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09-26-2017, 11:47 AM
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Join Date: May 2012
Location: Jazz Town, USA, TX
Posts: 501
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A/F Ratio Setting
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?
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09-26-2017, 01:25 PM
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Join Date: Dec 2012
Location: Greenback, TN
Posts: 534
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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.
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Marvin McGraw, 5TN4
RV-14. #140039 Complete
Flight hours: 500+
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09-26-2017, 03:46 PM
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Join Date: May 2012
Location: Jazz Town, USA, TX
Posts: 501
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Quote:
Originally Posted by M McGraw
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.
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09-26-2017, 04:11 PM
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Join Date: Aug 2010
Location: Newport News, Va
Posts: 325
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Speed / Density System
Quote:
Originally Posted by TXFlyGuy
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.
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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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09-26-2017, 05:24 PM
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Join Date: May 2012
Location: Jazz Town, USA, TX
Posts: 501
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Quote:
Originally Posted by johnbright
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?
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09-26-2017, 05:38 PM
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Join Date: Aug 2010
Location: Newport News, Va
Posts: 325
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Open loop
Quote:
Originally Posted by TXFlyGuy
Is open loop an efficient way to control air fuel ratio?
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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.
Last edited by johnbright : 09-26-2017 at 05:42 PM.
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09-26-2017, 05:46 PM
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Join Date: May 2012
Location: Jazz Town, USA, TX
Posts: 501
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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.
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09-26-2017, 05:51 PM
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Join Date: Aug 2010
Location: Newport News, Va
Posts: 325
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Quote:
Originally Posted by TXFlyGuy
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?
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09-26-2017, 06:02 PM
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Join Date: May 2012
Location: Jazz Town, USA, TX
Posts: 501
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Quote:
Originally Posted by johnbright
The system also uses intake air temperature.
What manufacturer / system are you using?
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Link G4+ Extreme. It is being used by a number of pilots, with very good results.
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09-26-2017, 08:29 PM
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Join Date: Aug 2010
Location: Newport News, Va
Posts: 325
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ECU
Quote:
Originally Posted by TXFlyGuy
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?
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