Industrial engine electronic management system development - HBA style

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blane.c

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I suppose it doesn't in regards that electronically it can compensate with a few more instructions. I am still lowering the bucket by hand and crank it back up, standing right next to brand new electric pump. Once I use the switch a few times I doubt if I'll go back to the bucket. Does limp mode care if it gets twice as many signals?
 

blane.c

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Even a lineal passage of a magnet past a coil will induce emf. So anything in the valve train side that moves that is easy to attach a magnet bingo. Keyway, washer under a bolt, hole in gear, … if it's going back and forth or round and round it's fair game.
 

nerobro

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Why do we even care about having two injection events per intake valve opening? "normal" airplane injectors are continuous flow. Those are injecting against a closed intake valve for what, at least 3/4 of the time. Why would this operating mode even ~be~ limp mode? I.. am not fond of "modes".

Airplane engines are mostly steady state, and operate over a quite narrow rpm range. This all leads to making the system really simple. Like, it's reasonable to run an engine on a ball valve, a fuel pump, and an orifice in the intake. (I think that setup was suggested by rv6ejguy ... As a backup plan for when the EFI quit)

If all you want it simple and cheap - it doesn't. The engine will run, but it's not elegant.
It is elegant. Simple, is elegant. :) The question is what benefit does the complexity bring? As I understand it, getting injection timing down "really well" helps at really small throttle openings, like at a 30mph cruise in a car. At big throttle openings, some car and motorcycle engines even have secondary injectors that kick in to provide more flow more of the time...

They also have injection systems that "just don't care" about engine rpm. If you have a MAF, you can inject based on the MAF alone. Completely blind to the action of the engine.
 

blane.c

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A friend of mine lost engine power up in the Brooks Range hunting Sheep. He found he could keep enough power to fly pumping the primer, so he got good at it for a while. So whatever works in a pinch is OK.

Dismantled the carb and went over every speck of it … nothing was ever found wrong. Ice is the suspect, but there is no proof.
 

Hot Wings

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Why do we even care about having two injection events per intake valve opening? "normal" airplane injectors are continuous flow. Those are injecting against a closed intake valve for what, at least 3/4 of the time. Why would this operating mode even ~be~ limp mode? I.. am not fond of "modes".

Airplane engines are mostly steady state, and operate over a quite narrow rpm range. This all leads to making the system really simple. Like, it's reasonable to run an engine on a ball valve, a fuel pump, and an orifice in the intake. (I think that setup was suggested by rv6ejguy ... As a backup plan for when the EFI quit)


It is elegant. Simple, is elegant. :)
Way back in my youth I had a Clinton engine with no carb*. It had a shop rag wired across the intake and I dripped gas on it by ear to keep it running. It was simple, but I don't think anyone would call it elegant......or safe.:shock:

I wouldn't call current mechanical aircraft FI elegant, just out dated. Even those antiquated systems had/have advantages over carburetors for aircraft or they would have never made it to market.

* it was free.
 

nerobro

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Way back in my youth I had a Clinton engine with no carb*. It had a shop rag wired across the intake and I dripped gas on it by ear to keep it running. It was simple, but I don't think anyone would call it elegant......or safe.:shock:
And that's more or less how the wright flyer worked. I think they were called surface carbs, but they were utterly useless at adjusting the mixture, and the open suraface of gasoline was a bad idea. But a certain Damler and Maybach came up with the atomizer updraft carb, and here we are. :)

I wouldn't call current mechanical aircraft FI elegant, just out dated. Even those antiquated systems had/have advantages over carburetors for aircraft or they would have never made it to market.

* it was free.
You don't need to justify making a janky engine run. :)

Mechanical fuel injection is cool and all. We even could get it on cars from time to time. (Gullwing Mercs, "fuelie" chevys) But MFI just seems to be... tricky. The low fuel pressure means restrictions are a big problem, and on the cars were never as reliable as carbs.

