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#1 2008-10-22 20:37:38

Från: Gbg
Registrerad: 2003-11-01
Inlägg: 6022

HANDY RULE OF THUMB for Drag race.

Once you have a baseline, you should probably use a rule of thumb that each additional 6 HP will give you another mph. That's for a 3200 lb car that runs 88 mph. If you want the real formula for different weights or speeds, here it is:
HP for another mph above "X" speed: = Wt * (((X+1)^3-X^3) / (228.4^3))
For instance a 89 mph quarter vs. an 88 mph quarter for a 3200 lb car:
HP delta = 3200 * ((89^3-88^3) / 228.4^3))
HP delta = 6.3 HP
Once you're going 110 in the quarter, it would take an additional 10 HP to go 111 mph in the 3200 lb car.

This is the standard measurement tool to evaluate your launch. It's the time that it took you to travel the first 60 feet of the track. Naturally, patterns emerge again after looking at lots of runs and of course these correlate best to time, not mph. Typically, most everyone's 60' time will be between 14% and 16% of their quarter mile time. If it's under 13% or over 17%, this was not your best pass.

1/8 MILE VS. 1/4 MILE
After monitoring tons of good passes, patterns emerge. Typically, the mph at the quarter is around 1.26 times of the mph at the eighth, and the time at the quarter is around 1.55 (många räknar runt 1,56) times the time at the eighth. You can use these values if you only have a 1/8 mile track and get a real good idea of the theoretical 1/4 mile.

One fact of the quarter mile is; no matter how slow or fast your car is, the mph multiplied by the ET will pretty much be the same number every time. Before the NHRA changed the way that speed is measured in 1989, the product of speed and time was around 1400. Let's calculate some easy examples of this. A 14.00 et usually resulted in a trap speed very near 100 mph. A 10.00 et meant around 140 mph. A 200 mph pass usually takes around 7.00 seconds. These are still good rules of thumb to remember, but now the product is more like 1380 for us - The example from Car and Driver above comes out at 1350. (The reason for this shift is explained below). Remember, most everyone focuses on ET so much that they'll even optimize a car for slower mph if it gets them a better ET. (Rear end gearing is one way to do this). Those guys tend to have a product closer to 1300.

Anders Forsberg.
-67 Chevrolet chevy II Nova super sport hard top coupe.
-71 Pontiac LeMans sport



#2 2008-11-07 19:56:49

Från: Linköping, när jag är hemma
Registrerad: 2003-01-30
Inlägg: 3850

Re: HANDY RULE OF THUMB for Drag race.

Men hur blir nu på 1000 fots banorna?


Lägger ofta upp inlägg från min äpplefån, ber om ursäkt för udda, rolig eller missvisande stavning pga av det!
-97 Z28 M6 12,70s 109mph
"I think its better to do right, even if we suffer in so doing, than to incur the reproach of our consciences and posterity" Robert E Lee


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