Octane Ratings

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Mike_Levy
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Octane Ratings

Post by Mike_Levy »

A little help for those of you outside North America, who get 91, 95, and 98 octane from your pumps.

Octane is rated in multiple ways, RON, MON, AKI. Lets explain them.

RON - Research Octane Number. RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane (RON & MON 100 by definition) and n-heptane (RON & MON 0 by definition). This is how they measure gas in most of the world. You'll normally find 91, 95 and 98 octane.

MON - Motor Octane Number. MON is also known as aviation lean octane. MON is a better measure of how the fuel behaves when under load, as it is determined at 900 rpm engine speed, instead of the 600 rpm for RON. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON, however there is no direct link between RON and MON. Normally, fuel specifications require both a minimum RON and a minimum MON.

In the US, we add both RON and MON together and divide by 2 (RON+MON/2)to get our pump octane (87, 89, 91, 93, etc). This is the octane rating that the DiabloSport tunes are based on. Its also known as the AKI, or Anti Knock Index. Because of the 8-10 point difference between RON and MON, the octane rating in the US and Canada is 4-5 points lower then the rest of the world, for the exact same fuel.

RdON- Observed Road Octane Number. Derived from testing gasolines in real world multi-cylinder engines, normally at wide open throttle. It was developed in the 1920s and is still reliable today. The original testing was done in cars on the road but as technology developed the testing was moved to chassis dynamometers with environmental controls to improve consistency. Its rarely used in the automotive world, and most people don't even know it exists.

I hope this clears up the confusion for those of you not in the US/Canada. Use the 91 tune if you use 95 RON octane fuel. Use the 93 tune if you use 98 RON octane fuel.
scnomadc
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Re: Octane Ratings

Post by scnomadc »

hello mike, im from Chile (93 , 95 and 97 RON fuels here), im using the 91 canned tune with 97 octane RON , i want to try the 93 tune but 97 is the maximun octane fuel here. Can i run the 93 tune with the 97 premium ron with out knock? 97 ron its like a 92,15 mon? I have 2011 dodge ram hemi 5.7 Thanks! sorry for my bad english
jibla
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Re: Octane Ratings

Post by jibla »

Octane numbers differ between regions based on the method used to calculate.

RON: Research Octane Number – European Standard

MON: Motor Octane Number – Motor sport applications, Measured under more severe conditions than RON (higher revs etc). Usually 8-10 units lower than the RON.

PON: Pump Octane Number – USA Standard, The average of RON and MON (RON+MON/2).

Check your gas cap to see if it designates PON or RON..

in Kuwait, octane measured in RON:
--------------
RED Pump: 91, Regular, Arabic Name: 'Aadi' , 60 fils/liter
GOLDEN Pump: 95, Super, Arabic Name: 'Khasosi', 65 fils/liter
GREEN Pump: 98, Ultra, Arabic name: 'Ultra', 90 fils/liter
(1 Kuwaiti Dinar, KWD = 1000 Fils)

Ref: http://www.knpc.com.kw/en/Products_and_ ... ducts.aspx
http://www.diablosport.com/forum/viewto ... 15#p229330
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Mike_Levy
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Re: Octane Ratings

Post by Mike_Levy »

Oh, and only use good name brand fuel, Exxon, Mobil, BP (my choice), Sunoco. Never, EVER, use Shell. It has additives that cause knock. And if you have a Hemi, and live in the NYC area, you better not put shit gas in. If I catch you, I'm gonna stop and ream the shit out of you. Just ask the jackass I busted on tonight who was putting Citgo in his Challenger. :normal:
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smackdownsrt
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Re: Octane Ratings

Post by smackdownsrt »

Mike_Levy wrote:I'm gonna stop and ream the shit out of you.
The ole Saskatoon Totem Pole huh? :shock:
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Mike_Levy
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Re: Octane Ratings

Post by Mike_Levy »

smackdownsrt wrote:
Mike_Levy wrote:I'm gonna stop and ream the shit out of you.
The ole Saskatoon Totem Pole huh? :shock:
Nah, thats more your style.
2018 Chevy Equinox LT 2.0T
K&N Drop in, Burger JB4 Alpha

2021 BMW M550i xDrive
BMC Drop ins, Waiting for a tune.
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smackdownsrt
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Re: Octane Ratings

Post by smackdownsrt »

Mike_Levy wrote:
smackdownsrt wrote:
Mike_Levy wrote:I'm gonna stop and ream the shit out of you.
The ole Saskatoon Totem Pole huh? :shock:
Nah, thats more your style.
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tn dodge
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Re: Octane Ratings

Post by tn dodge »

Around here all we have is 87, 89, and 91 octane ratings. In south TN/North GA area. What issues will it cause if I use the 93 tune with 91 octane gas?
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Mike_Levy
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Re: Octane Ratings

Post by Mike_Levy »

tn dodge wrote:Around here all we have is 87, 89, and 91 octane ratings. In south TN/North GA area. What issues will it cause if I use the 93 tune with 91 octane gas?
Its gonna knock. You'll end up with less power than you started with. And if you do it long enough, the detonation will blow a hole right through your pistons.

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In other words, DON'T DO IT.
2018 Chevy Equinox LT 2.0T
K&N Drop in, Burger JB4 Alpha

2021 BMW M550i xDrive
BMC Drop ins, Waiting for a tune.
MMueller
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Re: Octane Ratings

Post by MMueller »

If you go to a dragway they normally have locations available that vendors sell high Octane fuel, normally for racing. I use 112 Octane Unleaded. Works really well and I normally mix it with 100 Octane I can purchase at one of the gas stations, this high level of Octane is actually pretty hard to find, but I guess I am lucky to live were I do in Arizona.

I certainly would not want to use the 93 Oct Tunes and use less or even equal to that level. I believe that Mike pointed that out fairly effectively.
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