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View Full Version : Speed in gears at redline c7's



froggy47
12-07-14, 09:32 PM
Can't seem to find anywhere for the stick shift cars. Car & Driver has it for the z06 automatic.

Thanks if you can help.

:)

froggy47
12-12-14, 03:07 PM
Can't seem to find anywhere for the stick shift cars. Car & Driver has it for the z06 automatic.

Thanks if you can help.

:)

So, uh, this is secret info?

Someone has to have it, cars have been sold for some time now. This is basic car test info.

:)

Hib Halverson
12-12-14, 07:45 PM
You can figure it with math.

You need to know, the engine speed, the ratio of the gear in question, the final drive ratio and the tire height.

kpic
12-12-14, 11:11 PM
Disregarding aerodynamics, top speed is limited by however long the engine can pull torque in the highest gear.

Judging by anything from formula cars to NASCAR, how long the road is straight is also a factor. Then there is something called pucker factor. ;)

It is not mathematical as more factors enter into it than the gearing analysts can define.

Hib Halverson
12-13-14, 11:22 AM
Disregarding aerodynamics, top speed is limited by however long the engine can pull torque in the highest gear.

Judging by anything from formula cars to NASCAR, how long the road is straight is also a factor. Then there is something called pucker factor. ;)

It is not mathematical as more factors enter into it than the gearing analysts can define.

The OP was asking about speeds in gears not top speed but, with C7, I'll guess that, like C4,5 and 6, that top speed is attained in fifth gear and, given enough distance (say 4-5 miles) is determined by the rev limiter.

Top speed in sixth and seventh (manual) will be aero-limited and may likely be slower than what the car does in fifth. As far as top speed with the new eight-speed auto, I don't have enough info on its ratios to add anything to the conversation.

kpic
12-13-14, 12:14 PM
As RPM is what counts, speed in gears is irrelevant. No engine manufacturer governs speed; they govern RPM. Using imaginary values, swapping diff gears from 3.00 to a 4.00 will not change the potential RPM in any gear but it sure will change the speed.

Correct, no different than most cars, using a 6 speed manual as the example, depending on overall ratio (product of transmission and differential gearing) 5th is usually the last power gear.
After 35 years in power train (engine, transmission, and differentials) design, one learns the numbers calculated by the analysts do not reflect the real world.

The real answer to the OP's question is if one wants to know, run it up to red line.

froggy47
12-15-14, 04:13 PM
As RPM is what counts, speed in gears is irrelevant. No engine manufacturer governs speed; they govern RPM. Using imaginary values, swapping diff gears from 3.00 to a 4.00 will not change the potential RPM in any gear but it sure will change the speed.

Correct, no different than most cars, using a 6 speed manual as the example, depending on overall ratio (product of transmission and differential gearing) 5th is usually the last power gear.
After 35 years in power train (engine, transmission, and differentials) design, one learns the numbers calculated by the analysts do not reflect the real world.

The real answer to the OP's question is if one wants to know, run it up to red line.

If I had one, I would do that. 1st & 2nd are the main gears I'm interested in.

Most car tests will provide speed in each gear @ limiter whether they calculate it or test it using their test gear.

For a car used in autox the max speed in 1st and more important 2nd is paramount as to whether the car will work well or not. The m12 transmission with 3.42 diff gears being an example of an almost perfectly geared car for autox.

It is just a real puzzle that no tester has published this common test info by now? Likewise no owner has it for at least 1st & 2nd.