Random Noisy CAS
 

Attachment 453042

Okay, so driving today I randomly encountered a lot of sync 11 and 17 losses in the 1000-3000rpm range.

Pulled over because it made the car nearly un-driveable. Freaked out because this had happened last summer and I had to replace my MS2 V3 board with MS2 V3.57.
https://www.rx7club.com/megasquirt-forum-153/sync-loss-11-17-a-965155/

After replacing the board I found out replacing my cas with another solved the issue.

Looked around to make sure I have no loose connections, etc, started it back up, it all was fine.

I came across the same issues again a few hours later in some slow bumper to bumper traffic, enough for the car to stall a few times, with sputtering, it would clear out and then get worse when moving, then it was fine to drive for a while, since I was on the other side of town I didn't really have a choice, pulling over as soon as things developed.

I ended up home, looking through DIY autotune's page regarding the VR conditioner circuit, played with it for a bit while watching Tuner Studio's composite logger, to no avail.

http://www.diyautotune.com/tech_arti...tm#nippondenso

Saw this page, thought it was pretty close to what's going on.

Changed my first and second triggers from Rising Edge/Rising Edge to Rising Edge and Falling respectively and now it only occasionally happens. However it has developed a small infrequent inconsistent stumble in the idle, showing a sync loss 11 during each occurrences.

Maybe I need to make sure I turned all of the potentiometers back to full counter-clockwise, though I think I did.

I also noticed that my 2 tooth wheel was the one that inverted on the tunerstudio composite log, though I could have sworn that the 24tooth was the 2nd trigger. Perhaps not.

tl;dr

Lots of Sync 11 and 17 losses.
Only seems to happen when car is hot
Stopped then started again later in the day
played with VR conditioner, no dice, not 100% sure if I went full counter-clock again
Flipped the edge of my secondary trigger as per DIY autotune's VR page.
significantly better, still two other combinations left untried.
occasionally see the 17 loss, and the idle stumbles a little inconsistently with a sync loss 11.
solutions?


I have done:
Nice Braid AND Foil shielded cables grounded at megasquirt end
megasquirt grounded to grounding pad/block and then three 10ga wires to engine block (acting as parallel resistors)


Considering:
a car audio friend said to maybe use a car stereo style inline RFI EMI Noise filter on the power line going to the Megasquirt and it's fuseblock.

also just ditching the cas and using Full Function Engineering's Trigger kit, just because I am very tired of dealing with this, don't want to have to switch to a new cas every couple of months as they seem to "wear out"

Noise filter settings? The only ones that seem to work is the "polarity check" since the rest of the filter options generally prevent the megasquirt from registering RPM

Thanks for all the help in advance guys.
-Marc

have you changed any wiring lately? could have wired up one of the vr sensor incorrectly.

haven't touched the wiring in a long while, was about to add boost control but all of the wiring is already run for that, just haven't added it to the board.

this jumping only happens when the car is warmed up*

The main causes of noise are usually noisy power or noisy grounds. How did you ground the ms?

Ken

Grounded to a ground block like this (stolen from Aaroncake)

http://img.photobucket.com/albums/v6...nel_in_car.jpg

Then three equal length 10ga wires run from there to the engine block.

I've been having some weird alternator issues lately, perhaps it's wearing out and getting noisy. Swapping them out this morning.

Moving the ground to the engine block may help, though I've never had any issue grounding to a ground block. Maybe check your engine ground cables to make sure they have a solid connection to the chassis.

okay just checked my grounds.
pulled off my AIT sensor, checked with a multimeter between it's ground and battery cable as well as various screws bolted to the chassis in the engine bay. ~0ohm resistance.

same with the 4ga engine to chassis strap
same with the ground panel wires where they terminate at the engine

pulled off the alternator and ran it off the battery at idle, still has a little skip in rpm's, engine is still cold though

considering adding an additional chassis strap or two.

so I cleaned up my grounds, sanded the bolts, the lugs, hit them with some grease.
Replaced my alternator with another used one.
Swapped the triggers back to rising/rising.

Started right up.
set the timing because I pulled the cas
apparently if I spin the cas at a particular point, it causes tons of 11/17 sync losses, this is just before the correct timing point.

Drove it around the block, and then took it out and everything seems fine.

Also, I pulled some timing to stop some of the popping at idle.
is 12degrees @~12.8afr 850rpm too little?

You should probably switch back to using the rising edge of both CAS signals again. That is assuming you have VROUT wired to TSEL. not having that right will probably cause sync loss above 4000 RPM.

Ken

Yea, I am using VRIN/OUT instead of the inverted one. I set it to rising/rising again, it's running fine so far.

My question is that it normal for our cars while setting timing to find a point where there is just 11 and 17 sync losses? like a point where the cas's reading to the ECU just confuses it? It happens a handful of degrees retarded of the leading crank mark

It can happen if you start getting misfires because those can cause excessive noise to the point where the CAS wire shielding can't solve it.

You can also see issues if you use too much dwell and the ignitors go into current-limiting mode.

Poor grounding can cause issues throughout the operating range and most often those take the form of sync loss.

Ken

okay, so everything is fine now, at right around 1500rpm I can make the car misfire with a certain amount (very little) throttle and it causes a 11 and 17 sync loss.

I'm going to replace plugs, fuel filter, and wires and see what happens.
probably should get Accel Enrich working right too, would probably help with the misfire, but not so much the idle, everything fuel related is cleaned/newish so I guess it's time to replace worn ignition components.

Any harm in cleaning blackened very low mileage spark plugs? or should I go ahead and dump the box of them I have?

Any news as to what cause the sync loss of 11 and 17?

I too currently have this problem, but only after the fact that the car is warmed up completely (above 175* Fahrenheit) after a few miles of driving. But the thing is I modified my CAS, by cutting out two teeth cause I do not have the 2nd VR nor do I have the Zeal Daughter Card. I also modified my leading coil as per instructions by MegaSquirt. I was told that the sync loss may be my coils though, I will need to look into this further.

Both errors can be caused by the MS seeing teeth that are not there. In other words, noise.

And with missing tooth being more prone to misinterpretation than 2nd trigger, it's vital that wiring and VR sensor be in good shape. You can try tightening up the gap between the VR sensor and the CAS wheel. As the engine warms, everything expands which may move it out of tolerance for a good signal. Use a piece of paper or business card to gap it.