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Discussion Starter · #1 · (Edited)
Hi Guys,
New to your forum and new to the Vette scene as of late. Last car was an 88' Z52 bought new. I'm waiting now to get my order in on Blade Silver/Adrenaline Red 3LZ Z06. I'm ordering a 7spd manual trans and don't know a thing about what sounds like the coolest gizmo ever....Rev Matching.
Now I'm an old Long Haul Trucker (seams like a different lifetime ago) that had his own "Pete Conventional" w/a 13 spd Fuller Roadranger transmission. I could leave LA and drive all the way to Phoenix and never touch the clutch pedal. I did my own rev matching to find that next gear. So I come from a different angle in trying to understand "Rev Matching" in my new Z06.

HELP

Rick
 

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I also have 7 speed manual I love the rev matching feature . When you down shift the engine holds the throttle so there is virtually no lag . Back in the day we would heal toe to do the same thing . Most Proffessional drivers use the heal toe method .
 

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I drive a truck also. You'll have fun trying to remember not to double clutch. I'm lucky now, the company I drive for has switched to all automatics.
Once you turn rev match on, (and you have to each time you start the car) the computer will speed up the engine to match the next gear as you down shift. If you are just driving around town it helps a little. You notice it more as you do more spirited driving. It smooths out the down shift so the car doesn't get unsettled.
They say it also does the up shifts, I haven't noticed it do anything yet.
 
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When breaking the car in, first 500 miles, with its 4,000 PRM maximum recommended engine spped, do not use the rev match, for on downshifts, rev match can result in going over 4,000 RPM. Perhaps that is one minor reason that you have to, as noted above, turn that feature on every time you start the car if you want it.
 

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Do we have a table of MPH speeds versus gear selected at 4,000 RPMs for each of the transmission/rear end combinations?

Even with rev match off, someone could go over 4000 RPMs as soon as they let the clutch out if they shift to a lower gear at too high of an MPH.

If we don't have such a table, do we have any volunteers to create one? :)
 

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When breaking the car in, first 500 miles, with its 4,000 PRM maximum recommended engine spped, do not use the rev match, for on downshifts, rev match can result in going over 4,000 RPM. Perhaps that is one minor reason that you have to, as noted above, turn that feature on every time you start the car if you want it.
thanks for the tip!
 

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Do we have a table of MPH speeds versus gear selected at 4,000 RPMs for each of the transmission/rear end combinations?

Even with rev match off, someone could go over 4000 RPMs as soon as they let the clutch out if they shift to a lower gear at too high of an MPH.

If we don't have such a table, do we have any volunteers to create one? :)
Okay, there were no volunteers, so I did it. I also did it for automatics because people may choose to use the paddle shifters during break-in.

All standard disclaimers apply: I could have made a mistake in various places in the spreadsheet, so use it at your own risk!

If I have not made any mistakes, then the bottom table shows the "maximum safe speed in MPH" at which you can downshift into each particular gear for each type of car (1YY*7 StingRay without ZF1, 1YY*7 with ZF1 wheels, Z51, et cetera) for each model year, transmission type and rear end. If someone wants to use that, there is the data (where I put 4,000 RPMs in the bottom table for break-in - after break-in, those speeds will be more relaxed [higher]).

On the other hand, I doubt but what very few people would want to memorize the column for their specific car. Therefore, I found the minimum safe speed across each transmission/rear end/wheel type for each year and gear :), and then looked for a simple equation which will satisfy every transmission/rear end/wheel type for each model year (it turns out that the 2015 Z51 with the A8 is the most restrictive setup). In many cases, this "minimum MPH" column toward the right much more conservative than necessary, and the "Safe MPH" column is even more conservative, but, well, it should be safe for everyone, and it is easy to remember. What appears to work for every type is (Gear_you_are_switching_down_into + 1 ) * 10 MPH is safe. In other words, if you are not skipping gears but rather are hitting every one on the way down, then the conservatively safe equation is you can downshift safely after your MPH goes below Gear_you_are_in * 10 MPH.

