trap speed vs traction?

Let's say two different cars trap the same, but one runs half a sec faster.

14.0 @ 100 mph
14.5 @ 100 mph

It would seem the lower et would be produced by way of better traction. If we eliminated the starting line advantage and went from a roll say 40 mph what would the end result be?
I would guess that weight and gearing will be factors, curious to hear your opinion.

Thanks

1/4 mile trap speed is almost directly proportional to hp-to-weight ratio, especially in the 100 mph range. 100 in 14.0 is very typical for a street car. The 0.5 second difference could easily be the start. Have you ever been 0.5 slower in the 1/4 than your best time? If you haven't you probably will!

IMO, with a 40 mph roll, both cars would reach 100 in approximately the same distance in the same time presuming the 40 mph start didn't favor one car. This could occur if the optimum 1-2 shift for car A was say 37 mph and 43 mph for car B.

My conclusion: gearing could make a difference, but the cars have the same power to weight.

the roll-on advantage comes when two cars have the same ET, but one has higher trap speed.

14.0 @ 100
and
14.0 @ 105


the 105mph car is gonna take the lead in a roll-on because it probably has more power.




keep in mind though, you usually trap 1-3 mph faster when you get a ****ty 60ft time, probably because you cross the line in a faster accelerating part of your power band.

trap speed is calculated by the time it takes you to pass through a small section at the end of the track (i forget the distance)

60ft distance, one laser 60ft before the finish line, and one
laser on the finish line..

it just so happens back many years ago they used to have
a laser 60ft before the line, and 60ft after. which would really
screw up the mph readings since anything can happen in 60ft
after the line, like hitting the brake.

wow 14.0 at 100mph... mine's only 97mph running 13.88's :)

I agree with the consensus here, power to weight ratio! An engine making 400 hp and pushing 3800 lbs vs an engine making 350 hp pushing 3400 lbs could end up with the same trap speed.

It's not all in the launch! It's also got to do with the torque curve of the engine, especially in the mid RPM range. Many times you will find a cars running near identical trap speeds and MPH even though one might cover the first 60' several tenths faster.

Case in point: My 94 Formula vs. my brother's 3.4L 4-cam 86 Fiero. Both run about 13.5 @ 105. But my 60 foot is 2.2 seconds. His is 1.8 seconds. The Fiero can launch HARD off the line (5000 RPM clutch drop) with all the weight over the rear, where the Formula has to be walked out slow. Fiero jumps out to a quick lead but the Formula reels him back in and pulls even by the 330' mark. Then we just sit side-by-side the rest of the run. My big LT-1 has a much broader, fatter torque curve which helps low acceleration considerably in the lower speeds and the first 2 gears. But once that's over it's purely HP/weight from that point up.

Originally posted by Nitromethane
wow 14.0 at 100mph... mine's only 97mph running 13.88's :)
Hmmmm, and my car ran 14.008 @ 103 mph last year?!:irk:

Well, I pretty much agree with the direction people are going in, but I will add a couple of things. First, it doesn’t have to be the launch, it could be something like bad shifting, mismatched gear ratios (shifting right before you cross the line)…

Second, if this was just a driving issue (bad launch, bad shifting…), typically, if the car running the 14.5 fixed the issue (by that I mean, learned to drive, not put slicks on it), it would more likely run something like a 13.3@104, while the 14 would probably be more like a 13.5@101.

From a roll I’d expect both cars to stay pretty even…

FWIW, my near stock ’87 L98 formula went 13.5 @ 98-99 (slowest run in the 13.5’s was a 97.6) on factory, 16y/o radials with a 1.8 60. My ’97 WS6/M6 car turned a 13.03 @ 106 with a 1.74 on the stock gsc’s with nothing but gears and a HPP+ to move the rev limiter.