87/89/93 Octane

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FL2005GT

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Oct 28, 2005

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Oct 30, 2005

#1

• Oct 30, 2005

• #1

I've been running on 87 octane in my GT, no problems. Now, the manual says 87 is recommended. The dealership says you'll notice no difference regardless of what octane you run, with a stock tune.

On some of the forums, though, I've seen claims all over the place on this. Some say there's no noticable difference. Some say there's a 3-5 HP gain from using 93 in stock tune. Others say 93 can somehow cause knock problems.

Has anyone with a stock tune tried out 87/89/93? If not, I'll try full tanks of 89 and 93 and post if there's any difference in engine behavior/seat-of-the-pants.

 

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ruffy

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Apr 10, 2003

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Skopje, Macedonia

Oct 30, 2005

#2

• Oct 30, 2005

• #2

If you start using 89 it might not make a difference, but if you up it to 93 the car won't run as well. 93 octane actually burns slower than 87 octane and unless you retune your car to run 93 I recommend you stick with the 87.

 

cleveland

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Feb 19, 2002

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SF>...

Oct 30, 2005

#3

• Oct 30, 2005

• #3

You are just wasting your money on the purchase of higher octane if you dont retune for it. At least advance your timing.

-Dan

 

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spdbrake

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Apr 5, 2005

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Oct 30, 2005

#4

• Oct 30, 2005

• #4

I noticed with mine and a few other cars/trucks I've had that sometimes (during hard accel) the you will hear the valves rattle, knock sensor kicks in and the rattle is gone. (87 octane)
The octane of the fuel is related to the ability of the fuel to resist detonation, and they all have the same BTU release when burned. The higher octanes burn a little slower also though.
Advancing your timing BTC does give you more power, add a longer slower burn and there is more power on the stroke.
Hear the knock sensor and be assured that your computer is retarding the timing, which reduces your power significantly.
I really simplfied this and missed alot issues that can effect why you get the knock in the first place.
Sooooo... If you hear the rattle @ 87 octane your running under powered, and if you run 89/93 octane you are likely running @ factory spec.
Get an SCT tuner and run the 93 w/advanced timing (what a difference!).

 

Big-Foot

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Aug 20, 2005

123

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Kenyon, MN

Oct 30, 2005

#5

• Oct 30, 2005

• #5

Stock tune - 93 Octane made no difference in economy in either city or highway driving from 87 Octane. Now, the 89 Octane with 10% ethanol - it was different. I got roughly 10% worse economy. Must have been due to the lack of BTU content in alcohol vs. gasoline.. I'm sticking with 87 for now until the Sniper is release and then I will play with tunes and octane.

 

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FL2005GT

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Oct 28, 2005

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Oct 30, 2005

#6

• Oct 30, 2005

• #6

Yeah. With the new Ford Power Pack, I wonder how much of that advertised 20 HP at the wheels comes just from the retune for 93 octane, rather than having much to do with the new intake and exhaust.

For those who have retuned to run at 93, did you notice significant seat-of-the-pants (or better, dyno) improvement?

 

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I8URVTEC

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Sep 2, 2004

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Oct 31, 2005

#7

• Oct 31, 2005

• #7

93 without a tune is a waste. However, I have a tune for 93 and notice some pretty good gains. Tough to say though if the gains come from the 93 octane. Most likely all the gains are from my CAI and exhaust. Basically when they were tuning my car for the mods they pushed up the octane to 93 on the tune to get just that much more power out of it.

 

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05 GeeTee

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May 11, 2005

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Nov 2, 2005

#8

• Nov 2, 2005

• #8

I heard the 05's are actually tuned for 93 stock but rely on knock sensors to allow it to run on 87 as indicated in the manual.

 

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FL2005GT

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Oct 28, 2005

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Nov 2, 2005

#9

• Nov 2, 2005

• #9

Has anyone here actually TRIED running a stock 05 on 93? I know it's hard to judge seat-of-the-pants with so many variables involved...

 

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discofan

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Apr 21, 2005

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Nov 3, 2005

#10

• Nov 3, 2005

• #10

FL2005GT said:

Has anyone here actually TRIED running a stock 05 on 93? I know it's hard to judge seat-of-the-pants with so many variables involved...

Click to expand...

Dear FL2005GT,

I tried a few tankfuls of 93 octane gas and did not feel any difference in performance...

I run a 91 octane tune from Diablo in which I bumped the timing up 2 degrees to compensate for the higher 93 octane gas...

The performance was about the same...

I guess I'll have to buy a custom tune next spring from one of the specialty tuners...

Now, I run a 91 octane tune with 87 octane gas...

Normal driving is OK, but I will "knock" a little if I floor it... Not bad tough!!!

Dave

 

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FL2005GT

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Oct 28, 2005

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Nov 3, 2005

#11

• Nov 3, 2005

• #11

OK, thanks. Looks like best deal is to get CAI/exhaust/custom tune all at once.

 

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ski

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Dec 14, 2004

380

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Nov 4, 2005

#12

• Nov 4, 2005

• #12

discofan said:

Now, I run a 91 octane tune with 87 octane gas...

Normal driving is OK, but I will "knock" a little if I floor it... Not bad tough!!!

Dave

Click to expand...

You should cease that practice, and use either an 87 octane tune with 87 octane gas, or a 91 octane tune with 91 octane gas. Even a little knocking is bad, and will cause piston damage.

 

Big-Foot

Member

Aug 20, 2005

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Kenyon, MN

Nov 4, 2005

#13

• Nov 4, 2005

• #13

ski said:

You should cease that practice, and use either an 87 octane tune with 87 octane gas, or a 91 octane tune with 91 octane gas. Even a little knocking is bad, and will cause piston damage.

Click to expand...

Ski is exactly correct.....

Every PING you hear actually takes a small bit of metal out of your pistons and/or combusiotn chambers and also shocks the rings up against the ring lands which will eventually fracture them...

 

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thump_rrr

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Nov 25, 2004

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Montreal, Canada

Nov 6, 2005

#14

• Nov 6, 2005

• #14

FL2005GT said:

Has anyone here actually TRIED running a stock 05 on 93? I know it's hard to judge seat-of-the-pants with so many variables involved...

Click to expand...

My buttdyno doesn't work that well so I use actual numbers from actual testing.

In the timeslips below I'm testing with 94 Octane Petro-Canada gas.

I ran 3 configurations

1) Bone stock intake,tune, and tires
2) C&L Intake, Diablosport Predator with C&L 93 Octane Tune and stock tires.
3) C&L Intake, Diablosport Predator with C&L 93 Octane Tune and BFG Drag Radials

I ran 6 runs in each of the 3 configurations and these were the results.

1) 13.535@104.557
2) 13.220@105.185
3) 13.053@101.018 (on the brakes during ET Bracket eliminations.)

I ran a 12.954@106.992 the following weekend in the same configuration.

With the addition of Steeda Underdrive pulleys I further reuced my time to 12.821@111.273(7mph. tailwind)

With the addition of JBA Longtube Headers and a Catted H-Pipe I further reduced my time to 12.691@109.170

 

Notchbck93

New Member

Dec 9, 2003

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IL

Nov 11, 2005

#15

• Nov 11, 2005

• #15

^^^ Your times are very respectable!