“For a good launch off the line, such as at the start of a drag race, a certain amount of tire spin is desired.”
I am curious about how many people actually believe this? Also, is it true (No)?
I think it’s a pretty simple concept: Peel out, lose time. Small peel=small loss in time, long peel=large loss in time. Maybe I’m being ignorant, but peeling out, even chirping, is technically not the best way to get your best time, unless your car for some odd reason has a unbelievably crappy low-end torque curve, which doesn’t really exist in production cars.
Just talking with people here and there, there seems to be a HUGE amount of disagreement with this, so please either prove me or the site wrong. And don’t say that peeling out gets the tires hot and sticky or “gets the RPM’s up”! I hear that too much already!
Did you read the entire section? It has some interesting insights on getting the most acceleration from a car that is poorly suited to drag racing because of front wheel drive and a flat torque curve. Small displacement engines don’t develop as much power at low RPM as big fat V-8s. They suggest allowing a little wheelspin to allow the engine to get close to peak power then carefully modulating power to get the wheels to grip as the car catches up to wheel speed.
It doesn’t get the tires hot and sticky? Last time I was at the race track, I saw cars peeling out in place, making huge clouds of smoke, and that was the reason everyone gave me. That was before the drivers were given the signal to start, though.
Mr2001 what you were told is true but the OP is asking about spin while actually leaving the line.
It seems that some amount of spin is desirable. I have heard 10 to 15% seems to be a benefit. It seems to me that if I lift enough to completely stop spin, the engine is not producing lots of power. If I hit it as hard as possible I get to much spin and that is not good.
There seems to be, as in many things, a give and take involved. No spin and one does not use enough power, to much spin is over powering the tires, and just a small amount is making sure that one is applying as much power without over powering the tires. Kinda like raising the price of movie tickets causes a loss in sales but also increases profit. Too much of an increase will lose enough sales that the profit increase will not help.
…which then takes more engine power to overcome said traction and produce the desired amount of slippage, meaning you launch with the engine in a more effective RPM range.
But as suggested above, this a technique to PREPARE for launching, as opposed to the controlled wheelspin WHILE launching.
In physics, friction is considered to be one of two types: static or dynamic. Generally, static friction (where the two objects are not moving against one another) produces twice the force as dynamic friction (where the two objects are moving against one another) when all else is equal.
If friction was the only consideration, and assuming car tires aren’t a special material that somehow produces similar friction statically and dynamically, spinning tires reduces the force transfered to the pavement. I’d think that would reduce the acceleration.
If RPMs are a concern I’d rather slip the clutch than the tires, as I have much more control over it. Is it the fine-tuning of the clutch slippage that produces the slight tire spin? Is this fine balance of power transfer through the clutch one of the important skills in drag racing?
Wheel spin is too hard to control to use as part of your race strategy. You want to rely on the consistency of the clutch and the torque converter to get the best launches. Racers will use wrinkle wall tires and underinflate them to get the most contact patch with the track.
Spinning tires expand and get narrower so the cantact patch is less.
Spinning the tires results in less HP getting down on the track.
Ive seen cars with less HP beat cars with more HP because they didnt spin out. A consistent controlled lauch is always best.
FWD import tuners are often rodded out with turbos, and turbos need revs to produce the required boost. Since its easier…and possibly cheaper…to change tires than it is to change clutch assemblies, peeling out during launch may take the place of letting out the clutch, and thus preventing burning the clutch material.
That is if one has a tunable clutch - not a common thing
in drag racing the launch happens far to fast for the driver to moderate the throttle and the clutch. The driver will hold the rpm’s at a level then just dump the clutch If there is no wheel spin there is a good chance that more power can be used and on the next run the rpm’s should be held higher before dumping the clutch.
There are tunable ignition systems that allow the driver to just hold the throttle wide open and the engine will only rev to a set rpm so that the most can be applied to the tires.
IF youre using race tires, do this on street tires and all youll do is make 'em wear out sooner. A little spin on street tires is good to get teh dirt and gravel of, but thats it.
