fast shifting mn6
Thread Starter
Racer
Joined: Jan 2005
Posts: 433
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From: Northridge southern california
fast shifting mn6
when you guy are shifting your z51 mn6 what rpm do you hit from first to second, in other words when i get on it while getting on the freeway, i shift from 1st at around 6400 rpm and get into second at around 5200- 5300 rpm, is that any good?
what do you guys usually see.
do you let go of the gas? (i do)
also i feel like the torque is strongest from 2 -4500 rpm and after that it dies out, will headers take care of that or will i need headers and a cam?
what do you guys usually see.
do you let go of the gas? (i do)
also i feel like the torque is strongest from 2 -4500 rpm and after that it dies out, will headers take care of that or will i need headers and a cam?
Drifting
Joined: Feb 2006
Posts: 1,250
Likes: 3
From: Honolulu HI
6500 rpm 1st to 2nd.... 6200 rpm 2nd to 3rd....
that's it for me.... once i shift into 3rd i let off the gas.....
the pull is deceiving.... it is really even up to 6000 rpm... almost to smooth and not the normal "seat of the pants" feel....
its a 12 sec car.... be sure to get it tuned if you start modding for HP...
are you turning off the AH and TC??
that's it for me.... once i shift into 3rd i let off the gas.....
the pull is deceiving.... it is really even up to 6000 rpm... almost to smooth and not the normal "seat of the pants" feel....
its a 12 sec car.... be sure to get it tuned if you start modding for HP...
are you turning off the AH and TC??
Race Director
Joined: Aug 2000
Posts: 10,649
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From: Central Florida
Acceleration is strongest if the shift is made as close to the limiter as possible without kissing it.
Reason is that this will put your post-shift rpm higher on the torque curve.
Now, at what point you begin the shift depends on how fast you can make the shift. Engine revs faster in 1st than 2d than 3d, etc. So the start-shift point will progressively get closer to 6600, the fuel cut-off (rev-limiter) point. Gotta keep in mind too that in watching the tac needle move right, you need to take into account your reaction time.
A point of ref on a C6Z, a 300 rpm short shift on the 1-2 costs about a tenth in ET, a significant penalty for missing one shift-point. Results on the LS2 will vary from that. But getting the shift-points right has a significant effect on acceleration.
Ranger
Reason is that this will put your post-shift rpm higher on the torque curve.
Now, at what point you begin the shift depends on how fast you can make the shift. Engine revs faster in 1st than 2d than 3d, etc. So the start-shift point will progressively get closer to 6600, the fuel cut-off (rev-limiter) point. Gotta keep in mind too that in watching the tac needle move right, you need to take into account your reaction time.
A point of ref on a C6Z, a 300 rpm short shift on the 1-2 costs about a tenth in ET, a significant penalty for missing one shift-point. Results on the LS2 will vary from that. But getting the shift-points right has a significant effect on acceleration.
Ranger
Last edited by Ranger; Jun 19, 2006 at 07:46 AM.
Safety Car
Joined: Dec 2004
Posts: 3,565
Likes: 5
From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
Originally Posted by Ranger
Acceleration is strongest if the shift is made as close to the limiter as possible without kissing it.
Reason is that this will put your post-shift rpm higher on the torque curve.
Now, at what point you begin the shift depends on how fast you can make the shift. Engine revs faster in 1st than 2d than 3d, etc. So the start-shift point will progressively get closer to 6600, the fuel cut-off (rev-limiter) point. Gotta keep in mind too that in watching the tac needle move right, you need to take into account your reaction time.
A point of ref on a C6Z, a 300 rpm short shift on the 1-2 costs about a tenth in ET, a significant penalty for missing one shift-point. Results on the LS2 will vary from that. But getting the shift-points right has a significant effect on acceleration.
Ranger
Reason is that this will put your post-shift rpm higher on the torque curve.
Now, at what point you begin the shift depends on how fast you can make the shift. Engine revs faster in 1st than 2d than 3d, etc. So the start-shift point will progressively get closer to 6600, the fuel cut-off (rev-limiter) point. Gotta keep in mind too that in watching the tac needle move right, you need to take into account your reaction time.
