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By Plus6g
#61967
Hello All, advice required!

I have an experimental air cooled 9 cylinder radial engine (3600rpm max) which I would like to modify with the addition of a centrifugal supercharger.

In order to better control the fuel and ignition timing I would like to upgrade the ignition and fuel delivery.

At the moment the engine has dual distributors with fixed timing (2 spark plugs per cylinder) using a Hall effect sensor located in each distributor running an ignitor and coil for both distributors.

Fuel at the moment is via a very basic carburettor.

TIM018 - Ignition Modules | Tridon

Bosch Ignition Coil 0 980 AG0 700 | Sparesbox

The initial idea is to utilise 2 x NO2C Speeduino units each with its own power supply and sensor inputs to retain some redundancy.

The Distributors would remain but I would like to run the ignition through the ECU so that I have a degree of timing adjustment available. (Triggered by the existing hall effect units ) The engine has a 3:2 drive reduction unit, obtaining a crankshaft speed trigger would be challenging.

Fuelling will be by single point injection and a throttle body, (actually 2 injectors, one for each ecu but with a switchable live to each injector so that only one is running at a time for redundancy purposes).

My initial research would suggest that this should work.

Small niggle though.

The ecu is listed as capable of supporting 4 cylinders, of course I have 9! Presumably this restriction is when using crank triggering and individual coil on plug / cylinder injection?

In my case the ignition timing is already sequenced by the hall effect trigger wheels and fuel injection will just piggy back off this signal (Fuel injection timing is not critical)


Before I get too deep in trying to figure out how this could be set up in the software ( and how many cylinders I need to specify in the basic setup), can anyone confirm that my idea is possible?

Thanks
User avatar
By Pim205gti
#61968
Plus6g wrote: Sun Mar 19, 2023 8:11 pm The ecu is listed as capable of supporting 4 cylinders, of course I have 9! Presumably this restriction is when using crank triggering and individual coil on plug / cylinder injection?
Radial engines have a perfect ignition spacing and because you run it with an ignition distributor and a single point of injection you could run it as a single cylinder engine
By Plus6g
#61983
Hi, thanks for taking time to respond. Good idea, I did wonder about the single cylinder option. Only problem being that this then exceeds the maximum selectable software rpm. Not sure if the max rpm restriction could just be selected 'off' or if this is a software / hardware-electronic restriction that would limit rpm anyway? Someone else suggested setting as a 3 cylinder, I'll give that some thought. However, If the only trigger signal is coming from the distributor then would this give enough resolution to be able to adjust the timing anyway ? If not, then would I be as well to leave the ignition fixed 'as is' and use a coil signal input to the ecu to then control just the fuel injection?
User avatar
By jonbill
#61986
I think treating it as 3 cylinder might work OK. The code has max rpm defined as 18000, so you engine would be within bounds even at 3x.
There is no option speeduino for single point injection ,and on 3 cylinder engines no two cylinders are at TDC together, so speeduino will operate 3 injection channels. People do often wire only one of those channels to an injector for single point - but behind the scenes, speeduino is running 3 channels.

NO2C supports 2 channels of ignition and 2 channels of injection (so max 4 cylinder engine, with paired injection and wasted spark). You'll only be using 1 channel of ignition, so you can reallocate the 2nd ignition channel as the 3rd injection channel (but I think you'll need to custom build the firmware for that).

so: I think your trigger pattern would be basic distributor and injection layout is paired and ignition layout is single channel.

Sounds like fun.
User avatar
By PSIG
#61995
Without running some math these are just opinions, cautions and suggestions; but I would use multiple injectors, in order to maintain good fuel distribution. Second, because your "cycle" is short (e.g., 3-cylinder is 1/3), you have little time to inject multiple injections for that distribution. So third, the injectors would have to be relatively large to handle supercharged power, while still opening-injecting-closing each time in the shortened time-frame available. Fourth, this is fine, except control of huge injectors with multiple injections at low loads may then present a control issue. Supercharged engine loads require even fueling, with multiple injectors, or even fueling with multiple injections, or both.

