1/4 Mile 93 vs 87 Lobo

[wax87]

down grade of the road I was on

OHHH so this was not at a track with a real time slip, right?

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[MosesP]

OHHH so this was not at a track with a real time slip, right?

No track, dragy device; similar results.

 

[MosesP]

I was able to find the exact spot I launched from on my 87 octane run. .13 faster on 93 costco gas vs 87.

 

[colinl]

Doesn't take that long, once the octane change has made it through the loop of fuel lines, the engine has adjusted. I notice the change in throttle response within 2 miles when changing fuel types.

This is wildly incorrect. Ford uses a knock octane modifier (KOM) which has a max value of 1.00 and a minimum of 0 but in reality even junk 87 would be at least .200 on a stock map.

This value is used in the fuel maps and affects boost and timing advance. it decreases immediately when sensing knock, but it primarily relearns increases after a cold start warm up. This can take more than 1 tank to relearn so my first guess is that the OP didn't have a full tank of 87 and did the test shortly after fueling with 93 one tank, then 87. It's also possible to be the opposite and the KOM was still low from using 87 and then switching to 93 and not allowing enough time to relearn for 93 fuel.

You can see KOM on various OBD2 scan gauges as well as any reflash tuning device such as a Cobb Tuning Accessport. Or you can just run at least 2 full tanks before testing, after changing fuel octane. You still can't be sure than your 93 has actually let your engine reach 1.00 KOM though unless you can display it somehow.

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