calculating HP on 930

[vmisquez]

Hi All,

What mean-effective-pressure value is used to calculate HP for the 930?

Thanks for your time.

V.

[patkeefe]

BMEP? That's a really good question. I'd like to know the answer myself. Seems like a factory engineering question, which they never answer (at least when I ask).
Pat

edit:
here's a link from an aircraft site. From our perspective, calculation of BMEP is done backwards from horsepower rating. The question as you posed it made me wonder if the factory has a test rig to evaluate average cylinder pressures.

http://www.epi-eng.com/ET-BMEP.htm

[fredmeister]

You can instrument the cylinders with pressure sensors which is done all the time and get an actual trace of the cylinder pressures during the combustion cycle. I work for an engine component supplier in Detoit and this is routine on engine dynos. You can calculate BMEP from there.
However, I have seen the values published somewhere in literature or do a search on the web. They published values for lots of engines, like the 917 flat-12, motorcycles,F1 cars, etc. Sorry I cannot remember where.
Of course that is the advantage of a turbo in that you can increase the BMEP via boost without monkeying with Comp Ratio or internal design of parts. Still limited by strength of components and cylinder head seals.