Is it safe to run a programmer for a long period of time?
Junior Member
Joined: Jan 2009
Posts: 7
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From: Northeast PA
Sorry to revive this old thread, but this topic has me curious.
(I think) what Darnell is trying to say is that the new 5.4 is a very "octane tolerant" engine design, meaning, it has very efficient, fast-burning combustion characteristics. You always want max combustion pressure right at the ideal leverage point of the crankpin & rod, and the 5.4 can get it done quicker with 87 octane, no need for slower burning high octane fuel. It's a great engine design in this respect, and I'm sure some of the other manufacturers whose engines require hi-test fuel are slightly jealous of Ford's accomplishment.
However, and maybe Darnell can answer this better as to internal tune workings: these motors do have knock sensors, so, even if the low octane tune can (more or less) match the high octane tune under ideal conditions, things might be different once the tuned engine becomes heat-soaked. At that point, the high octane fuel might keep on trucking at the higher (tuned) power levels, where the low octane fueled engine might have to start dialing back power to keep any knock or ping in check (should the sensors detect and report anything to the ecm).
(I think) what Darnell is trying to say is that the new 5.4 is a very "octane tolerant" engine design, meaning, it has very efficient, fast-burning combustion characteristics. You always want max combustion pressure right at the ideal leverage point of the crankpin & rod, and the 5.4 can get it done quicker with 87 octane, no need for slower burning high octane fuel. It's a great engine design in this respect, and I'm sure some of the other manufacturers whose engines require hi-test fuel are slightly jealous of Ford's accomplishment.
However, and maybe Darnell can answer this better as to internal tune workings: these motors do have knock sensors, so, even if the low octane tune can (more or less) match the high octane tune under ideal conditions, things might be different once the tuned engine becomes heat-soaked. At that point, the high octane fuel might keep on trucking at the higher (tuned) power levels, where the low octane fueled engine might have to start dialing back power to keep any knock or ping in check (should the sensors detect and report anything to the ecm).