Hi I have a question and would like your expert opinion.

I belong to and follow a few forums and also search the internet lol, there seems to be an argument on the best medium to flow rate fuel injectors. One side says heptane the other says whatever is the closest to the specific gravity of the fuel being used. I know the industry standard is heptanes but flows less than gasoline .681 compared to standard gas at .74 specific gravity. Some shops use heptane others use a Stoddard solvent or something close to gas. An injector rated 750cc with heptane will flow more with gas. Your opinions please and how do you compensate for the difference? Thanks

 

They're all guidelines anyway. The fuel trims will always dial in the fueling system if your injector tuning is close. You can fine tune your injector constant based on the long term fuel trim correction percentage.

 

There are too many variables... is the injector being rated in mass flow units (e.g. #/HR) or in volume flow units (e.g. cc/min)? There is no "standard gas".... the density varies all over the place. The discussion omits the issue of viscosity and fluid temperature. Then there's the issue of energy content. A fuel that is high density but low BTU/# may not contain as much energy as a fuel that is low density and has a high BTU/#. Now you have to introduce the concept of "specific energy content", or BTU/volume unit. The injector is an orifice, and is a volume flow device. But everyone wants to treat it like a mass flow device.

Then try and pick the size for your setup. Unless you know the actual brake specific energy consumption for your engine at peak fuel demand, you've introduced another assumption.

As Mike points out, it all comes down to how the injector performs in your fuel system, with your choice of fuel, and your engine's BSFC.

 

Thanks for the input I think it's starting to click in my head lol. Then the calculators on many sites would be a good starting point idk. Thanks again for the reply.