Fuel consumption (food for thought)

SFC figures (or more accurately Brake Specific Fuel Consumption) figures are still a major selling point for industrial engines, moreso gensets, and even moreso the huge cathedral engines where 0.01% improvement on sfc will be a huge fuel saving. It's also where most of the gas turbine development is heading - shaving the efiiciency rather than increasing power output.

Sounds like a good idea to me - simplest method would be to record, for each engine, how long it will run at a particular constant condition on a pint of fuel (measuring receptacles are also easily obtained from the big tent with a bar in it;-). As long as the amount of fuel and the time run is recorded comparisons can be easily made. I predict that there will be wild variations even on the same model - most current engine suppliers quote a tolerance on power output of about plus or minus 5%, and for old restorations the tolerances on timing etc won't be as close as that!

Happy New Year to all,

Cheers

Dan

These measuring containers can only be bought full of course and being plastic can only be used for petrol once. I foresee the need for many such tests. The accuracy of the later ones may be suspect though. I will try a test on my two engines when I next show them. It will be interesting to compare the results with your older lumps. I would hesitate to suggest that my relatively modern stuff, running at its governed speed should be thirstier. I assume that all engines will be run at their maximum governed speed to ensure that the comparisons are valid. I know that my engines use a lot more fuel at high speed than low speed. Part of their reason for this is that their load cannot be disconnected and certainly the B&S load has a fan to rotate all of the time. That is in addition to the engines own fan. Could be an interesting comparison. Happy new year to you all.

John

Yes, this does sound like a worthwhile idea.

As to loaded or unloaded at tickover, I think there are enough of us with enough engines of the same or similar makes and models to readily do both comparisons. As an instance, we have Norman T300's both driving dynamos and unladen, don't we?

Shall we make a start on them?

Here's a modern one to start off with. We have a two year old Honda 160cc

Regards,

Kim Siddorn

Kim:

Don't we need a steady load for the figures to have some meaning?

I don't want to put obstacles in your way, but something as variable as a PA system isn't a load in the sense for which you are doing the trials is it?

Just a thought...

P.

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

"Peter A Forbes" said

The load from the PA is pretty steady (which is why I mentioned it as a mean) as it is not dependent on whether or not the speakers are carrying voice, music etc, as the main amps are not in the desk unit (two CD players, a mixer, two radio mic transmitter/receivers and a pre-amp) but in the RCF speaker units, separately fed with mains from the genny.

The load is a lot more irregular with power tools working hard, of course, which is why I only mentioned it in passing.

Are we after dead accurate readings? For myself, I was going to drain the tank on the T300 and pour in a litre of unleaded, running it until it was dry against the clock. Isn't that the kind of standard were looking for?

I ask for the sake of information only ;o))

Regards,

Kim Siddorn

- who wishes you and yours all the very best for the New Year.

sounds a great idea! It's usually the hardest piece of information to find. If anyone wants to do the testing in or near S. Wales/leominster, I have an electronic balance that weighs to 2g accuracy. We use it for measuring fuel consumption of diesel on rolling road tests - as it will measure up to 14kg which allows plenty of leeway for the tank. It is generally a lot more accurate than trying to measure fuel with a measuring cylinder