CACalomino

iTrader: (1)

Well Im buying a EVO but I have been reading posts saying that the manual asks for a gas of 94 octane or better. SO does teh CA mitsu dealers prep the car *retard the timing* to accept 91 octane or is my knock sensor going to get a work out and possibly cause damage to my engine?

I know of a few 76 stations in my area that sell 100 octane but I dont want to go buy 1 or 2 gallons of it and mix it with my 91 to make 94 every fill up.

thanks for any feedback in advance

Chris

NRG

iTrader: (2)

Actually 91 octane is fine because your ECU is suppose to adjust accordingly to it......

IzenGreyEvo7

iTrader: (3)

You can run 91 safely. However, it will retard the ignition rather dramatically around 5,200rpm. I have found that running a 93/94 mix increase top end power to a large extent and is well worth the money for going out on mountain and canyon runs.

CACalomino

iTrader: (1)

SO how many gallons of 100 octane do u add to your tank to get that mix?

zx6r

See :
http://www.76.com/cgi-bin/b2cpt01/sc...d=-8318#100OCT

And scroll to about the bottom of the page where you'll see a table of 91 versus 100 octane.

From the chart, 8 gallons of 91 Octane ( Premium ) and 4 gallons of 100 Octane ( Race gas ) will give you 94 Octane

Chris in HB

iTrader: (3)

Chris -

For the meet this weekend, I am adding about 3-4 gallons (1/4 tank or so) of 104 to the mix. It should be around 95 octane. With that, plus the ECU flash to read the A/F mix, I should make some nasty power. I haven't had any detonation and you know my car...

IzenGreyEvo7

iTrader: (3)

Chris, just make sure the 104 is not leaded. I usually add 4 gallons if it's a full tank and a fraction thereof if it's not near empty. Remember though that there is about .2-.3 gallons of fuel in the fuel system post pump. You have to burn that gas off before you see the new mix. Then once you do, disconnect your battery to reset the ECU. You'll be pleased. Sure it costs 35 bucks for a tank of gas now. On the brighter side that's still almost half of what it would cost you in Europe or Japan.

CACalomino

iTrader: (1)

I know when the gas guage comes on there is about 3gallons of fuel left in the car. Why is it important to get rid of that? would it be wrong to just throw in 4 gallons of 100+ octane and then just fill the rest up with 91? Mabe it has to do with the mixing etc but if u could alborate on this that would be great.

Chris

IzenGreyEvo7

iTrader: (3)

The first time you mix to get 93 you can do that. My post was a bit confusing. When I wrote about adding a fraction I was referring to maintaning 93. I have run a blend every tank after my first two tanks of gas.

mlambert

Its much cheaper to buy toluene in bulk and mix that with 91 pump than 100oct race fuel. Just open an account at sherwin williams.

Its 114octane, a 10% mixture will give you 93.3, 15% mixture will give 94.45

Its considered safe to run up to a 20% mixture on a daily driven car, after that you need to add a lubricant and might run into cold starting issues.

IzenGreyEvo7

iTrader: (3)

I won't even begin to discuss the dangers of adding toluene into pump gas. Do it at your own risk. There's much misinformation on toluene on the net.

evoturbo131

iTrader: (2)

so i have to disconnect the battery and reset the ecu in order for the Evo to read the new blend of gas? i thought i heard somewhere that the ecu is able to adapt to the new gas and will automatically read and use the new blend of gas properly. Does anyone know about this? i'm using about 5% 76 racing gas (100) and 5% of either xylene or toluene (117, 114). So do i have to disconnect the battery??

IzenGreyEvo7

iTrader: (3)

The computer will learn faster to exploit the gas if you reset it. Otherwise it might take a while for the system logic to re-asses the given parameters on knock.

mlambert

Go ahead and discuss it.

What do you think makes the 100oct race fuel you pump into your tank 100oct? Thats right, aromatic hydrocarbons. What do you think makes the 94oct that people get on the east coast? Thats right aromatic hydrocarbons! What do you think makes the crappy 91oct in california? Same answer, aromatics like xylene (which is 117oct) and toluene (which is 114) Depending on the state there is already up to a 20% mixture of aromatics in everyday pump fuel.

Toluene has a stoichiometric air/fuel ratio of ~13.4:1, so when companies blend fuel they increase other contents in the fuel mixture to end up with 14.7:1 <-- this is the only thing you need to consider but only when you get towards a 20% homebrew mixture. A slightly lean mixture, something that a stock EVO8 sure could use.

Guys have been doing it for years on maybe forced induction vehicles.

I know of a handful of daily driven subarus that havn't had a tank thru them that didnt include a 20% toluene mixture, dumped right into the tank at the pump. Almost 2 years and no fuel system issues. Oh the horrible dangers of toluene!

IzenGreyEvo7

iTrader: (3)

How can you be sure of the refining quality and purity of the toluene from sherwin williams? How can you assure it was formulated to be blended with the various detergents and additives in modern gasoline? There's too many variables to contend with for my own fairly conservative tastes. You may recall in college chemistry how chemical energy is released. It's more complicated than simply stating each hydrocarbon molecule has a specific energy release. To say Toluene has a certain octance rating which you then dilute down with pump gas is an extreme simpification of the process of combustion and the release of chemical energy.