---------- > From: Plunkett, Dennis > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: Ignition timing, 2nd iteration.... > Date: Tuesday, May 02, 2000 5:18 PM > > > -----Original Message----- > > From: Andrew Warren [SMTP:fastfwd@IX.NETCOM.COM] > > Sent: Wednesday, 3 May 2000 9:05 > > To: PICLIST@MITVMA.MIT.EDU > > Subject: Re: Ignition timing, 2nd iteration.... > > > > andy howard wrote: > > > > > > I read that pro street stock racers use timing computers to help > > > > with traction, and guard their curves with their life. > > > > > > Do you need to tweak the timing for that? > > > > Andy: > > > > He doesn't have many other choices; traction-control is banned > > in his form of motorsport, but ignition timing curves, gearing, > > and rev limits are "free" (i.e., they can be set to whatever he > > likes) in most classes. > > > > > I'm just thinking out loud here. Since you have maximum traction > > > when there's no wheelspin, maybe you could devise a system that > > > compared the rotation of the front and rear wheels and slightly > > > backed off the throttle if it detected any slipping, checked again > > > and backed off if... etc. > > > > > > If it detected no slipping and your foot still hard down on the > > > pedal it could nudge the throttle up again until wheelspin started > > > again. > > > > That's the way the traction-control system on my car (and most > > others) works, and it's fine for keeping the wheels from > > spinning on ice or other slippery surfaces. It sucks, though, > > for drag racing... For many reasons, some of which are: > > > > 1. Wheelspin on launch is NECESSARY for the fastest times > > > > 2. The deformation of the rear tires under heavy > > acceleration changes their circumference (in the wrong > > direction), so the traction-control system will incorrectly > > see slippage when there is none > > > > 3. Maximum traction isn't developed with no wheelspin, > > anyway; the most acceleration is developed when the tires > > are slightly slipping > > > > -Andy > > > Correct, it is around 6 to 10% slippage > > Dennis > > > > > === Andrew Warren - fastfwd@ix.netcom.com > > === Fast Forward Engineering - San Diego, California > > === http://www.geocities.com/SiliconValley/2499 This is so cool. I can't believe it, but I am learning more on the piclist than I do on Car techboards. I am leary about the claim that tires offer more traction when slipping, but have been in many circumstances when I get poor 60 foot times when the track is sticky and my tires hook. And real good short times when my tires "chirp, chirp, chirp"! So I am going to take this seriously. The thing I wanted to say though, is that I am using street radials. The reason they are so poor with acceleration is that they don't deform. They are like accelerating with wooden wheels. John