What RPM should I be shifting at
07-02-2017, 06:48 PM
#1
Pro
Thread Starter
What RPM should I be shifting at
If my cam makes peak HP @ 6000 rpm is that when I should be shifting or should I be pushing a little past that?
07-03-2017, 08:13 AM
#2
Le Mans Master
07-06-2017, 09:00 PM
#3
Pro
Thread Starter
Thanks. I've been doing the math. Should I be basing my shift points off the HP graph, the Torque graph, or some combination of both?
07-09-2017, 06:22 AM
#5
Race Director
Shifting past the point of max power is simply beating up your engine ...you will not go any quicker/faster...remember, when you shift, the motor probably goes 1-200 rpm higher before the shift is complete...
07-09-2017, 06:52 AM
#6
What you are looking at is torque to the rear wheels. This is multiplied by the transmission/differential. You will usually get maximum torque to the rear wheels by going to redline in 1st and 2nd because of the big difference in gear ratio.
Look at your torque curve. Compare the torque to the wheels, (engine torque multiplied by gear ratio, you can ignore the differential because it doesn't change). See where calculated torque to wheels in 1st exceed that in 2nd at all rpms. It usually doesn't happen. Same for 2nd. When you find a point where the torque to the wheels in the next higher (number) gear exceeds the torque in the lower gear that is you **** point. Keep in mind tach lag and reaction time so the real number is a bit lower.
Look at your torque curve. Compare the torque to the wheels, (engine torque multiplied by gear ratio, you can ignore the differential because it doesn't change). See where calculated torque to wheels in 1st exceed that in 2nd at all rpms. It usually doesn't happen. Same for 2nd. When you find a point where the torque to the wheels in the next higher (number) gear exceeds the torque in the lower gear that is you **** point. Keep in mind tach lag and reaction time so the real number is a bit lower.
The following 2 users liked this post by juanvaldez:
Cool95vette (07-09-2017),
HardcoreABN (07-09-2017)
07-09-2017, 02:51 PM
#7
Le Mans Master
Member Since: Nov 2005
Location: Kendall Park NJ
Posts: 6,964
Likes: 0
Received 335 Likes
on
247 Posts
Absolutely false. You need to look at your shift recovery rpm and corresponding HP. Shifting an N/A car with a manual trans at peak HP will yield too low HP at its recovery. Technically, shift rpm will mostly change for different gears unless the ratios provide equal drops.
07-09-2017, 06:26 PM
#8
Drifting
What you are looking at is torque to the rear wheels. This is multiplied by the transmission/differential. You will usually get maximum torque to the rear wheels by going to redline in 1st and 2nd because of the big difference in gear ratio.
Look at your torque curve. Compare the torque to the wheels, (engine torque multiplied by gear ratio, you can ignore the differential because it doesn't change). See where calculated torque to wheels in 1st exceed that in 2nd at all rpms. It usually doesn't happen. Same for 2nd. When you find a point where the torque to the wheels in the next higher (number) gear exceeds the torque in the lower gear that is you **** point. Keep in mind tach lag and reaction time so the real number is a bit lower.
Look at your torque curve. Compare the torque to the wheels, (engine torque multiplied by gear ratio, you can ignore the differential because it doesn't change). See where calculated torque to wheels in 1st exceed that in 2nd at all rpms. It usually doesn't happen. Same for 2nd. When you find a point where the torque to the wheels in the next higher (number) gear exceeds the torque in the lower gear that is you **** point. Keep in mind tach lag and reaction time so the real number is a bit lower.
07-10-2017, 06:56 AM
#9
Race Director
"Absolutely false."
While it may be false for a stick shift car, the OP never said which he had...he only mentioned "shift"....I did not assume he had a manual shift car...my bad...
While it may be false for a stick shift car, the OP never said which he had...he only mentioned "shift"....I did not assume he had a manual shift car...my bad...
07-10-2017, 04:17 PM
#10
Le Mans Master
HP graph as Gary stated.
These cars drop 2200 rpms or more on each gear change.
If you shift @ 6000K it may drop down to ~3600rpms.
How much power are you making @ that rpm? Probably not enough.
So it's likely, for max performance, provided traction, that you will need to shift as high as your tuner or setup will allow based on safety and stability.
But do the match from dynograph and see. 4th gear dyno pull is fine for all gears for now.
These cars drop 2200 rpms or more on each gear change.
If you shift @ 6000K it may drop down to ~3600rpms.
How much power are you making @ that rpm? Probably not enough.
So it's likely, for max performance, provided traction, that you will need to shift as high as your tuner or setup will allow based on safety and stability.
