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Octane Rating at Elevation

Discussion in 'Colorado' started by Geeder48, Jul 31, 2017.

  1. Aug 2, 2017 at 7:48 AM
    #21
    wheeliest

    wheeliest ///////////////////

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    Eh, Its not nearly as destructive on low compression N/A Motors... (a.k.a. 1GRFE)
     
  2. Aug 2, 2017 at 7:56 AM
    #22
    Ostrichsak

    Ostrichsak Don't taze me bro!

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    Bingo. With compressed applications everything is magnified. This is why you tune with more of a cushion in mind with forced induction applications. Light pinging on an n/a motor like our 4.0L V6 isn't that bad here & there. It's not something you want happening regularly so see my previous reply for a simplified way to avoid this. Making it sound like someone is going to melt holes in pistons from a single bout with light pinging isn't helping anyone.
     
  3. Aug 2, 2017 at 8:21 AM
    #23
    GPsevinSixx

    GPsevinSixx Well-Known Member

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    Yes, the air/fuel mixture burns slower due to the thinner percentage of air. Lower oxygen percentage mixed with lower octane = less chance of detonation/ spark knock/ ping. Lower octane fuels burn more easily than higher octane as mentioned.
    Basically the same as using 87 at sea level to having 85 octane available up in the mountains of CO. 87 octane will be closer to having mid-grade in the truck. If you get access to 91, you'll be running race fuel. LOL


    Here's a chart for an idea of oxygen percentage based on location elevations the vehicle ecu has to account for, and adjust for the ideal Air-Fuel Ratio. Hope this helps.

    upload_2017-8-2_8-8-15.jpg

    :burnrubber:
     
  4. Aug 2, 2017 at 8:22 AM
    #24
    GPsevinSixx

    GPsevinSixx Well-Known Member

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    LOL...

    "shut up"
     
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  5. Aug 2, 2017 at 8:34 AM
    #25
    CO MTN Steve

    CO MTN Steve Well-Known Member

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    Dam, was wondering if that was better than my Unicorn Fart/ Wolverine Piss fueling
     
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  6. Aug 2, 2017 at 8:48 AM
    #26
    JayRolla

    JayRolla Well-Known Member

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    Still anything pinging is destructive. No madder how you look at it. When its detonating its burning the valve and pitting the piston. Detonation is detonation no madder how you look at it. If it was not an issue the motor would not need a knock sensor.
     
  7. Aug 2, 2017 at 8:52 AM
    #27
    wheeliest

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    ok you know more than I! i'll just go back to my lame ass job of building race bike motors and dyno tuning lol.
     
  8. Aug 2, 2017 at 9:01 AM
    #28
    US Marine

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    If you really want to know how altitude affects performance then do what Drag racers like me do and chase the DA ( Density altitude ) all day long at a the track . The DA is also referred to as corrected elevation and this can mess with your engines performance

    I live in the High Desert of Socal at 3500ft elev and over the last month I've been seeing DA or corrected elev of over 9500ft . I can't wait until Fall when the DA gets closer to actual elev

    Edit ..

    Just checking my corrected elev right now I'm at 5519ft corrected with Relative Density at 84.6% .The air is still fat even with forecasted T storms in my area
     
    Last edited: Aug 2, 2017
    wheeliest likes this.
  9. Aug 2, 2017 at 9:10 AM
    #29
    JayRolla

    JayRolla Well-Known Member

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    I think we are both right. Your right when being n/a the cylinder pressures are way lower so detonation should not cause as much damage say with high compression or power adder. But you have to agree constant detonation would cause damage to even a lot compression n/a.

    I've tuned 4 bangers running 30+psi from 7.8:1 up to 10.8:1 compression and any detonation caused visual damage to pistons and valves.
     
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  10. Aug 2, 2017 at 9:29 AM
    #30
    wheeliest

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    Yes, in upper psi applications, you detonate... p2v finds itself on the wrong side of clearance lol. The 5VZFE sounds like a jar with marbles in it being shaken violently when they have a SC installed running 6lbs yet those things last for ever.

    My world, a tic n toc here an there typically aint no big thang, most the time it happens the end user has no idea it happened and no harm done..
     
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  11. Aug 2, 2017 at 10:03 AM
    #31
    Ostrichsak

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    No, you're not both right because nobody in here is running 30+ psi so nobody has anything to worry about taking the advice I & others have given. You rushed in here saying a single ping is melting pistons & not to listen to any previous advice. You're wrong. Period.
     
  12. Aug 2, 2017 at 10:08 AM
    #32
    CO MTN Steve

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    I'm Intrigued, is this achieved via Barometric pressure readings?
     
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  13. Aug 2, 2017 at 10:11 AM
    #33
    US Marine

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  14. Aug 2, 2017 at 10:13 AM
    #34
    CO MTN Steve

    CO MTN Steve Well-Known Member

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  15. Aug 2, 2017 at 10:32 AM
    #35
    JayRolla

    JayRolla Well-Known Member

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    So if pinging does not cause any damage why does the ECU pull timing to stop the pinging? I believe it does this to ssave the motor from the detonation. I came in saying detonation is bad. And it is no madder the application.
     
  16. Aug 2, 2017 at 10:38 AM
    #36
    Ostrichsak

    Ostrichsak Don't taze me bro!

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    Matter.

    You also realize that the ECU pulls degrees of timing, right? Why degrees? Because smaller amounts of knock are less dangerous.

    It CAN lead to damage LONG TERM. That's a very important designation you conveniently left out. It's also exactly what I and others have said numerous times in this thread. You continue to use 100oct gas in your N/A Tacoma to make sure it never pings once in it's entire life.
     
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  17. Aug 2, 2017 at 10:42 AM
    #37
    coopcooper

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    or just change cam gears and call it a day
     
  18. Aug 2, 2017 at 10:49 AM
    #38
    wheeliest

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    What lol
     
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  19. Aug 2, 2017 at 11:56 AM
    #39
    coopcooper

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    I mean ignition timing not cam timing lol nvm ignore me..
     
  20. Aug 2, 2017 at 2:36 PM
    #40
    eazyrider711

    eazyrider711 Well-Known Member

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    Not to derail, but does any of this conversation have anything to do with a supercharged engine? I saw a few comments that seemed to dismiss forced induction as a completely different discussion, but I don't know enough about it to know why.
     

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