looking for some discussion on " wheel speed" in dirt racing..... what is it and how it is applied?
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looking for some discussion on " wheel speed" in dirt racing..... what is it and how it is applied?
How fast your tire is turning over. More in the rear means you are spinning. Your traction control sees it and acts to limit it.Quote:
Originally Posted by north louisiana dirt
yeah, ok.. :-) .. So if your going to stay Legal, I was thinking more along the lines of lower gear ratio, speed through the center and exit in the slick vs the theory of high gear ratios in the slick , helping traction......The engine not having to go from a lower rpm to higher...Higher ratio spins the tires faster when they do break traction..... I always thought Lower was better in the slick..... some like it the other way..... slower on exit with more end of straight a way speed..... they were talking "tire speed" , "forced traction" and "rebound" .... some new theories or maybe just renewed again....
I wasn't sure where you were going, so I was kinda joking around. In general, operating with a lower ratio (bigger number) can have some advantages. You can rotate the car into the corner with the gear if you coast it and tighten entry right back up with the gas pedal and trail braking. Obviously, a lot is going to depend on your engine torque curve and what the driver is comfortable with.Quote:
Originally Posted by north louisiana dirt
A higher gear creates more engine breaking which will help slow the car down on entry with less driver input(braking) which keeps momentum thru the middle. That momentum is what makes forward bite getting off the corner.
A lower gear will carry more momentum into the corner requiring more braking. More braking hurts momentum, and results in less forward bite getting off the corner.
I used to subscribe to the lower gear reduces wheel spin off the corner, but that was before I tried higher gear ratios.
Your problem always starts before its apparent.
My rules to more or less gear are as follows and are just very generalizations and will vary: This IMO is where a lot of the confusion on this subject and can vary person to person.
1. More or less gear to help hook up rear tires from wheel spin: If you have a small engine or peaky engine more gear will generally make wheel spin easier to control. A larger motor or one will a really flat or smooth torque curve might be easier to control with less gear.
2. If you drive with a very small % of wheel spin and drive very straight, your more likely to fall into the more gear helps hook the car up off the corner. If you drive a tighter car and more bent with more wheel spin, you will likely find less gear helps hook you up.
3. More gear tends to loosen you up on off throttle entry and less tightens you.
4. Corner RPM vs torque peak of your engine: Say an engine torque is still climbing at say 5000 RPM and is still making large increases to its peak at 5600 RPM. Lets also say at this track your lowest corner RPM is 5000. By adding gear and increasing that to 5400 you can hold the gas pedal steady and not have a large increase in torque output from the engine as it increases RPM thus induce wheel spin when you didn't move the gas pedal. All of this comes into play but if you have an engine or scenario where you having a hard time hooking up, running the engines corner RPM's past the torque peak can help by running on the back side of the torque curve where torque is lowering as rpms increase vs front side where they are increasing. That is sort of hard to explain but hope that makes sense.
4A. This goes with #4: A paperclip type track that has a larger variance from lowest RPM to highest RPM vs a momentum track that has a smaller range of low to high RPM. Again this comes back to torque curve, on the paperclip where rpm will fall much lower below torque peak adding gear may help exit but you have to deal will excessive RPM on straight. Where on the momentum track where RPM's barely change, taking gear out to reduce the overall torque to the rear wheels may help (Torque output x gear ratio).
Actual wheel speed used around the track (tire slippage %) is a whole other subject in itself, lol,
Mr. Flat Tire: I guess I am a little confused.... when I say "lower ratio" .... I think like going from a 567 (high) to a 668 (lower)... when I say "higher ratio" .... I think like going from a 668 to a 567........ 668 lots more rpm overall on the motor, 567... less rpm overall on the motor.... just making sure we are comparing apples to apples.....thanks
Yes, peoples terminology is different but pretty sure that's what flat meantQuote:
Originally Posted by FlatTire
my post was more gear = higher number/more gear ratio and less gear = higher number/less gear ratio
Sorry, Yes Billet has me figured out. Higher Gear=Higher Number and Lower Gear=Lower Number.