Dyno numbers

[Bill Wells]

if you take your numbers and use a 20% loss number at rear wheels, your calculated crank hp would be 473, 477 and 481. torque numbers would est to be 486, 491 and 481 ft lbs.

those numbers are not so far off of the advertised 515 hp and 500 trq, but your loss would be 26%on hp and 22% on trq.

not sure that is worth getting upset over as there are still so many other variables in a chassis dyno real world setting vs a clinical perfect condition engine test stand dyno. chances are the engine numbers at that time are correct and there are additional parasitic losses , or different other variable conditions attributing to the lower than anticiapted rear wheel numbers.

as i said before, to most, chassis dyno numbers are humbling and less than expected based on 'supposed' engine crank numbers. the truth is in the tuning aspect and some sort of reasonable explanations for losses.

in a perfect world, your rear wheel numbers at a 20% loss would be expected to come in at 412 hp vs your average of 382 and trq numbers at 400 vs your average of 389.

other thought is : engine or advertised numbers are NOT as high as advertised. short of an actual engine dyno for your specific engine you can only use the adv figures. some engines most likely produce more than adv and some less . just like some new car mfr's found out not too many years ago. their customers started complaining on low chassis dyno numbers and the mfrs said 'gee, guess what..we just retested and found out our hp numbers are indeed LESS than we advertised...mazda for one as i recall and ford svt mustang for another. i recall some vipers perhaps in that same situation too based on some local viper owners here whose club rented a chassis dyno shop for a day of bragging rights / comparisons and one owner had his engine replaced due to low chassis dyno numbers. however, another put his car on the dyno at the viper plant and got a whole different set of hp/trq numbers, higher than the local shop. whose was right ? hmmmm....ya never know.

so, as bill clinton said : what is the definition of IS ? IS it as advertised or not ? or is it ok and your losses for some reason specific to your car or similar cars showing higher % losses than what is norm. then the debate of what is NORM ? this is a snowball in hell or a snowball rolling down the hill..does it melt or get bigger ? you will never know unless you yank your engine for test stand dyno (unlikely)< live with the numbers ( they aint shabby) and/ or solicit similar input from other owners of same car with same engine /driveline/ ratios and see what they experience. then a new variable starts... what is the real world accuracy between dynojet A and dynojet B three states away.

me, i would live with it. accept the chassis dyno numbers for tuning purposes and go out and enjoy driving one of the finest cars on the market that can kick 98% of all other cars butts, regardless of what an estimated or calculated hp is...

my $ .02 worth, and wish i had a coupe, no matter the engine. b