JasonC SBB

Just remember you MUST SYNC on the CRANK RISING edge, never falling.
The falling edges go berserk during cranking. The rising edges don't.

y8s

iTrader: (8)

Right... I do. It wont even start if I change to falling edges because they come so randomly.

(Incidentally, the MS3 has only one edge option that applies to both cam and crank--if you want rising on one and falling on the other, you have to invert one of them)



The question remains, why does it act funny when running?

muythaibxr

James and I are not clear on what it's actually doing wrong while running.

Braineack

iTrader: (62)

it idles great.

Y8s, send him the composite log you took last night. there was a pattern of it losing sync. the same pattern of 5 error spikes showed up repetitively when he tried to revs the motor up.

y8s

iTrader: (8)

I'll post it over at the squirt forums.

Ken, I have built the "standard 99-00 miata" input circuits that replicate the stock ECU's input circuitry in the VR area to compare and contrast. I still really like the idea of using the 9926 because of the tiny pcb I can slap on the backside of the V3 board.

Joe Perez

iTrader: (8)

Could you clarify something for me- since "rising" and "falling" vary with regard to where in the system one is observing it (before or after an inverting input circuit), are we referring to the LEADING or TRAILING edges? Until somebody installs an MS3 in a DeLorean, those are the only absolute points of reference.

y8s

iTrader: (8)

Based on Jason's previous research, he's been scoping the raw signal between sensor and ECU. His "rising" edges are the trailing ones which I've shown in pink here:



The problem becomes when the signal gets so jacked up that an observer assumes "the signal goes high on a tooth and the trailing edges are in fact falling" <--- this is not true.

I think we all agree that the output of the sensor goes to ground on a tooth.

Joe Perez

iTrader: (8)

While I admit that I know little about the composite logger, the pink edges in that picture certainly look like leading edges to me, at least by the definition with which I am familiar.



Maybe I just have the polarity wrong, and this signal is depicted as active low?

You know what? This log still looks like somebody smeared runny cat feces on a scope to my eyes. I still can't figure out what the hell it's trying to tell me, and I'm used to reading binary on high-speed logic analyzers in realtime.

I really with this device would just show us actual port states in this view. They've got such a rich display for single-trigger mode...

y8s

iTrader: (8)

Joe, remember my signals are not inverted. They follow the "rest at 5, tooth at 0" open collector of the sensor output.

here's a fixed graphic from a previous post:



Remember also that on the NB sensor, the "big" tooth comes first for pair of adjacent teeth.

muythaibxr

So Braineack: the engine idles fine, and it misfires etc.. when revved up corresponding to lost sync errors. Is that an accurate description of the problem?

I just keep seeing all the info about the edge you're triggering on and composite logs, etc... but no reference to the actual observed issue with the way the engine runs.

I was trying to figure out why you (y8s) thought you needed to be looking at the composite logs so I had a good idea of why I was looking at them!

Ken

Braineack

iTrader: (62)

I came over last night, and he cranked it over for me and it idles very smoothly. but when given throttle, it went lean and then would misfire and seemed to run out of sync. When looking at the composite log of it, it kept losing sync in a constant pattern. I believe y8s uploaded it on his msextra.com thread.

Tonight he's going to try using the same input circuit that Peter is using on the '99 car he helped out with, and that I've used with success as well.

muythaibxr

OK thanks. I'll keep my eye on the thread to see how it goes.

IF/when you guys run out of ideas, I'll try to find some time to take a look in person myself.

Ken

y8s

iTrader: (8)

OK lets see if I can break it down from a driver's perspective.

Initially I had problems getting sync on the car but I got fine sync on the stim.

After going over my cam and crank input circuit, I changed nothing (though maybe cleaning up joints helped?) and eventually got the car to run. I had some temporary issues with a pair of backwards diodes on the peak & hold board that made it run on 2 cylinders but Braineack spotted that and from then on I was firing on all four.

So now I can walk out and start the car just like normal and it fires right up (30F weather--not bad for no tuning) and idles relatively smoothly. I found out last night that my cheap and dirty alternator control method was bunk and causing wild swings in batt voltage so I turned the output off and the idle smoothness returned.

---

MY SYMPTOMS:
Aside from obvious fueling issues, when the car is idling and the timing is set to "Fixed Timing" (10°) the timing light doesn't show a steady timing mark. It jumps around a lot. It wont even stay in place long enough to know what my timing really is.

On top of that, when I rev the motor and hold the pedal at some nominal position, it cuts in and out (leanness at least) and doesn't hold a steady RPM with no engine load (guessing 40 kPa). The RPM just bobs around all over the place.

---

I'm currently in the process of building the following circuit into the VR area and building the alternator control circuit that was tested by JasonC SBB (and previously worked on my car).



This circuit is pretty well accepted to a) be inside the stock ECU and b) work with the MS. I figure it's worth a shot to see if my 9926 implementation is part of the problem. No big deal, I had the parts on hand.

I figure that and the alternator control circuit will rule out some of the variables so I can move on and find out why the upper revs are so nutso.


....


I've been using the composite logger because it's the only way I know how to verify what the megasquirt is seeing from the cam and crank sensors. Sorta. Should I ignore it?

muythaibxr

if you're getting sync loss, it's good to use the composite longer, although you might want to consider using the sync error logger, which will allow us to actually see definitively why you lost sync.

Ken

y8s

iTrader: (8)

who knew. I will try that tonight if there are not icicles on my car.

muythaibxr

Actually check out your thread on msextra:

http://www.msextra.com/forums/viewto...268226#p268226

James found some problems with your signal.

Ken

y8s

iTrader: (8)

Abe's input circuit does indeed have more awesomeness than my own. Car seems to run very well.

But F ME it's cold outside. "Feels like" 18F.

Oh also the alternator circuit works great too. I had to tweak the set point but now it's a very solid 14.3V.

shuiend

iTrader: (24)

So Abe's circuit works and the max996 or whatever does not?

y8s

iTrader: (8)

there may be some issue with my implementation--i dont know for sure.

y8s

iTrader: (8)

Some follow-up:

I built the Abe circuit and it works. I managed to fit it in the VR area as per Frank's Implementation.

The alternator circuit helped smooth out some of the crazy voltage swings that my ridimentary generic output was causing--that helped the idle oscillation. Scott had a wrong value cap instead of the 100uF so I swapped that out of his kit and tuned the circuit to 14.3V set point and it works very well. For those of you who have had problems with this circuit, it is a tuning issue and you may need to tweak the 1% resistor values to get the right set point. I'm thinking the revised version might be nice with a 47k resistor and maybe a 5k 20-turn potentiometer in series. But only if the pot doesn't drift.

So in the meantime, I discovered that running the composite logger while using Miata 99-00 triggering caused the megasquirt to lose sync and kill the engine. James hit me up with some revised firmware and it fixed that issue.

So then the topic of VVT came up. And with the composite logger working, I was able to do this:



That's basically what I discussed in the vvt current vs. advance thread. I just set a PWM output (at 78Hz--the highest I can select) with the advance region at 80% duty and the megasquirt happily complied followed by cooperation of the spool valve and cam.

So dead stupid open loop control is not a big deal. The car doesn't lose sync because the edges Abe's input circuit requries are the ones that don't cross over the crank pulses.