Stuff
So much stuff to learn,so little time
EFI Stuff
http://sdsefi.com/aircraft.html It's got to be good it's made in Canada.The following taken from their web site
Advantages of SDS Over OE EFI Systems in Aircraft
While there are many automotive engined homebuilt aircraft flying with the OE computer controlling fuel and ignition successfully, many users may not be aware of some potential pitfalls of using these systems. Many OE computers can either shut off the injectors if certain things fail such as a water temperature sensor to protect the engine from a perceived or real overheating condition or go into a very low power limp home mode. Either of these scenerios mean that you are coming down in an aircraft. The designers of these automotive ECUs did not take aircraft use into account during the design phase obviously. Their considerations were likely as follows, in order of importance: 1. Reliability- keep the engine from destructing ( shut the injectors off if necessary), 2. Emissions, 3. Fuel economy, 4. Driveability, 5. Power. Fortunately modern EFI systems, sensors and ECUs are VERY reliable. Just be aware, that as on your Continental or Lycoming, anything CAN fail equally so on your automotive/EFI conversion, making you an unwilling glider pilot.
Many people have spent countless hours trying to unravel programming code on OE ECUs for use on aviation applications, to undo unsuitable code or responses or security interlocks sometimes successfully, sometimes not. Others wonder what the ECU might do when certain sensors or inputs are modified or disconnected. What some people have attempted to do in dozens or hundreds of hours with often unknown consequences using OE ECUs can generally be done in minutes with SDS. You know exactly what the system will do without any hidden secrets or repercussions. All OE ECUs were designed to use an O2 sensor for closed loop feedback of the air/ fuel ratios at part throttle. As such, they may not be very suitable for use with leaded avgas. SDS does not require an O2 sensor at all.
Disadvantages of SDS vs. Conventional Aircraft Engine Systems
The big disadvantage of EFI compared to a carb or mechanical injection and magnetos is that electrical power is required for the pump, computer, ignition and injectors. The likelihood of both the alternator and battery failing simultaneously is practically zero with standard aircraft maintenance procedures. Generally, a good battery will allow you to keep essentials powered for 20-30 minutes after an alternator failure permitting diversion to another airport. We consider proper gauges and/or warning lights to indicate an alternator failure to be very important. We have an ammeter, voltmeter, low voltage warning light and buzzer now on our RV6A and also added a backup battery in Feb. 2005.
Advantages of SDS vs. Conventional Aircraft Engine Systems
Virtually zero maintenance, lower fuel flows due to better mixture distribution, automatic mixture control, no carb heat, smoother running, no mag checks, no live mag issues, longer engine life due to proper mixture control and less bore washing are some of the major benefits of EFI.
Quick Aviation Q&A
Q. What about redundancy?
A. SDS does not offer redundancy in the aviation systems that we offer. Our thought is that the extra wires and switchgear required to isolate all potential faults makes it more likely to have a failure of both systems. On twin plug engines, it is posible to retain one mag and add a fuel nozzle into the plenum as a backup. For pilots who are not comfortable with this idea, there are other systems to choose from on the market which might better suit your needs- including magnetos and carburetors.
Q. Are the aviation units any different from the automotive ones?
A. SDS was conceived as an automotive system so most of the components are identical. The advantage of this compared to units developed specifically for aviation is that we have accumulated several million hours of operation due to the greater numbers in automotive service where conditions are usually more severe. Hardware differences would be things like the Hall Effect sensors used on aviation systems comply to a higher temperature spec than the automotive ones and the aviation programmer is different to be able to be panel mounted. Minor software differences include MAP calibration in inches of Mercury absolute and special programmed defaults to help minimize the effects of sensor failures.
