87 or 93 Octane

Higher octane is useless without having your vehicle tuned. Enjoy the lower gas prices.

the new mm&FF in the 05 mustange witht he KB SC said that 91 does give a few hp..

My manual also says that higher than 87 octane can damage the vehicle.

Cheers

From what I've been told, the car is in a constant state of tuning itself.
If you use a higher octane gas, 89 or 93 the car will gradually bump the ignition timing up a bit.
Especially if you have your foot in it most of the time.

Not a problem, until you go back to 87... then let the knocking begin!

At least that is what I've been told.

That's probably true to a certain extent. If you have the cash and want to run 89 or 93 you can probably gain a few horses, but don't jump around between low and high octane.

The octane rating of fuel is simply a measure of its resistance to pre-ignition, or knock. The higher the rating, the more resistant it is to pre-ignition. Unless you start increasing the cylinder head compression (where higher octane is needed to avoid knock), you probably aren't going to see much horsepower benefit from using higher octane gas.

Save your money/price difference and spring for a dyno tune and hand held SCT tuner. That way you can have your cake and eat it too. Anyway, if you do any engine mods, you'll need a tune. With a hand held tuner, you can have the stock program, and two additional programs stored in the tuner. I swap back to the OEM tune prior to going to the dealer for work. I've got one set for 89 and one for 93. Right now with the gas prices as they are, I'm running 89. You may say that I'm not saving much, but with my daily commute of 100+ miles a day, it saves enough to take my wife out for a nice dinner every month.

Long post...

cheezsnake said:

The octane rating of fuel is simply a measure of its resistance to pre-ignition, or knock. The higher the rating, the more resistant it is to pre-ignition. Unless you start increasing the cylinder head compression (where higher octane is needed to avoid knock), you probably aren't going to see much horsepower benefit from using higher octane gas.

Click to expand...

This definition of octane is exactly correct. Octane is the ability do resist detonation or pre-ignition (Yes, two different but similar problems).

Detonation is spontaneously igniting the mix prior to the spark event (Due to high cylinder pressure). Pre-Ignition is carbon or some hot spot igniting the mix prior to the spark event (Most likely on high mileage engines). The "pinging" sound you hear is the two flame fronts colliding. Cylinder pressure is abnormally HIGHER and can cause damage. To keep it simple, the higher octane fuel burns slower.

Our cars and designed to run 87 octane, and you should see the best performance by using it... Faster burn, more power... No detonation, more timing... Again to keep it simple.

Now, I posted on this thread because I had already intended to ask you guys and girls if detonation has been experienced with the STOCK PCM calibration.

I had light detonation when going WFO (WOT to some). No detonation is acceptable to ME, as a Ford tech. Please understand that EEC V (Our computer) has adaptive strategies to retard timing and lean fuel curves based on the LOUD PEDAL and how you use it (I like to feel the power daily... LOL). Drive like your grandmother, and you drive the PCM to go lean and back off timing for economy. In addition, if detonation is sensed by the PCM, timing is retarded through the adaptive strategy. This does take a drive cycle or two... Not necessarily immediate.

With that said, and knowing I only have 2K miles on mine and want to have NO problems, I tested 89 octane. No more detonation, so I feel more confident with WOT. What I think is, based on the way I personally drive (Mostly in a legal manner), I ended up allowing the PCM to lean the fuel curves, so when I powerslide into a turn, I noticed the pinging noise. Mostly under heavy load (100 %), and tires hooking though. If the tires get blown away, there was no perceivable detonation (The system goes RICH when you mash the LOUD PEDAL).

Knowing Ford, IF this becomes a wider spread problem ("X" number of cars detonating), they release a revised PCM calibration or software version upgrade. I am not saying this is the case, just stating what I have seen while working with these systems in the dealership. No cause for alarm.

So I am asking if anyone notices any detonation first, and also reiterating the fact that you will want to use 87 octane if no issues occur, for best performance and lower fuel cost. You should NEVER need 91 or 93 octane unless you recalibrate or add a supercharger or turbocharger. At that point, custom tuning is required anyway.

To crash, I haven't read the article, but ther've been a lot of references to a MM and FF article that claimed a hp increase with the stock computer with 91 octane. as 91 is not available locally i started using 93 is there any risk of damaging the motor?

Sorry, I meant to answer that question in my post.

No, engine damage is not likely, with a stock car. Higher octane is safer when you advance timing with a device like the X-Calbrator or Predator. You WILL need the additional octane to support the performance mods. NOT doing so CAN damage the engine.

Adding octane to a stock PCM will allow the adaptive strategy to advance timing and add fuel to make more power. The added octane itself is not responsible for the gains.

