Physics behind trap speed and horsepower correlation?
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From: Michigan (Macomb or Lansing)
Physics behind trap speed and horsepower correlation? As anyone has heard, trap speed correlates closely to horsepower. It seems that trap speed isn't very affected by traction or lack thereof either, while E/T relies heavily on traction. Can anyone explain this concept to me and why it works out the way it does?
I dont think it works out as well as you might think. In a perfect world there might be some kind of equation that will leave you with an X +/- Y =trap speed. In reality, everything is codependent. Traction is first, which is related to torque and available adhesion; HP is a function of torque and engine speed, then wheel speed is a function of available adhesion and engine speed multiplied through a gear set. One of those things changing will falsify any derived equation.
No traction=lower trap
Engine tuned for the top end=higher trap (likely)
Tall gears= lower trap, unless they promote traction off the line, then they are of benefit.
Make any sense? I just slobbered information and opinion.
No traction=lower trap
Engine tuned for the top end=higher trap (likely)
Tall gears= lower trap, unless they promote traction off the line, then they are of benefit.
Make any sense? I just slobbered information and opinion.
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Joined: Nov 2002
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From: Berkeley, California
It is very easy to see why trap speed is a better indicator of horsepower than elapsed time. You could stall the engine at launch, take five seconds and ten feet to restart and still have 1310 feet left to run. There would be almost no difference in your trap speed but your ET increased by 5 seconds. The principle is the same if you spin through first gear. Spinning kills your sixty but has little effect on trap speed. You can waste a lot of time spinning without using much distance.
Last edited by Gary Z; Jul 8, 2009 at 11:11 PM.
Good question. I can usually pull the times in my sig at around 115 mph. Last friday for kicks I made a pass on street tires and ran a 12.80 with a nasty 2.0 60ft, but more interesting to me was I lost 6mph without the slicks. For some reason I thought I would have trapped around the same, since I always hear the same thing about hp and trap speed. A while back when I was trapping 113 with the same slicks and more weight, I launched it and spun really bad and trapped 116mph when 113 was the norm for all day and previous runs. I still cant pull 116 now with less weight
Good question. I can usually pull the times in my sig at around 115 mph. Last friday for kicks I made a pass on street tires and ran a 12.80 with a nasty 2.0 60ft, but more interesting to me was I lost 6mph without the slicks. For some reason I thought I would have trapped around the same, since I always hear the same thing about hp and trap speed. A while back when I was trapping 113 with the same slicks and more weight, I launched it and spun really bad and trapped 116mph when 113 was the norm for all day and previous runs. I still cant pull 116 now with less weight
a normal street wheel/tire combo weighs quite a bit more thus taking more Hp to get that extra rotating mass going and slicks grow on the big end which will help you MPH some as well. This sound reasonable?
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I'm no expert, just trying to come up with an idea of why your trap speed dropped.
a normal street wheel/tire combo weighs quite a bit more thus taking more Hp to get that extra rotating mass going and slicks grow on the big end which will help you MPH some as well. This sound reasonable?
a normal street wheel/tire combo weighs quite a bit more thus taking more Hp to get that extra rotating mass going and slicks grow on the big end which will help you MPH some as well. This sound reasonable?
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I think lack of traction in effect makes the 1320 "longer" for you. You're going through the powerband and winding out your gears but not covering any ground. That 's why trap speeds aren't really effected by traction loss...I think anyways. Sometimes less traction can get you an even faster trap speed.
Instead of thinking of the quarter mile as simply a track you drive down. Think of it as a distance you want your tires to cover while doing the least amount of revolutions, with your engine in it's best powerband all the time.
Instead of thinking of the quarter mile as simply a track you drive down. Think of it as a distance you want your tires to cover while doing the least amount of revolutions, with your engine in it's best powerband all the time.
