Megasquirt Support Forum (MSEXTRA)

While looking at a datalog to tune cold starting, I noticed something weird about ASE. It looks to me like the ASE taper counter might start as soon as RPM is detected, rather than when the engine actually starts? So if you have a long cranking period, once the engine catches you get less ASE than expected. This image shows what I'm talking about: Note that on the second starting attempt, in which the engine starts much faster than on the first attempt, the initial ASE value is higher, even though the CLT value has not changed.

Log (same as in the image above) and .msq are attached.

Your post interested me because since, I think, I installed 1.5.1 my after start taper sometimes gets truncated.

Looking at your data log, I'm seeing cranking behaviour that I can't understand so it's hard to see when you start cranking so it's hard to then see how your ASE is behaving.
At t=8.508 secs there is a cranking event (rpm goes to 98) but at 9.082 it drops back to 0. Approx 0.5 secs later it cranks again for 0.5 secs and so on. You are also getting sync loss register each time RPM goes to 0 so it looks to me like a false RPM trace.

The Engine status register bit 3 shows whether ASE is active or not. According to that register, around t=8.5 secs for the next couple of secs, Engine status is (decimal) 0, 3, 0, 0, 13.
The 13 has bit three going high which aligns with when the engine actually starts at t=11.869 secs, not when the cranking commenced. After the 13 is 141 which also has bit 3 high. However Engine register then drops to 131 at t=12.065 which does not have bit 3 high so ASE has ended.

On your next crank starting t=24.759, it also has the RPM trace up and down, and a sync loss increase. ASE stays active in the Engine register all the way through to t=51.388.

Have not look at your MSQ to see what the time should be just yet

Arran

Is the temperature wherever you are really around 5 deg F? It has been around 35 deg C here for weeks

arran wrote:Is the temperature wherever you are really around 5 deg F? It has been around 35 deg C here for weeks

It was at the time!

We actually broke a record for the number of days in a row the temperature didn't exceed 20F... it was something like 14. Daily high temps were mostly in the teens, and 0 +/- single digits for overnight lows.

That's not typical for here... at this time of year on average we have lows in the low 20s and highs between 30 and 40 (F).

I've traced this back to a change made for pre 1.1 alpha 6 (nearly seven years ago!)

In previous behaviour, the ASE counter was set to zero every time the engine when to "Run" mode. This was happening if there was minor sync-loss and re-starting ASE. Customers noticed and complained about this false ASE, so the behaviour was changed.

James

How about set the counter to 0 only at power-up, but only increment it when in "run" mode?

That way if there's a sync loss, the counter will not reset, it'll just "freeze" for a moment which would have much less impact. And it would solve the issue I mention above.

Or even better, only when "ASE" state is active?

James

Is that how it works?

I figured it was the other way around... "ASE" state was determined by the timer count/setting, not the opposite.

elaw wrote:I figured it was the other way around... "ASE" state was determined by the timer count/setting, not the opposite.

Partly.
Status ASE "on" is determined by crank->run
Status ASE "off" is determined by the counter exceeding the target.

James

I missed the point in my first reply. I think I've got what you are referring to elaw. For anyone else reading this, by way of a bit more explanation this is what I understand:
The relevant parameter for ASE is "Fuel: warmup corr".
At t=11.869 secs the engine starts and Fuel warmup corr value is 229 (%).
On the second start at t=25.903 secs the Fuel warmup corr goes higher to 240.
The point being made is that the first start had more cranking time so the taper reduced the Fuel correction more than on the second start.

Just curious, I assume you are not modulating the engine starter every 0.5 secs, why does your rpm trace jump up and down like that during start? My engine will occasionally see a sync loss increment if I stall it but never on start up

arran wrote:Just curious, I assume you are not modulating the engine starter every 0.5 secs, why does your rpm trace jump up and down like that during start? My engine will occasionally see a sync loss increment if I stall it but never on start up

Hmm... honestly I hadn't noticed that, and I have no idea what caused it! I went back and looked at a bunch of other logs (and not all at low temperatures) and most of them have the same thing.

I can see it happening once because I have a very strange trigger arrangement on this engine. The flywheel actually has a pin and sensor that gives 1 pulse/revolution and another sensor picks up the ring gear teeth for 135 pulses/rev and a special chip combines the two and outputs a signal that mimics a 45-1 tooth wheel. And I think the output pulsetrain may do something weird the first time the pin passes the sensor. But why it would happen multiple times is beyond me. Both sensors are Hall which should work to 0 RPM.

elaw wrote: I can see it happening once because I have a very strange trigger arrangement on this engine. The flywheel actually has a pin and sensor that gives 1 pulse/revolution and another sensor picks up the ring gear teeth for 135 pulses/rev and a special chip combines the two and outputs a signal that mimics a 45-1 tooth wheel. And I think the output pulsetrain may do something weird the first time the pin passes the sensor. But why it would happen multiple times is beyond me. Both sensors are Hall which should work to 0 RPM.

could you not remove that chip/module and pass both sensors direct to the ecu, setup as dual wheel and both at crank speed and adjust your tooth 1 angle accordingly?

No, because with dual @ crank speed you can't have sequential injection or COP because the ECU doesn't know where the engine is in its cycle.

MS3 does have a "triple trigger" mode that's supposed to accommodate this kind of setup but I had trouble in the past when I tried it so I'm sticking with the hardware approach.

Although it looks bad in that log because the tuning wasn't right for the cold weather, my engine generally starts very quickly and otherwise runs really well so I'm not that concerned about this issue... it's more of a curiosity.

You might be able to lessen the impact of long cranking time on ASE by changing your ASE Count Units from 0.1s to events

elaw wrote:No, because with dual @ crank speed you can't have sequential injection or COP because the ECU doesn't know where the engine is in its cycle.

MS3 does have a "triple trigger" mode that's supposed to accommodate this kind of setup but I had trouble in the past when I tried it so I'm sticking with the hardware approach.

Although it looks bad in that log because the tuning wasn't right for the cold weather, my engine generally starts very quickly and otherwise runs really well so I'm not that concerned about this issue... it's more of a curiosity.

but thats no different to what you said you have?? ie your currently mimicing a 45-1 wheel from the crank teeth and a single pin?

No, the two signals (pin and ring gear) get combined to mimic the crank wheel, plus I've got a cam sensor. 3 sensors total.

you can get away with just using the two, ie the flywheel teeth and the single cam tooth should work ok, its not hugely different to some of the jap setups in that instance

With 130 flywheel teeth or so, it is very unlikely to work. Timing chain stretch will allow the cam pulse to 'move' and it will cross a crank tooth.

James

elaw wrote:No, the two signals (pin and ring gear) get combined to mimic the crank wheel, plus I've got a cam sensor. 3 sensors total.

WOW!!! Are you using one cd4013a and the crank pin resets the first D flip-flop??

For the rpm glitch, it looks like timing belt/chain vibrates around 2 Hz at the low rpm and cam trigger happens to overlap crank one. I believe, changing slightly the position of cam sensor will cure the issue.


UPD... Uppps. Looks like it has been previously discussed in the Audi 5 cyl topic like 8 years ago