how much et time does each 100lbs of car weight cost

If a car goes the quarter in 13 seconds at a weight of 3400lbs how much would that same car go if it weighed 3500lbs? and is it linear?

 

about 1 second and tenth/sec ET

You would need to plot it out, but there are variables that would affect the curve.

where HP/Torque is made on the curves, and air resistance of the car.

Once you start getting near the traps, the resistance can have a big influence on ET and 100 lbs delta can be lost.

 

Not linear. More than you probably wanted to know, see the graphs and various formulas for estimation here: http://www.stealth316.com/2-calc-hp-et-mph.htm

Devon

 

I've always heard 100 lbs is worth a tenth. In general, but as stated above, there are variables.

 

ok. i change my goal to sub 15

 

http://www.wallaceracing.com/Calculators.htm

 

What does your car weigh Gary?

As a rough estimate here is some info from the calculators:

4000 pound car with 300 rear wheel HP = 13.81 seconds and 97.00 MPH 1/4 mile
3900=13.70 seconds and 97.83 MPH
3600=13.33 seconds and 100.47 MPH
3200=12.82 seconds and 104.49 MPH

 

To put it easily, and in an extreme case, think of a vehicle weighing 1,000 lbs. If you take of 100 lbs., you've lost 10% of the weight, and the quarter mile will be significantly better. If you have something that weighs 10,000 lbs., and you take off 100 lbs., you've lost 1% of the vehicle weight, and it's barely going to make a difference at all.

 

4400 with me and couple gallons of gas

 

but doesnt hp have to do with an absolute mass variable not a percentage? to take 100lbs down the track in 10 seconds takes a certain amount of horsepower. and 200 takes twice as much and 400 hundred twice that. If you have a 10000lb vehicle and you add 100lbs does it not take the same more hp to dothe same time?

 

Horsepower is not a variable of the weight of anything.....It's a result of a mathematical formula that is derived from actual measured torque. Ok, think of one of those gigantic dump trucks that work on the oil pipeline. Let's say I'm taking one of those loaded down the quarter mile, and it weighs 100,000 lbs. I add 100 lbs. to the load. That truck is going to have no idea it's packing 100 lbs. more dirt in it.

 

My buddy used to have a 450 lb. drag bike, and he and another one of my friends used to drag race it. They were both good riders. The 250 lb. guy used to turn 9.8s on it, and the guy that weighed 175 lbs. would run deep in the 8s, usually 8.7s. That's only 75 lbs. and over a second drop.

 

but will it still take 1/10 of a second longer to go the distance? or no difference because the extra weight is so relatively small. It makes sense that it would slow it down some because the same hp is carrying more weight.

 

Gary take your LeSabre to the track for TNT night and find out how it does:grin:
Then figure out whats needed to make it go fasterp

 

i plan to but i already know it is slow. prob 20 sec.

 

I'm of the opinion that you don't have to use any measurement system whatsoever to get your car to go faster, just use tricks that you know and/or learn about to give it a better feel (that's if you don't care what the numbers are), and what gives you the most satisfaction out of your ride.

If you can't tell if your car is faster without having to take it to the track or pull it out and dyno it each time, then your butt dyno is severely disabled. :laugh:

What you'll feel more than anything is the torque. Perform things that you know for a fact improve it, and with some tuning there will be improvements. Know what you want and where you want it (as well as how to get it), and it'll become a reality.

Engineers do not need to build 10,000 bridges to understand that they need to calculate things out before putting the materials together, and they'll know what to expect within reason as long as they over engineer it to withstand anything that could be thrown at it. Experience is always desired, and if you have enough of that, you can put something together and reasonably expect a predictable outcome.

If you're looking for nickels and dimes for each thing done on split second improvements or 1 MPH increase increments, then take'er to the track.

As others have suggested here and elsewhere (if it matters to you), take it to the track and get a baseline, no matter how it turns out, and then make changes and measure the difference each one made.

For me personally, I don't really care how fast my car can get to 120 mph, it's fast enough for me. It burns rubber and drifts around curves, and I don't need an atomic clock to tell me where I am every inch of the way.

Have fun and be safe, no matter what you do or how you do it.

 

You can find a G tech or other accelerometer for cheap on Ebay.
I found my replacement one for $10.
The G force setting is more useful than E.T's., it factors out driver's error and tire/traction problems.
G force can be correlated to what's seen in the first 60ft of the track (if you have consistent traction, otherwise use higher speeds).
Keep track of weather conditions and use the same procedures every time.

 

I was just reading about those a few minutes ago. 299 at summit. what $10? same thing?

 

Any accelerometer could be used.
I got lucky and replaced mine for a whopping $10, by bidding on one without competition...on Fleabay.
I wasn't looking for ANYTHING more than a G force readout, no fancy features for me.