Dyno vs. Dyno

[HYRDGOON]

Just curious how many of you have had the opportunity to have your engine dyno'd and then also run on a chassis dyno and what you thought of the numbers?

Obviously chassis dyno's are a great tool for test & tune but I was surprised talking with a buddy yesterday that worked at a shop with a chassis dyno when he told me he was afraid to use it because it started so many fights and grief by people disappointed in the number. He claimed usually a difference of 30% and I know most say about 25%. Also told me they use to do "Dyno Days" and a Corvette club would always come in and guys with new Z06 Vette's rated 500hp would flip out when they say they only made 325 at the wheels!

 

[tallhair]

excellent idea for a thread goon .. I"m looking forward to the responses. Oh and neat story

 

[Budnicks]

parasitic friction loss thru the drivetrain, wheel weight, tires, suspension movements, the whole reciprocating weight/friction drag, clutch, converter, drivetrain lock up, brake drag, how tight the rear end is set-up, even what rpms & even how it's ran on the chassis dyno's will effect final HP even, whether there's cool fresh air flowing thru & over it, the drum size & type of dyno, temperature &/or elevations also RAD, heat in the engine & types of oils/fluids, all can make a big differences, than just an engine dyno/crank HP, wheels is net HP, I've personally seen #'s more like 15%/17%-20% loss, but that's racecar stuff, not street cars, the track is my dyno usually... allot of factors, you can't race dyno's they rarely are comparable....