Launch RPM

[weedburner]

Originally Posted by terry1

What would be an acceptable drop in RPM between the launch RPM and when the clutch is released?
Terry K

Something has to slip to get a manual car launched, there are a few schools of thought...

Most common is that slicks need a few rotations of the tire off the line, which helps keep the car from bogging too hard until the car has a chance to gain some speed. Problem is the engine likely does not have enough power to break the tires loose on it's own, so the clutch needs to hit hard enough to cause some rpm drop. That rpm drop is evidence of the engine borrowing power from it's rotating assy to get the tires turning. If the tires are pretty closely matched to the conditions, it won't take much rpm drop to get the tires turning. If the tires stick too good, it's going to take more rpm drop to break them loose.

Personally I prefer to keep the tires stuck and let the clutch do the slipping, which makes it possible to leave without any bog or rpm drop at all. This maximizes power production by raising your average rpm during launch, and after all shifts made using the clutch. The fast Coyote Stock guys i mentioned above use this method.

[CJME]

This is a strip only car. Current clutch is a non adjustable Ram powergrip (Sintered iron/Organic). The trans has a 2.20 first gear. Engine is a 12.5:1 iron headed 327 running on VP 110. Is there a way i can get the clutch to slip more on the launch? I will try raising air pressure.

[btrc]

Just curious about the Coyote Stock guys. What transmission are the fast ones using? 4 speed, 5 speed?

[weedburner]

Originally Posted by btrc

Just curious about the Coyote Stock guys. What transmission are the fast ones using? 4 speed, 5 speed?

They are allowed to select from a menu of approved 5 and 6spd transmissions and ratios. 4th is always 1:1, so they only use 1-4 and generally remove the overdrive gears. I might add that they are required to shift using the clutch, no clutchless shifts allowed. Here's a link to their '16 rules... http://www.nmradigital.com/dl/rules/cs.pdf

Permitted Manual Transmissions:
1. Tremec T5
2. Tremec T45
3. Tremec T56
4. Tremec TR3550
5. Tremec TR3650
6. Tremec TKO
7. Tremec TKO-II
8. Tremec TKO500
9. Tremec TKO600
10. Ford Getrag

[Stephen & Horace Johnson]

Originally Posted by weedburner

They are allowed to select from a menu of approved 5 and 6spd transmissions and ratios. 4th is always 1:1, so they only use 1-4 and generally remove the overdrive gears. I might add that they are required to shift using the clutch, no clutchless shifts allowed. Here's a link to their '16 rules... http://www.nmradigital.com/dl/rules/cs.pdf

Permitted Manual Transmissions:
1. Tremec T5
2. Tremec T45
3. Tremec T56
4. Tremec TR3550
5. Tremec TR3650
6. Tremec TKO
7. Tremec TKO-II
8. Tremec TKO500
9. Tremec TKO600
10. Ford Getrag

They are using the gforce 101A trans. All those listed above were breaking like toothpicks!!

[weedburner]

Originally Posted by Stephen & Horace Johnson

They are using the gforce 101A trans. All those listed above were breaking like toothpicks!!

Sorry, i copy/pasted from the original '16 rules instead of the mid-season update, didn't notice that the additions were not on there...

• G-Force –G101A, GF4A – 2.933, 1.867, 1.333, 1.000
3.000, 1.870, 1.340, 1.000
3.173, 1.960, 1.346, 1.000
3.252, 2.009, 1.380, 1.000
3.300, 2.100, 1.406, 1.000
• Jerico –DR4 -
• Liberty -LCS 5000 4-Speed**
• Andrews Transmission –A431 H-Pattern 4-speed**
**Contact NMRA Tech Department for permitted gear ratios

[weedburner]

Originally Posted by CJME

This is a strip only car. Current clutch is a non adjustable Ram powergrip (Sintered iron/Organic). The trans has a 2.20 first gear. Engine is a 12.5:1 iron headed 327 running on VP 110. Is there a way i can get the clutch to slip more on the launch? I will try raising air pressure.

Here's a few options...

1- less aggressive disc
2- smaller diameter disc or reduce the effective diameter of the disc you have
3- reduce clamp pressure by either swapping to a weaker PP/spring or shimming your existing PP away from the flywheel
4- temporarily hold back some clamp pressure with your foot, basically ride the clutch out for 5-10 feet. Adding an adjustable spring loaded pedal stop can make it easier to consistently find the sweet spot in the pedal travel
5- temporarily hold back some clamp pressure with a timed mechanical device