Alternatively, the code be modified to allow the odd number of cylinders in the cycle. Another alternative to take the 3:2 input gear for timing, and add a cycle signal. Alternative to take the 3:2 output for 6-cylinder fuel timing and multiple injections on some. Lots of approaches, some junk, and hopefully one will surface as preferential and suitable within all the constraints and requirements.

I have not run any numbers to get any idea how much of this could be a problem for this specific setup, but suggest you do, as it has been a common issue for similar projects in the past. You have the issues of odd cylinders and possible traits similar to Siamese runners to consider. Paired or batched injectors, staged sets, rising-rate fuel pressure, TBI wetting to "spread" the fuel delivery, or 90°+ runner placement for wall-wetting to same effect, and other options can provide some flexibility if needed. I don't know if it's needed, but you should, just to be sure and know what to expect before you get there. ;) Not throwing a wet towel at all, and offering some thoughts to hopefully skip you forward to success quicker and ultimately easier. 8-)
By Plus6g
#62009
PSIG wrote: Mon Mar 20, 2023 9:48 pm Without running some math these are just opinions, cautions and suggestions; but I would use multiple injectors, in order to maintain good fuel distribution. Second, because your "cycle" is short (e.g., 3-cylinder is 1/3), you have little time to inject multiple injections for that distribution. So third, the injectors would have to be relatively large to handle supercharged power, while still opening-injecting-closing each time in the shortened time-frame available. Fourth, this is fine, except control of huge injectors with multiple injections at low loads may then present a control issue. Supercharged engine loads require even fueling, with multiple injectors, or even fueling with multiple injections, or both.

Alternatively, the code be modified to allow the odd number of cylinders in the cycle. Another alternative to take the 3:2 input gear for timing, and add a cycle signal. Alternative to take the 3:2 output for 6-cylinder fuel timing and multiple injections on some. Lots of approaches, some junk, and hopefully one will surface as preferential and suitable within all the constraints and requirements.

I have not run any numbers to get any idea how much of this could be a problem for this specific setup, but suggest you do, as it has been a common issue for similar projects in the past. You have the issues of odd cylinders and possible traits similar to Siamese runners to consider. Paired or batched injectors, staged sets, rising-rate fuel pressure, TBI wetting to "spread" the fuel delivery, or 90°+ runner placement for wall-wetting to same effect, and other options can provide some flexibility if needed. I don't know if it's needed, but you should, just to be sure and know what to expect before you get there. ;) Not throwing a wet towel at all, and offering some thoughts to hopefully skip you forward to success quicker and ultimately easier. 8-)
All very valid points and again, I really appreciate your input. As you probably know most radial engines incorporate a centrifugal supercharger at the back of the crank case that also helps distribute the fuel. This particular engine also has a crankcase driven fan to help fuel distribution, but it is just at crank speed so does not provide any real boost pressure. I'm hopeful that it should ensure even distribution of fuel though with a single injector in the same way that it does with a single carb. Individual injectors with a separate set for redundancy would require a total of 18 injectors so not really practical. At the moment the engine is rated at 150hp. I would like to see 180 - 200hp. My calculations would suggest around 5psi of boost pressure (provided by an auxiliary driven centrifugal supercharger) and a Single ID1700 injector should support this with room to spare. I agree that an injector of this size in normal applications can be problematic at low rpm settings and is true for individual cylinder injection setups. However in this case, as there is only one injector feeding all cylinders, at low rpm/ idle speed it should be operating at a more 'happy' (technical term) range? I'm liking the potential of using the 3:2 reduction to get around the 9 cylinder issue using a 6 cylinder option. 3x6 = 18/2 = 9 . I'll need to get my head around that one and check that the reduction is indeed exactly 3:2 and that the spec sheet has not just rounded the numbers. Keep the ideas coming :) Thank you..
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By PSIG
#62014
So my intent is not misunderstood, I'm suggesting as many injectors as practical, and only enough flow to meet requirements, plus a margin for warmup fuel, accel shot, etc. I do not know that engine's typical BSFC, but for 200hp at 0.5, it should need around 1200 cc·min total, or 40 lb·hr across 3 injectors. This makes the common 42 lb/440cc injectors practical, allowing 3 squirts per-rev for nicely even distribution. An oversized injector such as the 300hp ID1700 could not control multiple squirts per-cycle well, negatively impacting low-load control, and the excess capacity is effectively useless.

