The "calculator" is this case is actually my calculator and the formula average whp (NOT flywheel hp) = 197 * weight / et^3. This is straightforward to derive from basic physics and gives the minimum hp needed to run the et. It's a minimum because it only takes into account hp used to accelerate the car and ignores hp that goes to overcome wind resistance and friction, and if the hp isn't constant the peak hp will of necessity be higher than the average. I think that at this level what it really says is how hard it is to get accurate hp measurements from a dyno, especially with a turbo motor and automatic transmission with unlocked torque converter.
Big Dyno Numbers from a TSM 109
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The "calculator" is this case is actually my calculator and the formula average whp (NOT flywheel hp) = 197 * weight / et^3. This is straightforward to derive from basic physics and gives the minimum hp needed to run the et. It's a minimum because it only takes into account hp used to accelerate the car and ignores hp that goes to overcome wind resistance and friction, and if the hp isn't constant the peak hp will of necessity be higher than the average. I think that at this level what it really says is how hard it is to get accurate hp measurements from a dyno, especially with a turbo motor and automatic transmission with unlocked torque converter.
turbocliff
I Slang in my white T
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If your calculator does not take into consideration "friction" (which could translate to loss through the drivetrain...) would that not be FLYWHEEL HP?
Cause to be honest I believe that number to run a 3550lb car into the 8.90s is pretty dead on.... if we are talking Flywheel...
I know several cars heavier than 3550lbs, that all make less than 900 to the tire and run 8.60s and quicker..... But using your formula I think the result is very close on what the FLYWHEEL HP should be.....
johnplogii
Senior citizen
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My moroso calcutator says it takes 926 hp to run 9.0 at 150mph in a 3550lb car. I always thought the moroso calculator was a little conservative compared to online calculators. The TCI calculator says it takes 935. I know these numbers are rear wheel as you could only guess flywheel hp because of varying power loss through the drivetrain. If the car in question is a 9 flat car maybe the dyno is off? I have only dynoed my car one time and it was on a mustang drag simulation dyno. I ran a 5.42 at 132mph 1/8th mile on the dyno. My car has run an actual best time of 6.22 at 110.xx so this shows how far off dynos can be.
John
John
turbocliff
I Slang in my white T
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LOL
I'm just sayin... If my 3550lb buick made 950+ to the tire and ONLY went 9.0 @ 150.... I'd f@#king BURN it.
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Back in 94 my 218 cu.in SS/DX car ran 8.93 154 weight 3500 with driver I estimated 950 on a quarter JR. program & never was on a dyno. I don't know if it was calculated at the wheels or engine. I did all the tuning on the back street & the neighbors would come out & watch . Fun times back then. You guys are making me feel bad that I no longer have a race car.
Back in 94 my 218 cu.in SS/DX car ran 8.93 154 weight 3500 with driver I estimated 950 on a quarter JR. program & never was on a dyno. I don't know if it was calculated at the wheels or engine. I did all the tuning on the back street & the neighbors would come out & watch . Fun times back then. You guys are making me feel bad that I no longer have a race car.
For as long as I've been online (20 years
), every time someone posted a number from any of the online hp calculators the next question was always "Is that flywheel or rwhp?" . Most people seem to believe the answer is flywheel hp. I finally got curious enough about 8 years ago and went through the physics to derive the formula myself so I would know what assumptions were made, and the formula I posted is definitely as I said, the hp applied to the track that results in acceleration of the car (which means the online calculators and slide-rules give whp, not flywheel). There are no fudge factors or loss guesses. The factor of 197 results strictly from using the units of hp, pounds, seconds, a standing start, constant acceleration, and a 1320 foot long track. There is no way to measure or calculate the hp that goes into any losses like friction or wind resistance from the time slip so the formula ignores all those. That is why it is a minimum estimate - you have to put at least that much hp to the track to run the number. The more your tires or converter slip or the worse the aerodynamics are the more hp the engine has to make (flywheel hp) above the calculated minimum to put the same amount of hp to the track to accelerate the car to that et, but to run that et you have to have at least the calculated hp.Eric Rankin once told me back in the late 90's that his slicks were only lasting 10-15 passes once he got down to about 8.50. Then he added a rear wing for downforce, lost at least 10 mph, picked up a tenth or two, and his slicks started lasting 30+ passes. If he was spinning the tires that much on well prepped tracks with hot slicks, how much is the average 8.50 car spinning on the dyno rollers? I've checked the formula using at least a dozen hp-et/mph pairs from postings and magazine articles and up to about 650-700 hp the agreement is very good, maybe +/- 20-30 hp at 700 hp (or +/- 4%). Above that the calculated hp from the et is usually higher than dyno numbers, sometimes as much as 30-40%.
