atb

Joel, is this graph from an engine dyno (not chassis) or is it an extrapolation based upon the rwhp figure?

Hilton

Its an extrapolation - multiply the rear wheel numbers by some fantasy made up number that doesn't tell you anything.

For some reason its standard practice in the UK to do this.. despite the fact that there's a significant variation in driveline losses between the many configurations and types of gearboxes on cars.

Judging by Joel's rwhp number he mentions, this dyno shop's software is set to automatically add 20% to wheel numbers.

Joel's unusual by UK standards, in that he asked the dyno shop what the peak rear wheel number was, which is good as it provides a basis to get meaningful data out of the graphs

Hilton

Nope, its different up until 83 - it changed to the common type in 84 when the LH cars were introduced.

http://www.mailordercentral.com/928i...615%20113%2001

Iwanna928

Maybe I am lost here but 237rwhp seems a little low, that is if it is 237. Seems they do things a little different there.

What's important is that it is running well!

Hilton

Not all places use the Dynojet horsepower scale

Dyno Dynamics (which Joel used) are interesting - fairly conservative, but importantly they're calibrated so you don't have to go to the same dyno all the time to get comparative results.. any Dyno Dynamics machine will do. The ramp rate etc. is all determined by the computer under something called "Shootout mode" which makes for a standardised test.

Also note that he doesn't have headers, which makes a huge difference to early cars. He's running the original heavy as hell cast iron restrictive manifold. I'd expect another 20+ rwhp for an exhaust improvement.