I have personally done this before, as part of a Hot Rod Magazine experiment at Sceptre years ago, using MS (EFI Pro) to see how much N2O a stock Ford I6 could take. It immediately jumped to mind, as the setup was a "crown" of 6 injectors spraying down-throat on the 1V carburetor, now being used only as a throttle body. A similar setup could accommodate 3 primary + 3 redundant in a setup like yours. Just thinking out loud.

As injectors very rarely fail, the control could be switched instead of redundant injectors, but that's your call. Your engine did not come with every redundant thing (carb, sensors, pumps, electrical distribution, etc) so much as efficiency stuff, that could be called redundant; e.g., dual magnetos or distributors were not often redundant (some siamesed or cross-shaft so both failed together), but for improved combustion efficiency (reason for the specified rpm drop on "mag check"). ;) This is all your call.
By Plus6g
#62031
PSIG wrote: Wed Mar 22, 2023 12:26 am So my intent is not misunderstood, I'm suggesting as many injectors as practical, and only enough flow to meet requirements, plus a margin for warmup fuel, accel shot, etc. I do not know that engine's typical BSFC, but for 200hp at 0.5, it should need around 1200 cc·min total, or 40 lb·hr across 3 injectors. This makes the common 42 lb/440cc injectors practical, allowing 3 squirts per-rev for nicely even distribution. An oversized injector such as the 300hp ID1700 could not control multiple squirts per-cycle well, negatively impacting low-load control, and the excess capacity is effectively useless.

I have personally done this before, as part of a Hot Rod Magazine experiment at Sceptre years ago, using MS (EFI Pro) to see how much N2O a stock Ford I6 could take. It immediately jumped to mind, as the setup was a "crown" of 6 injectors spraying down-throat on the 1V carburetor, now being used only as a throttle body. A similar setup could accommodate 3 primary + 3 redundant in a setup like yours. Just thinking out loud.

As injectors very rarely fail, the control could be switched instead of redundant injectors, but that's your call. Your engine did not come with every redundant thing (carb, sensors, pumps, electrical distribution, etc) so much as efficiency stuff, that could be called redundant; e.g., dual magnetos or distributors were not often redundant (some siamesed or cross-shaft so both failed together), but for improved combustion efficiency (reason for the specified rpm drop on "mag check"). ;) This is all your call.
This is brilliant and very helpful! Thanks again for your time in responding.
The redundancy requirement is more a regulation issue that hasn't changed much since Orville and Wilbur were plying the sky's. Then again, neither has piston engine tech when related to commercial operations. My day job is flying behind 2 of lycomings finest. Mag / injection issues crop up with alarming regularity.
Just a thought, if we assume that using the 3 cylinder option is best for now. As the 3 cylinder engine firing is equally spaced, would it be possible to use a single injector but fired 3 times with each ecu injector driver? So one injector, one live feed but grounded by the separate ecu channels? Presumably this still requires a large injector so that duty cycle doesn't become a problem? Or would there likely be some sort of interference feedback loop between the injector and the ecu? I'm just thinking from an ease of packaging / less parts to go wrong perspective. My initial calculations suggested an ID1300 injector and that agrees with your calculations / suggestion, however when I increased the BSFC to 0.65 to account for the Supercharger power requirement it became marginal. I might have to start looking at blow through carbs again :lol:
By Plus6g
#62032
Plus6g wrote: Wed Mar 22, 2023 4:05 pm
PSIG wrote: Wed Mar 22, 2023 12:26 am So my intent is not misunderstood, I'm suggesting as many injectors as practical, and only enough flow to meet requirements, plus a margin for warmup fuel, accel shot, etc. I do not know that engine's typical BSFC, but for 200hp at 0.5, it should need around 1200 cc·min total, or 40 lb·hr across 3 injectors. This makes the common 42 lb/440cc injectors practical, allowing 3 squirts per-rev for nicely even distribution. An oversized injector such as the 300hp ID1700 could not control multiple squirts per-cycle well, negatively impacting low-load control, and the excess capacity is effectively useless.

