[ZR1] ZR1 Road Speed in each Gear
11-21-2010, 03:13 PM
#1
Pro
Thread Starter
ZR1 Road Speed in each Gear
Calculating the road speed you can achieve in each gear is possible if you assemble the correct information.
GM’s gearing chart for the ZR1 shows we have the following ratios:
Gear 1st 2nd 3rd 4th 5th 6th
RATIO 2.289 1.611 1.208 1.000 0.818 0.675
The rear axle ratio = 3.420
The next bit of information we need is the rear tire rolling circumference. I looked on Michelins web site and found our rear tire make 782 revolutions per miles. From this we can determine the circumference of the rolling tire to be 0.001278772 miles or 3.3760 ft.
Since the ZR1 redline erpm = 6,600 we simply multiple the eprm times the gear ratio, times the rear axle ratio and you get the road speed for each gear. The graph below illustrates the results.
Above you will observe each gears road speed is plotted from 1,200 to the 6,600 erpm limit. At the top of each gear’s line is the maximum road speed for that gear or your shift point speed if you run it out to redline each time. The dashed black vertical line then drops down to the next higher gear and the intersection indicates the erpm you will be at when the clutch is engaged, assuming a quick gear change and no loss in speed. The resulting engagement erpm for each gear is as follows: 2nd = 4,645, 3rd = 4,949, 4th = 5,464, 5th = 5,400 and 6th = 5,446 erpm.
These initial erpm speeds for each gear are connected by a green dashed line. The shape of this line indicates how well spaced the gear ratios are. The ideal green dashed line is a smooth shape that has a gradual upward slope. As you can see 4th gear on the ZR1 was not the ideal gear ratio, between 3rd and 5th, as the green dashed line rises more sharply from 3rd to 4th and then drops down from 4th to connect with 5th. The engineers probably had the 4th gear 1:1 ratio as a constraint and called this close enough instead of creating a new set of parts. How much this affects track performance and acceleration times is an unknown at this time.
The top speed of the ZR1 is geared for 221 mph. Chevy states the top speed is 205 mph. The actual top speed is probably in-between these two numbers knowing Chevy propensity to understated performance, but environmental conditions of the speed run and length of track will probably be the determining factors. We will discuss this in more detail in a future post I have planned explaining the potential top speed and the aerodynamic and frictional forces.
If you have any questions just ask as always. I hope you enjoyed the discussion and information. Just trying to add value to the CF.
GM’s gearing chart for the ZR1 shows we have the following ratios:
Gear 1st 2nd 3rd 4th 5th 6th
RATIO 2.289 1.611 1.208 1.000 0.818 0.675
The rear axle ratio = 3.420
The next bit of information we need is the rear tire rolling circumference. I looked on Michelins web site and found our rear tire make 782 revolutions per miles. From this we can determine the circumference of the rolling tire to be 0.001278772 miles or 3.3760 ft.
Since the ZR1 redline erpm = 6,600 we simply multiple the eprm times the gear ratio, times the rear axle ratio and you get the road speed for each gear. The graph below illustrates the results.
Above you will observe each gears road speed is plotted from 1,200 to the 6,600 erpm limit. At the top of each gear’s line is the maximum road speed for that gear or your shift point speed if you run it out to redline each time. The dashed black vertical line then drops down to the next higher gear and the intersection indicates the erpm you will be at when the clutch is engaged, assuming a quick gear change and no loss in speed. The resulting engagement erpm for each gear is as follows: 2nd = 4,645, 3rd = 4,949, 4th = 5,464, 5th = 5,400 and 6th = 5,446 erpm.
These initial erpm speeds for each gear are connected by a green dashed line. The shape of this line indicates how well spaced the gear ratios are. The ideal green dashed line is a smooth shape that has a gradual upward slope. As you can see 4th gear on the ZR1 was not the ideal gear ratio, between 3rd and 5th, as the green dashed line rises more sharply from 3rd to 4th and then drops down from 4th to connect with 5th. The engineers probably had the 4th gear 1:1 ratio as a constraint and called this close enough instead of creating a new set of parts. How much this affects track performance and acceleration times is an unknown at this time.
The top speed of the ZR1 is geared for 221 mph. Chevy states the top speed is 205 mph. The actual top speed is probably in-between these two numbers knowing Chevy propensity to understated performance, but environmental conditions of the speed run and length of track will probably be the determining factors. We will discuss this in more detail in a future post I have planned explaining the potential top speed and the aerodynamic and frictional forces.
