Tci horsepower calculator
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KL Mallender
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- Apr 16, 2007
I'm not familar with TCI's calculator, but have used Moroso Power Speed Calculator #89650 for years, if you use net or rwhp numbers it will be dead on, and it's projected ET at actual mph is closer than any program I've ever used and once you have truthful engine power numbers you will have a mph you can expect, ET has and always will be decided by your ability to "Apply" that power, if you align your mph speed first, you will see how close or how far off your ET is, power to weight is dead on when based from mph.
Kevin.
Kevin.
Most of the online calculators that I've looked at estimate wheel hp applied to the track, although almost none of them say one way or the other and most people have no idea, and many will argue that it must be flywheel. All of that is why I derived them myself a long time ago. You have to make some kind of assumption about the variation in hp to get an answer from physics, and the simplest one to make is to assume that hp is constant for the entire pass. This gives a minimum average hp estimate, which to me is a good thing - you might make more hp some of the time but if so, you must be making less hp some of the rest of the time 
. ET's are hard to reproduce but ignoring that you can derive (I posted this 6-8 years ago if you want to see all the equations) that the average whp = 197 * weight in pounds going down the track / (et * et * et). This equation is exact and includes no fudge factors of any kind, just unit conversions. So if your car weighs 3600 and you weigh 150 lbs so the total is 3750 lbs and you ran a 12.0 you averaged 427.5 whp applied to the track. Relating et and mph with any accuracy at all requires a fudge factor to account for aerodynamics, and here you will get different numbers from different online calculators. The formula is et = constant / mph, and if you ignore aerodynamics then physics says the constant is something like 1450 (that's a real fuzzy memory and a number NOONE uses ). For G bodies I fit the 180 reader's rides times at gnttype.org and got 1356, so I use et = 1356 / mph, so a 12.0 would be at 113.0 mph. F bodies usually mph 2-3 higher for the same et so that number should be changed for them, etc. The mph is much more reproducible at the track than the et, so what I like to do is use the mph to calculate the et then use that in the hp formula. That's what the online calculators do that start with mph, they just don't show the equations and don't tell you what they are using for the fudge factor (I've seen anywhere from 1340 to 1370 ). Do the math yourself, and even if the number is a little wrong it will be consistent so you can evaluate changes. For example, if you ran that 12.0 at 3750 lbs and want to know how much taking 100 lbs off the car would help, calculate hp at full weight to get 427.5 hp, and then use that and the lighter weight to calcuate the new et, 11.89. [Hmm, maybe there is something to this cleaning out the trunk business .]
. ET's are hard to reproduce but ignoring that you can derive (I posted this 6-8 years ago if you want to see all the equations) that the average whp = 197 * weight in pounds going down the track / (et * et * et). This equation is exact and includes no fudge factors of any kind, just unit conversions. So if your car weighs 3600 and you weigh 150 lbs so the total is 3750 lbs and you ran a 12.0 you averaged 427.5 whp applied to the track. Relating et and mph with any accuracy at all requires a fudge factor to account for aerodynamics, and here you will get different numbers from different online calculators. The formula is et = constant / mph, and if you ignore aerodynamics then physics says the constant is something like 1450 (that's a real fuzzy memory and a number NOONE uses ). For G bodies I fit the 180 reader's rides times at gnttype.org and got 1356, so I use et = 1356 / mph, so a 12.0 would be at 113.0 mph. F bodies usually mph 2-3 higher for the same et so that number should be changed for them, etc. The mph is much more reproducible at the track than the et, so what I like to do is use the mph to calculate the et then use that in the hp formula. That's what the online calculators do that start with mph, they just don't show the equations and don't tell you what they are using for the fudge factor (I've seen anywhere from 1340 to 1370 ). Do the math yourself, and even if the number is a little wrong it will be consistent so you can evaluate changes. For example, if you ran that 12.0 at 3750 lbs and want to know how much taking 100 lbs off the car would help, calculate hp at full weight to get 427.5 hp, and then use that and the lighter weight to calcuate the new et, 11.89. [Hmm, maybe there is something to this cleaning out the trunk business .]KL Mallender
Certified Dumb****
- Joined
- Apr 16, 2007
Very concise explanation Carl, but I'll bet a lot of racers just can't/won't think all that through, that's not the "Easy Button", lol.
