I was just wondering how you would take the WB O2 reading and adjust the PE tables to correct it. For example if i had an AFR of 13.5 and my target was 12.8, how much would I adjust the PE table ?

 

A 10% change of PEvsRPM well change AFR aprox 1.0 point

 

Just a guess, but having been there and tried that, I'd suggest going with a 10% adjustment on your PE curve and see what it does.

Then go from there, that is of course you are doing this on a wide band dyno.

Hope this helps

LWM

 

At WOT, my O2 sensor readings are averaging 919 mV. Is there a conversion table anywhere that I can see about what A/F ratio this is? Granted it's not a wideband I'm just curious to see if it's relatively rich or lean to 14.7. Also, is it worthwhile to program it to be a little lower than 14.7, say, 14.0, to make more power without running too lean?

 

You need a wide band sensor for wot tuning, your o2's are not accurate. 13-1 is a good starting point for wot afr, some like 12.5-1 or even lower.

 

I understand that the O2 sensors aren't accurate at WOT but I was wondering if the ~920 mV readings are rich or lean compared to 14.7, I wasn't looking for an exact ratio. What is the O2 sensor value for a 14.7 a/f ratio anyway does anybody know?

 

The problem is, again I repeat they are NOT accurate, so you cannot say safely if it is rich or lean. As an example, at 13.0:1 some narrow band O2s might report .880, some might report .930, they are ONLY accurate at stoich, since this is exactly where they are made to work, no extra investment was made in making them accurate elsewhere. You can sort of make a guess that you are in the mid to high 12s for AF, but without hitting the dyno you really have no way of knowing for certain.

High numbers are rich, low numbers are lean. 14.7:1 should be ~.450mv

 

Ok I got it now, thanks again guys For my case should I leave the a/f ratios the same since I don't have a wideband to test it with? I was just gonna lean it out a little bit and see at the track if the times get better but if it's already somewhat lean maybe I shouldn't?

One more question about the wideband O2 dynos... how do they measure the O2, is it like the emissions testing that puts the thing over the tailpipe or do you have to take out the engines O2 sensors to put in the widebands? and... also hehe, why doesnt the aftermarket sell wideband O2 sensors to put in the manifolds, are they too expensive?

 

A wideband sensor typically costs approx $350, and has a "life" of 500 hours. It also takes a substantial amount of software to calibrate it correctly, since not all wideband sensors have the same output characteristics or sensitivity to temperature. The typical cost for a complete wideband sensor and readout will be about $1,000. That might explain why you don't get a pair of them from the factory.... and also explained by the fact that the entire purpose of the factory O2 sensors is to minimize emissions rather than to maximize power output.

MOTEC PROFESSIONAL LAMBDA METER

To correctly tune, the wideband sensor needs to see "pre-cat" exhaust composition.

Just to emphasize what people have said above, combining it with my statement about the singular purpose of the factory O2 sensor being "emissions", and not "power"..... the stock narrow band sensor concentrates its entire linear output to the very narrow range of 14.7:1 +/- 0.05 A/F units..... beyond that linear range, very roughly 200-700mV, the curve of mV's vs. A/F ratio flattens out considerably..... hence a very tiny change in mV's can represent a fairly large change in A/F ratio. As noted above, readings above 750mV are "richer" than the stiochiometric 14.7:1, and in this range the narrow band sensors are extremely sensitive to operating temperature... i.e. a small change in operating temperature can produce a larger mV change than a significant change in A/F ratio. There are tables available on the 'net that claim to calibrate narrow band sensor mV's to actual A/F ratio, but those are generally posted by outfits trying to sell narrow band sensors mislabled (or at least misleadingly advertised) as "wide band sensors".

 

Cheap NTK sensors can be had for under $175 each, but again they dont last that long, they are not plug ins (most of them are 5 wire, and have a different voltage input/output, so they do NOT work with a stock computer thats for sure).

Honda is the only MFG that I'm aware of that had a wideband in OEM form, and thats on the Hybrid I believe. If you look at aftermarket wideband setups expect to pay $350+ with no data logging capabilities, only a readout. The boxes you see in magazines that are $200-$300ish, and even more, are narrow band, even $350 for a wideband setup in working form is "cheap."