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Old 02-22-2010, 12:33 PM   #1 (permalink)
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1/4 et estimate

just wondering what you guys think i could run in the 1/4. i tried using the hp calculator on comp d but i dont know my actual weight. i know my 0-60 is around 4.8 and 0-100 is 12. i also have 315/70/17 tires.
im going to be racing a guy with a 07 shelby gt when he gets a chance, it comes with 320hp. do you think i could take him?
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Old 02-25-2010, 05:50 PM   #2 (permalink)
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Assuming your 0-100 was accurately measured and is exactly 12.0 seconds (there is a big difference in quarter mile times between 0-100 in 12 seconds, 0-100 in 12.5 seconds, and 0-100 in 13 seconds), I'd say you run somewhere between a 12.8 and a 13.0 through the quarter at between 104 and 106mph. Your 0-60mph time is also consistant with these 1/4 mile times (one of my cars used to go 0-60 in 5.0 seconds flat when logging the speed sensor, and it ran consistant 13.3s at 103mph).

Is the Mustang's 320hp wheel or crank? If it is wheel, it'll be a good race. If it is crank, it is probably only a 14 second car.
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Old 02-26-2010, 12:22 AM   #3 (permalink)
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I dont think a HP calculator would work for these. These run totally different than a n/a gasser. HP calculators go off of weight/hp. In a race against the mustang....MPH is the last thing i'd be going for. ET and MPH are nothing related..
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Old 02-26-2010, 10:38 AM   #4 (permalink)
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I dont think a HP calculator would work for these. These run totally different than a n/a gasser. HP calculators go off of weight/hp. In a race against the mustang....MPH is the last thing i'd be going for. ET and MPH are nothing related..
I agree with your conclusion, but for a different reason - I've gone through several people's posted 1/4 mile times/trap speeds and used the calculator, and it hasn't worked very well. The reason is simple, I think. It is because in the end, what really determines how fast a car goes through the 1/4 mile isn't just weight/hp, but weight/average hp over the racing rpms. Being diesels, and especially those with automatic transmissions, these trucks have a very narrow rpm range when drag racing. As a result, they are always at or near peak hp when racing - this dramatically increases the average hp seen when racing compared to a typical gasoline vehicle which makes the same peak hp, and as a result, tends to make these trucks much faster than the hp calculator would predict.
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Old 02-26-2010, 10:44 AM   #5 (permalink)
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the mustang is 320hp at the crank, it is also a standard and i dont know how well he can shift. i think he is a bit scared of loosing because i havent heard back from him lol

i am going to the track tonight so i will be able to find out what im running
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Old 02-26-2010, 11:00 AM   #6 (permalink)
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It is because in the end, what really determines how fast a car goes through the 1/4 mile isn't just weight/hp, but weight/average hp over the racing rpms.
Your MPH will reflect your weight/HP

Your TQ on the other hand it wont....that would benefit your ET. Also your ET can vary all over the place....HP/weight mean nothing to it. The numbers calculators give you is generic.

A car/truck with 300HP can run 12.5@105mph and a different car/truck with the same 300HP can run 13.5@105.... Granted they weigh the same....ET and your ability to 60ft. Having a ton more TQ would extremely benefit your ET, but might not be that impressive MPH wise.

Thats why w/ all wheel drive, a ton of TQ, race him on a short road
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Old 02-26-2010, 11:38 AM   #7 (permalink)
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Your MPH will reflect your weight/HP

Your TQ on the other hand it wont....that would benefit your ET. Also your ET can vary all over the place....HP/weight mean nothing to it. The numbers calculators give you is generic.

A car/truck with 300HP can run 12.5@105mph and a different car/truck with the same 300HP can run 13.5@105.... Granted they weigh the same....ET and your ability to 60ft. Having a ton more TQ would extremely benefit your ET, but might not be that impressive MPH wise.