But do the match from dynograph and see. 4th gear dyno pull is fine for all gears for now.
07-10-2017, 11:29 PM
#11
You can also increase power production by raising the lower parts of your rpm trace. Basically I'm referring to controlled clutch slippage after the shift, you can often raise recovery by about 500rpm. Most people think that any clutch slipping at all after the shift is a simple waste of energy, but net gains are possible if you do it right.
Just throwing this out there-
Coyote Stock is a heads-up factory sealed, naturally aspirated 302 cid crate engine class. The $6500 engines run at 3175lbs on a .400 pro tree. They even flash ecu's in the lanes to make sure everyone is on the same tuneup, Ford says 412hp@6500 / 390ftlbs@4250. Current class records are 10.075 / 131.86, according to the calculators it would take around 583-614fwhp to post those numbers.
With basically the same power/weight/tires and spec ratios, controlled slipping of the required 10" min diaphragm clutch is pretty much the only mechanical variable that allows some C/S cars to produce significantly more power than others. So far this year my ClutchTamer customers in C/S have set quick ET and top MPH at every race and have the current ET and MPH records. They have also brought home both winner AND runner-up hardware at every race this year with a single exception.
Grant
Just throwing this out there-
Coyote Stock is a heads-up factory sealed, naturally aspirated 302 cid crate engine class. The $6500 engines run at 3175lbs on a .400 pro tree. They even flash ecu's in the lanes to make sure everyone is on the same tuneup, Ford says 412hp@6500 / 390ftlbs@4250. Current class records are 10.075 / 131.86, according to the calculators it would take around 583-614fwhp to post those numbers.
With basically the same power/weight/tires and spec ratios, controlled slipping of the required 10" min diaphragm clutch is pretty much the only mechanical variable that allows some C/S cars to produce significantly more power than others. So far this year my ClutchTamer customers in C/S have set quick ET and top MPH at every race and have the current ET and MPH records. They have also brought home both winner AND runner-up hardware at every race this year with a single exception.
Grant
07-11-2017, 10:15 AM
#12
Le Mans Master
You can also increase power production by raising the lower parts of your rpm trace. Basically I'm referring to controlled clutch slippage after the shift, you can often raise recovery by about 500rpm. Most people think that any clutch slipping at all after the shift is a simple waste of energy, but net gains are possible if you do it right.
Just throwing this out there-
Coyote Stock is a heads-up factory sealed, naturally aspirated 302 cid crate engine class. The $6500 engines run at 3175lbs on a .400 pro tree. They even flash ecu's in the lanes to make sure everyone is on the same tuneup, Ford says 412hp@6500 / 390ftlbs@4250. Current class records are 10.075 / 131.86, according to the calculators it would take around 583-614fwhp to post those numbers.
With basically the same power/weight/tires and spec ratios, controlled slipping of the required 10" min diaphragm clutch is pretty much the only mechanical variable that allows some C/S cars to produce significantly more power than others. So far this year my ClutchTamer customers in C/S have set quick ET and top MPH at every race and have the current ET and MPH records. They have also brought home both winner AND runner-up hardware at every race this year with a single exception.
Grant
Just throwing this out there-
Coyote Stock is a heads-up factory sealed, naturally aspirated 302 cid crate engine class. The $6500 engines run at 3175lbs on a .400 pro tree. They even flash ecu's in the lanes to make sure everyone is on the same tuneup, Ford says 412hp@6500 / 390ftlbs@4250. Current class records are 10.075 / 131.86, according to the calculators it would take around 583-614fwhp to post those numbers.
With basically the same power/weight/tires and spec ratios, controlled slipping of the required 10" min diaphragm clutch is pretty much the only mechanical variable that allows some C/S cars to produce significantly more power than others. So far this year my ClutchTamer customers in C/S have set quick ET and top MPH at every race and have the current ET and MPH records. They have also brought home both winner AND runner-up hardware at every race this year with a single exception.
Grant
It might be a bit much for many who occasional visit the track and are learning but a savvy move for a 1/4 mile veteran. lol
07-12-2017, 02:14 AM
#14
lets say a car has the power to gain speed at an average rate of 6000 rpm per second in 1st gear. Let's also have the clutch slipping until 0.5 sec into the run with the tires remaining dead hooked (i like radials). If the car launches at 6000 and the tires are stuck, that clutch will pull engine rpm down to 3000 by the 0.5 sec mark. Rpm then begins climbing from 3000 as it recovers lost rpm, to 6000 rpm by the 1.0 second mark. During the initial 1 second after launch, the engine's average rpm was 4500, which means the engine made 75 revolutions over that 1st second of the run.
