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Bump...
Inspired by a mostly-BS thread in the Performance-Shop forum about dyno numbers, comparing Mustang dynos to Dynojets, etc., I phoned Matthew and asked him some questions directly.
First of all, our dyno numbers were corrected to SAE J1339 or whatever that spec is. Basically it corrects not to sea level, but to 500' ASL (we're at 3650' ASL). My particular dyno run was corrected by 15.3%, and all of yours would be pretty close to that, meaning we were all actually producing 15% LESS wheel horsepower than was shown on the dyno.
Second of all the dyno doesn't know if your car is turbocharged or not, and turbocharged cars aren't as sensitive to elevation changes as naturally aspirated cars are. Therefore, that correction factor should be altered for the turbo cars by 14.5 divided by roughly the total manifold pressure. Example - you're showing 10 psi on the gauge, meaning you had (corrected) 24.5 psi in the manifold. Your correction factor for your car should be:
15.3 * (14.5/24.5) = 15.3 * .59 = 9%.
To figure out your actual, turbo-friendly horsepower, assume you showed 160 WHP that day running your 10 psi. Take that 160 hp number and divide it by 15.3 and you get the uncorrected, actual observed horsepower of 139. Then multiply it by the new correction factor of 9%, and you get 151 turbo-friendly horsepower.
Now, as to how hard Matthew's Mustang dyno is on power numbers, he offers this insight: Matthew's dyno shows about 13-14% lower than a Dynojet, which is the glory machine when it comes to power figures. He also says that most Dynojet operators give a drivetrain loss figure of about 15-20% when estimating SAE net flywheel horsepower. Matthew personally has tested several completely stock vehicles, and has observed 30-35% powertrain loss between claimed SAE net and his corrected observed numbers. This lines up nicely with the Dynojets, somehow not surprisingly.
Anyway, I'm skeptical about 33% drivetrain loss and frankly Matthew is too, but time and time again he's seen that much power somehow get lost when he's testing stock vehicles, so it's obviously a combination of the actual powertrain loss, plus the heat soak on the dyno, plus the amount of added frictional losses due to the dual-roller setup of the Mustang, etc.
Therefore, if your 151 horsepower Volvo has a manual transmission, it's making close to 197 horsepower at the crank.
Got it?
Ian, your car and mine make about 336 SAE net flywheel HP, according to matthew's numbers. All the other boosted folk are on their own, figuring out their own boost / elevation correction.
Final point, don't forget, turbo boyz, that some of your intercoolers were getting seriously hot due to a lack of air thru 'em. I'm certain all of you were making more power than was being shown, on the road with 60 mph air rushing thru the IC.
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