Looking for best EFI system for lycoming 540

[rv6ejguy]

Ok, here are couple shots of the data log gauge screen, first at 2300 rpm and second at 2700 rpm. No O2 sensor hooked up so AFR is invalid here. On most Lycoming maps, we ramp up the rpm fuel values (richening AFRs) at 2600-2700 rpm for cooling at full power and in the initial climb. That's why the injector duty cycle is so much higher here with only 400 more rpm, same MAP. Users can program values as they wish of course to suit their preferences and mission.

[DanH]

Originally Posted by rv6ejguy

Ok, here are couple shots of the data log gauge screen, first at 2300 rpm and second at 2700 rpm.

Ok, the given values say the all the injectors open together for 50% of a 720 degree crank rotation at 2252 RPM. At 2672 RPM, the injectors are open 72% of a 720 degree crank rotation.

As noted, with batch injector operation it doesn't much matter exactly when the injectors open. Are you triggering from #1 TDC? Here I've arbitrarily started the open periods about 90 degrees before #1 TDC, but it's just a random pick for illustration.
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[rv6ejguy]

Code to generate the injector pulse is executed 120 microseconds after the falling edge of the crank sensor pulse occurs and then the injector windings take around 0.4 to 0.7 milliseconds to saturate and start opening (dependent on type, voltage and fuel pressure).

The trigger pulse on Lycomings occurs around 90 deg BTDC, depending on type of Hall Effect sensor used.

[airguy]

Ross - what fuel pressure is being used for those data logs?

[DanH]

Originally Posted by rv6ejguy

Code to generate the injector pulse is executed 120 microseconds after the falling edge of the crank sensor pulse occurs and then the injector windings take around 0.4 to 0.7 milliseconds to saturate and start opening (dependent on type, voltage and fuel pressure).

The trigger pulse on Lycomings occurs around 90 deg BTDC, depending on type of Hall Effect sensor used.

Excellent. That means the open point in the diagrams is pretty darn close, certainly close enough for this illustration.

Ok, I've attached a similar diagram for mechanical constant flow, i.e. the Bendix style injection common on our Lycomings (Bendix, AFP, Precision, AvStar).

For those on a learning curve here, mechanical constant flow operates as its name describes, flowing fuel all the time into every intake port. The system varies flow rate to vary the volume delivered. An EFI has roughly the same flow rate any time the injectors are open, and varies the time the injectors stay open in order to vary the volume delivered.

Now, can we get Mr. Paisley or a System 32 user to diagram semi-sequential, and offer a technical explanation of why it was chosen?
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[rv6ejguy]

Originally Posted by airguy

Ross - what fuel pressure is being used for those data logs?

This was just a bench test to shoot the data screen for Dan. We normally recommend 45-50 psi static (pumps running, engine not).

[DanH]

Now, can we get Mr. Paisley or a System 32 user to diagram semi-sequential, and offer a technical explanation of why it was chosen

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Come on now, don't be Bashful...
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[scsmith]

Originally Posted by rcpaisley

Carl,


The biggest challenge of mechanical injection is achieving fuel balance between the cylinders - there is no positive control of the fuel distribution like there is with electronic injection. You can try to balance mechanical injection at one operating point with precision injectors. But the balance will fall apart at every other operating point. And it's really bad at low spider pressures such as during engine starting (hello hot start).

Robert
EFII

My experience with a Bendix RSA-5 and balanced injectors is that this statement is not true. I have essentially zero GAMI spread over a reasonable range of RPM and MAP. The balance does not "fall apart" at all. I can run 100F LOP smoothly at anything between 2300 and 2600 RPM, WOT throttle anywhere from 6,000 to 12,500 ft. I have one electronic ignition and one mag.

During engine start, who the h#*l cares how well the injectors are balanced? Once you get it lit, you can trim mixture to get a reasonable idle. YES, hot starting is a PITA and one of the strongest reasons for EFI. And, yes, sure, the EFI engine likely idles smoother. Not so much that I really care.

[akschu]

Originally Posted by scsmith

During engine start, who the h#*l cares how well the injectors are balanced? Once you get it lit, you can trim mixture to get a reasonable idle. YES, hot starting is a PITA and one of the strongest reasons for EFI. And, yes, sure, the EFI engine likely idles smoother. Not so much that I really care.

Well, with a purge valve even the hot restart issue largely goes away. I think the biggest reason for EFI is you could darn near **** in the tank and it would run.

Some people are hellbent on running crappy fuel. I'm not one of those people, and I think you can safely run some mogas with mech-inj if you mix or only use it as cruise, but for sure EFI is better in this regard.

[airguy]

Originally Posted by akschu

Some people are hellbent on running crappy fuel.

If the engine and fuel system are set up so that they don't care, why wouldn't you run a cheaper fuel?