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evo_dadi
11-18-2003, 12:08 AM
for you guys who uses 100 octane with 91,how do you come up with the calculation for the mixed gas.ive tried xylene a couple of times and not much noticeable dirfference except for the smoother response.i wanna try this and see how it will work for the evo.

vtluu
11-18-2003, 12:45 AM
I use 3.2 gallons 100 + 10.8 gallons 91. The octane rating is ((3.2 * 100) + (10.8 * 91)) / 14 = 93.06 octane. You can mix 100 and 91 to achieve any octane between 91 and 100.

Remember your high school algebra? Solve for:

A = (x * 100 + y * 91) / (x + y)

Where "A" is the desired octane (a predetermined constant of your choosing), "x" is the amount of 100 and "y" is the amount of 91. To make things simpler, let's just go for a full tank, which is 14.0 gallons according to the owner's manual (section 9-8 ). Therefore we have "x + y = 14" and "y = 14 - x" which, substituted into the above equation, gives:

A = (x * 100 + (14 - x) * 91) / 14

Simplifying further:

A = (100 * x + 14 * 91 - 91 * x) / 14
14 * A = 9 * x + 1274
14 * A - 1274 = 9 * x
x = (14 * A - 1274) / 9

So for example, (14 * 93 - 1274) / 9 = 3.11111... gallons of 100 required to make exactly 93.0 octane (assuming you have exactly 100.0 and 91.0 octane, of course). I fudge the number up to 3.2. If you try "A" with a value over 100 you'll still get a result, but it will mean putting more than 14 gallons of 100 in, which is impossible.

DB8GSR
11-18-2003, 02:08 AM
wowsers! That's a lot of numbers vtluu. I'm getting dizzy! :shock:

Here's a link chart blend from Unocal 76. It shows 92 instead of 91 octane but you get the idea.

http://www.osbornauto.com/racing/blend.htm

vtluu
11-18-2003, 02:37 AM
Sheesh, you'd think people could at least work a calculator. :roll: Fine, here's a chart, courtesy of Microsoft Excel:

http://www.norcalevo.net/gallery/albums/album06/octane.gif

vtluu
11-18-2003, 02:49 AM
And here's a better one; don't say I never do anything for you people! :P

http://www.norcalevo.net/gallery/albums/album06/octane2.gif

evo_dadi
11-18-2003, 07:42 AM
:shock: :shock: :shock: see thats why i hated my math teacher :wink: thanks a bunch u guys,now all i have to do now is take a trip to 76 in sj right?buy me a few gallons.

JanSolo
11-18-2003, 10:48 AM
76 off of Almaden Expressway. Travel north from 85 and it will be on your right a few blocks up.

wilson1
11-18-2003, 10:18 PM
Good job, Tam

EvolvedDSM
11-25-2003, 03:14 PM
I found an official one that may help out ;)

http://www.columbusdsm.com/forum/files/gaschart.jpg

So, does anyone know of a location near Vacaville/Fairfield that sells 100?

vtluu
11-25-2003, 07:50 PM
My table has the same data (official or not, the math doesn't change) but goes up to the full tank capacity of the Evo. :P

I think the second table I made is a more useful one to consult. Just pick your octane and follow the recipe...

warpspeed
11-26-2003, 09:56 AM
I am just wonering if those stickers on the pump are true about what octane the gas is. You see before I use to fill up at a well know gas brand. but a couple of nights ago while I was in my civic I needed gas really bad. So I went to this "hokie" mom and pop station. As I was filling up I noticed that on the supreme pump the octane sticker read 93 octane and it was way, way cheaper than where I use to get super from by about .20 . I was wondering is this true. If not how can we be sure what octane we are putting in our cars,not just the Evo. Can we trust those well known gas companies? Hell I'm from the North Bay and alot of times when I go to the chevron/76 unocal/shell station, I see tankers come in to refill the tanks but there is no name on the tanker itself. Just the name "Beneto" on the truck. So waht gas are we actually getting. I know somebody out there is going to say that the company is trying to same money by using a 3rd party contract. But how can we be sure gas "a" is any different from gas "b." just my .02

vtluu
11-26-2003, 10:09 AM
I noticed that on the supreme pump the octane sticker read 93 octane and it was way, way cheaper than where I use to get super from by about .20 . I was wondering is this true.

If you know where to get 93 octane in NorCal we'd love to know where... :-)

I imagine the state has an agency whose job it is to check this kind of thing...

warpspeed
11-26-2003, 12:29 PM
I'm still looking for a station that do sell a higher octane. I'll pass it along when I do.

thomas
12-20-2003, 02:20 AM
i hated math in high school. lucky for me, there were people like vtluu around to drag me along :D

thanx for the charts, im sure theyll come in handy.

y'kno, speaking of octane...can somebody clarify for me if boosted cars can use "octane boosters" or not. i used to use it when i had my talon tsi when i knew i was going racing, but ive heard that its bad for turbo cars?

any thoughts?

EvolvedDSM
12-20-2003, 10:25 AM
Octane boosters don't do squat. If you're going to spend money, just get the 100.

vtluu
12-20-2003, 12:12 PM
A lot of octane boosters are just overpriced bottles of toluene or xylene (which are 114 and 117 octane, respectively), which you can buy for a lot less at, say, Home Depot.

I did try putting a gallon of xylene into my tank (giving me almost 93 octane) early on but can't honestly say I could feel much of a difference.

The actual effectiveness of either "home-brew" or store-bought octane boosters is something of a matter for debate. I suggest doing a Google search (http://www.google.com/search?sourceid=navclient&ie=UTF-8&oe=UTF-8&q=xylene+toluene+octane+booster), reading up, and drawing your own conclusions. :?

As for me, since xylene only really becomes cheap in large amounts (think drums), which I can't store, I'll stick with using 100 from the 76 station.

GokuSSJ4
01-05-2004, 10:33 AM
thanks for the chart !!!