100 Octane Fuel [Archive] - Cherokee SRT8 Forum

: 100 Octane Fuel


Squilly D
03-07-2007, 06:07 AM
Good morning

Has anyone tried using some 100+ octane fuel in the JGC? If so, was there any noticeable performance gains? I may be going to the track this weekend and am thinking about getting some if it increases performance.

FastSRT8GC
03-07-2007, 07:25 AM
You will have gains. Cleaner hotter burn = More HP!

Just dont go above 100 octane You get into Leaded gas then.

kramsay1234
03-07-2007, 07:33 AM
I am no expert, so just sharing what I have read.

With stock ECU you will get no noticeable gains as the computer is not designed to adjust up for higher octane. My understanding is that it will not hurt anything, but adding more octane to a system that already has all that it was designed for will yield nothing. This is why ECU chips come in different octane modes, because everything in the computer has been forced adjusted upwards for the higher octane. If you have a 100 octane chip and run 93 octane fuel you will do damage. But if you have a 91 octane setup and run 93 fuel you are just spending more money for octane you don't need.

The computer for safety will retard timing, etc if you put in lower than 91 fuel as part of the knock sensor, but I have just not heard anything to lead me to believe that the computer will adjust upwards.

Again, I am no expert so if I am incorrect, or if someone has proven different, then please share.
________
MAGIC FLIGHT LAUNCH BOX REVIEW (http://mflbvaporizer.com)

GRNENVY
03-07-2007, 07:39 AM
You only get a benifit from using higher octane if the car calls for it or tuned for it. I actually have seen cars slow down even mine.



I am no expert, so just sharing what I have read.

With stock ECU you will get no noticeable gains as the computer is not designed to adjust up for higher octane. My understanding is that it will not hurt anything, but adding more octane to a system that already has all that it was designed for will yield nothing. This is why ECU chips come in different octane modes, because everything in the computer has been forced adjusted upwards for the higher octane. If you have a 100 octane chip and run 93 octane fuel you will do damage. But if you have a 91 octane setup and run 93 fuel you are just spending more money for octane you don't need.

The computer for safety will retard timing, etc if you put in lower than 91 fuel as part of the knock sensor, but I have just not heard anything to lead me to believe that the computer will adjust upwards.

Again, I am no expert so if I am incorrect, or if someone has proven different, then please share.

RAMM
03-07-2007, 09:31 AM
:) Hello everyone, I am new to this forum and the wonderful world of GC SRT-8's but certainly not to Mopar or high-performance vehicles. I will be purchasing my GC SRT-8 soon and have been observing this forum with great interest. FWIW my take on the 100 octane is this: Although most of what has been said is correct, I don't fully agree that it won't provide a power gain. The stock compression ratio for these engines is 10-1 that is a lot of compression for most 90-94 octane pump fuels. The addition of 100 octane unleaded fuel should provide a much higher threshold of detonation which should = less knock (however little) which will = the over zealous factory computer from pulling so much timing out. A good aggressive spark curve is paramount to building cylinder pressure (torque) and that is what these relatively heavy trucks need to get them moving. Something else to be considered is the highly oxygenated unleaded racing fuels that are becoming more and more prolific every year. I have witnessed (via engine dyno) with the addition of an unleaded/oxygenated fuel (Pro-fuel Mark II) gains of 2%-3% in torque and HP across the board. These were street engines with anything from 9.8 to 10.5 static compression. When I receive my GC SRT-8 I plan bump to compression into the 12's and run E-85 (105 octane) with all of the supporting mods of course (PCM, fuel system ) and then we'll have some crackle (think lightning) to go with the thunder. Sorry about the long first post everyone I hope someone got something out of it.

FastSRT8GC
03-07-2007, 09:48 AM
:) Hello everyone, I am new to this forum and the wonderful world of GC SRT-8's but certainly not to Mopar or high-performance vehicles. I will be purchasing my GC SRT-8 soon and have been observing this forum with great interest. FWIW my take on the 100 octane is this: Although most of what has been said is correct, I don't fully agree that it won't provide a power gain. The stock compression ratio for these engines is 10-1 that is a lot of compression for most 90-94 octane pump fuels. The addition of 100 octane unleaded fuel should provide a much higher threshold of detonation which should = less knock (however little) which will = the over zealous factory computer from pulling so much timing out. A good aggressive spark curve is paramount to building cylinder pressure (torque) and that is what these relatively heavy trucks need to get them moving. Something else to be considered is the highly oxygenated unleaded racing fuels that are becoming more and more prolific every year. I have witnessed (via engine dyno) with the addition of an unleaded/oxygenated fuel (Pro-fuel Mark II) gains of 2%-3% in torque and HP across the board. These were street engines with anything from 9.8 to 10.5 static compression. When I receive my GC SRT-8 I plan bump to compression into the 12's and run E-85 (105 octane) with all of the supporting mods of course (PCM, fuel system ) and then we'll have some crackle (think lightning) to go with the thunder. Sorry about the long first post everyone I hope someone got something out of it.


