MS req_fuel fuel density calculation?

[ravensierra]

Just curious, is the specific gravity of the fuel taken into account in some way when calculating req_fuel?

i.e. when entering injector flow rate in cc/min and providing displacement, stoich ratio and # of injectors, does the code assume the gasoline specific gravity of ~.72g/mL to come up with req_fuel?

Ethanol for example has a specific gravity of ~.78g/mL

Of course it doesn't matter from a tuning perspective but would be nice to know

[ol boy]

The injector flow you enter accounts for fuel density already. Change the density, changes the flow. Your injector flow numbers (measured or word of mouth) are based on some assumed density.

[ravensierra]

The injector flow you enter accounts for fuel density already. Change the density, changes the flow. Your injector flow numbers (measured or word of mouth) are based on some assumed density.

This does answer my question, thanks, but not in the way I was expecting.

In my country (New Zealand) NO-ONE talks about injectors in terms of lb/hr flow, only cc/min.

To my understanding, if an injector flows 560cc/min, that would be 53.3lb/hr gasoline. If we're using E100, that would be 49.2 lb/hr assuming the viscosities are the same.

Obviously Megasquirt converts the 560cc/min into lb/hr to come up with a mass:mass stoichiometric ratio and determine injector open time required.

So when you fill the tank with ethanol, req_fuel isn't correct as the injector flows a different mass of fuel in a given time period.

Again, not that it matters. Just nitpicking