MPi cam sensor trigger point
Turbo Mini Forums

On 9th Jan, 2009 Sprocket said:
......and its been too bloody cold to do anything in the garage

Schrödinger's cat - so which one am I ???

it was -2 last night when I got home from work, it was -4 on wednesday when i got home from work and on tuesday it was -5. Plus the fact we are both still suffering, which makes a working day very tiring. Last thing you want to do is start work on something that isnt realy that important when its -5 outside and -1 in the garage :(

Just means the list of stuff to do tomorrow is too long

Me too, my ratio is 5 minutes in the garage to 1 hour inside recovering....

I bet Jean is laughing at us suffering from -5 though

Schrödinger's cat - so which one am I ???

On 9th Jan, 2009 Rod S said:
I bet Jean is laughing at us suffering from -5 though

http://www.jbperf.com/

Jean,

One for you really (again!)...

Basically two questions....

Firts, I've just finished my phase sensor - a simple optical trigger from a seriously modified dizzy - but have yet to cut the slot in the optical wheel. Is there any optimum pulse duration that MS would like ??? I'm just thinking how wide (ie, long in duration) to cut the slot. I can easily see the on/off ramp times from the opto switch data sheet so can make sure I don't work outside them, but does MS have any requirements, especially as a second input ?

Second, and this is more out of interest... If you want to allow MPI sensor equiped cars to run the siamese code with a second (pahase) input, as it's another VR sensor, where would it be wired too ???

I've modified my MS to use the "spare" opto-in circuitry for the second sensor and, from earlier posts, Paul has done the same (albeit with a Hall switch rather than opto) but wouldn't you need some extra circuirty for a second VR input ???

Rod.

Schrödinger's cat - so which one am I ???

Paul,

The slot can be almost any width because this is done with an interrupt so the code will only look at the first transition. That's not entirely true because there is some code to prevent against noise so if the signal is too short it will be ignored. But any physical slot in a distributor wheel will generate a signal long enough to be easily detected.

As for the second VR sensor, it does indeed require some additional circuitry. I actually have a board available for such a purpose which has an LM1815-based VR conditioner circuit. The board actually has 2 such circuits for those who have 2 VR sensors and are using the old V2.2 MS board (or those who don't like the V3 VR circuit).

The LM1815-based circuit can also be installed in the proto area of the MS V3 board.

Jean

http://www.jbperf.com/

Schrödinger's cat - so which one am I ???

Hard Luck

Just swing your cam sensor through 180 degrees. But, of course, you now know that.

I set mine by getting it running, turned the cam sensor anti-clock until the engine stumble, then clockwise till the engine stumbled and then fixed it half way between.

The cam sensor just sets a flag in the software to tell the procesor which part of the cycle it is on, so precise settings are not important.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Yes....

I would just like us all to agree an optimum position....

As the 36/1 wheel is 90 degrees BTDC is it best to put the cam at say 135 BTDC or 45 BTDC.

Obviously keeping it away from the missing tooth is paramount but, bearing in mind others are showing some interest, I honestly think some consistency in this detail will help in comparing results

I'm going to move it to 135 initially but my spread (without knowing leading or falling edge) is already 40 degrees.....

More boring plots/graphs later....

Schrödinger's cat - so which one am I ???

I've always found that the biggest problem is working out the engine position, ie compression stroke or exhaust stroke, without resorting to taking the rocket cover off.

Easy enough to set the engine at TDC but which one.

If you know where the engine sits then setting the cam sensor is easy......or is it? You have a slot, wheras I have a tag.....

Bugger this I'm going on noliday.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Rod,

You can select which edge is used as the trigger. And it's only this edge that matters. So in your case you can use the rising edge and you'll be fine as long as that edge doesn't move a lot through the engine rpm range.

And if I had a choice between 135 and 45 BTDC with the missing tooth at 90 BTDC, I'd chose 135 because it could reduce slightly the sync time at cranking. But that's probably not significant.

So I would leave it as you have now and just try it. If you have problems starting and/or syncing then you can check the composite logger in TunerStudio which will show you what the MS is actually seeing and if you see that the triggers are not consistent then you can change the position.

Jean

http://www.jbperf.com/

One more thing is that the first 360 degree of the engine cycle will be after the missing tooth following the cam trigger. So choosing 135 or 45 BTDC will mean that the 720 degrees engine cycle doesn't start on the same cylinder.

That's not a problem but if you use COPs you may need to swap cylinders 1 and 4 coil driver wires and cylinders 2 and 3. You'd need to also swap the injector drivers from one port to the other.

Jean

Edit: I changed what I had written about the injector drivers which was just plain wrong.

Edited by jbelanger on 25th May, 2009.

http://www.jbperf.com/

Sorry Jean, I'd missed the basic rising/falling setting in the basics (or forgotten about it....)

A mechanical move though is simple in my design of phase sensor - without rotating the cut-down dizzy body, just moving the slotted wheel on the shaft...



Next testing on the injectors...

EDIT - typos (BH afternoon, pub, etc...)

Edited by Rod S on 25th May, 2009.

Schrödinger's cat - so which one am I ???

This one should be safe no matter which edge you select.

Jean

http://www.jbperf.com/