I have personally done this before, as part of a Hot Rod Magazine experiment at Sceptre years ago, using MS (EFI Pro) to see how much N2O a stock Ford I6 could take. It immediately jumped to mind, as the setup was a "crown" of 6 injectors spraying down-throat on the 1V carburetor, now being used only as a throttle body. A similar setup could accommodate 3 primary + 3 redundant in a setup like yours. Just thinking out loud.

As injectors very rarely fail, the control could be switched instead of redundant injectors, but that's your call. Your engine did not come with every redundant thing (carb, sensors, pumps, electrical distribution, etc) so much as efficiency stuff, that could be called redundant; e.g., dual magnetos or distributors were not often redundant (some siamesed or cross-shaft so both failed together), but for improved combustion efficiency (reason for the specified rpm drop on "mag check"). ;) This is all your call.
This is brilliant and very helpful! Thanks again for your time in responding.
The redundancy requirement is more a regulation issue that hasn't changed much since Orville and Wilbur were plying the sky's. Then again, neither has piston engine tech when related to commercial operations. My day job is flying behind 2 of lycomings finest. Mag / injection issues crop up with alarming regularity.
Just a thought, if we assume that using the 3 cylinder option is best for now. As the 3 cylinder engine firing is equally spaced, would it be possible to use a single injector but fired 3 times with each ecu injector driver? So one injector, one live feed but grounded by the separate ecu channels? Presumably this still requires a large injector so that duty cycle doesn't become a problem? Or would there likely be some sort of interference feedback loop between the injector and the ecu? I'm just thinking from an ease of packaging / less parts to go wrong perspective. My initial calculations suggested an ID1300 injector and that agrees with your calculations / suggestion, however when I increased the BSFC to 0.65 to account for the Supercharger power requirement it became marginal. I might have to start looking at blow through carbs again :lol:
Having looked through the software adjusting the number of squirts per cycle to 3 would be the same as wiring as above?
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By PSIG
#62046
We need some clarity here. For example, 3 injectors would actually be firing 3 times each per-cycle, on 9 cylinders. Using injectors small enough but enough of them to total the required fuel, means each injection only has 80° to inject the entire cylinder's-worth of fuel. To inject less than 3x3 per-cycle would be less than optimal for fuel distribution. You can see I'm looking for best-case first, and compromise later if necessary. I would think altering the code to allow for 9 cylinders on any divisible number of injectors (1, 3, or 9) would be preferable to these gymnastics, though it is theoretically possible.

Disregarding redundancy for a moment, that's 3 injectors, each one on one of 3 channels, with 3 squirts each (every 80° repeating every 240°), on 9 cylinders, in 720°. :lol: To use fewer injectors may be attractive for simplicity, but then you have one injector opening 9 times per-cycle, and just the latency will suck-up much of the available cycle time. A single injector capable of that is possible, but then (again) raises concern that control of a humongous injector like that at cruise and lower loads. This would be like trying to perfectly fill a drinking glass with a fire hose. :lol:

A single injector firing 3 times per-cycle is an option, if fuel distribution is adequate and does not compromise reliability. I hope you can see why I'm hedging towards multiple injectors, as being "simpler" and more effective from a different perspective. Ultimate from that perspective would be 9 port injectors at 133cc each for optimum control, but will be compromised by other factors in balancing the system goals.

I also have concerns about raising BSFC to 0.65 for two reasons. First is if the heat-shedding ability of the engine could be insufficientl to support 200hp of cooling. That is unreliable, unless aux cooling is added, and any addition to allow for a shortage is teasing unreliability. If it can shed 200hp of heat, then enriching when you don't need it is wasteful and invites unreliability. Second, a BSFC of 0.65 for aux cooling, assuming peak torque at (example) 12.7:1 AFR, would mean running at 9.77:1 AFR. That is borderline on misfire, can quickly foul plugs, hurts power, and again invites unreliability. Just sayin', and using a lot of "ifs", but hoping to make the points. Fill me in if I'm short of info or assuming too much.

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