MegaSquirt trigger wheel sensor solution, What's your design?? Options

[draganc]

Hi guys!

I’m planning to upgrade my D-jet system on a 75 2.0 (2056) with a MegaSquirt system.

I’m still debating how to mount the trigger-wheel-sensor and would like to see some of your solutions.

Thank you for your input,
Dragan

[dr914@autoatlanta.com]

We took a new 009 distributor and designed a pickup for it. Works perfectly but very expensive as we had to machine parts to make this functional and reliable. the best thing though is that it uses the original distributor hole so there is no need to machine anything nor drop the engine
Mcmarks is a very economical solution.

Hi guys!

I’m planning to upgrade my D-jet system on a 75 2.0 (2056) with a MegaSquirt system.

I’m still debating how to mount the trigger-wheel-sensor and would like to see some of your solutions.

Thank you for your input,
Dragan

[draganc]

We took a new 009 distributor and designed a pickup for it. Works perfectly but very expensive as we had to machine parts to make this functional and reliable. the best thing though is that it uses the original distributor hole so there is no need to machine anything nor drop the engine
Mcmarks is a very economical solution.

What is "very expensive"?

[underthetire]

We took a new 009 distributor and designed a pickup for it. Works perfectly but very expensive as we had to machine parts to make this functional and reliable. the best thing though is that it uses the original distributor hole so there is no need to machine anything nor drop the engine
Mcmarks is a very economical solution.

What is "very expensive"?

Ya, inquiring minds want to know. I'd love to put my MS back to fuel and spark. The point pickup (or electronic) sucked for it during start.

[JamesM]

Ya, inquiring minds want to know. I'd love to put my MS back to fuel and spark. The point pickup (or electronic) sucked for it during start.

Some advice on using spark control with a distributor pickup…

When using the point pickup for ignition control with Megasquirt it is VERY important that your "cranking speed" variable be set correctly to have decent starts, ie. set to what your engine is actually cranking at. Technically all your variables need to be set correctly but I find this one to be overlooked and it can cause lots of problems.

Just guessing at this or going off specs in a book is not good enough, you need to disconnect the ignition and crank the engine for a bit to see what Megasquirt is reading the exact RPMs at and use that for your cranking speed value. If it bounces around a bit chose a value in the middle or on the lower end of what you are seeing. You may also want to delay ignition events for a cycle or two at start to allow the engine to get up to this speed.

When using the points pickup Megasquirt does a time calculation based on engine speed to decide when to fire the spark. The distributor pickup does not give enough sensor events (or any for that matter) to calculate engine speed for itself by the time the first ignition event occurs so it needs to have a proper cranking speed variable given to it to get the timing right on startup. Getting this wrong, or just leaving set to whatever default value it had, and you wind up with an engine that has a hard time starting, wont start at all, or maybe even give yourself a flywheel with broken teeth from kickback against the starter.

Think about it, if Megasquirt thinks your engine is spinning at 200rpm when cranking and you are actually only getting 150rpm it is thinking your engine is running 25% FASTER THEN IT ACTUALLY IS! Now think about where a 25% discrepancy in your timing would put your spark.

Correctly set cranking speed makes a world of difference when starting!

Of course if you are willing to put in the extra time and money, crank sensors are the way to go.




Another issue you could be having with starting is a weak tach signal due to how the tach input circuit on your MS was set up (usually when people mod them to filter noise), but I won’t get into that here.