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Fuel Octane???

Discussion in '308/328' started by 285ferrari, Jul 14, 2005.

  1. 285ferrari

    285ferrari Two Time F1 World Champ
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    Sep 11, 2004
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    Robbie
    What kind of fuel and what octane do you guys run in your 308, 328"s??
    I have been told 93 or better and someone else told me regular 87 is OK...
     
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  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Are you asking what they ARE running or what they SHOULD BE running ;)?

    Seriously, your question assumes a single, correct answer, but the answer varies with model (and its compression ratio):

    Euro 328 with 9.8:1 CR spec a 98~100 RON octane (which corresponds to about 93 AKI octane here in the US).

    US 328 at 9.2:1 CR drop down to a 95 RON octane spec (which corresponds to about 90 AKI octane here in the US) so 91 AKI is A-OK.

    All stock US 308 with 8.6:1 or 8.8:1 CR drop down to 91 RON octane (which corresponds to about 86 AKI octane here in the US) so 87 AKI is A-OK.
     
  4. 285ferrari

    285ferrari Two Time F1 World Champ
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    OK 1989 US 328 GTS-stock
     
  5. FasterIsBetter

    FasterIsBetter F1 Veteran

    Jul 22, 2004
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    Steve,

    Do you know the CR for the 308/Mondial QV engines, Euro spec.? Mine is an '84. What octane would be needed? Thanks.
     
  6. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Steve -- You can look up these values up in the 241/82 and 248/82 OMs yourself ;):

    Both are shown as 9.2:1 CR and 98~100 R.O.N. (93~95 A.K.I.) octane fuel, but that seems a little overkill to me (perhaps from a time when high octane fuels were more commonplace so the spec-setter could be more conservative). Unless you're at sea level in high temperature, I'd try 91 AKI in everyday use and decide from there if the 93+ AKI is absolutely required -- JMO.

    What have you been running?
     
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  8. matteo

    matteo F1 World Champ

    Aug 1, 2002
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    I use 91 in Ca. Sometimes I go to the unical and put 100 in. I notice NO performance gain from 87 to 91 to 100. I do notice that on 100 it idles better and sounds louder. That's about it.
     
  9. jonathan70

    jonathan70 Rookie

    Feb 25, 2005
    22
    Although I had always believed that higher octane did not increase engine performance (assuming the engine was using the correct octane already), I was absolutely amazed when my '69 Corvette went from 14.05 @ 98 mph to 13.78 @ 101 mph - with ONLY a change to the gasoline. The engine is fairly mild - 5.7L with 9.5:1 compression. I was using 93 octane Mobil - which should be more than adequate for the low compression engine - and when the tank ran dry at the track (Lebanon Valley Dragway in NY), I added 120 octane racing fuel and picked up much more performance than I would have ever dared to expect - as much as 15 hp based on the ET and trap speed !!.

    If it wasn't the octane alone, it may have also been the switch from oxygenated (street) fuel to "pure" race fuel. Nonetheless, I will never underestimate the power of good racing fuel again.


    FYI - If you happen to have drag strip data, this website has a horsepower calculator than seems to be fairly accurate: http://www.dsm.org/tools/calchp.htm
     
  10. matteo

    matteo F1 World Champ

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    I THINK the compression on the 308QV is 8:8:1 so octane will not have that much affect on the motor
     
  11. parkerfe

    parkerfe F1 World Champ

    Sep 4, 2001
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    I know when I put 110 octane racing gas in my BB512i it runs much better IMHO. I do that about once every couple of months and then refill the tank with 93 octane every time it gets down to 3/4 tank in order to keep the octane level mixture high. I figure that gives me an average of 100 octane at any given time.
     
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  13. sjvalin

    sjvalin Formula Junior

    Aug 31, 2004
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    My Euro 365GTB/4 supposedly has an 8.8:1 CR. I tried 87 octane pump gas, since a few other vintage V12 owners with the same CR had not had a problem. The car was NOT happy. It was not developing power. It was reluctant to rev. Bad News. I drained half the tank and filled with 92. It was much happier. It made a huge difference. I haven't tried 89 yet, but am reluctant to at this point!

    -steve
     
  14. BlackRX7Turbo

    BlackRX7Turbo Karting

    Sep 18, 2004
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    Aaron
    Of the people out there that actually have those cars, how many of you fill up with the octane gas that should be "ok" as per those specs above?
     
  15. kdross

    kdross Formula Junior
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    Feb 10, 2002
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    When I was at the local airport several of us filled our cars with aviation fuel which I believe has an octane reading of 105. My 308QV loved the stuff, but I doubt it the aviation fuel added any power.

    Ken
     
  16. Benzino

    Benzino Karting

    Jul 6, 2005
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    ...higher octane wont add power unless mapped for it.....just makes the engine less prone to det using the higher...the UK cars can run on 95 ron according to the handbook but i run the official Ferrari fuel Optimax 98.6 ron :D
     
  17. marco246

    marco246 Formula Junior

    Mar 25, 2004
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    Here in Hawaii my choices for fuel are 87/89/92 octane. I've been using 92 in my U.S.-spec 328 but have been thinking of trying out 89. Not so sure after having read this thread!
     
  18. f355spider

    f355spider F1 World Champ
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    May 29, 2001
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    I had run both 91 and 92 octane (the only grades available) it made absolutely no difference, the cars (78 308GTS and 87 328GTS) ran great regardless.
     
  19. jon s

    jon s Formula Junior

    Mar 9, 2005
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    went from 93 to 87 in my 81 308 i with no change in performance (and no detonation even when very hot). jon s.
     
  20. Dino 208gt4

    Dino 208gt4 F1 World Champ

    Jun 24, 2003
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    Always using 98 with leadreplacer and runs very well.
    (1982 Mondial8 eu spec)

    Only other choice available here is 95 non-lead.
     
  21. Gimme Fuel

    Gimme Fuel F1 Veteran

    Mar 15, 2003
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    My 348 has been fed with Shell V power, 95 unleaded for several years - and I think I'll keep it that way ;)
     
  22. kerrari

    kerrari F1 World Champ
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    Oct 22, 2004
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    See a related thread over in Tech Q&A "Safe way to carry emergency fuel". I've always used 98RON - used to use Shell Optimax but there is a problem with this fuel and some spark plugs (NGK) now use BP Ultimate but following the discussion in the other thread I may use 95RON if stuck. For the few cents difference in price I don't think I'd bother with anything less than this.

    Interesting note - I've never had a problem with running on or high temp running.
     

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