In other words, during break-in, it should be safe to shift 2 --> 1 when you are under 20 MPH for all drive-train combinations (this is very conservative for many combinations [as some will allow 35 MPH], but oh well).
You should be safe to shift 3 --> 2 when you are under 30 MPH (again, some will even allow > 50 MPH here on the 3 --> 2 shift, but, again, I was looking for something that works for everyone and is easy to remember).
You should be safe to shift 4 --> 3 when you are under 40 MPH (this is really, REALLY conservative here)
You should be safe to shift 5 --> 4 when you are under 50 MPH (again, this is really, REALLY conservative here),
and beyond this it gets laughably conservative...

Anyway, again, I could have made mistakes, so I am not responsible if you use this as a "do not exceed" guide, yet things still go wrong. On the other hand, if you do try to shift down at a speed higher than that listed in left-side columns within the main bottom table directly under and corresponding to your drive train type, I am quite convinced you will exceed the break-in red line of 4000 RPMs (which is, of course, a no-no - so don't do it!). For example, if you shift a manual Z06 down 3rd --> 2nd gear above 44.8 MPH, you will exceed 4000 RPMs. Of course, I don't think you want to do that, so my "conservative" suggestion outlined above would be do not downshift from 3 --> 2 until you are under 30 MPH, which should be safe.

I hope this is helpful. Cheers!

-Rodney

P.S. If you find any errors in my tables (Mark, Mobius, other people :) ), please let me know so I can correct them. Thanks!

P.P.S. Of course, the diameter of the front tires do not matter for this exercise, but I listed them anyway just for completeness if people happen to look at the second table for other reasons.
 

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Discussion Starter · #9 ·
Hey Corvettrob,

An old friend asked me last night about Active Rev Matching in my new Vette (still to b built) and I couldn't answer him. Can the trans b shifted without using the clutch? Or is this a device that makes the shift smoother w/the clutch?
What rpm do u turn in high gear at say 70mph?
 

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Using the values GM does within the controllers as to rev limiter, tire size, and tire revs per mile.
As to HP, Tq rating and car/driver total weight

Plotting 1-5th gears, to 4,000 RPM to MPH and running MPH to a 6,500 RPM limit
 

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Hey Corvettrob,

An old friend asked me last night about Active Rev Matching in my new Vette (still to b built) and I couldn't answer him. Can the trans b shifted without using the clutch? Or is this a device that makes the shift smoother w/the clutch?
What rpm do u turn in high gear at say 70mph?
No, this is not something that removes the need to use the clutch, it's simply an electronic "heal toe". At 70 mph in 7th gear the engine is turning around 1400 rpm. 70 mph is too slow for 7th IMHO.
 
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I only use rev matching when I am ricky racing around , you still need to use the clutch to shift . I cannot or like 7 th gear it bogs the engine down . 5 th I think is the best gear at freeway speeds .
 

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I only use rev matching when I am ricky racing around , you still need to use the clutch to shift . I cannot or like 7 th gear it bogs the engine down . 5 th I think is the best gear at freeway speeds .
I cruise between 80-85 and use 5th, 6th or 7th depending on terrain and traffic. I average around 28 MPG on the highway, at least on the two longer runs I've made.
 
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The simple answer to your question is ARM is there for road racing, or some spirited driving on the streets. If you are on a road course and turning high RPMs, when you approach a turn you will brake in two ways, one with your foot and the other with the engine when you downshift (engine braking). At high RPMs you must match the engine speed to the driveline or wheel hop can occur and possibly have the ass end of the car come around. If not done correctly, good chance you will run off the track (not good!). With all Corvette generations from C1-C6, this was accomplished through the heel/toe process of braking with the ball of your right foot while blipping the throttle with either your heel or side of the right foot. Takes a little coordination and practice, but with you experience with the Pete and 13 speed, I would not expect this to be a huge challenge for you. Now, with the C7, you no longer have to use the heel/toe process to match the RPMs. Just turn on the ARM and the computer does it for you. If you really want to see this in action, take the opportunity and go out to Spring Mountain where you can learn to put a C7 through it's paces, using their cars, brakes, tires, gas, etc. You won't regret it!
 

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I'm like you I was A tractor trailer driver.Mostly 9and 10 speeds.Yes I was the same way only used the clutch when starting from A stop.
I have A 2014 C7. The rev matching isn't no big deal.just rev's up A few RPM's when down shifting.Nothing to write home about.
I seldom use it.People say it's fantastic on the track.I don't need it I street race.Good day.
 

