Help with building your Speeduino, installing it, getting it to run etc.
@LPG2CV - The only time excess air is needed is when starting or during hard deceleration when the throttle plate(s) are closed. Here's a picture of the air inlet holes on the cylinder side of the throttle plates:
Air Inlet Holes.jpg
Air Inlet Holes.jpg (156.1 KiB) Viewed 1040 times
Project has slowed down, but not stopped. Going to restart the trials in about two weeks, but have some work to do first to prepare for the second phase. Continuing to read through the various forum threads for information.

Thought about the trigger angle and what it means. Noticed that for the Squirt family the trigger angle is BTDC, Speeduino is ATDC. Have always thought of timing as BTDC, never ATDC.

I then thought about what happens when I change the trigger angle with it being ATDC. The calculated trigger angle for my engine is 260 degrees ATDC - presently at 267 degrees (CW rotation). If I reduce this number say to 240 degrees - rotating the trigger angle CCW, I am in essence advancing the timing an additional 20 degrees. Conversely, changing the trigger angle to say 280 degrees ATDC, I am retarding the timing an additional 20 degrees.

Using this analogy and doing the math, to get a 15 degree advance at idle (ignition timing locked at 15 degrees at start), I should be looking at decreasing the trigger angle towards the 245 degree mark. If this was a trigger angle BTDC, I would expect that reducing the trigger angle would retard the timing (trigger angle moving ATDC), whereas increasing the trigger angle would advance the timing.

I had to refresh my memory regarding this. "If the rotor turns clockwise (my engine turns CW), you'll advance the timing by rotating the distributor counterclockwise, and vice versa. (move the trigger angle CCW (decrease the trigger angle setting) to advance and CW (increase the trigger angle setting) to retard"

Thinking I have been staying on the timing retard side of the equation (increasing trigger setting) instead of on the timing advance side (decreasing trigger setting).

Will be testing this premise when trials restart. Chime in if I'm too far off the mark.
Rednaxs60 wrote: Tue Mar 14, 2023 2:46 amThought about the trigger angle and what it means. Noticed that for the Squirt family the trigger angle is BTDC, Speeduino is ATDC. Have always thought of timing as BTDC, never ATDC. … Chime in if I'm too far off the mark.
You are waaaay overthinking this. Trigger Angle has nothing to do with BTC or ATC. It has to do with telling the processor where zero is. That's it. With Speeduino, it can be -360 to +360 (720°), so the correct 0° TDC is identified for compression TDC of #1 cylinder. Follow the directions, set TA so timing is zeroed, the timing table reads correct and actual timing, and run that thing. 8-)
Yes, you are correct in that incorrect TA will add or subtract advance. This is why I was previously giving you concise instructions on how to set it, check/adjust with a timing light, and then leave it alone. :D. It's a one off configuration setting. It will only ever need altering if you change the trigger edge.

For clarity, all alterations to ignition advance are then made through the appropriate table. :)
Thanks to both. The reason for the post is that I understand the timing, but when adjusting for initial, which way do you change the TA settings to suit. My past is haunting me, on the old steam destroyers had to know how a system functioned and how each component worked and was put together - got into the weeds quite often. This philosophy followed me throughout my career, and into my retirement.

That's fine, but you could get instant answers if you tried it on the bike. You know it is to set relative TDC (sensor signal to TDC) for the processor, and if not correct with a timing light, it is in-error. Trying to out-think something you are unfamiliar with goes a lot faster if you see the results of actions, and make corrections. Then understanding floods in and you can explain what happened. This is why I suggested getting it to run and tune it, as you will be buried with info about how it actually works. The big picture, made of many little ones, in your face. :lol:

If I've never used ice skates, my mind could race. What if I lean forward? What if I'm not balanced over the blades? What if my blades are not sharp enough? What if ...
Just go try it. You know the basic concepts, now go see how it works. It will all become clear, including answers to questions you never thought of.

You will eventually see the benefits of this, as you will be able to manipulate the operation in ways not yet conceivable. This will make a huge difference in your ability to tune and accomplish stuff better, or at all, in ways others cannot. Awesome! Get there quicker by just doing it. Try stuff when you know how it actually works. So much easier and quicker!

You want to lean how to cook, and it's good to briefly read labels in the grocery, but you need to get home and turn on the burner. 8-)
Thanks - bailing wire and duct tape, our Navy keeps its ships well past the best before date.

Going to treat this next phase as a new install, incorporating the lessons learned from the first go round (do as I'm told :lol: ), and what I have found from other EFI GW conversions. Hopefully a lot less of a grind.
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