locating an O2 sensor in a side pipe

[eschaider]

Originally Posted by olddog

I would have guessed Laughing gas and blown as my second guess.

Back in 89 to 93 years, Ford commanded about a 10:1 AFR at WOT. Chip makers were commanding 12:1 AFR and getting about 30 Hp gain. They stated must use premium fuel with the chip installed. Those who didn't read and head often ended up with pistons like you pictured.

In the ovoid detonation world of tuning, pulling timing or going rich is the only tools. Timing kills more Hp than going richer. Obviously fuel and combustion chamber matter but the tuner has no control over those. My guess is that the tuner tuned the engine with a good premium fuel and the owner bought low octane fuel. He didn't hear a ping and thought he got away with it, and he did for a while. Now he thinks it was the tunner's fault. The tuners should make you sign a paper acknowledging that you were warned that you must run a premium fuel.

You're pretty close to the mark, Rick. If I remember correctly the tune commanded a 12:1 AFR on 93 octane E10. A supercharged car will normally want an 11.8:1 AFR on pure 93 octane with moderate timing. The timing was not that wild on this engine, I want to say it was 18 degrees IIRC. For those unfamiliar with these small bore Modulars, 21 to 23 degrees is a lot of advance.

When you go to E10 the equivalent AFR for the change in stoich point becomes 11.08:1 which puts the 12:1 AFR out in a patch in the back 40 that is getting progressively leaner. This particular whoops occurred well over ten years ago so a lot of the 'tuners' at that time were just getting their sea legs and some of their customers were paying for those legs.

Your point about fuel choices is absolutely spot on, Rick. If you take your car to be tuned on whatever fuel. Be prepared to run that fuel all the time or you are putting your 'stuff' at unnecessary risk.


Ed