I agree, The reason for the chip manufactures to have a 91-93 tune is because of the bump in timing, If you didn't use the higher octane fuel with these tunes you will get detonation, and would end up frying something.

You will see some increase in power with higer octane just do to the efficacy of the burn/combustion.

Razorecko
03-07-2007, 10:43 AM
I tried 100 unleaded before, and I definitley felt a difference, the response was much more sudden and there was a definite increase in hp. I tried to measure it out with my gtech but it was too difficult as it was cooler out and i was having issues with traction.

Blown-WK
03-07-2007, 11:59 AM
I am running 100 in my Jeep now and will be going on the dyno soon to compare against 93. I will post the results with no other mods done.

kramsay1234
03-07-2007, 12:04 PM
I am running 100 in my Jeep now and will be going on the dyno soon to compare against 93. I will post the results with no other mods done.

Thats the best way to tell.

By the way - RAMM - where abouts are you in Ontario?
________
Wifes First Black **** (http://www.****tube.com/video/35978/wife-gets-a-black-****-for-the-first-time)

mattedmunds
03-07-2007, 12:34 PM
Since "premium" pump gas here in California is only rated at 91 octane, lots of people add a 2-4 gallons of 100 octane "racing fuel" to boost the tank to the normal premium rating of 93-94. I did this all the time with my M5 and the difference was night and day. That engine would ping on 91 gas. So far I haven't heard any pinging on the Hemi with 91, which is a really good thing since 100 octane runs $9/gallon in westLA.

-Matt

Blown-WK
03-07-2007, 01:22 PM
100 octane runs $9/gallon in westLA.

-Matt
Wow, its only $6/gallon here in Florida and that is expensive enough.

GotStroke?
03-07-2007, 02:47 PM
You can have up to 104 octane unleaded (VP), and E85 is 110 octane.

GotStroke?
03-07-2007, 02:50 PM
I am running 100 in my Jeep now and will be going on the dyno soon to compare against 93. I will post the results with no other mods done.


Are you taking about your blown 5.0/OHC? If so we're talking about two completely different motors not to mention the forced induction.

RAMM
03-07-2007, 04:09 PM
Thats the best way to tell.

By the way - RAMM - where abouts are you in Ontario?

I am 1 hour south of Ottawa and 1 hour west of Montreal.

Blown-WK
03-07-2007, 08:52 PM
Are you taking about your blown 5.0/OHC? If so we're talking about two completely different motors not to mention the forced induction.
Yes, it runs a stock ignition curve/pcm so any gains could be compared to an SRT8 with just a fuel change.

GotStroke?
03-07-2007, 10:18 PM
Yes, it runs a stock ignition curve/pcm so any gains could be compared to an SRT8 with just a fuel change.

The 4.7 and 5.7/6.1 run the same tune?

Aside from that your motor is blown, has less displacement, completely different heads, etc. etc.

I just don't see the correlation.

BlackedOut
03-08-2007, 12:10 AM
i put 3/4 tank of 100 octane in last week and i didn't feel any difference til about the last 1/4 tank. what I've heard is that the ECU has to "learn" the new octane. But once it did learnt the new octane it was faster. not a huge difference, kinda felt like a small mod was done, like intake or exhaust maybe and was more responsive

Mango
03-08-2007, 08:03 AM
You will have gains. Cleaner hotter burn = More HP!

Just dont go above 100 octane You get into Leaded gas then.


No, you will not.

With modern vehicles, using higher octane fuel will yeild no benefit other than emptying your wallet faster.

UNLESS you are running a specific programming to take advantage of this, or a forced induction system that requiers it.

justyli
03-08-2007, 09:22 AM
I always use Shell Optimax 100 octane (for US$ 6,90 per gallone!!) and unfortunately there is no gain to a car without.

German car magazines did a lot of testing with the 100 octane stuff and cars not designed for higher octane, there will be no advantage.

I only take it, because of having a Shell filling station next to mine office where is no "normal" premium fuel only the 100s.

BlackedOut
03-08-2007, 12:30 PM
Wow, its only $6/gallon here in Florida and that is expensive enough.

Yeah $6 a gallon here too, i put it in as a test probably wont be doing it again unless i can find it alot cheaper, not worth the money.

SRT8Inferno
03-08-2007, 12:34 PM
Higher octane fuel will definitely benefit any of these late model high compression engines that run oxygenated (10% Ethanol) gas. It allows your PCM to run full timing advance with no knock retard. The knock sensors today are very accurate & fine tuned to your engine and the slightest inaudible knock caused by poor performing oxygenated fuel will make the PCM pull timing. I run this additive instead of race gas & it works great plus it's cheaper overall. It's convenient for me to put a bottle in at every fill up. OctaniumPower.com

GotStroke?
03-08-2007, 01:26 PM
Torco is another great fuel additive that's helped many over the years.