[LPG2CV]

I dont know your coil, or its specs, but your dwell compensation appears to drop off quite quickly. Also, the spark duration appears high!

Can I suggest a test.

With the engine warm and idling, reduce the Running Dwell until it just starts to mis fire. Then increase and decrease until you have found where it is just on the cusp. Then add 0.02 ms to the value.

The Dwell voltage correction slope compensates for the dwell charge when the voltage supplied to the coil changes.

As voltage decreases the dwell needs to be increased, for example when cranking, or extra load such as lights and/or AC.

As voltage increases, for example, as the rpm increases, the dwell needs to be reduced to avoid the coil overheating.

Its possible that your slope is removing to much dwell as the rpm and hence the voltage increases.

[Jcrotts]

Its been a while, but I found my problem. It was either a bad vr sensor or GM module. I switched to a hall sensor and it goes to max rpm with full advance.

I have another issue though. I'm trying to set up injection now and it keeps giving me a message that the required fuel is exceeding the maximum value. The only issue is that this 70 year old, 2000 rpm, flat head will never see 70% VE, much less 100% VE. I dont want to add another injector just to get around this when what I have is plenty. Will it still inject if I leave required fuel at the max setting and use what I have, or will it cause some kind of issue that will stop injection from working all together?

[PSIG]

… I have another issue though. I'm trying to set up injection now and it keeps giving me a message that the required fuel is exceeding the maximum value. …

I've seen occasional weirdness in the R_f calculator and VE Table Generator, where the values or the units will change when clicked to calculate. Like the values won't 'stick'. I always click on another box to set the last value before letting it go. It also has limits on what it will consider acceptable, and return garbage results if outside that range, so you may have to do your own hand-calc's. Else, post your values and units for someone else to try.

[Jcrotts]

I think it is just the case of my engine more than a calculation error. 19 lb injector. 2000 cc engine. It probably would be undersized on a car engine. This engine is rated 26 HP governed at 2000 rpm. I'm not hoping for crazy numbers, maybe 30-35 depending on how hard I want to push it, and if I can find a tractor dyno. I already got it to idle uphill, at 300 rpm, in 4th gear. I've never seen an engine pull that low and not stall. Just the ignition timing control has made a world of difference. I just want to know if I can leave the values, ignore the error, and it will still function .

[PSIG]

I think the TS response is out-of-range, as that single 19# injector should support about 32 hp at 85% duty cycle on gasoline. As you have plenty of time for it , I would set for 4 squirts per-cycle, which will also change your Req_fuel requirement if it's set for any less. As your PW will get tiny at such a low idle, be sure your injector dead time and voltage corrections are spot-on. Go for it, and tell us your results. And a results log would be interesting.

[Jcrotts]

I have thought about a few other options for injection. I have a 23 lb. injector I could use , but that might cause low rpm problems like you said. I also thought about using 2 13 lb. Injectors and alternating them, but that would still probably give the error.

Also, engine runs fairly rich. About 13:1 idle and 11:1 under load. That's on a carburetor, but I want to keep it in that range.

How does the VE table actually work? Is it just a percentage of the pulse width you get from required fuel calculation, or is there more than that going on? Most old tractors are rated at 55% volumetric efficiency, so it wouldn't be too hard to fudge the numbers a little with some math.

[PSIG]

I have thought about a few other options for injection. I have a 23 lb. injector I could use , but that might cause low rpm problems like you said. I also thought about using 2 13 lb. Injectors and alternating them, but that would still probably give the error.

The TS error is non-specific. It is warning of out-of-range, but not specifying why, in obvious terms. Your own calculations should make it apparent where operation is borderline or inadequate (or not), and then you can confidently take corrective steps. For example, can you confidently say that a larger or more injectors will solve any apparent issue, or without introducing new ones? I'm not trying to be dodgy here, but rather trying to help by directing you to better facts.

Also, engine runs fairly rich. About 13:1 idle and 11:1 under load. That's on a carburetor, but I want to keep it in that range.

Only a comment, but as a general rule, running any Lambda other than what your testing shows as most efficient for best performance purpose has down-sides. For example, a common effect of consistent rich running is reduced valve and/or valve seat life. Exceptions to this may be present in specific conditions, such as detonation suppression. But, you can only find that through tuning to best, then altering or de-tuning based on response, under real-world conditions.

How does the VE table actually work? Is it just a percentage of the pulse width you get from required fuel calculation, or is there more than that going on? Most old tractors are rated at 55% volumetric efficiency, so it wouldn't be too hard to fudge the numbers a little with some math.

Answers are in the Wiki, and demonstrated in the Calculations.dash you can load and run in TS to see real-time effects. Like the injector sizing, running your own fueling calculations for confirmation and understanding may be of greater value than for most hobbyists and applications.More-so than most hobbies, information is power.

[Jcrotts]

I'm at the point of wiring my fuel pump and have some questions. Since the fuel pump control requires a ULN (which I dont have) I want to switch to the VVT output. When I switch the output do I use the number of the Speeduino pin or the Arduino pin to set it? Also, do I need any kind of resistor in the circuit? I'm using a relay with a common 12v input wire and split output. Should the inputs be separated, or will each leg only draw the current it needs?

[LPG2CV]

its the arduino pins. If I recall, VVT is pin 4. The default pin for FP is pin 45. Its good practice to swap them to ensure no conflicts.

Speeduino switches the FP relay via the relay ground. I've not heard of anyone adding additional resistance. I would think there would be sufficient resistance in the relay winding.

[PSIG]

See if this example of pin reassignment of FP control to the Boost pin helps. If you want to use VVT output, just use that Mega pin instead.