...Now repeat the launch, but with the clutch slipping just enough that the engine does not lose any rpm at all over that same 1 sec period. Now the engine's average rpm has increased to 6000, which means it made 100 revolutions during that same initial 1 second period.
...The launch that didn't lose any rpm actually packs 33% more revolutions of WOT power production into the same 1 second time period. If the clutch also slips just right after the shifts, you can pick up a little power production there as well. You might lose a little of that 33% gain due to increased slipping, but there’s a lot left over to make the car faster. Balancing a small loss of mechanical efficiency against a 33% increase in power production can result in a HUGE net gain!
The benefit comes from raising the engine's average rpm over the duration of the run, basically narrowing the engine's operating band by elevating the lower areas of it's rpm trace. It all boils down to adding power at a faster rate than any related loss of efficiency. It's the same concept that makes it possible for the automatic guys to install a "less efficient" converter with a higher slip ratio, but yet still produce a faster run.
Grant
07-21-2017, 12:43 PM
#15
Race Director
Member Since: Apr 2017
Location: Hickory NC
Posts: 10,211
Received 863 Likes
on
667 Posts
2022 C5 of the Year Finalist - Modified
2020 C5 of the Year Finalist - Modified
St. Jude Donor '17-‘18-'19-'20-'21-'22-'23-'24
Here's some copy/paste from my ClutchTamer.com website that helps explain how clutch slip can be exploited to make a car quicker-
lets say a car has the power to gain speed at an average rate of 6000 rpm per second in 1st gear. Let's also have the clutch slipping until 0.5 sec into the run with the tires remaining dead hooked (i like radials). If the car launches at 6000 and the tires are stuck, that clutch will pull engine rpm down to 3000 by the 0.5 sec mark. Rpm then begins climbing from 3000 as it recovers lost rpm, to 6000 rpm by the 1.0 second mark. During the initial 1 second after launch, the engine's average rpm was 4500, which means the engine made 75 revolutions over that 1st second of the run.
...Now repeat the launch, but with the clutch slipping just enough that the engine does not lose any rpm at all over that same 1 sec period. Now the engine's average rpm has increased to 6000, which means it made 100 revolutions during that same initial 1 second period.
...The launch that didn't lose any rpm actually packs 33% more revolutions of WOT power production into the same 1 second time period. If the clutch also slips just right after the shifts, you can pick up a little power production there as well. You might lose a little of that 33% gain due to increased slipping, but there’s a lot left over to make the car faster. Balancing a small loss of mechanical efficiency against a 33% increase in power production can result in a HUGE net gain!
The benefit comes from raising the engine's average rpm over the duration of the run, basically narrowing the engine's operating band by elevating the lower areas of it's rpm trace. It all boils down to adding power at a faster rate than any related loss of efficiency. It's the same concept that makes it possible for the automatic guys to install a "less efficient" converter with a higher slip ratio, but yet still produce a faster run.
Grant
lets say a car has the power to gain speed at an average rate of 6000 rpm per second in 1st gear. Let's also have the clutch slipping until 0.5 sec into the run with the tires remaining dead hooked (i like radials). If the car launches at 6000 and the tires are stuck, that clutch will pull engine rpm down to 3000 by the 0.5 sec mark. Rpm then begins climbing from 3000 as it recovers lost rpm, to 6000 rpm by the 1.0 second mark. During the initial 1 second after launch, the engine's average rpm was 4500, which means the engine made 75 revolutions over that 1st second of the run.
...Now repeat the launch, but with the clutch slipping just enough that the engine does not lose any rpm at all over that same 1 sec period. Now the engine's average rpm has increased to 6000, which means it made 100 revolutions during that same initial 1 second period.
...The launch that didn't lose any rpm actually packs 33% more revolutions of WOT power production into the same 1 second time period. If the clutch also slips just right after the shifts, you can pick up a little power production there as well. You might lose a little of that 33% gain due to increased slipping, but there’s a lot left over to make the car faster. Balancing a small loss of mechanical efficiency against a 33% increase in power production can result in a HUGE net gain!
The benefit comes from raising the engine's average rpm over the duration of the run, basically narrowing the engine's operating band by elevating the lower areas of it's rpm trace. It all boils down to adding power at a faster rate than any related loss of efficiency. It's the same concept that makes it possible for the automatic guys to install a "less efficient" converter with a higher slip ratio, but yet still produce a faster run.
Grant
This was a common practice at least in the late 60s/early 70s, in many of the lower classes. Tires then were nowhere near the capability they are now. It took this clutch slippage to keep the engine in their peak range.