Lifetime Premium Member
Join Date: Sep 1998
Location: Highland Village TX, USA
Re: Chassis Dyno=Engine HP
Several iterations ago I tested my SBC on an engine dyno at 672 HP. I then installed the engine in the car. The difference being the engine had an alternator installed in the car. TH350. 8" 5000 RPM converter, 12-bolt rear with 4.56 gears. MT 28x10.5 stiff sidewall bias ply slick.
I then tested on the chassis dyno - 548 RWHP or about 18.4% difference.
Similar test years later with a different engine configuration and the engine had more changes between the engine dyno and the chassis dyno. Same drivetrain, but MUCH looser converter (flashed to 6800 RPM on dyno). 915 HP engine dyno. 689 RWHP. 24.7% difference.
The converter fall back RPM is usually 6400-6600 RPM at the track depending on the weather/DA. Flash stall at 1800 RPM off the footbrake is 5400-5600 RPM.
Converter efficiency is a big factor in drivetrain efficiency.
Naturally Aspriated 450 SBC - 915 HP / 714 lb-ft
1.36 - 60', 5.93 @ 116.7 MPH - 1/8th