A point of ref on a C6Z, a 300 rpm short shift on the 1-2 costs about a tenth in ET, a significant penalty for missing one shift-point. Results on the LS2 will vary from that. But getting the shift-points right has a significant effect on acceleration.
Ranger
yep, if i recall correctly, my dyno pulls showed peak torque around 4200 rpm. imo, as long as your shifts are completed before your rpms drop below peak torque you will notice the most acceleration. the closer you can keep peak torque and hp together the better it will pull. high torque and no hp won't go fast and high hp and low torque won't go as fast either. keeping the 'completed' shifts where the 'peak' torque and hp numbers are as close as possible will result in the most potential for the application of power.
Last edited by Zig; Jun 19, 2006 at 09:06 AM.
Racer
Joined: Jun 2006
Posts: 383
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From: harlan KY
well my 2006 vette is not a z51, but when you shift you must reach peak hp. which is at 6000 rpm, any past 6 k, and your hp will start to go back down. pay attention to how much rpm your engine falls to after a shift. shift to early and you will run to low of a rpm when you shift. the higher you rev the engine the higher the rpm after the shift. but dont hit the rev limiter.the best iv found is to shift at 6200 rpm. in all gears. and never lift from the gas keep it to the floor.
Last edited by COALMINER,KY; Jun 20, 2006 at 03:02 AM.
Team Owner
Joined: Jun 2001
Posts: 26,714
Likes: 344
From: Houston, TX
Originally Posted by Ranger
Acceleration is strongest if the shift is made as close to the limiter as possible without kissing it.
Reason is that this will put your post-shift rpm higher on the torque curve.
Now, at what point you begin the shift depends on how fast you can make the shift. Engine revs faster in 1st than 2d than 3d, etc. So the start-shift point will progressively get closer to 6600, the fuel cut-off (rev-limiter) point. Gotta keep in mind too that in watching the tac needle move right, you need to take into account your reaction time.
A point of ref on a C6Z, a 300 rpm short shift on the 1-2 costs about a tenth in ET, a significant penalty for missing one shift-point. Results on the LS2 will vary from that. But getting the shift-points right has a significant effect on acceleration.
Ranger
Reason is that this will put your post-shift rpm higher on the torque curve.
Now, at what point you begin the shift depends on how fast you can make the shift. Engine revs faster in 1st than 2d than 3d, etc. So the start-shift point will progressively get closer to 6600, the fuel cut-off (rev-limiter) point. Gotta keep in mind too that in watching the tac needle move right, you need to take into account your reaction time.
A point of ref on a C6Z, a 300 rpm short shift on the 1-2 costs about a tenth in ET, a significant penalty for missing one shift-point. Results on the LS2 will vary from that. But getting the shift-points right has a significant effect on acceleration.
Ranger
Hard to argue this. I have found the same think in my limited drag racing. If you want maximum acceleration, they like to be shifted at redline. Shifting is one of my few God-given talents. I can usually bang them off right at redline.
Of couse, in street driving, when and where you shift has a lot more variables.
Safety Car
Joined: Dec 2004
Posts: 3,565
Likes: 5
From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
if nobody minds, could someone help me with a theory ?
looking at dyno graphs i've begun to wonder if the following would prove true.
if i plotted an area on a dyno chart/graph using the following reference points would the conclusions be true ?
using 5250 rpms as the center point.
point one = the point on the torque line of peak torque
point two = the point on the hp line of peak torque
point three = the point on the hp line of peak hp
point four = the point on the torque line of peak hp
is the area inside all four points when maximum 'acceleration' would occur ?
looking at dyno graphs i've begun to wonder if the following would prove true.
if i plotted an area on a dyno chart/graph using the following reference points would the conclusions be true ?
using 5250 rpms as the center point.
point one = the point on the torque line of peak torque
point two = the point on the hp line of peak torque
point three = the point on the hp line of peak hp
point four = the point on the torque line of peak hp
is the area inside all four points when maximum 'acceleration' would occur ?