Q. What use is the mixture knob on an automatic aviation system?
A. We recommend the mixture knob be panel mounted in all aircraft to allow the pilot to make a mixture adjustment in case of certain sensor failures. This gives you independent control of the mixture from the programmer. Some pilots prefer to manualy lean with the knob once cruise power is set also.
http://groups.yahoo.com/group/aerovee/message/3029 A great post on the above product
Advantages of SDS Over OE EFI Systems in Aircraft
While there are many automotive engined homebuilt aircraft flying with the OE computer controlling fuel and ignition successfully, many users may not be aware of some potential pitfalls of using these systems. Many OE computers can either shut off the injectors if certain things fail such as a water temperature sensor to protect the engine from a perceived or real overheating condition or go into a very low power limp home mode. Either of these scenerios mean that you are coming down in an aircraft. The designers of these automotive ECUs did not take aircraft use into account during the design phase obviously. Their considerations were likely as follows, in order of importance: 1. Reliability- keep the engine from destructing ( shut the injectors off if necessary), 2. Emissions, 3. Fuel economy, 4. Driveability, 5. Power. Fortunately modern EFI systems, sensors and ECUs are VERY reliable. Just be aware, that as on your Continental or Lycoming, anything CAN fail equally so on your automotive/EFI conversion, making you an unwilling glider pilot.
Many people have spent countless hours trying to unravel programming code on OE ECUs for use on aviation applications, to undo unsuitable code or responses or security interlocks sometimes successfully, sometimes not. Others wonder what the ECU might do when certain sensors or inputs are modified or disconnected. What some people have attempted to do in dozens or hundreds of hours with often unknown consequences using OE ECUs can generally be done in minutes with SDS. You know exactly what the system will do without any hidden secrets or repercussions. All OE ECUs were designed to use an O2 sensor for closed loop feedback of the air/ fuel ratios at part throttle. As such, they may not be very suitable for use with leaded avgas. SDS does not require an O2 sensor at all.
Disadvantages of SDS vs. Conventional Aircraft Engine Systems
The big disadvantage of EFI compared to a carb or mechanical injection and magnetos is that electrical power is required for the pump, computer, ignition and injectors. The likelihood of both the alternator and battery failing simultaneously is practically zero with standard aircraft maintenance procedures. Generally, a good battery will allow you to keep essentials powered for 20-30 minutes after an alternator failure permitting diversion to another airport. We consider proper gauges and/or warning lights to indicate an alternator failure to be very important. We have an ammeter, voltmeter, low voltage warning light and buzzer now on our RV6A and also added a backup battery in Feb. 2005.
Advantages of SDS vs. Conventional Aircraft Engine Systems
Virtually zero maintenance, lower fuel flows due to better mixture distribution, automatic mixture control, no carb heat, smoother running, no mag checks, no live mag issues, longer engine life due to proper mixture control and less bore washing are some of the major benefits of EFI.
Quick Aviation Q&A
Q. What about redundancy?
A. SDS does not offer redundancy in the aviation systems that we offer. Our thought is that the extra wires and switchgear required to isolate all potential faults makes it more likely to have a failure of both systems. On twin plug engines, it is posible to retain one mag and add a fuel nozzle into the plenum as a backup. For pilots who are not comfortable with this idea, there are other systems to choose from on the market which might better suit your needs- including magnetos and carburetors.
Q. Are the aviation units any different from the automotive ones?
A. SDS was conceived as an automotive system so most of the components are identical. The advantage of this compared to units developed specifically for aviation is that we have accumulated several million hours of operation due to the greater numbers in automotive service where conditions are usually more severe. Hardware differences would be things like the Hall Effect sensors used on aviation systems comply to a higher temperature spec than the automotive ones and the aviation programmer is different to be able to be panel mounted. Minor software differences include MAP calibration in inches of Mercury absolute and special programmed defaults to help minimize the effects of sensor failures.
Q. What use is the mixture knob on an automatic aviation system?
A. We recommend the mixture knob be panel mounted in all aircraft to allow the pilot to make a mixture adjustment in case of certain sensor failures. This gives you independent control of the mixture from the programmer. Some pilots prefer to manualy lean with the knob once cruise power is set also.
http://groups.yahoo.com/group/aerovee/message/3029 A great post on the above product