Absolute Shower

Any turbo experts out there know a formula for power from air flow and injector cycle? Taking it from std internals, STi7 jets, uprated pump?

dnb

I think you'll need RPM in there as well. Don't know for sure how to do the rest of the maths though.

Absolute Shower

Got that too...with XXX (Secs) monitor. So it's possible...hmm would Mr Banks know the formulea?

Leslie

I think it would depend on how efficiently the engine used the charge as well. That means practical measurement om the rollers.

Les

Absolute Shower

I agree...there's got to be differences in rolling parts, oils (friction), fuel etc...but just as a ruff figure, a calculation could be made - it can't be that much out of a true reading (anymore than rollers vary between different performance centres like Power Engineering and Powerstation?)

john banks

Some examples...

1.42 CFM/BHP - ie 356 BHP from a TD05 with flow 505 CFM
5.5 CC/BHP - ie 400 BHP from 4 x 550 injectors

Lots of caveats to these, as I say just some guesses to get you started.

Absolute Shower

Excellent, thanks John. Out comes the calculator!

Absolute Shower

Being a plank again...what's the 'cc' stand for under the 550 injector example? I take CC to be cubic capacity but that can't be right surely...help!

john banks

Injectors are measured in cubic centimetres per minute at 3 bar differential fuel pressure (standard). This is their flow capacity, note that they go static open (no time to close) somewhere between 85 and 100% IDC, so you may well not get additional fuel from an injector by going too high with it, and if you do it may do a step change, however I've never noticed this on wideband.

Change in fuel pressure helps a lot - go up to 4 bar and you increase the flow by 15.5%.

Some dynos which read on the high side will make the figures I quoted look very tame. The bright side is that a car making an honest figure when actually driven may make another car look tame with the same or more power from an over-reading dyno

Absolute Shower

Cheers John...like the sound of that.

I'll have to do a fast run somewhere soon in top gear to get the air flow, then get the calc out again...just don't tell the cops!