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Old 10-03-2006, 03:04 PM   #18
Drew in Houston
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Join Date: Aug 2006
Location: PA/MD
Posts: 2,430
Originally Posted by Sleepr56 View Post
Order up the autometer a/f gauge, or any basic a/f gauge and wire it into your stock o2 sensor. Thats what you are looking to do, and you are all set to do it. Just dont look for acurate incomming readings from that gauge unless you are wot. And even then its a pretty basic reading.

Im sure though by the time you notice it go completely lean at wot (if a fuel problem ever occured), it will be to late anyways, not to bring your hopes down or anything
The problem is that you won't know as you're leaning out, at WOT, or under any conditions. 14.0:1 is way too lean at WOT but would still be shown on a narrowband gauge as rich because there's more fuel than air present.

The only useable information that a narrowband gauge tapped directly into a narrowband sensor can tell you is if you're above a 14.7:1 ratio or below. That's it. So in fact the only time a narrowband reading is accurate is when you're at a perfect combustion ratio.

Maximum power for any gasoline fueled spark ignited engine is found around 12.1 to 12.6:1 AFR. If you get much leaner than 13.0:1 at WOT you are too lean and are beginning to approach a dangerous situation--meanwhile a narrowband AFR gauge is telling you that you're rich. Lean is hot and hot starts to melt things and cause predetonation. As I understand it, a lot of turbo tuners will argue that ratios closer to 11:1 are more appropriate at WOT because it allows some extra safety margin--especially when you're doing things like mail order tuning where the software isn't exactly tuned to match the particulars of an individual engine. Still, AFR's in the range of 12.1-12.6:1 have been repeatedly tested and proven to provide maximum power.

If you were only going to get one gauge and wideband AFR was not an option it would probably be better to get an EGT setup and mount the sensor pre-turbo.

Last edited by Drew in Houston; 10-03-2006 at 03:40 PM.
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