Horsepower calculation

Here is a formula to get a close idea for your cars' HP if you have not had it to the dyno yet (or have other things to spend your $$$ for):

HP = (MPH/234)3 x weight (MPH is your 1/4 trap speed)

For me I put these numbers in:

HP = (109.89 x 234)3 x 3675 (I don't know how much my Trans Am wieighs, I am guessing 3500 plus my 175)

HP = (0.4696xxx)3 x 3675

HP = .1035581 x 3675

HP = 380.57601

I don't know if this is flywheel HP for sure, but my guess is it is. If I multiply 381 x 88% (I think you have about a 12% drivetrain loss for M6 cars) I get 335, which is about what I see for other cars like mine, long tube headers, lid, ORY, muffler change.:flex:

That trap was last October, last May I had a trap best of 107.5. When I plugged in that trap speed I got 346 HP (305 with 12% drivetrain loss). I did no tuning between these days at the drag strip, I think the weather was 20 degrees cooler last October. Interesting to see this calculation shows ~30 HP difference for a little over 2.3 MPH trap speed change.

i was looking at that same formula online...there is another one for et...which is different.
i ran a 13.5 @ 106. the formula you first gave suggested 343 hp and the et suggested 297hp. i have the free mods and an ud pulley..accurate??

Sounds accurate. Maybe the one you found is for RWHP? Can you post the formula? But ET is highly variable, all depending on your 60 ft traction. If I were brave and used slicks with my stock differential, I bet I could get some 1.7x 60 foot times. On my 12.89 @ 109.89, my 60 foot time was a 2.01, that would drop my ET by .2x-.3x I'm sure. Last October my MPH were all over 109, my 60 foot times were from 2.01-2.31 with ETs up to 13.3x

the formula is at http://www.musclecardrive.com/calcul...calculator.php
12.89 is what im really shooting for as i worked the formula backward using the 343 number and the weight of the car and it pointed to 12.89 et....figure that s a reasonable target. you are at that time with only long tubes? did it do that much? i have the free mods and a pulley...oh and the 10hp from royal purple..the jury still out on that one. i used to race in the late 80's...12's were/are wicked fast im still in awe of these cars!

im only guessing its for RWHP ...seems strange to put the 20% reduction in the foumula?

I agree it seems to be for RWHP on the ET equation. I did their calculator both ways and it came out as what I said in my first post. Using their calculator sure is easier!

Before my Hookers and ORY (I have a lid also) I was running 13.3x-13.5x @ 104.5-105.x. My ultimate goal for the car is to run 12.99 @ over 110 MPH on my slow nights (hot weather). I think I can do that with a LS6 intake and a tune.

I raced in the late 80s as well with a '67 400 4-speed Firebird, its' best times were 13.2-13.4 @ 104 -105.7. No slicks. Yeah, 12s are very fast. That old car got 8 MPG city/10 on the highway. New car gets 16 or so and 25-28 on the highway. And doesn't overheat. And stops more than once, with antilock. My '67 handled pretty good due to massive front and rear sway bars and modern rubber.

i dynoed my car @ 341HP AND 351LBS OF tq to the wheels and i ran a 12.9 @ 110 with a 2.0 60 ft im thinking next time i take it out ill get a 12.8 and a 1.9 60 ft