This seems like it should be a simple enough question because there are quite a few good pages in the documentation out there on this subject but, I am having a hard time figuring out exactly what my 'Tooth #1 Angle (BTDC deg)' value should be. In pretty much all of the documentation I've seen, the VE sensor is on the left hand side of a clockwise rotating trigger wheel. Mine is on the right hand side. Following the instructions, I counted the gaps from the hall sensor to tooth #1 when the engine was at TDC and I came to roughly 24 gaps. A friend of mine said I did it wrong and I should have counted the opposite direction and have 12 gaps instead. This wouldn't be a problem but I am having severe issues getting the engine running and I want to rule timing out. I made a couple pictures to help illustrate the situation.
This is the trigger wheel on my engine:
This is a drawing of how my setup looks:
So, should my tooth angle be 240 degrees or 120 degrees?
Please ignore and remove the TDC pointer from your diagrams and thinking. As per the manual, set the engine to TDC and leave it there. It is intentional that the manual does not show a TDC mark on the wheel and shows the timing pointer and timing marks independantly. The Megasquirt does not care where the sensor is positioned on the engine or whether the missing tooth is at 1 o'clock, 7 o'clock or 11 o'clock.
What does matter and is critical is the number of tooth gaps between the sensor and tooth#1 when the wheel rotates in the normal direction.
(If there isn't one already, I'd like to make a short video describing this.)
You are correct. As Jim suggests - with the engine at TDC, just count around the wheel (CCW for a CW rotating engine) from the first tooth after the missing tooth to the tooth in front of the sensor.
To think of it in another way. The offset is specified as degrees BTC. In your case, how many degrees pass between the sensor picking up the first tooth after the missing one and the next TDC? Without me being too precise your drawing would suggest something around 270.
I apologize, I didn't mean to imply in the second diagram that a particular gap or tooth is top dead centre. In the first picture, I had the engine set to TDC via the flywheel markers. The drawing is meant to look like what my engine at TDC looks like.
That being said, another way to ask the question is, since my engine rotates clockwise, when I count the gaps from the hall sensor to tooth #1, should I count clockwise or counterclockwise / with the rotation of the engine or against it? It sounds like I had it right the first time by starting with the tooth directly under the sensor and counting clockwise to tooth #1.
This is an illustration of 80 degrees (8 teeth on a 36 tooth wheel) on a CW rotating engine. Engine is set at TDC. Sensor is 8 teeth CCW from the missing tooth.
perhaps another stupid question,I have a similar situation, my timing sems about 120 degree' s off
I cannot find where i can actually set a large initial offset angle in Tunerstudio.
most parameters suggesting the initial ignition timing allow only small angles ( eg -10 to 10, or -30 to + 30) perhaps I am looking at the incorrect settings?
robertkraal wrote:perhaps another stupid question,I have a similar situation, my timing sems about 120 degree' s off
I cannot find where i can actually set a large initial offset angle in Tunerstudio.
most parameters suggesting the initial ignition timing allow only small angles ( eg -10 to 10, or -30 to + 30) perhaps I am looking at the incorrect settings?
Start a new topic. Describe your install and attach your MSQ.
So if I'm converting form EDIS to my MS directly controlling the coils and I'm still using the EDIS sensor and wheel, my trigger offset would be 90 deg, correct?