Racer
Joined: Jun 2006
Posts: 383
Likes: 1
From: harlan KY
i can see your point, and it is good thinking, but its kinda like this. torque is what gets the car going, what makes it get up and go like when your sitting still and nail the throttle you spin the tires, most of the time all the way through first gear. if you notice that is wy peak torque is always achieved at a lower rpm than peak hp. but torque is also important. hp is wher you get your acceleration after you are through spinning your car will accelerate at a massive rate and that is hp. were peak hp equalls peak acceleration
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Instructor
Joined: Feb 2006
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The reason you need to shift past the power peak is because the gear ratio's are too wide spread. Proper ratio's would allow you to shift at the power peak and end up on the torque peak. Both gearsets suck but IMHO the 2.66 low is better because 3 is closer to 4th. BTW chevrolet performance parts supplies a trans for these cars thats 2.30, 1.60, 1.27first three gears. The problem is that overdrives are way higher six is something like .75 and they want $8K for the gearbox. It's what used for the "stock" racing classes.
Safety Car
Joined: Dec 2004
Posts: 3,565
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From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
Originally Posted by C2BOB
The reason you need to shift past the power peak is because the gear ratio's are too wide spread. Proper ratio's would allow you to shift at the power peak and end up on the torque peak.
Both gearsets suck but IMHO the 2.66 low is better because 3 is closer to 4th. BTW chevrolet performance parts supplies a trans for these cars thats 2.30, 1.60, 1.27first three gears. The problem is that overdrives are way higher six is something like .75 and they want $8K for the gearbox. It's what used for the "stock" racing classes.
Both gearsets suck but IMHO the 2.66 low is better because 3 is closer to 4th. BTW chevrolet performance parts supplies a trans for these cars thats 2.30, 1.60, 1.27first three gears. The problem is that overdrives are way higher six is something like .75 and they want $8K for the gearbox. It's what used for the "stock" racing classes.
i understand your point about gearing and how it effects the engine. What i'm attempting to ask is, if it was possible to perform shifts at peak hp, complete it, and keep the rpms above or equal to peak trq, once you have engaged the new gear. would that be considered an optimum shift ?
after 5250 rpms, hp continues to climb but torque begins to drop, at what point does the hp/trq ratio no longer provide sufficient output?
Last edited by Zig; Jun 20, 2006 at 03:25 PM.
Instructor
Joined: Apr 2006
Posts: 206
Likes: 0
Please go to the track. Listen to your engine. This is sound advice. If you Dyno your car it will indicate +/- where to look for the optimal shift pt. My A6 shifts at 6,500, it sounds right, the motor does not sound neither over or under reved. On a stock LS2 that's a fact. When (if) you change cams, YOU will have to find that new shift pt. The Dyno sheet, the engine will talk to you and the time slips will confirm when to shift. Good luck.
Melting Slicks
Joined: May 2006
Posts: 2,891
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From: NJ..."the way I saw it, everyone takes a beating sometimes."
Originally Posted by COALMINER,KY
well my 2006 vette is not a z51, but when you shift you must reach peak hp. which is at 6000 rpm, any past 6 k, and your hp will start to go back down. pay attention to how much rpm your engine falls to after a shift. shift to early and you will run to low of a rpm when you shift. the higher you rev the engine the higher the rpm after the shift. but dont hit the rev limiter.the best iv found is to shift at 6200 rpm. in all gears. and never lift from the gas keep it to the floor.
Race Director
Joined: Aug 2000
Posts: 10,649
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From: Central Florida
Originally Posted by k0bun
Is this a good idea? Is there any damage that can be done by not lifting off the gas peddle when shifting?
Powershifting definitely increases the risk of damage to the tranny. Most of the Z06 racers I know personally that powershift have had their trannies rebuilt or replaced. My tranny is fine so far; but I powershift ONLY when conditions reward it. Otherwise, I shift very fast but ease the throttle.
The large number of trashed Z06 trannies bear testimony to the impact of missed shifts and poorly maintained clutch fluid.
Ranger
Safety Car
Joined: Dec 2004
Posts: 3,565
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From: stafford country, va. Avatar: Me on turn 3 @ Bristol (The World's Fastest Half-Mile)
Originally Posted by k0bun
Is this a good idea? Is there any damage that can be done by not lifting off the gas peddle when shifting?
if you're not fast enough with the clutch it won't grab but will slip. if you're too aggressive it'll snap something.
don't forget about being able to 'shift without the clutch'.....
Last edited by Zig; Jun 21, 2006 at 08:43 PM.
