Times and Speeds for drag racing, what do they mean?

[icebluecuda]

I am a newbie when it comes to anything beyond stock restorations and rebuilds. My background is in small and big block Mopars, specifically E Bodies. No real drivers seat race experience... Yet!

I helped a friend recently at Bandimere and he was discussing the ETs and MPH of his passes and his competitors. (Hi Ryan )

One of the my friends competitors was running slower ETs, like 10.5 @ 135 or so in heads up racing, and my friend was running a 10.3 @ 130. The other guy has a higher speed, but a slower time. What does this mean? Why is the other guy faster but with a slower ET?

When looking at timeslips, what information can be gleaned from the 60fts, 1/8ths and so on? In other words, what do you guys look for?

Thanks!

[Makina]

I personally look at the whole slip, or at least what the track reports out. Some give a better breakdown in times than others.

I typically run 12.1's @113 on 1.6 60's, at least before the new suspension. Most cars run 12.8's-13.1's at those traps, but my car is probably 500lbs ligther, and leaves the line harder.

ET's and trap speeds don't necessarily correspond from car to car, you have to look at the differences between setups.

You're buddy could have better gearing, has a lighter car or just leaves the line harder.

Hard to tell without comparing timeslips.

The higher trap car has more power though, that's for sure.

[Bubstr]

This may give you a little more incite to what a time slip can do for you.
http://www.motorsportsvillage.com/timeslip.html

[randy331]

One of the my friends competitors was running slower ETs, like 10.5 @ 135 or so in heads up racing, and my friend was running a 10.3 @ 130. The other guy has a higher speed, but a slower time. What does this mean? Why is the other guy faster but with a slower ET? !

If it's heads up (no breakout) drag racing, the finish line ET is what wins races, well that and the reaction time combined. Your friends car will most likely have a better 60'. 330" etc. but is most likely farther past it's peak power because of gearing,tire size, and maybe converter slip, if it's an automatic.

When looking at timeslips, what information can be gleaned from the 60fts, 1/8ths and so on? In other words, what do you guys look for? !

That depends on if you are bracket racing, and trying to find out where you gained/lost time, or hunting for lower ETs. If you are hunting for lower ETs, for me start with the 60' time.

Randy

[jim_ss409]

Here's a calculator that's pretty good... http://www.wallaceracing.com/etcalc.php
You input any one thing like et, mph or 60' time and it will estimate what all the other interval times should be. It seems really close for the average 3400 lb drag car on slicks.

[rskrause]

Mph through the traps is pretty directly related to hp, weight, and to a lesser extent aerodynamic drag (more effect the faster the car is). IOW, two cars with similar hp/weight will have trap speeds that are pretty darn close (unless there is large difference in aerodynamics). Suprisingly, traction does not play a large part in trap speeds. I have never understood the physics of this, but it is indisputably true, at least within the range of conditions commonly encountered. However, traction plays a big role in ET. Each incremental gain in 60' time will lead to a somewhat greater improvement in ET. That's pretty easy to conceptualize.

When two cars are very similar, or it's the same car after some changes in setup is where things get interesting. Subtleties like shift points, area under the hp curve (vs. peak hp) and so on become important in gaining the fractions of a second that win many races. For example, I recently changed cylinder heads on my bracket car. They flow better than my old heads but the compression is lower. Peak hp is essentially unchanged and occurs at about the same rpm on the dyno but torque is up ~7% in the rpm range that the car sees on the track. The trap speeds are a touch faster, but the ET is improved by nearly 0.1 second, corrected for conditions. That is what you would expect, but it is interesting to see it in the real world.

Interesting stuff.

Richard