93 vs 91 Octane With Stock Tune

Discussion in 'SRT Hellcat General Discussions' started by Robo21, Jun 2, 2016.

  1. Robo21

    Robo21 Gold Member

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    Is there a measurable difference in HP/Torque with 93 octane gas vs. 91 octane with the stock tune?
     
  2. GrndFnk

    GrndFnk VIP Hellcat Member

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    If you are not detonating with either, I would say no. But there are variables to take into consideration. Like how long has the gas sat in the ground tanks, premium unleaded is not used as much as regular. I would advise you to find the station that turns over the most 93 and use that..and the car still may detonate a little when it is hot. Keep in mind you are trying to make 700 HP on pump gas, something that was unheard of in the not too distant past in engines of this size.... Detonation is cumulative to the fatigue of headgaskets, pistons, rod bearings, everything. Yes your knock sensors will pick it up but you can't take back what has already occurred. I use a little VP 109 in with every tank of 93 to make sure I don't get any detonation.
     
    Last edited: Jun 2, 2016
  3. TNCHARGER

    TNCHARGER SRT Hellcat Supporter Gold Supporting Member

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    The higher the elevation the less octane number needed. This is why you do not GENERALLY see 93 in higher elevation areas of the country. The cars are tuned for at least 91 so I wouldn't worry about detonation as far as street driving. If you track the car you might mix in race gas to keep timing from being pulled under strain but I know many who run 91/93 pump at the track without issue..
     
  4. Catless

    Catless Silver Member

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    I'm seeing some ST KNK retard with 93 and the weather is not hot here yet. So in my case I would not bother to try 91 in the Cat.

    Actually it was hot here yesterday but the Trinity flew out of the console, unplugged itself and I lost the logging I was doing.:(
     
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  5. Aarcuda

    Aarcuda Gold Member

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    can the trinity log from the hellcat with the stock PCM? I have one left over from my '10 RT but never thought to try it on the HC
     
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  6. Catless

    Catless Silver Member

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    Yes it can log but not tune. I did update the Trinity with the newest firmware yesterday and it includes option to pick 6.2L. Before I was just using 6.4L and it worked. I have not tried it since the latest update. Somewhere when doing updates I lost all the PIDs and gauges I had setup so I have to start over....
     
  7. GrndFnk

    GrndFnk VIP Hellcat Member

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    Exactly...Most people have detonation and do not even realize it. And there is some really bad gas out there in some areas. I use the best and freshest 93 I can get and still get KR activity without some 109 in the mix. Bone stock tune.
     
  8. Robo21

    Robo21 Gold Member

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    I guess the question I have is as follows: Is it worth it to upgrade the 91 octane to 93 or higher octane for best performance and will I find the difference obvious in terms of power? Assuming I am aware and can notice the improvement which I think I am.

    Here in Southern California the cost of upgrading to 93 octane is steep. I would have to blend 100 octane race gas with the 91 octane to reach 93 or 93.5 it would cost roughly $50 a tank bringing the cost per gallon to $5.81, Clearly, for that kind of gas price I need some empirical evidence that there will be a noticeable increase in power.

    If we are talking 5 or 10 HP I think it's a waste of money. For 40 or 50 HP I would run it.

    Unless anyone knows where I could find legitimate 93 octane in So Cal at a more reasonable price.
     
  9. Robo21

    Robo21 Gold Member

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    I found 100 octane race gas last night for $9.39 per gallon. It would take 5.14 gallons combined with 13.36 gallons of 91 octane to reach 93.5 octane. The cost would raise my gas price to $5.81 per gallon. I don't know if it's worth it OR if I can find 93 octane anywhere in So Cal. If it made a big enough difference, heck yes.

    As far as detonation goes, I don't see how I could possibly detect it with the sound this beast unleashes at half to full throttle.

    I wish I could find 93 octane in a pump somewhere at a reasonable price. There has to be a better way to find good gas.
     
  10. GrndFnk

    GrndFnk VIP Hellcat Member

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    This tool or similar could be your best friend. Then you could add just enough good gas to solve any detonation issue that you may, and probably do have to some degree. At this point you will probably be making the most power. Any more octane would be un-necessary.
    Aeroforce Technology Inc | Products - Interceptor

    EDIT More octane does not make more power. It is resistance to detonation which causes the PCM to pull timing thus reducing power.
    The bottom line is... in a nutshell...run just enough octane to not see any knock retard and you will be at your peak with the stock tune. In my humble opinion.
     
    Last edited: Jun 2, 2016
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  11. Robo21

    Robo21 Gold Member

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    Yes, thanks for the info. And I am aware that it is not octane that makes more power. However, I did see a post here on this forum where the OP dyno tested 91 octane vs 100 octane. The difference was huge, but in all fairness the ambient air temp was hotter when he tested the 91 octane. However, the difference was about 70HP. Same car, same dyno same tune.

    Stock Hellcat Dyno Videos w/91 and 100 Octane

    More octane will only produce more power with a given tune if the ECU can adjust to take advantage of the increased octane. I wish he had tried some octane between 93 and 100.
     
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  12. Jungle Cat

    Jungle Cat Silver Member

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    93 or nothing for me. Not that much more in cost so why risk it. Owners manual says 91 minimum. I don't like minimums.
     
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  13. dragrcr

    dragrcr Gold Member

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    LAUNCH CROP.jpg
    I live in Pasadena. Once I got my car back from Texas all it ever got put in it was the 100 octane $9.39 a gallon gas. So I was 100% 100 octane gas. I pretty much raced my car every week at Irwindale. I am a serious racer. My car has never had street tires on it since I bought it. I even sold my OEM wheels/tires. Anyhow, in Feb I suddenly quit my Job at Caltech, so I cannot afford good gas anymore. I still race every week at Irwindale. And guess what.............My car is laying down it's QUICKEST passes ever on regular old 91 octane.

    Sure, at the Red List event the ambient was pretty warm 85 deg outside and I was brutally hot lapping the car and it was slowing down quite a bit. Was it pulling timing??? Probably. Do I care. No.

    Funny thing is, after I got back from the 27 passes at the Red List event, I improved my Personal Best by .02 with 200 foot worst DA at Irwindale........wait for it............on 91 octane right from the Mobile station.

    .
     
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  14. GrndFnk

    GrndFnk VIP Hellcat Member

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    Robo, some race fuel is substantially oxygenated which can produce bigger gains than the non-oxygenated fuel. VP-109 is oxygenated and advertised on the VP site as a direct replacement for pump gas, no timing adjustments needed or maybe even take a degree out. There is a chance the car you were referring to may have had some similar fuel. It works.
    Dragrcr I know you are on the ball pretty good based on our conversations and the fact you post allot of good, reliable info, but if you don't care about pulling timing or KR you should because it is cumulative to fatigue, trust me on that...and 2-3 or 5 years from now the jig might be up. I don't know much about allot of things, but after having a few turbo cars for the last 25 years I learned a few things about detonation. The hard way. Your car looks great BTW.

    VP 109.JPG
     
    Last edited: Jun 2, 2016
  15. GrndFnk

    GrndFnk VIP Hellcat Member

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    Here is some great reading. On the left articles by Tim Wusz are interesting. Yes, he is with Rocket Brand fuels out of Wisconsin which I have never used but some guys I know have in turbo cars and like it. Same goes with FUSE unleaded race fuel.

    new12

    new11
     
    Last edited: Jun 2, 2016

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