Using the OP's times in his sig and the Moroso calculator with a vehicle weight of 3750, 116 mph trap speed, his optimal ET would be 11.35 for his power to weight of 8.3 lbs to hp, which his car produced 450 average RWHP pushing his aerodynamic brick to 116 mph, with this knowledge, I see that he is only missing .15 from a "perfect run" for his mph, and experience tells me that if he "found" a .05-.08 reduction in his '60 foot times he would acheive that goal.
I guess there will always be different ways to skin a cat, but for me, using the known true mph figure takes in account for aerodynamic drag and frictional losses resulting in accurate hp figures, the rest is physical laws of motion.
Kevin.
Using the OP's times in his sig and the Moroso calculator with a vehicle weight of 3750, 116 mph trap speed, his optimal ET would be 11.35 for his power to weight of 8.3 lbs to hp, which his car produced 450 average RWHP pushing his aerodynamic brick to 116 mph, with this knowledge, I see that he is only missing .15 from a "perfect run" for his mph, and experience tells me that if he "found" a .05-.08 reduction in his '60 foot times he would acheive that goal.
I guess there will always be different ways to skin a cat, but for me, using the known true mph figure takes in account for aerodynamic drag and frictional losses resulting in accurate hp figures, the rest is physical laws of motion.
Kevin.
KL Mallender
Certified Dumb****
- Joined
- Apr 16, 2007
116 mph at 3600 lbs = 430 average RWHP.
ET is not changed using calculator, it only considers how much power it takes to accelerate vehicle "Mass" to known mph in given distance.
Kevin.
ET is not changed using calculator, it only considers how much power it takes to accelerate vehicle "Mass" to known mph in given distance.
Kevin.
I know, Kevin, but every so often I can't help posting
. Are you going to BPG? I've never met you in person but have seen lots of your postings.Using 3600 lbs and the sig data (11.499 and 116.12 mph), I get 466 average rwhp from the et, and and average et for 116.12 mph is 11.68 so your car is launching well for your hp. Using the 11.68 calculated from the mph I get 445 average rwhp. If you get better than 5% reproducibility on a dyno you are doing fairly well (better than 1% and you are doing great), and 5% of 445 hp is 22 hp, so I'd believe any of these hp numbers +/- 20-25 hp at best, just to keep things in perspective.
KL Mallender
Certified Dumb****
- Joined
- Apr 16, 2007
Thanks Carl, lol, you explained it perfectly using ET as the constant, but as you can see my point, we ALL want access to that easy button
V6Racer, I come up with 925 average RWHP or 3.75 lbs per hp, target ET goal of 9.00 flat with perfect hook, not exactly a street car, more like I'll rip your heart out and let you bleed car, that's "gettin it done" buddy. :biggrin:
Kevin.
V6Racer, I come up with 925 average RWHP or 3.75 lbs per hp, target ET goal of 9.00 flat with perfect hook, not exactly a street car, more like I'll rip your heart out and let you bleed car, that's "gettin it done" buddy. :biggrin:
Kevin.
Kevin & Carl
Thanks again for you interest and input
Now I have another question. I have applied the TCI calculator to my car's data, as well as, the weight and advertised horsepower of approximately 12 cars which have been road tested recently by Car and Driver magazine. The TCI calculator shows 440 hp for my car which is in the ball park of your calculations for my RWHP. When I apply this formula to the Car and Driver data (I added 200 lbs for a driver to the published curb wt.) the result is closer to the published SAE Brake HP. I wonder why the formula does not consistantly yield a lesser hp number which would indicate rear wheel hp? You guys may want to try the same exercise with manufacturer's published ratings and magazine's performance tests.
Leon
Thanks again for you interest and input
Now I have another question. I have applied the TCI calculator to my car's data, as well as, the weight and advertised horsepower of approximately 12 cars which have been road tested recently by Car and Driver magazine. The TCI calculator shows 440 hp for my car which is in the ball park of your calculations for my RWHP. When I apply this formula to the Car and Driver data (I added 200 lbs for a driver to the published curb wt.) the result is closer to the published SAE Brake HP. I wonder why the formula does not consistantly yield a lesser hp number which would indicate rear wheel hp? You guys may want to try the same exercise with manufacturer's published ratings and magazine's performance tests.
Leon
[Hmm, maybe there is something to this cleaning out the trunk business
Carl, your the only guy I know that races with every tool that he owns in the trunk!!!
Lord knows he's done enough number crunching for me. Mark your calendar for September 18th at 75-80!!! I'm sure will need some advice and number crunching. And don't forget general BSing. It would be even better if your car is there!
