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A/F Ratio Setting

T

TXFlyGuy

Well Known Member
Please help me with this. Exactly how does an electronic controlled engine (ECU), with fuel injection, accomplish leaning of the A/F mixture with altitude? The O2 sensor is not being used in our example.

Is it simply programmed into the ECU, for various MAP settings and rpm's?
 
Aneroid Barometer

If your using the SDSEFI, it has an aneroid barameter. I don't mess with the mixture to climb or descend. I'm not familiar with other systems.
 
M McGraw said:
If your using the SDSEFI, it has an aneroid barameter. I don't mess with the mixture to climb or descend. I'm not familiar with other systems.
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We will be running an "open loop" system, with a fuel ladder ECU look up table that will control the injector duty cycles dependent upon RPM and MAP.

I just found this out.
 
Speed / Density System

TXFlyGuy said:
We will be running an "open loop" system, with a fuel ladder ECU look up table that will control the injector duty cycles dependent upon RPM and MAP.

I just found this out.
Click to expand...

Speed / Density System: MAP and intake air temperature in order to calculate air density. RPM to look up volumetric efficiency of the particular engine model. Then it knows how much O2 is passing through the engine.

O2 sensor can close the loop, used briefly for calibration, lead destroys it.
 
johnbright said:
Speed / Density System: MAP and intake air temperature in order to calculate air density. RPM to look up volumetric efficiency of the particular engine model. Then it knows how much O2 is passing through the engine.

O2 sensor can close the loop, used briefly for calibration, lead destroys it.
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Is open loop an efficient way to control air fuel ratio?
 
Open loop

TXFlyGuy said:
Is open loop an efficient way to control air fuel ratio?
Click to expand...

Pilots close the loop with EFI by referencing EGT peak and being lean or rich of that. I'm flying a desk so I don't present myself as expert at operation. Planning on SDS EM-5 which has a knob on the panel to change A/F ratio and also allows individual injector trimming to get all cylinders to peak simultaneously. A map of RPM versus volumetric efficiency is provided in non-volatile memory and one can use an O2 sensor to adjust initially then remove the O2 sensor before lead destroys it. The sensor sees only one or two cylinders BTW.

Cars have tight emissions standards and unleaded fuel and close the loop other than cold start and full throttle to my basic understanding. I would think LOP would make too much NOx but my experience is twenty years old.
 
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We have no manual means of mixture control, it is all taken care of by the ECU. It is a non SDS unit.

The ECU has a lookup table that adjusts the duty cycle of the fuel injectors depending on manifold pressure and rpm.

As we plan to cruise in the low teens, I hope this is a good method setting the AFR.
 
TXFlyGuy said:
We have no manual means of mixture control, it is all taken care of by the ECU. It is a non SDS unit.

The ECU has a lookup table that adjusts the duty cycle of the fuel injectors depending on manifold pressure and rpm.

As we plan to cruise in the low teens, I hope this is a good method setting the AFR.
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The system also uses intake air temperature.

What manufacturer / system are you using?
 
ECU

TXFlyGuy said:
Link G4+ Extreme. It is being used by a number of pilots, with very good results.
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I looked it up online. More features than you need. Peak/hold injectors you don't need at 2700 rpm. Waterproof is great. Knock sensors don't work on air cooled engines. Electronic throttle, gear shift, throttle blips, 8 cylinders you don't need.

Gonna be interesting building the system with throttle body, sensors (intake air temp, engine temp, TPS, crank trigger, MAP), pump(s), regulator, coil packs, injectors and mounts, flywheel magnets. But it seems you have friends with experience applying this ECU.

No backup ECU?
 
Taking a class at EFI University (www.efi101.com) might not be a bad idea to help give you an idea of how all the sensors work together and how to setup and tune your system. It's been about 15 years since we put my daily driver on standalone, so I'm pretty rusty, but if you have a CS prop, you could set the mixture by rpm and map. If fixed pitch, you may want to have throttle position come into play so you can go "full rich" for a high DA take off, but pull it back 3-5% for lean cruise.
 
johnbright said:
I looked it up online. More features than you need. Peak/hold injectors you don't need at 2700 rpm. Waterproof is great. Knock sensors don't work on air cooled engines. Electronic throttle, gear shift, throttle blips, 8 cylinders you don't need.

Gonna be interesting building the system with throttle body, sensors (intake air temp, engine temp, TPS, crank trigger, MAP), pump(s), regulator, coil packs, injectors and mounts, flywheel magnets. But it seems you have friends with experience applying this ECU.

No backup ECU?
Click to expand...

Liquid cooled V8. Mechanical throttle. Max engine rpm is 4500.

Feed back from an ECU company leads us to go with a single ECU.

We looked at all of the historical data on this.
 
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