Track Tac

clutch or cam

foreverfaster

foreverfaster

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so running some Little bull rings. just can't get the rpms up where they need to be.. do i just keep increasing the engagement point on the clutch or should i do a cam change,, (build another motor) to lower the power band? tracks are just over 300 feet. long and narrow. clutch is kicking in around 4000. snapps in and out every corner.
 
Maybe the way to look at this is to use peak rpm you are looking for minus rpm drop.
Is that still above peak torque rpm?
If it is, set clutch lockup 2-300 rpm above peak torque and try that.
If it is below peak torque, you can slip clutch a little to keep you at or above peak torque.
Of course, any slippage converts power to heat. An overheated clutch slips more, more power loss, more heat, etc
Depends on how you feel you are at peak hp.
A cam with a wider power band will likely have less peak power. The advantage can be not giving away power to clutch slippage.

If clutch is too hot to touch after a race, you are slipping too much.
 
We have a lot of little indoor tracks around here during the winter and all the modified stuff run 11 drivers and as big a rear gear we can without it dragging in the dirt, usually 69-69. Seen a few 4 strokes with the Burris jackshaft setup but none of the guys running them could say it was good enough to justify the expense of it. Some went back to 11-69 setups. Myself, with the corners being so slow on these tracks, try to set up for the best corner exit speed. We arent in the throttle long enough really ever see the high end of the torque curve.
 
sounds like a gear issue not a clutch issue. set the clutch to torque peak and leave it alone. where does your motor builder tell you to set it at?4000 seems too high
 
OVALTECH1 said:
I’m actually lowering my engagement point 2-300 rpm from where I normally run it and dropping a driver if that’s the scenario
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clutch engagement is one spot and one spot only no matter what track, size, driver, sprocket, weight or style of racing. set at torque peak and only torque peak never 2-300 more or less.
 
J'-remy said:
clutch engagement is one spot and one spot only no matter what track, size, driver, sprocket, weight or style of racing. set at torque peak and only torque peak never 2-300 more or less.
Click to expand...
This is one example where I would disagree.
Say you are turning 7000 rpm max and dropping 3000 rpm in the corners and the clutch is disengaging.
If dropping the clutch engage a couple hundred rpm keeps it engaged, I can guarantee you that lap times will be significantly improved with the torque curves that most kart engines make.

I would agree that we "want" the clutch to engage at peak torque, but that doesn't "always" produce the best lap times. I'll do whatever makes the best lap times. Road course (sprint) racers are often faced with this decision based on track configuration. Slipping a clutch several times each lap is a recipe for disaster.

FWIW, I'd also throw more gear to it (ie larger rear sprocket) and turn the engine higher rpm...if you need to cam it differently, then do that.

-----
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Carlson Racing Engines
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CarlsonMotorsports said:
This is one example where I would disagree.
Say you are turning 7000 rpm max and dropping 3000 rpm in the corners and the clutch is disengaging.
If dropping the clutch engage a couple hundred rpm keeps it engaged, I can guarantee you that lap times will be significantly improved with the torque curves that most kart engines make.
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4000 clutch engagement? that's a bit high. clone and flathead are around 3600. predator is 2700-2900 it has a cam so its a 4 stroke. what motor has a torque peak at 4000? if it was set correctly at torque peak, it wold not be slipping in the corners. yes/no? he's asking if he should INCREASE his engagement. to me that's setting it at a higher stall speed and totally wrong direction to go. i'm concerned the kart has the wrong gear on it. he should lower the clutch engagement and keep the motor locked around the track i agree with you there.
 
J'-remy said:
4000 clutch engagement? that's a bit high. clone and flathead are around 3600. predator is 2700-2900 it has a cam so its a 4 stroke. what motor has a torque peak at 4000? if it was set correctly at torque peak, it wold not be slipping in the corners. yes/no? he's asking if he should INCREASE his engagement. to me that's setting it at a higher stall speed and totally wrong direction to go. i'm concerned the kart has the wrong gear on it. he should lower the clutch engagement and keep the motor locked around the track i agree with you there.
Click to expand...
WKA stock flatheads & animals have for years, and many current stock class clones, peak @ 3900-4000. The rpm I used is just an example...would it matter if he's dropping below the clutch engage @ 2700? Answer = no.

You could most certainly have the clutch engaging at peak torque and still have it disengage in the corners with enough drop. Sprint racers experience it regularly when they run on a technical (high rpm drop) course.

Another example:
Peak rpm 6000.
Drop 4000.
Peak torque & Clutch engage 2700.
Again, I can guarantee you that this clutch will be scortching hot after just a few laps and that the racer would have been considerably faster to set the clutch below peak torque to keep it engaged.

You do NOT want the clutch disengaging in each corner if the low rpm per lap is at or near peak torque.
 
Haven't noticed , but what class are you running in ? What engine ? What tires ? What gearing ? Making a guess at your problem isn't going to help you , without anyone knowing the whole situation ..
 
i'm back... gear, 10 or 11 depending on what's available and i'm on a 69.70,71 gear.. because the racing is tight and we get to bumping around,,, if i leave the edge of the track I wreck a rear gear almost every time. it's a lot of fun, mostly... just sick of the bog coming off the corner.. Note.. getting some new tires this week... maybe will help with some corner grip. Bully clutch red springs. one bolt, one washer out side hole if it matters.
 
If you are running bully gears and 10 tooth, the simple solution is to get a 9 tooth driver.
10-70 becomes 9-63

I've run one a lot and they don't wear terrible.
If running a briggs, less problem with crank breakage than running stock clone cranks.

I think you will find a little more pull off the corner. Might find you can run same ratio ond not bog motor as much
 
I made my own aluminum gear guards to fit a 82 .
Guards got beat up but gear didn't .
Running treads .
Held the kart in the turn if it was rough too .
 
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