Racing Fuel Systems

I always trusted the guidance and advice from many on this site (and previous site dating back to 2008). One tuning advice that I put a lot of effort and time into achieving is that AFR should continue to lean as you step into the throttle up to approx. 60% and that during this condition 15-16 AFR is a relatively safe target.

However the guys on Engine Masters (TV version) always panic and say its very bad when AFR leans above 14 during similar conditions I noted above. Have theories changed or are they just mis-informing us?

I think a lot is application specific, and they are dealing with every average joe watching and trying to mimic them. If the application is not knock limited and is not misfiring then a lean condition is helping improve mileage while keeping the chambers and oil cleaner. Anyway, that is just my thoughts on the subject.

Admittedly I have seen a few things they tested that I believe to be flawed. I won’t go into detail but one was a carb test and I plan on replicating the test on the dyno, but plan to keep testing variation tighter than they did as to eliminate some variables.

Paul

You can run lean until the engine load is high enough to create more combustion heat. It's that heat that needs more fuel to keep the temps in check. On a well tuned engine cruising above 14.7 to 1 is fine.

How do we know when the lean heat from increased eng. load is to high (presuming there is no noticeable detonation/pre-ignition)? Will there be evidence in the spk. plugs?

Don’t be scared of lean cruise AFR.
That’s what the power circuit is for. Watch your AFR gauge if you have one . I have ran a Quadrajet and a Carter 750 that would cruise at minimum 16:1 AFR and go to 18:1 with very light throttle acceleration on a 500 hp engine. More throttle brings on the power circuit and the AFR swings to rich and then richest at WOT to protect the engine.
This lean cruise slow burning mixture requires a lot of advance, up to 50-55 degrees. Usually from vacuum advance.
It only takes about 60 hp at cruise speed to push the vehicle along the highway at say 60 mph about 2500 rpm. Go too lean (cruise) and the engine will surge/trailer hitch. Pinging is usually the result of too much ignition advance and or not enough octane.
Look at your spark plugs.