
Likes: 0
From: Toronto Ontario
Originally Posted by cerino2000
Last time at the track (last week), I tried different shifting RPM's to see if 6500 was in fact the proper smack point. It was. I tried a few times at 6200 instead and was slower every time. 6500 in the real world was the peak. Never bounced off the rev limiter either.
So many M6 Vettes but not as many REALLY skilled drivers. I alas am not one of them....
So I bought an A4 3.15 and just mash the gas.
OK OK don't retaliate... just kidding guys honest... erGary
