ok so everyones theory on 100 pounds = 1/10 in the quarter mile is just crap, i mean how could that be a standard amount, it would end up being a ratio of weight to horsepower anyways so it should be a certain percent instead. well yesterday i put it to the test....


all done on my beltronics FX2 http://www.beltronics.com/images/fx2.jpg man i love that thing...

i did about 20 full quarter mile runs out by my dads house, (the country) i ran consistent 13.8s at 101 all day in my NA form. i have about 5 runs with the same exact readings give or take +- .05 and .5 mph

then... i brought my 180 pound brother with me to see how much it would slow me down.....

did about 6 runs with him, high 14.2s and low 14.3s at 95.5 to 96.5 mph is the best i could do, i kept running and running to see if i could get better times, it just wouldnt happen. so that would mean that 180 pounds in my car slows it down 4 to 5 mph and 4/10ths of a second,

now i waited about an hour to do the runs with him in it to make sure heat wasnt an issue. so this shows that weight has more of an impact than you think. just think about why stock Gs have the same exact engine as the Z and run 3 to 4 tenths slower, cause of a 200 pounds +- difference

 

The 100 pounds = .10 "rule" is just a guide.
Obviously if you add 100 pounds to a 800 hp 3000 pound car, it's doubtful
it will affect it by a full .10
As well as if you add 100 pounds to a 100 hp 2200 pound car, it's likely
to affect it much more than .10

But for your "average" car....say 200-250 hp and 3200-3400 pounds
you add 100 pounds and it will slow you down a tenth, give or take a couple
hundredths.

Keep in mind too, your car was probably pretty darn hot after making 20 1/4 mile runs, then adding 180 pounds and making it run hard 6 more times would
surely not make it run at it's best.

 

this was done over a few hours, a couple runs at a time, as i stated i let the car cool off for about an hour before i took him with me, i am going to the track soon and will use the beltronics to see how accurate it is.... and until yest, i would have agreed with the 100# =1/10 but i dont think thats close on our cars.... i think its more like 50-65 pounds equals a 1/10th

 

Some good points you've raised about the differences with the starting weight. I think though he has proved there is a bit more of a difference with the "average car" than what is normally accepted or what you have referenced.

 

I've had experiences to the contrary. One night at a local 1/8th mile, I had 11 runs. On 8 of those runs I had a passenger that weighs roughly 250. There was absolutely no difference with him in, or out, of the car.

Granted, I'm not the most experienced driver, so I still haven't achieved great consistency.

 

Now that's also very interesting.

I don't want to comment on your driving as I don't know you.

 

now after i read this i went out and checked the logs of all the runs, i am showing a 2 to 3 tenths difference and 2 to 3 mph by the 1/8th mile

my 60 foot times were all high 2.1s without him and all mid 2.2s with him, maybe i should have put him in the trunk!!

now i have an auto sedan that runs very very consistent, now i have no control over the other elements or any error cause by the beltronics, but these were all made on the same exact street going the same direction back and forth

the beltronic also measures 0-60 and it runs 5.2 every single time, now with him i couldnt get under 5.45

just having some fun with technology!!!

 

Whoa, wait a minute.
I can't speak for the Beltronics unit, but I know the G-Tech PRO is
amazingly accurate in 0-60 times and pretty darn accurate in the
1/4 mile ET's (but usually reads a bit fast on trap speeds)...
BUT you need to disclose what car you are driving and what mods
you have.

Because if your car is a G35 and it doesn't have a turbo or supercharger
on it, there is no way it's running 0-60 in 5.2 seconds.
That Beltronics unit might be the reason for such a large change in
your times with your 180 pound brother in the car.
It might very well not be as accurate as the G-Tech PRO and
be even more inaccurate as weight is added.

 

i have a G35 sedan with injen cold air, skunk2 plenum spacer, test pipes, greddy evo 2 straighthrough exhaust, lots of extra weight taken out, and a 125 shot, i wasnt using the nitrous at all yest. i have the factory 17s on it now, i ran 14.2 stock so its pretty fast for a sedan, i havent even ran it at the track NA since i have done the latest mods, i always just use the nitrous at the track, my best time at the track is 12.98 at 96, i hit the brakes at the end cause it was spinning a lot through first, i thought it would be a really bad run, my other times are a few 13.00 at 110. i just spin so much in first with N20. i have some slicks now and took them out for two runs last time. first run i put too much air in them, 20psi cause i didnt want to break anything if they just hooked up really well, i spun really really bad, second run i ran 9 psi and ran outta nitrous in second gear, ran 13.00 at like 103. that would have been a nice run had the nitrous not ran out.

 

Maybe track conditions were different that day than when you previously ran. Do us a favor and run again....say maybe 3 or 4 runs with him riding shotgun. Then have him sit on the sidelines and make a few more passes just by yourself. I'm interested to see what the result will be.

 

actually these were all done on the same day on the same exact street. a bunch without him, then an hour later with him riding shotgun, so all the conditions were the exact same, i have been racing cars for a while so i thought about all the elements and made sure they were all as close to the same....

 

G-techs are bs throw it out the window and test it at the track

 

i will have my beltronics at the track next week when i go and i will see how far off it is or isnt...

 

Actually, they've been proven MANY times to be pretty darn accurate!
For somebody who might not have a real track around or who can't afford
to dyno their car after each mod, a G-Tech is a wonderful thing.

 

+1 i think they are more accurate than people give them credit for...

you have to understand though, you have to be on level ground