I always thought (I drive a formula firebird) that off the line you should rev the RPM’s to whatever RPM you deem necessary and then use those RPM’s essentially as a “generator”. You dip into this easily-powerful-enough-to-peel-the-tires “generator” by letting out the clutch just enough so that the tires do not peel, all the while giving about 40-50% throttle, then when the cars’ speed reaches the corresponding previous engine RPM, you dump the clutch and give plenty of throttle and be on your merry way.
For my car, which has a pretty tall first gear (46mph), I rev to about 2.5k RPM’s (peak torque), then clutch it, and then eventually fully connect the engine to the wheels at about 2.5k RPM’s, and then pretty much floor it. This process, while admittedly putting some decent wear on the clutch, ensures that my car is testing the friction between the tires and road the whole way through first gear. By peeling a little, such as suggested, I would be losing time comparatively.
Am I driving my car correctly? How is this so much different than an acura? Just rev the acura to 4-5k or so… wear on the clutch is an issue, but not when money is on the line.
B&IWhat racing clutch is not capable of slipping controllably and strategically? Every car I have driven has enough play and stages in clutch pressure to allow minor adaptations while accelerating off the line to assure testing the friction but not peeling out. It’s all feel. After driving a car enough, I just know how far to let the clutch out and how slowly to let it out. I never dump a clutch when in a serious race… is this wrong or just preference?
hauss:
All the conventional racing clutches are just a pressure plate and a disc. The extremely high dollar transmissions/racing cars use clutches that have adjustable pressures that come on at different times.
Every car I have driven would rev to red line almost instantly if I were to just slightly apply pressure to the clutch with just moderate throttle.
If you mean by “slipping controllably and strategically” taking maybe a half a second to release the clutch in order to not totally shock the tires, while going from about 1/3 to WOT during the release, then yeah, especially with street tires.
If I punch B&I (automatic trans) at less than 60 mph I will experience some spin but if I let up the car will slow down.
The preference is to go fast and in my experience, a slight amount of spin is ensuring the most is making it to the street.
Something has to slip, otherwise the engine will bog down. Since it’s easier to dump the clutch (thus spinning/“slipping” the tires) than it is to finely modulate it (slipping the clutch), I’d say that is why the site listed in the OP reccomends peeling out. Also, clutches are going to be more expensive and challenging to replace than tires, which probably plays a role, especially with these guys who thinks Mom’s '87 Accord is an IHRA vehicle.
So, you guys just think you are not capable, or your cars are not capable, of sending almost the perfect amount of torque to the wheels without peeling? Ok, let’s say we all believe that we humans can’t do that. I would rather err on the non-peel side and lose some time, rather than err on the peel side and lose more time because of trying to re-gain traction. The key is patience for me. I play by the rules of my tires. I acknowledge the fact that my street tires won’t let me launch off the line, so I indulge in their inferiority and do only what they let me do, with some higher RPM’s, some clutch slipping and very little throttle. When it’s all said and done, there is a creep off the line, a small chirp when the clutch is competely released and a strong pull until redline, then another chirp. I do this, while the guy next to me is peeling out and waiting for his tires to regain traction. Then his car ends up falling behind in the workload, eveyrthing else held equal. I see other guys that like to peel out a little, and I see myself as a better driver over the long run with this method because it ensures that I never lose too much time. Is this wrong or preference? Pretty simple concept, considering dynamic vs. static friction and all… If you know your car well enough and your throttle and clutch are good enough, why not use the better of the two?
Yeah, this is just about what I am saying. But, not peeling out, mind you. I would rather have the most control over any slippage, so I want the slippage to be in the clutch, not the road. (I usually get halfway through the intersection before fully connecting the engine to the wheels.) Do you agree with this?
Sounds about right - it would be different for different cars.
Most of the faster cars I have driven usually still require some throttle control through the top of first and most of the way through second gear.
Also, by slightly spinning I mean just a little bit. Not smoking, going sideways, and fishtailing off the line. The slight spinning would barely be noticeable
