Tuning witout Timing Marks - Petrol Engines

And as i said the diagnostic machine can tell you the advance retard from TDC , which answered part of your question

How do you want it to tell you where TDC physically is without a reference mark?

ECUs are programmed, they run the tune, they don't 'get' tuned unless you re program them, the diagnostic machine reads the data from the ecu and can , as I said, give you the advance/retard/rpm values in real time and as a printout/log.

If you want to find TDC physically you are already doing it correctly short of pulling the head off.

Do you think you are going to spin it by hand and it will tell you where to stop?

Would be very surprised if any stand alone diagnostic machine could pick TDC, or an actual advance/retard ignition point without a starting reference point to start with, which I gather is what your asking.
TDC is a mechanical point, if you need to know it accurately, do it mechanically. Guessing you need to know it to set up ignition curve?

Ok thanks to everyone for the responses. I assume then the answer to my question is a 'No'.

So I will leave things there.

Cheers

Garry

Quote:

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Originally Posted by Rick1970

Would be very surprised if any stand alone diagnostic machine could pick TDC, or an actual advance/retard ignition point without a starting reference point to start with, which I gather is what your asking.
TDC is a mechanical point, if you need to know it accurately, do it mechanically. Guessing you need to know it to set up ignition curve?

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As above, we are answering the question but not sure if the answer is what you wanted to hear.

A reference point for a diagnostic machine is the vehicle parameters it is set to which then give it the relationship of crank sensor angle (physical positioning ) from physical tdc, exactly what the ecu uses mathematically along with rpm input to give you a basic ignition curve b4 cam sensors (if fitted) coolant temp, air density etc tables come into play.

So one answer to the 2 part question posed is NO it won't find you tdc magically, so what you have already done is correct (have some bloody confidence in yourself ! ), set the no. 1 at tdc thru plug hole or while head is off, then u can mark it off physically on the front pulley/balancer, the 2nd part answer is YES the diagnostic gear can plot a timing advance curve as vehicle is running (as well as give you base timing at idle of course) because it will pick up your crank pulse and pick up your HT pulse off no 1 and as the operator will have the vehicle specs you can still calculate timing without needing to read off the obd port, hence you can use a standalone aftermarket distributorless ignition setup and still work things out .

You need the right person with the right knowledge/experience/competency and tools.

Another trick, bit tedious, (I don't even know if they still sell them) is to physically mark tdc then use a schmicko timing gun with a rpm/degree display and an adjustable dial so as you hold at say 1500 rpm you adjust the delay to flash where the tdc marks align and it displays the timing before top dead centre on the screen, but you have to have a helper to adjust the throttle steadily as you go.

I haven't followed any threads to see what you are attempting to do or not do, this is just an answer to your thread question.

I have no specific knowledge of your engine (or much of my td5 when it comes to it, still familiarising) but I have a lot of understanding of how engines work by practical application and study, not by parroting others or playing google professor.

Sure I said a much shorter spiel on this few posts up...

A modern scan tool can give you the ignition timing but as far as TDC no. It uses the crank trigger as the reference and the ECU determines the correct timing from that.

One thing you could do is to remove the crank angle sensor at the flywheel end and look at the flywheel as you bar the engine around as you pass TDC on #1 you should see the detent on the timing ring of the flywheel. That would be your #1 TDC timing mark to mark on the pulley and timing cover.

I have been looking at this post and also think "no" but doubt I have enough knowledge of tuning gear to comment.

However it is pretty simple to see what advance you are getting from your EDIS.

All you do is use the assumption that the start point is 10degrees while idling, and then mark degrees say at every 5 on the pulley. BTW given you are saying that EDIS starts at 10degrees, then 10degrees back should be TDC , that should give you a check whether your starting point IE the sensor is positioned correctly.( compared to what you have calculated TDC to be). It should not be too far out anyway. I assume you have turned the engine to u near TDC in the correct direction to a fixed point eg spark plug with shaft welded, then turned backwards to the same point, then TDC will be midway between. It is pretty impossible to know exact TDC without doing that.

Then look at the advance using a timing light at various revs.

I had a look at the EDIS Jaguar site and they go to 39degrees which is about right .

What is the curve of the EDIS you are using?

Remembering my TAFE training from nearly 40 years ago the answer is a qualified yes to "can it calculate the timing" BUT the machine had to be synchronised to the timing marks by using a timing light with an adjustable wheel to synchronise the machine with TDC using the timing mark. The machine could then read out the timing when it "knew" where TDC was. In answer to your intended question there was at that time no magic gadget that could tell you TDC electronically.

Fast forward to the land of crank angle sensors and the answer might be a qualified yes, provided the crank angle sensor is accurate, the diagnostic machine knows where it's relative trigger point is to "real" TDC and whether the diagnostic interface can access the crank angle sensor output in a meaningful way.

Regards,
Tote

the answer to the machine and can it determine top dead centre is maybe yes.
I saw a very fancy tune up machine around 25 years ago that could do nearly everything including a compression test.
Mind you it cost around $40 k in the nineties. It was probably one of the last machines before cars got computers. Some of the very top end non model specific machines may be able to do what you are asking today. But most workshops tend to have smaller stuff now or are dealerships with model specific gear.
Ian
Bittern