Lc1 showing 5.0 afr at wot

[VHR]

Has anyone seen this. Readings seem normal at idle or when staging, but in the burnout or during a whole pass it reports about 5.0 AFR. Open headers. Wide o2 state shows Lambda. Also, the data is confined to a narrow range-4.5-5.8.

[joecar]

[ This is using serial comms connection to V2 ]

What do WO2LAM1 and WO2EQR1 show...?

Using the LM Programmer software, connect to your LC-1 and check the value of Stoich AFR (it should be 14.7)...
it may have changed (LC-1 has been known to do this).

For this (and other) reasons do not rely on WO2AFR, but rather on WO2LAM and WO2EQR.

[VHR]

WO2LAM1 is more sane-approx 1.00 at WOT. At idle its whacked out around 2.4. I guess I,ll just have to get used to lambda numbers. To me its like Fahrenheit vs. Celsius. Thanks again Joe.



Vinny

[joecar]

Hi Vinny,

Something is wrong... at WOT you want WO2LAM1 to read something like 0.87, and during CL it should be 1.00.

Check this:
- did you do a heater calibration...?
- did you do a free air calibration...?
- is the LC-1 reporting errors (LC-1 LED is flashing a sequence)...?

Have you seen the youtube vid on how to test the sensor...?

[VHR]

I think the weird readings(lean)are an artifact of the Wo2 being 5-6 inches from the end of an open 3.5" collector. As fate would have it, I removed my collector extensions the same day I finally got the o2 working, so I cant say how much of a difference there would be. Maybe at some point I'll put them back on-or one anyway-but I'm not really concerned about a number per se.
There is a possibility that my fuel system is marginal at high RPM, so what I really want to see is if I can drive it rich to see if it is being limited by capacity. I have trilled up and down the VE table with little/no effect on MPH. Time to investigate that possibility.

[joecar]

Exhaust travels down primaries as a high pressure pulse, and there is a low pressure "anti-node" (lower than baro) immediately behind each exhaust pulse...

the anti-node is what sucks air back into the collector... you can't tune it like this.

David Vizard says (based on his dyno testing) that collector extensions are good for some 10 HP across the range and for quite a lot of low end torque (see current issue of Popular Hotrodding).

[VHR]

I would think if I raised the VE table some great amount, 20-30 percent for instance, that I would see that in the O2 data. If the fuel system had sufficient capacity that is.
Regarding the collector extensions. I went from a forth harmonic to fifth. I found the outcome and the data quite interesting. I wont bore you with it unless you want me to.

[Laychut]

Hi VHR,
As it would have it I have been reading up on the installation of the LC-1 AFR. One thing that quickly comes to mind when I read your post is how you have your earths wired. They seem to go into a lot of detail when it comes to wiring your earths. Ideally they prefer all the earths to come from the same earth point on the engine. The manual states that this must be done to avoid noise (data distortion). This noise can affect the accuracy of the reading. A long shot but this could be some of your issue.

Also the manual states that using the Narrow band is not as accurate when using the gauge as the wide band. I do not know if it is the same for sampling??

Cheers,