If you have any questions just ask as always. I hope you enjoyed the discussion and information. Just trying to add value to the CF.
11-21-2010, 04:22 PM
#2
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That is some cool stuff. I was thinking 3rd was a thad higher,but that might be cause I go thur it so fast.4th and 5th is there !Its kind of hard to wright all that stuff down at 180---190 but I'll try!!
11-21-2010, 04:28 PM
#3
Drifting
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Interested in WHY they would gear the ZR1 to require a shift from 3rd to 4th just before the quarter mile drag .. the Z06 would hit the quarter right at red line.
11-22-2010, 10:34 AM
#5
Race Director
Hey, Garry - excellent graph and info!!!
For those interested in comparing the ZR1 to other model Vettes that have different ratios, take a look at the calculator by forum member leres:
http://xse.com/leres/ss/calculator.html
His calculations are based on slightly different gear ratios (the ratios published by GM, rather than Garry's 3 decimal place numbers), and also shifting at redline RPM instead of going to the rev limiter.
Bob
For those interested in comparing the ZR1 to other model Vettes that have different ratios, take a look at the calculator by forum member leres:
http://xse.com/leres/ss/calculator.html
His calculations are based on slightly different gear ratios (the ratios published by GM, rather than Garry's 3 decimal place numbers), and also shifting at redline RPM instead of going to the rev limiter.
Bob
Last edited by BEZ06; 11-22-2010 at 10:49 AM.
I was wondering what the actual speeds were. I was thinking 4th redline was about 150. I know when you hit the rev limiter in 4th you're moving pretty quick
11-22-2010, 10:36 PM
#10
Pro
Thread Starter
eaglei, if it had a 2 speed rear differential it would be near perfect
Thanks Jim, Kelly and BAAAD. Just wait till you see the next analysis and graphs.
Keep the discussion going.
Thanks Jim, Kelly and BAAAD. Just wait till you see the next analysis and graphs.
Keep the discussion going.
11-23-2010, 01:57 AM
#11
Well, this excellent graph and analysis answers one question I've had lately....that is why anyone who owns a ZR-1 would want to do performance mods to increase the hp.
The answer is obvious. The car is geared for a top speed of 221 but, alas, is power limited to 205-210. All that additional potential top speed must be the reason for needing more hp. I understand now.
It occurs to me to ask what would happen if a new ZR-1 were to undergo a "narrow body" conversion to the size of the standard coupe. I wonder if elapsed time to speed and/or top speed would improve due to the lowered wind resistance.
The answer is obvious. The car is geared for a top speed of 221 but, alas, is power limited to 205-210. All that additional potential top speed must be the reason for needing more hp. I understand now.
It occurs to me to ask what would happen if a new ZR-1 were to undergo a "narrow body" conversion to the size of the standard coupe. I wonder if elapsed time to speed and/or top speed would improve due to the lowered wind resistance.
11-23-2010, 07:05 AM
#12
Race Director
I have been wondering about the top speeds for each gear for the ZR1 prior to this thread. I would have thought the car mags would have published such data in their reviews of the car a couple of year ago. I will have to go back and look if the data was stated.
11-23-2010, 07:35 AM
#13
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10-12-2015, 07:45 PM
#14
Instructor
10-12-2015, 11:40 PM
#18
Burning Brakes
Great graph. In real life I used the 90, 120, 150 and 180 at the Mojave Magnum in April. Topped out at 195 mph in the 1.5 mile event. Might have even been a little bit quicker if I had shifted at 180 into 6th. Red mist slowed me down a bit yet not bad for a rookie.
10-13-2015, 08:20 AM
#19
Melting Slicks
True ,but......
In order to achieve the best E.T and trap speed the c6 z06 needs to finish the quarter mile in fourth gear.I ve tried it both ways and had much higher trap speed when crossing the finish line in fourth.126.5 mph all stock and 127.9 with just a CAI and a tune.Third gear runs were 2 mph lower.
12-09-2016, 12:03 PM
#20
Gentlemen. 2009 ZR1 stock tranny and diff. 750 RWHP and 710 ft lb torque. running stock size Michelin Cup tires. Best Texas Mile 189.9 mph in 5th gear. from chart it does not appear possible. Have recently added larger throttle body (maybe 25 HP additional) and aftermarket shifter. Goal is 193-195 mph. Is a taller 5th gear ratio the answer. Going to 6th doesn't seem an option. Inputs would be greatly appreciated.