PLANT PROTECTION

iTrader: (6)

My craig moates software is showing an average of 12:1 air/fuel ratio at WOT. My question is if I were to tune to get it at 14.7:1 at WOT, in theroy would I get better performance or just better WOT gas mileage? BLMs are at 144 under WOT if that helps any. Thanks

F-BIRD'88

While in theory 14.7:1 is the chemically correct A/F ratio.
If a motor is operated at this ratio at WOT it will burn up.
The combustion chamber will become too hot within seconds.

Extra fuel is needed to internally cool the chamber
to avoid overheating and detonation/ preignition. At WOT.

Some where around 13.5 to 12:1 works best depending
on the individual engine design and fuel.

Don't worry what your A/F guage is reading as long as it is richer than 14:1 and makes the most power without detonation.

A/F gauges that use a standard o2 sencer don't read accuratly
enought to deturmine the exact ratio while opeating either richer or leaner than 14.7. but they will tell you wether you are richer then 14.7:1 At WOT the guage should remain rich at all times.
If it goes to or near 14.7:1 or leaner @ wot , fix the problem quick. Adjust your jetting for best power with in this rich(safe) range. (Best MPH)

Also, be aware then if your engine is tuned either too rich (exessive cooling fuel)
or too lean it will want more ignition timing than when you have it
tuned right (13.5/12:1 afr). for WOT.

So if your engine wants more than the usual 32 to36 deg timing
@wot, your AFR may not be right yet.

Part throttle cruise operation is different story.
You can tune for 14.7:1 A/F ratio for best emissions device operation or even leaner for better mileage.

Most V8's with either TBI or a carb will need a slightly richer than 14.7:1 idle ratio to avoid drivability problems.

Be sure your exhaust system doesn't have and exhaust leak cause it can just as easily suck in outside air @WOT,
throwing off the AFR guage.

RB83L69

Few of us are concerned with WOT gas mileage... a car motor will not operate that way for very long. That's why car motors installed in boats have "hour" meters, not "hundreds of thousands of miles" meters like they do when they're in cars. A boat motor does in fact operate continuously at large throttle openings, as opposed to a car's "cruise" operation.

Most typical car motors will produce the most power and otherwise run the best generally with about 12.7:1 A/F ratio. That varies from one individual to another; it's just a generalization.

Power comes from releasing the energy in the fuel by burning it. This fact is so simple, obvious, and trivial that people overlook it. The more fuel you can burn, the more energy will be released, up to the point that the extra fuel present in the cylinder interferes with efficient combustion. A little extra in there will promote cylinder cooling, and will help provide extra fuel molecules so that every last possible oxygen molecule actually enters into a reaction with fuel molecules.

But since the car spends so little of its time operating that way, unless of course your busiest work day is Sunday and your co-workers have names like Earnhardt, Gordon, Martin, etc., it's kind of pointless to tune for continuous WOT. Give it the right amount of fuel to make the most power; use the A/F meter as a guide to find that point.