The problem with using et to get hp is the problem of running the same et over and over - it is hard to get a consistent answer. The mph is usually much more consistent because it is much less dependent on the 60' time while the et is all about the 60'. For a given vehicle type you can come up with a formula like et=1356/mph, use that to calculate an average et for a given timeslip mph, and then use that to estimate hp. I think that is more consistent but the problem is that "1356". You will find numbers ranging from 1320 to 1370 built into various online calculators and the slide-rules, but the "correct" one will be different for each vehicle type. I fit the quickest 160 or so et-mph pairs from the gnttype reader's rides list covering et's from 13.50 to Tweaked at 7.70, and 1356 gives et's +/- about 0.2 sec or so for Regals. Camaros, dragsters, whatever, will all need slightly different "constants"
, but 1356 works well for TR's so long as you understand that it isn't perfect. The online hp calculators and slide rules that start with mph instead of et all have this constant built in, and none tell you the type of vehicle they were optimized for, which is one reason each one gives a slightly different answer than the next.[The Reader's Digest derivation, from a post in Nov, 2001 is: I wasn't sure myself so a while ago I went through the derivation. If you assume constant acceleration (use s, v, a, t for distance, speed, acceleration, and time) then s = 1/2 * a * t^2 and a = 2 * s / t^2. Also, force = m * a (m is mass), work (W) is force times distance, and power (P) is work divided by time. That gives P = W / t = F * s / t = m * a * s / t or
P = m * 2 * s^2 / t^3
With m in kilograms, s in meters, and time in seconds, P will be in watts. Put in 1/4 mile and convert kg to pounds and watts to horsepower and I get:
P (hp) = 196.9 * weight (lbs) / (elapsed time (sec))^3
]
[On the count of three you will awaken feeling refreshed and calm; one, two, three, SNAP
.]It takes more than HP to get a number on a TSM car. Its more about you manipulate what HP you have. But the more you have the more you've got work with.
I hope I can hang with a 800+hp car, caus I know I'm not making that much. I guess we'll find out in Reynolds.
I hope I can hang with a 800+hp car, caus I know I'm not making that much. I guess we'll find out in Reynolds.
V8Assassin
100mi away ready 2 strike
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Have you guys found a car hauler yet???
wow.... crazy numbers . what kind of cam profile is a Buick V6 running to throw those kind of numbers up ?
I heard someone was using a 248/248 a while ago...
lol, you guys are funny. The power has been there all along. Getting it on the track and having that perfect pass is a little harder to do..
This dyno session just proves that some changes that were made to the car actually raised the HP above what this car had on previous runs. It is very promising cause with more HP that "perfect" pass isn't as important to put "the" number down.
This dyno session just proves that some changes that were made to the car actually raised the HP above what this car had on previous runs. It is very promising cause with more HP that "perfect" pass isn't as important to put "the" number down.
I heard someone was using a 248/248 a while ago...
Talk about BBC numbers there...
I guess that little 218 hydraulic roller isn't quite enough anymore.
I heard someone was using a 248/248 a while ago...
get it right 244/244 turbo killer
I'll second that on turbo killer lol.
Team Banana
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I like the changes you made to your sig Kevin!!!
The big cam was supposedly in Tony Occhopinti's engine...the one that split the block in two!
