MyE28.com

from a month or two ago.

First two pics are the dia TDC mark from crank dampner, second is the lower crank cover mark alignment.



I found it curious that the diag TCD alignment is not equal in align with the case cover mark? Any ideas why that is. According to Bentley the lower cover mark is #1 TDC. The diag sensor is not the same position as that? Im a little confuesed. But onward...

Heres the reference sensor mark in red on the block with the engine at #1 TDC


The reference tab is not visable in that picture. It is around just under the other side 31.5 teeth around. Since the engine turns clockwise(?), that makes sense. Its past the reference sensor with that rotaion direction with the #1 @ TDC.

I verified there are 116 teeth. The reference tab is located between 2 teeth. So I figure the tab needs to pass the sensor to fire it, so that half is taken down 1/2 tooth. So...

Degrees per teeth is 360/116=3.1034
Reference tab is 31 teeth before.
So, the reference mark is 3.1034*31=96.2deg BTDC

I would not have though it would be that far advanced, but it is. A WAG is that the 059 ECU is of such low processor speed, it needs the time to set up timing well before the first firing event.

For the first timer, this is the info needed to use the existing rpm and reference sensors instead of installing a BMW 60-2 or Ford 30-1 wheel on the crank.

To make this work, you need to understand these two pages from the MS website:
http://megasquirt.sourceforge.net/extra ... wheel.html
http://megasquirt.sourceforge.net/extra/wheel2.html

The way I see it is to combine the two signals with the circuit on wheel2.htm page then use a divide by 2 CMOS circuit and go in the the U4 pin 6 input.

I know that not straight forward, but it should work. The circuit would need som tuning and the appropriate software setup in MS.

Ill put some more time into this later after som of my time gets freed up.

RussC

thanks for the legwork =]

Russ, isn't the diag pickup for simple rpm readings and not a TDC indicator? If just for rpm, it's location doesn't matter.

Sweeney wrote:Russ, isn't the diag pickup for simple rpm readings and not a TDC indicator? If just for rpm, it's location doesn't matter.

OK,
The ETK calls it TDC sensor. That way you can get timing info from the diagnostic port. With TDC and the ignition output at the diag port, the techs can look at timing for debug purpurposes. It may not be TDC for #1 cylinder????

RussC

Russ,

Have you found out anymore on the reference mark? I will be getting into some of this pretty soon myself, and it would be great to use to flywheel reference points rather than set up the crank wheel.

roeboat wrote:Russ,

Have you found out anymore on the reference mark? I will be getting into some of this pretty soon myself, and it would be great to use to flywheel reference points rather than set up the crank wheel.

What are you asking me? You have all the info except the div circuit on the MS. I haven't gotten to that yet.

RussC

i dont know about the stock ecu or megasquirt, but the with the haltechs the distance between tdc and the trigger is your maximum advance, the ecu cannot fire the spark before it see's that signal.

maybe this is the same? in that case 62 degrees is plenty safe..... i dont know piston engines, but mazda does use the max advance (48 degrees) on decel, on the rotary.

mike

Well,
I would think in this case that 90deg is plenty. I know by looking in the 059 ECU maps, the maximum advance is in the part throttle map, minimum load(8%) and 3400rpm and above. In that part of the map the advance is 44deg BTDC.

RussC