I see/ hear alot of people talk about what mph they got in the 1/4. Is it just a way of showing what times they could run with traction.

If you have 2 firebirds running 13.00 one is at 100mph and the other is at 105 what should that tell me?

 

Trap speeds (mph at the finish line) are a good indication of how much power a car has. ETs are a good indication of traction, suspension, and driver skill. In your example, the 105mph car has a bit more horsepower than the 100mph car, but the 100mph car got a better launch.

I was at the track with my GN the other day, for the first time. I'm still learning how to launch it best, so my times were anywhere between 14.1 and 13.6, but my trap speeds were ALWAYS 99.xx mph. That means the car makes consistent power from run to run, but that I'm not launching it very consistently.

 

I trapped 106.5 but only ran a 13.4 @ 1475 ft of elevation. There were guys out there trapping lower than me but whopping my *** ET-wise since they had much better traction than I did.

I'm sort of curious as to what kind of times I could be running if I were to try out a pair of DR's and install a few supporting suspension mods with that type of trap speed .

 

Is their a rule of thumb that if a car goes XXXmph then they have XXXHP?

 

It would depend on weight as well.

 

I do believe there is some calculator program for this, where you put in weight, horsepower, and gearing and it gives you a ET and MPH. I think Threxx uses it.

 

My Camaro typical 1/4m: 10.20 @ 144
My Race car 1/4m: 9.40 @ 141

Why is the race car so much quicker but a bit slower? Primarily traction.
Camaro: 10.5x27" tire, ~4,000lbs, "street" type suspension, posi
Race car: 14.5x32" tire ~2,000lbs, 4-link, spool

Why are the traps similar?
Camaro: ~4,000lbs/~900rwhp = ~4.4lbs/hp
Race car ~2,000lbs/~425rwhp = ~4.7lbs/hp

Think of it this way: ET is a function of traction, as well as power/weight. Trap speed is much more related to power/weight, along with aerodynamics.

Rich

 

http://www.cartestsoftware.com/cartest2000/index.html

Badass software takes into account literally hundreds of physics variables and you can manipulate any one or many and see the results. It has a very complete and up to date database of vehicles as well so that you don't have to go finding out all the details yourself.

So far it has given very accurate results for me for the most part. But the most consistant part is measuring the improvements that various changes in specs would make. IE: if I added 65 horsepower and dropped 80 pounds of weight off the car what kind of improvement in the 1/4-mile, top speed, fuel economy, and handling should I expect?

Cooler yet is you can tell it what type of race you're interested in performing best at (ie: 1/4-mile, 1/8-mile, 0-60, top speed), then what transmission you have (auto or manual, it'll know the gear ratios already for most cars) and it will tell you what rear end ratio will give you the best results, what your launch rpm and technique should be, what RPM you should shift at each time , etc. You can also see corrections for temp, humidity, altitude, wind, etc, estimated track times... and the list goes on.

No it's not a substitute for real life numbers, but it sure gives you a good idea of what you might expect as well as what you should consider doing to get to where you want to be.

Heck, I like giving it extreme examples sometimes too... like what if you had 5000hp and a badass aerodynamic rating but weighed a ton... it's interesting in that example to see how slowly the vehicle starts accelerating but at what an incredible top speed it ends up at, and help demonstrates how little weight affects top and acceleration and top speed compared to aerodynamics, gearing, and power.

 

You've always thought that, Rob, yet I don't really hear you offering any better solutions other than actually running the combo in question (which may not always be possible or convenient) - or reading times off the internet, which I find to be typically far over optimistic and/or overexagerated.

It's extremely consistant and far more accurate than any other calculation or "expert guess" I've ever seen - does it beat real life? No. But it's the most consistantly close calculator I've seen - especially when it comes to computing relative changes instead of just final outputs. IE: how many tenths and mph will I gain with 50 extra hp but 20 extra pounds... etc.

 

When you see a good time with high MPH, that car has some power.


Lots of cars are able to pull off a good time, but they're doing it with a lot of gear. So they have a lower trap speed.

My El Camino was like that, at the end of the quarter you'd better promptly get off the throttle or you'll blow the thing up

 

Like LS1's that actually run 12's from the factory?

www.michiganspeed.com
2002 WS6 Trans AM

Owner: MISOMWS6

 

Hey when did you get a new WS6?

 

Cartest estimates an average time, not a 'best' time. Problem with the internet is when a handful of people run 12s with a truely stock f-body suddenly every LS1 f-body owner I meet has a car that runs high 12s from the factory.

...oh really? So you mean you could get in your car right now and run a 12 second time?

Well they couldn't - both you and I know they couldn't, but half of them see to think so and the other half think they would be damn close.

Anyhow... with that said, one of cartest's unfortunate disadvantages is that it assumes factory power ratings are spot-on correct, and they aren't. As we all know the LS1 makes more than 305 hp, but you have to tell cartest what it really makes if you want a realistic average time and such.

 

Correct, it doesn't estimate random failure into its stats - that would ruin its consistancy and the fact that it's a physics calculator when you get down to it; not real life.

But still incorrect because it still estimates an average surface, average driver skill, average weather conditions, average car, etc... have you see where you can change surface traction, potential power output, driver shift time, weather conditions, etc, etc... I bet if I changed all that to 'best case scenario' it would run a high 12/low 13.

 

I agree with robvas. Cartest is fun and has some use. But it doesn't accurately predict 1/4m. times.

Rich