GRT EIS red cube vs injector pulse

[MolsonB]

I've read on here that the GRT EIS can use the injector pulse to determine fuel flow, instead of buying the red cubes + software. My system (mazda rotary) will be fuel injected and have a return line, so I'm really hoping not to plumb and buy 2 red cube systems.

I emailed GRT, but they said in my case I'd still need a red cubes & software ($750). I just don't understand why. Anyone here use the injector pulse and GRT? With fuel injection and electronics, it makes no sense to have manual red cubes anymore. Am I missing something here?

-Matt

[ccrawford]

Matt,

They do this for the Subaru engines, but they may not want to support it anymore. Might be able to find someone with an EIS and Subaru who wants to get rid of theirs. But the pulse width and such on a rotary may be completely different than on a Subaru.

[DanH]

Call Robert Paisley at EFii, California: (951)317-3473

[Greg_Toman]

Opps...that might have been my mistake. Jon just asked me if someone with a Mazda rotary and return fuel flow could use the PWM fuel flow function (which costs considerably less money than dual flow sensors), and I had told no. I didn't realize that the Mazda was electronic fuel injection.

The correct answer is that yes, the EIS PWM (Pulse-Width Modulation) fuel flow option will work with any electronic fuel injection engine as long as you are able to make an electrical connection to the fuel injector.

Fuel flow measured in this manner also requires that the fuel pressure in the injection system is constant over the entire RPM range, which I have found is typical.

Thanks
Greg Toman

[dynonsupport]

Greg,
I assume you mean the fuel pressure differential is constant against all manifold pressures? That's what you need if you are integrating fuel injector open time into flow. Fixed fuel pressure would lead to changing differential pressure which is an issue. RPM shouldn't factor in, but some systems run fixed fuel pressure and the computer compensates for MAP changes, which would be hard to do in an EMS that reads the injector.

--Ian Jordan
Dynon Avionics

[MolsonB]

Hi Greg, yes that was me.

I specifically wrote in the email "fuel injected" just to be clear. Even in my follow-up email to ask them to double check and confirm, I put "fuel injected". Glad I came on here, because for the life of me I couldn't figure out why it couldn't. I was about to buy a small microcomputer to be the inbetween man, and fake the 'red cube' signals. Glad that's not the case. I'm a little worried though, that other things might be missed like this when I place my order in a month.

Ian, I agree. Just like in a car, have a fuel regulator based on manifold pressure.

[BobTurner]

Originally Posted by MolsonB

Hi Greg, yes that was me.

I specifically wrote in the email "fuel injected" just to be clear. Even in my follow-up email to ask them to double check and confirm, I put "fuel injected". Glad I came on here, because for the life of me I couldn't figure out why it couldn't. I was about to buy a small microcomputer to be the inbetween man, and fake the 'red cube' signals. Glad that's not the case. I'm a little worried though, that other things might be missed like this when I place my order in a month.

Ian, I agree. Just like in a car, have a fuel regulator based on manifold pressure.

Suggestion:
Make sure you say "pulsed fuel injection". Lycomings are fuel injected but not pulsed.