Other than playing with the computer, is there any other way to adjust the ignition timing on an `03 GT? I remember reading a late model Mustang article somewhere that talked about adjusting some type of timing "adjuster", perhaps near the balancer, in order to adjust the timing. Can anyone shed light on this? I can't find the article now. That would be sweet to be able to bump the timing a bit across the board without having to mess with the computer. I tend to use 93 octane in my GT all the time anyway, so I may as well take advantage of a little extra timing if it is easy to dial in. Per prior experiments with other cars I've had, even a bump of 5 degrees can add a small bit of extra "zing" that you can feel... it might not lower your quarter e.t. much, but it just makes the car feel a tad bit snappier across the rpm range... worth it in my opinion.
Check out the Steeda timing adjuster. You install a new exciter ring on the crank, move the sensor from the block to a movable pointer on the new ring and seal the old sensor location. Now the timing can be advanced or retarded by moving the sensor in relation to the new ring. Advancing the timing to about 14* BTDC will gain horsepower using 93 octane just as it does on the
5.0. Using 93 octane without adjusting the timing is a waste, and will lower performance and mileage.
Just went to the Steeda site to have a look. Cool. Do you know off hand what is involved regarding installation? (Steeda does not have the installation instructions at the site unless I missed it.)
Using 93 will "lower" performance and mileage??? I never heard that before. I know that using 93 will not increase power if the timing is not adjusted to take advantage, but you're saying it will reduce power??? Please explain. Thanks.
I had planned on supercharging my 2000 GT so I didn't install one.
and mileage. >>
A gallon of 87 octane is an amount of fuel and an amount of additives. I don't know the percentages, but that gallon will make a finite amount of power in a specific engine tuned to use the 87. More additives are used to raise the octane to 93, so the percent of fuel to additives in that gallon is less, and less power can be made from that gallon in that same engine. Now tune that engine to take advantage the higher octane, and it makes more power from that high octane gallon than it could with the previous tune and the lower octane gallon. Using the 93 in an engine tuned for 87 can still make the same power, but needs more than that gallon to do it. The fuel mileage will be affected more than performance since we can add more fuel for more power. The performance loss will show up at high rpm's and full throttle when it's not easy to just add more fuel. I was using super when I first bought my 1998 GT and remember reading this somewhere but I don't remember where or if it was tested on a dyno. I switched back to regular and don't remember a power difference, but IIRC my average mpg went up. I'd have to search back in Google under my past screen names to see if I posted that sometime between 1998-2000. I also used regular in my 2000 GT since new without a problem.
It (using too-high octane-rated fuel) *might* lower performance and mileage. Octane-rating is a way of describing the ignition and combustion characteristics of a fuel. A higher rating means the fuel resists ignition and burns more slowly than fuel with a lower octane-rating. Think about the conditions in a high-compression engine - higher compression heats the air-fuel charge more and can cause ignition. Once a highly-compressed air-fuel charge is ignited, it's also likely to burn too quickly and release energy at too-high a rate. This is the basis of detonation and pinging.
This is why running a higher-octane fuel resists detonation and is necessary as compression and temperature are raised.
Now, why would too high an octane reduce efficiency and power? If the fuel burns too slowly and does not complete combustion during the power stroke, before the exhaust valve starts to open, then unburned fuel will continue out the exhaust pipe. That means you lose the energy in the fuel not captured during the power stroke.
This is all in theory; I personally don't think that the combustion time of 91 vs. 93 octane differ enough to make a difference in a motor that's not spinning at high RPMs. I don't even think 87 and
93 differ enough to make a difference in a stock 4.6l motor.
However, it's always true that too-high octane is wasted if you're not pinging or detonation on lower-octane fuel.
I've seen this FAQ before and it is not correct for the Mustang GT 4.6 engine management system. There is no octane sensor nor is there a knock sensor on the modern GT motor. The computer has no way of knowing the octane rating or if the engine is pinging from too low an octane. The first section is misleading, as the modern engine in the GT falls under the description of "Older cars without such systems". The second section is also incorrect, as the engine timing can be changed allowing better performance from a higher octane fuel. The last sentence is only true if the Mustang GT owner is using a higher octane fuel without changing the engine tune to take advantage of it.
On modern engines with sophisticated engine management systems, the engine can operate efficiently on fuels of a wider range of octane rating, but there remains an optimum octane for the engine under specific driving conditions. Older cars without such systems are more restricted in their choice of fuel, as the engine can not automatically adjust to accommodate lower octane fuel. Because knock is so destructive, owners of older cars must use fuel that will not knock under the most demanding conditions they encounter, and must continue to use that fuel, even if they only occasionally require the octane.
If you are already using the proper octane fuel, you will not obtain more power from higher octane fuels. The engine will be already operating at optimum settings, and a higher octane should have no effect on the management system. Your driveability and fuel economy will remain the same. The higher octane fuel costs more, so you are just throwing money away.
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