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By TZ350
#32592
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Thanks, I am excited too.

Fueling is real rubbish but its what you would expect with a first cut. Great news is that Pseudo MAP value behaves like I hoped. It increases as the motor starts making power and drops in areas where the TPS increased but the motor did not fire. Altogether it looks like the concept is going to work.

Now all I have to do is figure out how to use Tuning Studio properly.
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Attachments
Psuedo MAP.png
Psuedo MAP.png (127.58 KiB) Viewed 2439 times
By TZ350
#32839
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Ok. Another bump in the road. The 2S EFI fuel injected two stroke Pesudo MAP thing works pretty well.

BUT .... there seems to be another issue that comes up when the throttle is closed ie TPS = 0%.

With the pseudo crankcase pressure MAP (Phigh - Plow)*3. I get a range of 0.2 bar, TPS = just open and motor firing, to 0.9 bar, TPS fully open and engine firing. The motor responds to changes in MAP value just like you would expect.

But with the throttle fully closed ie TPS = 0% the pseudo MAP value is 0.6 bar when it should be 0.2 at most. Maybe this is due to the atmospheric pressure at the stinger/muffler tip overcoming weak suction by the pipe and pushing exhaust gas back into the crankcase.

And without the suction action of the pipe the residual average pressure in the crankcase is higher than it would be if the throttle was a little open and the motor firing well enough to get some suction action going in the pipe.

I think the 0.6 bar at closed throttle is the result of (Phigh - Plow)*3 working on a denser volume of contaminated gases filling the crankcase whereas, as soon as the throttle is opened a fraction and the motor fires properly the pipe sucks on the crankcase and the pseudo MAP value drops back to 0.2 bar.

The EFI CPU can't work with 0.6 bar for two entirely different situations.

So the fix might be to bring the TPS into the mix and when it is = 0% then force the pseudo map to be 0.2 bar. Easy enough to do with some software changes and I hope to try it soon. There is another interesting project on the dyno at the moment so it might be a week or so before I can get back to the 2S EFI project.
By TZ350
#33559
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Well after a bit of traveling away for work, a grand tour of New Zealand's South Island and helping out on another project last week I have finally been able to get back to my own fuel injection project.

I had the pseudo MAP co processor working and responding as hoped. But I was puzzled for a bit about why, when the throttle was completely closed the crankcase pressure went up. On reflection I figured that when there was no suction from the pipe atmospheric air and exhaust fumes flooded back up the exhaust pipe and through all the gaping holes in the cylinder.

Filling the crankcase to near atmospheric pressure with dirty exhaust gave the underside of the piston something to compress resulting in a misleading high pseudo MAP value. The crankcase pseudo pressure quickly dropped, actually the difference between max - min crankcase pressure dropped as soon as the pipe started sucking again and the piston was left chasing air that was rapidly disappearing up the transfer ports.

Some tweaks to the co processors software soon sorted that and now my two strokes pseudo MAP value looks much like you would expect from a four strokes MAP sensor and hopefully will be a good indication of changes in mass air flow for the EFI's CPU to work with.

I expect, with a bit more software tweaking and some time tuning the fueling map with Tuning Studio I might soon have a fuel injected two stroke bike I can race. :D
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By TZ350
#33588
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The 2S pesudo Map (Yellow line) is starting to behave like a good MAP should but is cutting out at about 6,000 rpm.

The code works Ok on the simulator and checked with a scope so I think that the map sensor itself may not be able to keep up with the changing crankcase pressure. Or the peak pressure has moved away from the sampling point. I will have to try different crank angles and maybe some different map sensors.
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Attachments
psuedo MAP.png
psuedo MAP.png (119.21 KiB) Viewed 2237 times
By TZ350
#34454
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I have been fighting a bit of a battle with the PesudoMAP sensors software thinking there was something wrong with it but after extensive testing with the simulator and oscilloscope I am very confident with it. The issue is that the PesudoMAP value drops away over 8,000 RPM or so as seen in the picture above (Yellow line).

Currently my code can make a sensible reading every 8 deg at 13,000 RPM and with a bit of clever coding it could make a reading every 2 deg. 8 deg is good enough for the three high pressure readings I make at 15 deg intervals. 115, 130, 145 deg ATDC. If the software code is good then the issue must be with the crankcase pressure sensor.

So I put the oscilloscope on the crankcase pressure sensor tonight, purple line, yellow line is the ignition pulse. I wanted to see what sort of signal it produced and what it looked like compared to EnginMod's prediction. Pretty close I recon. The next move is to try and capture a trace at 12,000 rpm.

I have been having problems with the MAP value dropping away above 8,000 RPM and suspect either the pressure sensor is not keeping up or the speed of response from it is so slow that the indicated pressure peak moves away from my last measuring point at 145 deg ATDC.
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Attachments
MAP sensor signal at 4k RPM.jpg
MAP sensor signal at 4k RPM.jpg (725.07 KiB) Viewed 2126 times
Crankcase Pressure Traces.png
Crankcase Pressure Traces.png (370.21 KiB) Viewed 2126 times
By TZ350
#34551
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Ok, not quite 12,000 RPM but it tells me everything I need to know. That the signal is consistent and instead of measuring at the theoretically correct crank angles I can allow for the delay in the sensor and measure the crankcase high pressure at BDC and the low pressure at TDC. Easy as.
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Attachments
11580 RPM.jpg
11580 RPM.jpg (739.53 KiB) Viewed 2067 times
User avatar
By PSIG
#34603
Heh. 12k rpm engines, with a primary power-band of ±1k rpm. Not unusual, but just goes to show how focused the tuning would be. Watching the videos, it would appear the next increment in that class would be brakes (and tire compound/design to handle it), in order to allow power deeper into turn approach before decel. Hmm... Anyway, strategy in the world of racing for another time.

Perhaps you need a curve to compensate for the MAP timing (read point) as it progresses through the range? Or process separately where timing is irrelevant, and it only holds last Delta value for the processor to read? I have a feeling you are going to emerge from your cave with something really cool. 8-)

David
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