Logged advance vs. actual advance (How does base timing come into play)

[CSXRT4]

Ok so im tuning the timing on my setup using turbonator. Im using risen's logworks plugin to log ignition advance. I was wondering if the logged advance is the actual advance or do I have to add in my base timing to get a "final timing advance being seen by the engine"???

[CSXRT4]

Anybody?

[risen]

The only way I can think of verifying is to get a timing light out and log the car at idle and check it's timing. If the 2 match, then the ECU already has the timing taken into account. I'm not sure off the top of my head, but I don't believe it knows or takes into account any of the mechanical advance.

[turbovanman²]

Wish I could remember all of this but if my memory is working, the cal doesn't show the 12 deg's but assumes its there, so if logging, you'd have to add the base timing in.

Rob would know 100% or Aries Turbo.

[CSXRT4]

Well here is what I did when I set the base timing. I didn't have an adjustable timing light and the engine is connected to a different transmission, so I wasn't able to time it at 12degrees using the window like your supposed to. So I went into the cal and set the "spark advance when setting base timing" table to 0degrees, then I made a mark on the crank pulley where #1 piston is at TDC. I used a fixed timing light to set the timing like this.

I assumed the computer just needed to be synchronized to the the distributor. So by setting the spark to 0degrees in the cal and then timing it to 0degrees physically I would basically get the actual timing when I log timing.

My problem is when I was tuning, the engine wouldn't run very well at what I though was reasonable timing (14-20 degrees in boost). I had to advance timing to ~30-35degrees in boost :eek: just for it to run decent. Ive been checking the plugs and I see no signs of detonation, and actually when it was at 14-20degrees I was getting knock which I thought was odd (I guess you can get knock from not enough advance??)


So the only thing I can think of is that the base timing is way too retarded?

[ShelGame]

Are you sure it's set to 0 degrees? I wouldn't have thought the engine would run with the ignition set to TDC...

To answer your question: The base timing is not added into the timing at all. It's just a reference point. The timing of the coil on/off times includes the assumption that the distributor reference is set to a certain point.

[Shadow]

Are you sure it's set to 0 degrees? I wouldn't have thought the engine would run with the ignition set to TDC...

To answer your question: The base timing is not added into the timing at all. It's just a reference point. The timing of the coil on/off times includes the assumption that the distributor reference is set to a certain point.

So when my DRB2 reads 20 deg Total advance your saying I'm really at 32 if I'm running 12 deg base? Or does the base only factor into the lower half of the timing table?

[ShelGame]

No, the total timing is referenced to TDC, not the base timing. So, 20deg should be 20deg, not 32.

But, if you set the distributor to 14deg, and the scan tool then reads 20, that's actually 22deg...

The 12 deg base timing doesn't get 'added' into the calculated timing. There's some math done to determine when to turn on/off the coil. It includes the dwell time, and an offset for the position of the rotor relative to TDC. I don't see how ChryCo got the offset, yet. But, I know that's what it is. I think it also must include some offset value for the width of the distributor rotor. I need to comb thru the patents again. I think there's probably something in there to explain it..

[zin]

OK, just to make sure I'm reading this right...

The Cal assumes a mechanical base timing? As far as I know it wouldn't have a way to know where the dist is set, so it could only assume it is set correctly, then add to it?

I can see how this could be confusing if you want to log your advance, to get true total advance, you'd have to add whatever base timing you run to the indicated electronic advance... Right?

Mike

[ShelGame]

The timing the ECU calculates is referenced to TDC. So, it is actual advance. But, the ECU assumes the timing reference was set using the procedure, and that it was set to 12 degrees. So, it sets the coil on/off times based on the rising and falling edges of the shutter wheel. If you move the shutter wheel, then it's true, the computer no longer knows where it really is since it is all setup assuming 12 degrees. But, again, the 12 deg is not added to or subtracted from the stored timing value at all. It's hard-coded in the coil on/off timing calculation.

[Shadow]

No, the total timing is referenced to TDC, not the base timing. So, 20deg should be 20deg, not 32.

But, if you set the distributor to 14deg, and the scan tool then reads 20, that's actually 22deg...

The 12 deg base timing doesn't get 'added' into the calculated timing. There's some math done to determine when to turn on/off the coil. It includes the dwell time, and an offset for the position of the rotor relative to TDC. I don't see how ChryCo got the offset, yet. But, I know that's what it is. I think it also must include some offset value for the width of the distributor rotor. I need to comb thru the patents again. I think there's probably something in there to explain it..


The timing the ECU calculates is referenced to TDC. So, it is actual advance. But, the ECU assumes the timing reference was set using the procedure, and that it was set to 12 degrees. So, it sets the coil on/off times based on the rising and falling edges of the shutter wheel. If you move the shutter wheel, then it's true, the computer no longer knows where it really is since it is all setup assuming 12 degrees. But, again, the 12 deg is not added to or subtracted from the stored timing value at all. It's hard-coded in the coil on/off timing calculation.

Good explanation, got it!

[zin]

But, again, the 12 deg is not added to or subtracted from the stored timing value at all. It's hard-coded in the coil on/off timing calculation.

OK, correct me if I'm wrong, but the value shown on a scan tool is the actual total advance as it should be, assuming it was set to factory specs, any additions of subtractions from stock base timing would have to be factored into what a scan tool would show...

Mike

[ShelGame]

OK, correct me if I'm wrong, but the value shown on a scan tool is the actual total advance as it should be, assuming it was set to factory specs, any additions of subtractions from stock base timing would have to be factored into what a scan tool would show...

Mike

Correct. If you adjust the reference point from 12deg, the ECU won't know. Therefore, the scantool won't know...