pictsidhe
Well-Known Member
How do you adjust for load?
Forum made EFI?
- Thread starter blane.c
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jbiplane
Well-Known Member
For simple predictable load like propeller not required.
RPM would controlled by throttle, engine get as much fuel as required on definite RPM.
One simple fuel table (open time vs rpm) will ensure lean mixture at nominal rpm and rich at full throttle to cool engine.
Possible make fuel table by throttle angle (instead of rpm) as well
I hope your French is as good as your English.
Also Laurent Boutin has done similar.
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pictsidhe
Well-Known Member
If you had a map sensor, making injection time proportional might not be far off. Trigger one shot each rev.
rv7charlie
Well-Known Member
Unfortunately, it's not that simple.
I can fly my RV6 at low altitude (around 1500-2000 feet MSL) at ~125 kts, with fuel flow anywhere from 5.3 gallons per hour up to around 8 gallons per hour. Same altitude, same speed, same rpm. Prop load hasn't changed.
Consider fuel required for an air cooled engine at full throttle/full rpm in climb, where rich mixture is required. Now, consider the same engine with the plane being flown in a high speed reduced power descent, where the prop is turning the same rpm as it was in the climb but throttle is nearly closed. A 'simple' injection system based only on rpm can easily flood the engine and cause power to be unavailable once the descent is arrested and power is again required.
If the controller doesn't know load (MAP) in addition to rpm, it can't supply appropriate fuel quantity. Even then, varying flight conditions can require different mixture settings (see 1st example).
Charlie
TFF
Well-Known Member
OS model engines has used EFI. The new one is quite advanced. The old originals had sensors for head temp and RPM. These were glow engines so no ignition. What was not evident off the bat was it used the throttle servo as the throttle position sensor. The servo had to be correctly installed or the system was off. This was a very small engine and efficiency was not that important. Power was. It had three place mixture map. You tuned the engine in each range and that is what you got. These things were 1.6 ci. The new OS engines have MAP, throttle position, generator, and more.
Protech Racing
Well-Known Member
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- Jul 10, 2020
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- 408
I use and sell Microsquirt. When I did the first few installs Iused all of the sensors. For racing you dont need much at all.
The base fuel map can use only a map sensor and rpm signal. At the same time, a coolant /head temp sensor can add a little fuel and reduce the timing a bit to reduce the temps, if you want it to .
The air temp input can also tweak cruise power lean and add timing, if you choose to use it.
But simply all you need is a map sensor and rpm signal for a good running engine. Foregot to note the wide band O2 sensor !!
No TPS even . I only use a TPS for street cars that like a little more out of gear response . Race cars dont get one.
You also make the tweak values of the temp inputs. That is, you get to change the fuel added or reduce value in the tables. This keeps the tweaks from stopping the engine by going to extereme values. like Minus 40 temp correction that might add 300% fuel tothe base map .
The base fuel map can use only a map sensor and rpm signal. At the same time, a coolant /head temp sensor can add a little fuel and reduce the timing a bit to reduce the temps, if you want it to .
The air temp input can also tweak cruise power lean and add timing, if you choose to use it.
But simply all you need is a map sensor and rpm signal for a good running engine. Foregot to note the wide band O2 sensor !!
No TPS even . I only use a TPS for street cars that like a little more out of gear response . Race cars dont get one.
You also make the tweak values of the temp inputs. That is, you get to change the fuel added or reduce value in the tables. This keeps the tweaks from stopping the engine by going to extereme values. like Minus 40 temp correction that might add 300% fuel tothe base map .
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jbiplane
Well-Known Member
Yes, I experienced since 2016 with Speeduino, Megasquirt, RusEFI. finally made in house EFI...
But after saw 2-stroke Stihl 550i chainsaw which perform exelent using only one integrated crankcase temperature+pressure sensor. It consume just few wats and do same like complicate classical systems. I know all concerns related "red neck" EFI, but I know guy who used attached simplest schematic on his heavy low power motorcycle Jawa and absolutelly happy compare carburator he used before. He use mechanical fuel pressure regulator which he turn like main jet and schematic attached. It works on dirty cheap ancient Atmega8. Yes, he have worse dynamic from 0 to top, but observe much better engine behavior on cruise. Seems if install something simular on stationar generator it will be perfect enough.
