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View Full Version : Horse power and drag times



Mest30
04-26-2008, 11:40 AM
Hey all,

I was wondering if there was a " in a perfect world" formula or something that dicates x amount of horse power will result in .xx less time at the strip. I realize that several factors play a role in track times, such as track conditions, weather, altitude, drivers weight and several other things. Just looking for a generic, arbitrary number. Say I bought UD pullies and got a before and after dyno run and it proved to gain 10hp. Is there something out there that states 10 extra rwhp is good for .1 at the track (or whatever the number is, just using this as an example). Thanks.

Mest30
04-28-2008, 05:22 AM
Bump. Anyone?

vkirkend
04-28-2008, 05:29 AM
MarauderMark had posted a website that helped you calulate this PM him.

Joe Walsh
04-28-2008, 05:36 AM
Hey all,

Is there something out there that states 10 extra rwhp is good for .1 at the track (or whatever the number is, just using this as an example). Thanks.

That is what was often used to estimate the ET reduction for a Fox body Mustang.
With our Marauders weighing 1000 lbs more than a Mustang, I would expect less of an ET reduction.

KillJoy
04-28-2008, 06:14 AM
I do not believe the HP = ET calcs myself.

They do not compensate for Vehicle Weight, Transmission Gearing, Torque Converters, Rear End Gears and 60' Times. We have seen many times, that some folks can hook, and other can't hook with the same car, tires, day..... etc

As for the possible ET reduction for additional HP Mods.... it "might" work????

KillJoy

ctrlraven
04-28-2008, 07:28 AM
I do not believe the HP = ET calcs myself.

They do not compensate for Vehicle Weight, Transmission Gearing, Torque Converters, Rear End Gears and 60' Times. We have seen many times, that some folks can hook, and other can't hook with the same car, tires, day..... etc

As for the possible ET reduction for additional HP Mods.... it "might" work????

KillJoy

Agreed.

I went from 14.19 on 255/55-18 street tires to 13.72 on 255/50-16 drag radials. 3500 stall converter worked better with the smaller effective gear ratio.

racorcey
04-28-2008, 07:49 AM
Hey all,

I was wondering if there was a " in a perfect world" formula or something that dicates x amount of horse power will result in .xx less time at the strip. Thanks.

In my experience, one of the best $95 investments you can make: http://quarterjr.com/

I've used this program, and its updates for over 15 years. It's so accurate, I, and my racing partner, could get within .1 sec of of its estimates.

Mind you - GIGO (garbage in/garbage out), so correct input is an absolute must, but it's not that hard.

As a general rule for our 4000+ lb cars...every 10 hp is about .1 sec difference. Every 100 lbs is about .1 sec difference. The weather can actually have more effect on your car than any other set of small mods. I always carry a portable handheld weather station with me when I go to the track so I can plunk the current conditions into the program. Just going from 50 to 70% humidity can make a .3 to .4 second change. Temps above 75deg ambient can increase times even more. And finally barometric pressure - going from 29.9 to 30.5 one evening, I gained a .4 second advantage.

BTW, we've used Quarter Jr to show several people how much over or under they've estimated their hp/tq to be.

The gentleman who wrote the program, Pat Hale, is not only an aircraft engine desginer, but a racer as well (in AZ). I've tested several updates for him in the past.

Paul T. Casey
04-29-2008, 06:56 AM
The weather can actually have more effect on your car than any other set of small mods. I always carry a portable handheld weather station with me when I go to the track so I can plunk the current conditions into the program. Just going from 50 to 70% humidity can make a .3 to .4 second change. Temps above 75deg ambient can increase times even more. And finally barometric pressure - going from 29.9 to 30.5 one evening, I gained a .4 second advantage.


This, as I have come to learn, is some of the best advice for the neophyte racer. I've had a front move in during racing, and watched my times drop like a rock, or quicken just as fast. Keep a log which includes weather conditions. Even if it's only descriptive (mostly clear, mostly cloudy, hot, humid, cool , crisp, etc), you'll be ahead of the game as to adjusting your dial as weather changes. Worst case scenario for me nowadays is get the info from the weatherchannel prior to leaving (humidity, barometer, etc.) then rechecking when I get back to where I'm staying. Then I can "average" it out for the event.