Thats why w/ all wheel drive, a ton of TQ, race him on a short road

Peak hp is only barely relevant to how fast a car can go through the 1/4 mile if all other variables are in fact variable (as they are between a turbo diesel and a gasoline engine). I have a perfect example - a friend of mine was making 400whp on a 3300lb car at about 6000rpm. He was paranoid about breaking his engine, so he shifted out AT 6000 rpm (so he was seeing that peak hp while racing) and only ran low 14s at about 100mph. Eventually, he got tired of being an underperformer and got over his fear and shifted at just over 7000rpm and ran a 12.6 at 115mph. SAME peak hp, but very different AVERAGE hp. When he was shifting at 6000rpm, the rpms would drop so low that he wasn't making any power down there, so his average power was more like 200whp (and his car took forever to get back up to an rpm range where he was making good power). When he shifted over 7000rpm, his average power jumped to probably over 350whp (it was a turbo charged gasoline engine). A typical n/a gasoline car making 400whp would probably only average 300-325whp, but a turbo diesel making 400whp would probably average 380+whp, since the rpm range is MUCH tighter.

By itself, torque is meaningless to acceleration (based on the physics definition of torque) - the only reason high torque vehicles tend to perform better at the track is that they tend to have much flatter hp curves and therefore make higher average hp numbers when racing because peak torque is always at a lower rpm than peak hp, and hp is calculated from torque and rpms, therefore a car with more torque at a lower rpm will also be making more hp at that lower rpm even if hp is equal between the two cars at the higher rpm. For example, lets say you have two identical cars, except the first makes 500ftlbs of torque at 4000rpm and 400whp at 6000rpm and the second makes 300ftlbs of torque at 4000rpm but also makes 400whp at 6000rpm. Both cars make the same peak hp. But, at 4000 rpm, the first car is making (4000X500/5250) = 381whp but the second car is only making (300X4000/5250) = 229hp at 4000rpms, so while both cars will accelerate the same at 6000rpm, the car making more torque is also making more hp at lower rpms and will therefore will accelerate faster between 4000 and 6000rpm, and therefore will get a better 1/4 mile time and trap speed.

But by definition, only hp affects acceleration.
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Old 02-26-2010, 12:19 PM   #8 (permalink)
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you have two identical cars, except the first makes 500ftlbs of torque at 4000rpm and 400whp at 6000rpm and the second makes 300ftlbs of torque at 4000rpm but also makes 400whp at 6000rpm. Both cars make the same peak hp. But, at 4000 rpm, the first car is making (4000X500/5250) = 381whp but the second car is only making (300X4000/5250) = 229hp at 4000rpms, so while both cars will accelerate the same at 6000rpm, the car making more torque is also making more hp at lower rpms and will therefore will accelerate faster between 4000 and 6000rpm, and therefore will get a better 1/4 mile time and trap speed.

But by definition, only hp affects acceleration.
It may work on paper....but in the real world in real life it doesnt work exactly the same.
The car with the more TQ would probably yeild a better ET, but theoretically both cars should yeild the same MPH.

Have you ever heard the age old saying "HP sells cars, TQ wins races"?

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By itself, torque is meaningless to acceleration (based on the physics definition of torque)
Physics are defied every day. This statement is pretty much entirely false. Not sure what book you got it out of.



HP vs. TQ when racing 1/4 mile are kind of irrelevant to each other.... If you shift at 6000rpms and drop all the way back down in RPMs to the begining of your TQ curve you have other problems to worry about.