So my idea if we have simple fast logic says taking into account
- fast changing inputs like TPS MAP and rpm. Processor will calculate ignition advance and nozzles times
- slow logic using slow changing inputs like themperature and external pressure
We will need much less calculations and got the same "fueling" precision.
But after saw 2-stroke Stihl 550i chainsaw which perform exelent using only one integrated crankcase temperature+pressure sensor. It consume just few wats and do same like complicate classical systems. I know all concerns related "red neck" EFI, but I know guy who used attached simplest schematic on his heavy low power motorcycle Jawa and absolutelly happy compare carburator he used before. He use mechanical fuel pressure regulator which he turn like main jet and schematic attached. It works on dirty cheap ancient Atmega8. Yes, he have worse dynamic from 0 to top, but observe much better engine behavior on cruise. Seems if install something simular on stationar generator it will be perfect enough.
So my idea if we have simple fast logic says taking into account
- fast changing inputs like TPS MAP and rpm. Processor will calculate ignition advance and nozzles times
- slow logic using slow changing inputs like themperature and external pressure
We will need much less calculations and got the same "fueling" precision.
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Gerald,
That link didn't work for me (it dead-ended at the "acversailles.free.fr" site without going to the underlying page/document). Any other ideas? My French is nonexistent, but if there's a schematic and French text, maybe I can figure it out with machine translation. Thanks.
pictsidhe
Well-Known Member
If I was going for super simple.
MAF sensor from a car, shrink the body to suit.
Analog circuit with 2 pots to vary high and low throttle fuelling. Injection time proportional to that adjusted MAF signal. One injection pulse per spark trigger.
MAF sensor from a car, shrink the body to suit.
Analog circuit with 2 pots to vary high and low throttle fuelling. Injection time proportional to that adjusted MAF signal. One injection pulse per spark trigger.
Original post edited with correct link .
It is a pdf so translation is not so easy.
I did go down this road a little, starting with this post:
Forum made EFI?
With a fixed-pitch prop, the relationship between RPM and fuel flow can be predicted fairly well. Per my guess/table in the post above, for a little indusrial engine that behaves analogous to a Lycoming, the amount of fuel needed per rev/cycle just about doubles from 2500 RPM (35% power) to 3600 RPM (100% power). That takes into account both prop load and the BSFC of the engine at varying RPM. It might be possible to get close enough to this curve using analog electronics (OPAMPS with various gains, etc), but digital electronics with software are a lot more flexible and would allow you to use either a formula or a lookup table to dictate the fuel flow.
But, as rv7charlie says, this hard link between a particular RPM and an injection pulsewidth won't be very accurate all the time (during descents, etc). Maybe it will be sufficient to keep the engine running and we can manually adjust with a mixture knob (as we would with a carb). The most common approach is to use a MAP sensor to tweak our pulsewidth "guess," but a MAP sensor isn't necessarily easy to use in some cases. For example, the MAP in a V-twin will bounce around a lot in each induction runner during each engine cycle. All we really care about for adjusting our fuel squirt is the MAP when the valve is open (so we can determine how open the throttle is by knowing the vacuum), but that's only a small fraction of the time. With a digital system it's not hard to just take the lowest MAP reading over a set sample period, and use that to adjust our "standard-squirt-for-this-RPM." Using MAP for this purpose will adjust for both changes in atmospheric pressure and load (because the throttle plate will be closed = lower MAP). I suspect that varying the injector pulsewidth (as is typically done in digital EFI) will prove to be easier than varying fuel pump pressure as you've suggested. I could be wrong.
I don't see a need for a TPS in this scheme, and maybe not a temperature sensor either (though you'd probably need a primer button/software loop to get the engine started when cold).
And, with batch injection you don't need to know cam position, so a single crank pickup (for RPM) and a MAP sensor in each runner would be the only sensors needed. Maybe you could get by with one MAP sensor if the induction systems to both sides were well balanced.
