Rage

I am using the Innovate LM-1 air/fuel meter and data logger with RPM converter. The question has to do with 'spikes' in the values of A/F recorded where the 'spike' value recorded is 22 A/F which is max scale of the meter's data logger data file. The engine generally runs in a range of from 11 - 13 A/F depending on the rpm and load excluding these 'spikes'. Innovate had previously advised that these 'spikes' are indicating an engine missfire.

I have recently added the ability to test each cylinder individually for A/F versus previously only the left or right bank of cylinders in a common riser. During similar acceleration runs from idle to WOT each cylinder's A/F was recorded. Four cylinders had no 'spikes', two cylinders had a some spikes to 22 A/F amplitude, another cylinder had some spikes that were just slightly 'spiked' into the 14's A/F and finally one (#3) cylinder was loaded with 22 A/F amplitude 'spikes'. The spikes are mostly occuring at higher rpm's

I am currently checking for equipment problems associated with #3 cylinder which is not yet completed.

My question for the A/F GURU is have you seen these 22 amplitude A/F 'spikes' and what was your conclusion as to their cause?

Young Performance

The only false lean spikes I have seen have been from water hitting the O2 sensor. All it takes is the tiniest little drop of water on the sensor to cause a false lean reading.

SB

Take a look at Innovate's forum for possible experiences too. I vaguely remember not just misfires, but electrical feedback wreaking havoc like this.

Highest I've seen is 18:1 as motor was coughing/belching/ and then quitting. Aerating of fuel issue in carb'd motor.

Outdrive1

I can't imagine it would even actually run with an a/f ratio of 22.

Rage

It is running at A/F of from 11.5 to 13.5 depending on rpm and load but the "missfire" is signaled according to Innovate Technologies by instantaneous spike(s) in the A/F of 22 (max scale of unit).

Rage

From a subsequent conversation with Innovate Technologies tech dept I learned now that if the o2 sensor lead is too close to ignition wires this can also generate such recorded spikes in the A/F data. This occured to me initially but because most of the individual cylinders exhibited no spikes, a couple exhibited some few spikes but one was loaded with spikes it seemed that was not the likely cause. My thought was that if ignition noise was the culprit I should see it in all cylinders to some degree but apparently proximity is the key. This now appears to be the likely source of the spikes subject to confirmation with a test.

bcarpman

I got the same thing a couple of weeks ago right before I lost a sensor. I couldn't detect any sort of misfire, and the engine sounded as smooth as silk. I decided it was a reversion issue with water hitting the sensor.

Do you keep your sensor powered up from the time you leave the dock, or do you wait till you're on plane to power it up? I've gottn conflicting advice on this.

Rage

I have always followed the Innovate LM-1 manual that says it should be completely powered up before starting the engine and while the engine is running or it could be damaged from the heat. So far so good. The cig lighter power connection drops voltage when I start the motor for a second causing the meter to reboot/rewarm the sensor. I keep the motor at idle until this is completed.

So far so good.

Rage

Both previous risers had an unknown internal leak at the same identical location in the o2 sensor bung weld. I thought that I had reversion for the longest time. I know first hand how fast a sensor goes out when contacted by water. Mine would just go flatline when they died. I do not recall any A/F spikes but I could have missed them.

My engine does not feel rough either but where I get the A/F spikes is at the higher rpms at just one cylinder (I have individual o2 sensor ports for each cylinder) and it is hard to hear anything at those speeds with the wind and all. Plus I just realized that there is no accomanying shudder in the engine rpm data that I record. When I hit the rev limiter and get similar A/F spikes the RPM definately shudders. Of course that will be affecting all cylinders not just one.

Question. When you got the A/F spikes did they show up just at higher rpms or at all rpm's or what?

bcarpman

The spikes in my O2 data were everywhere once they started, but they started while I was at 3500rpm, and the sensor died before I brought it off plane. I recorded all the data (have since erased it) and I seem to recall there being absolutely no patern in the spikes. Once they started they continued intermitantly until the sensor died. I ran a series of rpm steps up to 4500rpm, and the data looked the same everywhere.

I had a expert tig guy put the 02 boss in, and his work looked perfect, but it's certainly possible there's a small leak on the inside that didn't develop until after it was run for a while. I'm putting a new sensor in this weekend. We'll see how long it lasts.