At altitude … pressure carb.. So at what point is the difference between a pressure carb. and fuel injection exactly?
Looks like there's not a whole lot of difference. https://en.wikipedia.org/wiki/Pressure_carburetor https://en.wikipedia.org/wiki/Fuel_injection#Mechanical_injection wow, MFI was a thing in 1909....
 

rmeyers

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At first glance using the cam for crankshaft position and stroke info is a great idea. In practice you'll be greatly disappointed in the engine performance. There is just too much lash/wiggle/resonance/etc in the camshaft. Been there, several attempts, and done that. The ignition timing is so bad that it's noticeable to the ear at idle. Doesn't get better at higher rpms. Might be OK for injection. Four stroke cycle spark ignition engines with port injection, as opposed to direct injection, are pretty tolerant of a few degrees error in injection timing.

That being said, if you have decided that you will have a cam and crank sensor, there are things that you can do to increase overall reliability. Many vehicles today use the cam sensor as a fall back to keep the engine running in case of crank sensor failure. As I said above, it may not run very well, but it will keep running and making nearly full power. For example, the Cummins 6.7 uses a cam gear with 13 holes. Twelve evenly spaced holes and one hole between 2 of the evenly spaced holes. That way it always knows TDC and what stroke it's on. Of course, this increases software complexity.

On the issue of sensors; I think that you will find the the standard automotive sensors are the highest quality available, within their specification range. Simple put, you cannot buy better. I have tons of scientific quality sensors on our dyno. They fail at an amazing rate. Again, there are no better sensors than standard automotive sensors, within their specification range. Therein lies the rub. The specification range. Take for example the intake air temp sensor on a diesel. This would be the sensor at the intake, after the turbo and cooler. It sees elevated temps from the turbo boost. They never fail. But increase the boost 8-10 psig and the sensor will fail within hours. The factory sensor never gets out of calibration, is ridiculously vibration proof, and has a better than mil spec connector.

I've seen crank sensors spoken of here several times and the references have been to VR sensors. If I could convince anybody here of anything, it would be to stay away from VR sensors. They are obsolete technology. Tons of downsides and no upsides as opposed to modern gear tooth sensors.

For those unfamiliar with them, a 'gear tooth sensor', an industry term, is a Hall effect switch mounted in a case with an internal magnet. The magnet and the Hall switch are balanced so that the sensor is normally off. When a piece of ferrous metal is passed underneath the sensor it switches on and then off as the metal is removed. No need for magnets or anything else. Just a gear or toothed wheel work fine. Gives a clean and sharp 5V square signal. Works just as well at cranking speed as at 10,000 rpm. Highly noise resistant depending on your choice of pull-up resistor.

If you are looking to optimize reliability I think that you will have to make your own board. As Ross stated, input noise is a Big Deal. You will want signal conditioning and at a minimum, noise reducing ground tracks on the board. You will probably want overvoltage protection on the inputs. Amazing how many times some 'mechanic' shorts the battery to a sensor.
 

Hot Wings

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There is just too much lash/wiggle/resonance/etc in the camshaft. << >>

That being said, if you have decided that you will have a cam and crank sensor, there are things that you can do to increase overall reliability. Many vehicles today use the cam sensor
I'd forgotten about that. Been spoiled by nice tight OHC systems.

<< >>

I'm one of those that has been 'saved' by the back up cam sensor. Nice to be able to get home - even if the car won't start again until the crank sensor is replaced. Probably why I like the idea?

Amazing how many times some 'mechanic' shorts the battery to a sensor.

That is basically the tool I used to kill the one Arduino Uno. I'm sure there will be more........

I agree about the quality of automotive sensors (excluding the analog VW system of old) but the various Arduino type boards are unknowns in this kind of environment. I'm leaning more toward custom boards that are compatible. The China made boards should be good enough for proof of concept.

