MicroSquirt.com read only forum (Jan.15,2018)

I'm not sure I follow this either - with an odd number of cylinders and only a crank wheel, surely you may end up firing half a cylinder out?

James

78Spit1500Fed wrote:

racingmini_mtl wrote:

grippo wrote:The 60-2 wheel + msd, distributor should work with the MS II beta code (v2.672x7b). If it is set up to fire once every 24 teeth, the dizzy should take care of the routing.

Even with a distributor, with only crank trigger, how do you know it's not going to be 360 degrees out of phase? There's something I'm not getting here.

The distributor only rotates once per 720 degrees of crank rotation. The rotor is always only pointing at the cylinder in the compression stroke.

-Brian

How does MS know when synchronizing with the crank trigger if it's on the first or the second rev of the engine cycle as shown in the pictures below? The pictures show the position of the distributor rotor.

In the second case, it would either fire cylinder 3 really late or cylinder 4 really early.

Jean

Jean,

Yeah, I agree with you. The ignition events need to be in the same place on each crankshaft revolution (meaning there has to be an even number of cylinders for a 4-stroke engine for a missing tooth crank wheel to work).

With a 5 cylinder engine and 24 teeth between tach triggers, you would have:

0 teeth -- cyl #1
24 teeth -- cyl #2
48 teeth -- cyl #3
60 teeth -- one revolution complete
72 teeth (ie. 12 teeth on the 2nd revolution) -- cyl #4
96 teeth (36 teeth on the second revolution) -- cyl #5
120 teeth -- two revolutions complete -- cyl #1
...
etc., as in your diagram.

But, as you say, MegaSquirt has no way of knowing if it is on the first or second revolution at start-up without a camshaft position sensor. And even a wasted spark set-up wouldn't work, since there isn't a corresponding cylinder that is 360° out of phase.

Perhaps Al has a trick for this though.

Lance.

racingmini_mtl wrote:
How does MS know when synchronizing with the crank trigger if it's on the first or the second rev of the engine cycle as shown in the pictures below? The pictures show the position of the distributor rotor.

In the second case, it would either fire cylinder 3 really late or cylinder 4 really early.

Jean

Doesn't the MSD distributor have a TDC cyl-1 signal? I assumed that would be your reset for sync... maybe I'm wrong.

-Brian

How does MS know when synchronizing with the crank trigger if it's on the first or the second rev of the engine cycle as shown in the pictures below? The pictures show the position of the distributor rotor.

In the second case, it would either fire cylinder 3 really late or cylinder 4 really early.

Hmm.. Ok.. I see..

Now that I fully understand the need for a second trigger, would I need a cam trigger ,or can I use the hall-sensor in the dizzy? I have both a 1 and a 5 window dizzy.

I do NOT have a MSD dizzy, I'm just planning on using a MSD 6 or similar capacitive discharge unit to keep the sparks flying at higher RPM's.

The 20v head I'm going to use has the hardware for mounting a gear on the intake cam, but I would like to run MS on the 10v head, before converting. I would like to start with fuel only, then 5 window dizzy, then one window dizzy+crank, and when the engine is bored for 82,5mm pistons, I'm mounting the 20v head, with individual runners. To debug the whole setup with triggers, individual runners, etc. ,I think, would be a nightmare.

I understand this route means changing the ignition trigger circuit several times, but as this is the nemesis of most unsucsessful MS installs, I need the knowledge.

Thanks for all the exellent help, I have never recieved such detailed and useful feedback from anyone, neither forum, open-source og big Corp.

The only question I have left is:
My fear is that the sloppy gear in audi distributors could throw off the timing by one tooth.
How do the code use the second trigger? Does it expect the next tooth to be nr.1 or does it wait for the missing tooth? MS1e or MS2beta?

O.J.

With the MS1/Extra code a single window dizzy would be fine to say "we are on cycle one" it's precise phasing doesn't matter provide it doesn't overlap the missing teeth of the 60-2.

This code doesn't (yet) exist on MS2, but hopefully it may soon.

James

Hi Guys !!

I´v manage to run my s2 aby engine with MS1/Extra code, uses my deafult
VR and hall sensors, some problems on the way but me and my buddys solved them, uses the LM1815 and 4017 to fix the signals from the VR sensor. Im not a pro Ms user but there are hopefully some questions i can help you with. Im goin to du a pcb layout soon of my extra cards so you can see how we manage to solve the problem of the 135teeth to 15 teeth conversion.


//Supergizmo !!

Sounds like a nice piece of work. Well done.

James

Supergizmo is also running COP on that ABY engine


/Kenneth

Congrats. I'd like to see the circuit.

Any chance you could make a similar circuit to do divide by 2 or divide by 3 instead of divide by 9?