EXAMPLE- If you use the stock calibration and install a code where timing and fuel curves are FIXED (Not the case here), you will see less power because the fuel burns slower. Since the PCM adapts or "learns" if you will, then driving it hard will inherently increase performance because it WILL advance timing. If detonation is sensed, it will retard timing.

To summarize, you want to run the lowest octane that is safe for optimum performance. In your case, I would just go to 89 octane as I did. 93 is not needed until you bolt on a power adder or recalibrate the PCM with SCT or Diablo.

A good way to think about it is... "What octane fuel will SUPPORT my mods?". The answer? Follow the recommendations of the manufacturer of that particular mod. Reducing parasitic losses with underdrive pulleys would not require a new tune or higher octane, but a blower, turbo, or even a CAI or removing the HC trap DOES!

crash... where you been all this time?? you got to hit the SC posts... they are making me question prochagers..hahah.. ohhh btw.. any new info or where we can get it at a discount? =-)

crash,

Thanks for the detailed explanation. Very good information!

I ran a tank of super and noticed no difference. Will stick with 87 until tuned.

crash said:

A good way to think about it is... "What octane fuel will SUPPORT my mods?". The answer? Follow the recommendations of the manufacturer of that particular mod. Reducing parasitic losses with underdrive pulleys would not require a new tune or higher octane, but a blower, turbo, or even a CAI or removing the HC trap DOES!

Click to expand...

What is an HC trap?

New to the board, this part is painful to write but GM gives me no choice....
Converted Camaro guy looking to order an 05 GT

Marc

crash, that was very enlightening.
question for you. I have a 2004 ranger with 4.0 SOHC that has started to ping very badly. I tried 89 octane and it helps but why would I have to suddenly change from 87 fuel? I could believe in the winter/summer blend thing if it weren't so sudden. I have only made 1 "mod", a K&N air filter.
I had a '99 ranger 3.0 that did the same thing. Coasting downhill & not touching the gas pedal it sounded like it was going to throw a rod!!

I convinced my wife another ranger would be better than a GMC/chevy truck when we bought the '04. Now I'm really started to question FORD's current quality ( other issues with both trucks).

Can you figure this out ???

The first question... I specialize in supercharging Fords, so yes, I have spent time in the blower forums. In addition, I am a member of all the truck sites along with about 10 others... LOL!

Yes I DO have a line on blowers and turbos and they are very competively priced. I can also provide you information you need to make an informed decision, meaning the BEST bang for the buck.

FJO is right. 87 IS DEFINITELY the recommended fuel. That is exactly what I needed all here to understand. Don't change unless you need to. Besides, it is cheaper... You will know if you need 93, because the gas guage WILL say "Premium Unleaded Fuel ONLY" (IE Cobra and Lightning), or if you add a new calibration or a blower.

1st and goal- The HC trap is like an air filter between the MAF and the throttle body. Part of the OBD II (ON BOARD DIAGNOSTICS Rev. II) governmental "Clean Air" requirements. Any evaporative emissions are now controlled. It is an emission component that prevents fuel vapors from finding it's way out through the inlet duct. A coiled up corrugated filter like element.

Technically it is a restriction, and '05 owners remove it when they add a K&N or CAI. It requires a new tune when you change these parts. The PCM code is tougher to break than ever, due to FLY BY WIRE, and there is NO service port for a chip.

This means a CAI (Cold air induction) and removal of the trap will flow more air, but will drive the PCM lean (Not good)... And requires a new calibration.

vetwhat - During a season change, fuel in the station tanks changes. In this transition, you can get Summer gas before the hot Summer days hit, and this can cause the detonation. If this is a persistant problem, go up one level in octane until the atmospheric conditions
match the fuel needs. Then change back.

FOR COMPARISON ONLY- In the old days (EEC IV), there was an octane bar in the PCM harness that the dealer tech could remove to retard timing (Removal gave you a set 4-6 degree retard), but performance waned (We saw a loss of 40 HP). On the 4.0 example, this should be temporary. We do not want to sacrifice performancel this defeats the purpose. Just remember, the PCM on the GT requires a new code when modifying (Altering the efficiency). We now use the SCT programming and the IAT sensor to do this.

" Yes I DO have a line on blowers and turbos and they are very competively priced. I can also provide you information you need to make an informed decision, meaning the BEST bang for the buck.
" ====You rock Crash. Please e-mail me with the best deal for the procharger since you got me started on it .. haha.. tedwork@sbcglobal.net... thanks again

Quick question ... so you make a few mods that require a new tune / calibration. Where do you take it? Your dealer? Any service shop? I'm assuming that most, if not all, of the engine and exhaust mods I've seen discussed on these forums are going to void the warranty on the car?