Do any of the OEMs still use VR for EFI sensors? I'd think that had gone away by now. I'd even expect to see Hall wheel sensors on the upscale cars?
 

nerobro

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At first glance using the cam for crankshaft position and stroke info is a great idea. In practice you'll be greatly disappointed in the engine performance. There is just too much lash/wiggle/resonance/etc in the camshaft. Been there, several attempts, and done that. The ignition timing is so bad that it's noticeable to the ear at idle. Doesn't get better at higher rpms. Might be OK for injection. Four stroke cycle spark ignition engines with port injection, as opposed to direct injection, are pretty tolerant of a few degrees error in injection timing.
Injection timing is very, very forgiving. Spark, as we know, is not.


If you are looking to optimize reliability I think that you will have to make your own board. As Ross stated, input noise is a Big Deal. You will want signal conditioning and at a minimum, noise reducing ground tracks on the board. You will probably want overvoltage protection on the inputs. Amazing how many times some 'mechanic' shorts the battery to a sensor.
Protection diodes everywhere, well chosen resistors... :) Ideally, picking devices where the output (like the hall/magnet combo) starts clean...
 

rv6ejguy

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The EMI/RFI environment on an aircraft with high voltage ignition can be very challenging for digital devices trusted to keep the engine running. This involves a lot more than diodes and resistors. If the micro crashes, the airplane may end up following shortly after...

This has happened when people used non-tested hardware and software on aircraft.

The lesson is to test, test, test in the worst environment you can simulate on the ground. VHF antenna on top of the board while transmitting, Ditto transponder, running spark plug wires on top of the board, load dumps, voltage spikes, OV, vibration, cold, hot, thermal imaging etc.
 
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Tiger Tim

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Or mount it on a boat or a ice runner.
That thought crossed my mind too. Mount the test engine on an airboat (that way you get prop drive testing done too) and run the hell out of it, preferably for thousands of hours in all conditions. Of course then it's basically become a job that the tester will never be paid for.
 

Hot Wings

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That thought crossed my mind too. Mount the test engine on an airboat (that way you get prop drive testing done too) and run the hell out of it,
Good start but there will be situations that need to be tested that a fair weather boat won't duplicate. We need someone up north to test on a snow plane too.

Setting up a test cell might actually be cheaper? With a cell the temperature humidity and vibration can all be simulated. Add simulated EMF, and hope it doesn't annoy the neighbors. :roll:

[video=youtube;epSUCzLf50k]https://www.youtube.com/watch?v=epSUCzLf50k[/video]
 
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jbiplane

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So a multi-engine test bed, a couple of known engines and the big "experiment". Or mount it on a boat or a ice runner. Yep or a blimp.
All 3 variants of speeduino boards if use "industry grade", not military grade components are stable as hell. When we test unshielded ignition at 18000rpm 2 enginering workstation Lenovo and one portable in radii 2 meters hang up, but not speeduino board. You can install 2 undepended ECU and 2 sets of all sensors and components with simple relay schematics...

We tested ECUs at -50 and +40 C in thermo baro chambers and on 3-axial vibration stand.
The weakest thingies are Hall sensors (compare any inductive) connectors and wires.
 

jedi

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Copied from another thread. (Fun Engine Developement Tool)

Speaking of EFI and EEM systems, in doing roadable aircraft experiments with vehicles similar to those mentioned above I found that aircraft systems are vastly inferior to automotive systems. I tried to use a WSC trike carriage on the streets and was unable to drive it out of the driveway with the existing carbureted fuel system. I would not install an O2 sensor in an aircraft system. Preserve the 100LL option and add a JP4 option if possible. The primary requirement is that it run reliably. A manual lean at cruise similar to a typical mixture lean knob but done electronically would be sufficient.

A fellow engineer converted his Chrysler slant 6 Valient to run on diesel while his daughter was in college on the other side of the state. Got on the freeway and switched from gas to Diesel till he arrived at the destination. Two carbs, one for gas and another for Diesel/heating oil. Heater worked great. Car ran fine too.
 
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