2.1 WBX RPM surging - Diagnosing with the new "WBX Emulator"

[tjet]

[RGS Paul]

Have you checked your fuel pressure and fuel pressure regulator?

Paul
_________________
'87 Syncro 7-Pass. Adventure Touring Vehicle
"Simplicate, then add lightness." Colin Chapman

[Steve M.]

[Steve M.]

[jberger]

I would offer a comment..

Having spent lots of time watching O2 voltage and AFR readings, while the O2 voltage is swinging consistently.. that swing actually results in very stable AFR readings. The effectiveness is the swing. By quickly adjusting injector pulse width you end up with stable AFR. I forget who originally posted about the dash mounted 0-1v meter but it's really fun to watch it bounce happily from left to right and back again. I can't wait to see the emulator readout..

[Steve M.]

The RPM surging I am experiencing as seen on the WBX Emulator.



Link


Compared to the video DigiMatrix has of his running at idle mine is fluctuating like crazy.
I did not have time to get into the wiring connected to the Stabilizer module today like I wanted.
I'm starting to think if I am a "Chicken or egg" question. Today I did a 100 mile drive and filled the tank at the start, halfway and at the end.

At Thanksgiving I did 100 mile one way drive at average 70mph and got 11 mpg.

Today I drove sedately between 60-68mph averaging 63mph and the first 50 mi. the fill-up amount said it was giving 19mpg.
The return 50 miles fill-up said I was getting 25 mpg. It was also rush hour so there was at least 20 miles of slowing, stopping & starting again so it definitly was a steady consistent rpm for a mpg test.
Not sure if the short 50 miles run was a good base for a test. I've only done testing on full to empty tank fills before this

I find it hard to believe that the 8-10 mph difference gave me the great mileage.
_________________
This free advice is worth exactly what you paid for it.

There are seven days in a week. Someday is not one of them.

[Vana Guy]

What controls the advance on the WBX? Is that software or mechanical?

[Steve M.]

[DigiMatrix]

Steve, I watched your video and I'm wondering why you have no long term correction happening (integral gain). I also have the Marco injectors and the integral gain has to adjust for the extra fueling from the injectors. My proportional value immediately swings negative when the system goes closed loop. If the proportional gain is always negative, the long term correction goes negative to subtract fuel so the proportional gain can move towards a positive number and swing between a +'ve and -'ve number which is what it is programmed to do.

Does your exhaust pipe color look good? Plugs? I think I would disconnect the ECU and check the resistance of the wiring between the O2 signal terminal at the ECU and the connector at the O2 sensor. The O2 signal is very sensitive to voltage drop because the O2 sensor voltage is so low (between 0.1 and 0.9 volts). Any other added resistance in the wiring causes the O2 sensor signal to be seen by the ECU as "offset", so it controls around the offset value which causes the AFR to be incorrect. Any added resistance causes the voltage signal to be low (Lean) so the ECU compensates by richening the mixture by adding fuel - AKA poor fuel economy.
_________________
_________________
'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me

[Steve M.]

[DigiMatrix]

Those resistance don't look too bad. I always check with the meter probes touched together first - I bet they read close to 0.2 ohms anyway.

I would specifically check the resistance of the O2 signal wire between the O2 sensor and the ECU plug. I know the Mansi injectors are larger than stock, but your video indicates they are the same size as stock with your readings which doesn't make sense to me.

Maybe get some Deoxit or similar product and clean the 2 connection points of your O2 sensor and see if anything changes.
_________________
_________________
'91 Syncro Westfalia
soon to be 2.5 liter stroker WBX 10:1 comp
Digifant ECU with knock sensor and custom
cylinder selective knock control by me

[Vana Guy]

The O2 sensor wire is also shielded to ECU pin 19, (for my year model, yours may vary). The shielding is very important for low voltage signals. Check the entire length of shielding for continuity too just to be sure. Also check if that wire has been rerouted. Too close too something like ignition wires, coil, distributor, may cause interference.

[Steve M.]

[Steve M.]

[Steve M.]

[Vana Guy]

Is the O2 wire the original wire, unmodified, including the O2 connector?

[SyncroHead]

A while back after much diagnosis, we eventually checked the generally reliable fuel pressure regulator again and found that it was intermittently failing. Mostly showing proper pressure, but occasionally showing lower than normal. Swapped it out and the engine ran perfectly again. In addition to occasional low fuel pressure, it seemed that fuel was leaking through the diaphragm and into the manifold through the vacuum line.

Good luck!

Jim Davis
_________________
"A Vanagon? It's not a car or a van. It's a hobby!"

Check out:
www.VANAVATION.com
www.SyncroSafari.org and
www.Vanagons.org

[Steve M.]

[SyncroHead]

[DigiMatrix]