....its kind of a pointless arguement. Too many variables....to get THAT technical about.
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Old 02-26-2010, 02:38 PM   #9 (permalink)
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Didn't you read my post? I just explained why a car with more torque would win a race. And torque and hp are physics terms. Why would you use them, but deny their physical definition? I'm a practicing scientist, and I can tell you that sound science on paper DOES WORK in the real world, and the difference between torque and power are based in sound science. It is like saying that in real life red is actually blue and blue is red. No, red it red and blue is blue, by their own definitions. Torque is what it is, and it is a physics term with a physics meaning - and it doesn't influence accleration on its own, but, as I said, hp is torque in relation to rpm, so half of hp is based on torque. Therefore more torque often means more hp, and therefore will increase acceleration, but it doesn't HAVE to be so. 500ftlbs of torque has half the power at 2000rpm as it does at 4000rpm, and therefore 500ftlbs at 4000rpm will accelerate a given mass at twice the rate as 500ftlbs at 2000rpm.
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Old 02-26-2010, 02:50 PM   #10 (permalink)
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Have you ever heard the age old saying "HP sells cars, TQ wins races"?
I'm actually pretty sure the saying is the other way around - torque sells cars, hp wins races. When you drive a car with more torque, it just feels more responsive. When you climb hills, you don't have to floor it, it takes off from a stop with less effort. I used to have a 91 Olds Cutlass and a 98 Mazda 626. The Cutlass had a lot of torque, but very little hp. It ran 19s, but it felt easy to drive. The 626 had very low torque numbers, but the hp was quite a bit higher than the Olds and it ran low 17s (both at 6000ft - I'm sure they'd both be a lot faster at sea level). The 626 sucked to drive - going through the mountains, at times I'd have to drive at 6000rpm in second gear or it would decelerate. It was frustrating as hell. They were of similar weight. The average consumer not understanding that the higher hp car was faster would have preferred the feel of the higher torque car on a test drive.
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Old 02-26-2010, 03:33 PM   #11 (permalink)
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I'm actually pretty sure the saying is the other way around - torque sells cars, hp wins races. When you drive a car with more torque, it just feels more responsive. When you climb hills, you don't have to floor it, it takes off from a stop with less effort. I used to have a 91 Olds Cutlass and a 98 Mazda 626. The Cutlass had a lot of torque, but very little hp. It ran 19s, but it felt easy to drive. The 626 had very low torque numbers, but the hp was quite a bit higher than the Olds and it ran low 17s (both at 6000ft - I'm sure they'd both be a lot faster at sea level). The 626 sucked to drive - going through the mountains, at times I'd have to drive at 6000rpm in second gear or it would decelerate. It was frustrating as hell. They were of similar weight. The average consumer not understanding that the higher hp car was faster would have preferred the feel of the higher torque car on a test drive.
If your using them vehicles as examples Im going to have to end respectively end this debate. Sorry. This similar debate goes on forever with the Big block vs. Small block arguement. Lets just say it takes quite a bit more HP to overcome the lesser HP higher TQ big block. If you've ever rode in a large cubed BB car, and then a high reving high HP SB car.... there is a notable difference.... Each is good...but in its own way.
A ton of TQ will move you out of the hole (if traction permits) HP will keep you going..

On a big diesel truck....TQ will win you on the short track...with a better ET than MPH.. A HP car will walk past you at half track....and keep on going.

Understand?
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Old 02-26-2010, 04:19 PM   #12 (permalink)
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All I'm saying is that you could go to a car club where everyone in the club has the same car (but different engine's/ engine modifications to those cars) and show me their hp curves from a dyno (no rpms shown), and I don't need to see the torque curves at all to tell you whose car will be the fastest through the 1/4 mile and whose car will be the slowest (assuming fairly equal traction, weight, transmissions, etc). By the same token, if you were given only the torque curves (again, no rpms shown), then you would have a very difficult time telling which cars from that information would be the fastest. I remember in highschool doing nothing more than changing to a moderately bigger camshaft on my Chevelle, and the torque noticeably dropped, but my car was still 0.5 seconds faster through the 1/4 mile. If you had only looked at my torque curves with no rpms between the two cams, you would have thought the stock cam was faster.

Torque curves are great at telling you who can pull more weight up a hill without decelerating or without having to down shift, but it doesn't do a very good job of telling you who will win a drag race.

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On a big diesel truck....TQ will win you on the short track...with a better ET than MPH.. A HP car will walk past you at half track....and keep on going.

Understand?
No, I don't understand that (although I know it is asserted here often, that doesn't make it correct logic). There is more load put on the engine during the second half of the track (higher gears, more wind resistance), so if torque REALLY mattered, it would benefit you most during the second half of the track.
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