An Arduino-type processor has all the power needed for this. The Speeduino project is pretty well advanced and stable, but the base software is very "feature dense" with a lot of stuff we do not need (variable valve timing, etc, etc). It's easy to say "don't use what you don't need," but I'd think it much safer to write your own >simple< code (using their software as a guide/template in the applicable areas) than to try to use what they have written. You need to know everything that is in that flyable software and how it works. Chopping through/evaluating a thicket of unneeded code seems like a waste of time. Same for Megasquirt, IMO. Unless someone wants to get a PhD in Megasquirt.
With a simple open loop EFI we'll probably want to keep a manual mixture knob in the cockpit.
In your "Version 6" you could get fancy: the pilot presses a button in cruise that lets the EFI adjust pulsewidth with reference to EGT to achieve an EGT 50 deg F lean of peak EGT (replicating what we'd do with a mixture knob, but more precisely and independetly for each cylinder). That would be super deluxe--closed loop but without a lambda sensor. A fun long-term goal but surely not needed in a basic system.
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jbiplane
Well-Known Member
Speeduino news
2 injection+ 2ignition channels 47x25mm board
A bit bigger board
low-cost and mini-sized ECU for speeduino firmware (45 x 55 mm)
4 high impedance injectors
4 active ignition coils or 1 passive ignition coil with separate ground plane
1 crankshaft sensor with VR-conditioner
1 hall input for camshaft sensor
6 analog inputs: CLT, IAT, TPS, BAT, LMM, MAP
1 optional baro sensor MPXH6400A on bottom side
1 digital input for disco swaggering (aka. launch control)
Onboard Wideband Lambda Controller with Bosch CJ125 (LSU 4.9)
1 fuel pump out
1 idle valve out
1 tacho out
1 boost out
USB programming interface with CP2104
2 injection+ 2ignition channels 47x25mm board
A bit bigger board
low-cost and mini-sized ECU for speeduino firmware (45 x 55 mm)
4 high impedance injectors
4 active ignition coils or 1 passive ignition coil with separate ground plane
1 crankshaft sensor with VR-conditioner
1 hall input for camshaft sensor
6 analog inputs: CLT, IAT, TPS, BAT, LMM, MAP
1 optional baro sensor MPXH6400A on bottom side
1 digital input for disco swaggering (aka. launch control)
Onboard Wideband Lambda Controller with Bosch CJ125 (LSU 4.9)
1 fuel pump out
1 idle valve out
1 tacho out
1 boost out
USB programming interface with CP2104
Bill-Higdon
Well-Known Member
As far as I could suss out, it is article 2 of 2 describing Jean Paul Junqua's installation of EFI and electronic ignition (Leburg?) in his airplane. It didn't appear (to me) to cover the design of the EFI itself.
jbiplane
Well-Known Member
Finally my company ECU = digital ignition + injection integrating to throttle body will look like on this picture.
We will make it rather big 70x70mm placing most of components on one side to fit ECU+throttle body in $120 FOB
2 ignition and 2 injection channel allow install on most of 1...4 cylnder engines. MAP, IAT TPS onboard, so very
few and only required wires will go out which will simplify instalation. We trying make PWM modulation of
fuel pump to reduce electricity consumption.
We will make it rather big 70x70mm placing most of components on one side to fit ECU+throttle body in $120 FOB
2 ignition and 2 injection channel allow install on most of 1...4 cylnder engines. MAP, IAT TPS onboard, so very
few and only required wires will go out which will simplify instalation. We trying make PWM modulation of
fuel pump to reduce electricity consumption.
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Thanks, great news. Looking forward to more information as you can provide it.
rv7charlie
Well-Known Member
Are you saying that the controller mounts *on* the throttle body? Most controller companies recommend putting the controller on the cold side of the firewall, due to heat & vibration issues. Is everything on the board hardened to handle the heat/vibration from being attached to the engine? What about positive latching for the connectors?
The price point certainly sounds great!
The price point certainly sounds great!
I look forward to hearing more. Since we don't need a TPS in airplane use, that might make it easier to put the control board somewhere else-- I'd expect that it would be pretty easy to "remote" the MAP sensor input (with a tube to the manifold) and the air temp sensor.
The software "openness", tuning software or procedures, and the hardware "hardening" issues you mention (plus EMI and power filtering provisions) will be interesting to learn about.
