Quote:
Originally Posted by Nsxmatt
I'm aware. But if you've been running 87 the whole time before, the ECU is already on a map retarding the timing to remove the knock. Adding premium fuel won't suddenly add more timing and power, it takes many drive cycles for this to happen. You need to run 91-93 fuel consistently to get the added benefits of it. Going back and forth is just wasting your money.
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The ECU has low timing tables and high timing tables, every time the knock sensor detects knock it lowers timing and runs in that timing table for quite some time. The ECU eventually adds some timing as long as no knock is heard. The ECU completely resets after a fill up from less than a 1/4 tank of fuel to a higher timing table and that's the time to get immediate spark advance or a move to the higher timing table and the time to load the car with 93 octane. The knock sensor will probably never experience knock with 93 octane and the ECU high timing table will be constantly used.
Just one hint of spark knock with 87 octane on a WOT pull and retard spark here we come. Even if you lug the engine a little or on a typical hot summer day, your going to have spark knock with this wonderful little 11.5 to 1 compression ratio engine with 87 octane constantly keeping the engine in the low timing tables. Timing is horsepower, timing is gas mileage.
I realize the 3.6 was designed and is tuned to run on 87 octane safely. But there are high and low timing tables for a reason. dyno a heat soaked 3.6 after many tanks of 87 and again after many tanks of 93, I would bet a minimum of a 10 hp difference.