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Very interesting Bob. I never took the time to really compare the two (Manual & Automatic) side by side, but looking at the first gears and the 7th & 8th gear ratios in the transmissions and multiplying those by the final drive ratios (Rear end ratios), it reveals something interesting. The manual is a little softer in first gear with a torque multiplier of 7.8318 (2.29X3.42) vs. the 10.9896 (4.56X2.41) of the automatic. In other words, the automatic is going to have allot more snap off the starting line at a drag strip than the manual, not to mention the torque multiplication from the converter. Pro's: The automatic should launch harder on a drag strip, con's: The automatic will probably light the tires and lose traction easier. However, when looking at the final drive ratio's in 7th and 8th gears respectively, the manual has a 1.539 (.45X3.42) vs. the automatics 1.5665 (.65X2.41) final multiplier, which means the manual will be turning slightly less RPM's in it's highest gear than the automatic assuming the automatics converter is fully locked up....
 

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I have updated the image for the newly-published gear ratios for the Z06 (the M7 changed). The new image is attached below.

Thanks for pointing this out, guys!

-Rodney

Safe_MPH_versus_gear_UPDATED.jpg


Okay, there were no volunteers, so I did it. I also did it for automatics because people may choose to use the paddle shifters during break-in.

All standard disclaimers apply: I could have made a mistake in various places in the spreadsheet, so use it at your own risk!

If I have not made any mistakes, then the bottom table shows the "maximum safe speed in MPH" at which you can downshift into each particular gear for each type of car (1YY*7 StingRay without ZF1, 1YY*7 with ZF1 wheels, Z51, et cetera) for each model year, transmission type and rear end. If someone wants to use that, there is the data (where I put 4,000 RPMs in the bottom table for break-in - after break-in, those speeds will be more relaxed [higher]).

On the other hand, I doubt but what very few people would want to memorize the column for their specific car. Therefore, I found the minimum safe speed across each transmission/rear end/wheel type for each year and gear :), and then looked for a simple equation which will satisfy every transmission/rear end/wheel type for each model year (it turns out that the 2015 Z51 with the A8 is the most restrictive setup). In many cases, this "minimum MPH" column toward the right much more conservative than necessary, and the "Safe MPH" column is even more conservative, but, well, it should be safe for everyone, and it is easy to remember. What appears to work for every type is (Gear_you_are_switching_down_into + 1 ) * 10 MPH is safe. In other words, if you are not skipping gears but rather are hitting every one on the way down, then the conservatively safe equation is you can downshift safely after your MPH goes below Gear_you_are_in * 10 MPH.

In other words, during break-in, it should be safe to shift 2 --> 1 when you are under 20 MPH for all drive-train combinations (this is very conservative for many combinations [as some will allow 35 MPH], but oh well).
You should be safe to shift 3 --> 2 when you are under 30 MPH (again, some will even allow > 50 MPH here on the 3 --> 2 shift, but, again, I was looking for something that works for everyone and is easy to remember).
You should be safe to shift 4 --> 3 when you are under 40 MPH (this is really, REALLY conservative here)
You should be safe to shift 5 --> 4 when you are under 50 MPH (again, this is really, REALLY conservative here),
and beyond this it gets laughably conservative...

Anyway, again, I could have made mistakes, so I am not responsible if you use this as a "do not exceed" guide, yet things still go wrong. On the other hand, if you do try to shift down at a speed higher than that listed in left-side columns within the main bottom table directly under and corresponding to your drive train type, I am quite convinced you will exceed the break-in red line of 4000 RPMs (which is, of course, a no-no - so don't do it!). For example, if you shift a manual Z06 down 3rd --> 2nd gear above 44.8 MPH, you will exceed 4000 RPMs. Of course, I don't think you want to do that, so my "conservative" suggestion outlined above would be do not downshift from 3 --> 2 until you are under 30 MPH, which should be safe.

I hope this is helpful. Cheers!

-Rodney

P.S. If you find any errors in my tables (Mark, Mobius, other people :) ), please let me know so I can correct them. Thanks!

P.P.S. Of course, the diameter of the front tires do not matter for this exercise, but I listed them anyway just for completeness if people happen to look at the second table for other reasons.
 
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