Tuesday, July 21, 2009

Fuel Strategy, Strata & Pb


This year I have been trying to make a bit more HP without spending too much $$. One thing I tried was some different race fuel. I did a little research about E85 and thought that would be cool. Too bad it's not available around here, at all. I even got in touch with the local Rockett brand dealer about their new E85 race gas. He's not carrying it, no demand. Then I heard about some super new VP stuff called Q16. Apparently it's a little tough to tune. We (Adam Fuhs) and I eventually settled on C16.

I get the tank nice and low in the evo and add a 5 gallon drum of the C16. Did some driving to mix the fuel.

First set of logs results in very similar AFR's to pump gas. Second set of logs is a bit richer and the car stinks a bit more. By the 3rd logging session this car reeks. To the point I'm almost dizzy. The AFR's are also very rich. Pretty sure we're into the C16 now.

At this point we're a little confused. A little searching shows the specific gravity of gasoline is slightly higher than the C16. As it turns out the gasoline and C16 stratify. They form layers and don't create a homogeneous mixture. Gasoline on the bottom and C16 on top. Hence the leaner AFR's shifting to super rich AFR's. Called up VP and they confirmed the theory. Unleaded and leaded gas don't really "mix".

Off I go to drain the evo's tank so I can move onto something else. What am I using the leftover for??


I hate to say it but the lawn didn't get cut any faster.

One thing I finally learned was how much fuel my car has when it hits the "E" light. Without the luxury of a tow vehicle and trailer I bring race gas with me and mix with the leftover in the tank. This means I calculate how much fuel I need to get to the event site and make sure I'm at "E" or below. Thing is I never knew how much gas was actually in the tank. I estimated about 3 gallons. So I drained the tank fully. Then slowly refilled with pump until the light turned off. 2.3 gallons. At the 1/4 tank mark the evo has 4 gallons left. Sweet, now the octane numbers for the mixed gas will be more accurate.

Now you might wonder how to figure out what your octane is once you mix the gas. It's pretty simple as the octane is based on proportion of one fuel to the other.

Your variables:
A = Pump Gas Octane
B = Volume of Pump Gas (gallons)
C = Race Fuel Octane
D = Volume of Race Fuel (gallons)

The math:
(A x B + C x D)/(B + D) = New Octane of Mix

Example:
A = 93 Octane
B = 2 gallons
C = 104 Octane
D = 5 gallons

(93 x 2 + 104 x 5)/(2 + 5) = 101 Octane

So that was my fuel saga. I'm back to regular old 104 unleaded. Oh well.

-J






6 comments:

dan said...

c16 = $60 a can.. pay to play!

good stuff jay. i hope to get lots of seat time in evo v2.0 on august 1st!

Jay said...

$60....I wish. The 1st should be awesome on a couple levels.

dan said...

i guess i did get my can of c16 for free but we just used it up recently in a 2 wheeled 2-smoke. i think i'll bring the s2k up too. i'm itching to actually drive it in its element.

Char said...

What's on Aug 1st?

Jay said...

Char,
There's a Boston BMWCCA school/test and tune at Devens. We're instructing. Serious fun. In and out of cars ALL day, plus time for your own.

Jay

Char said...

Nice. I recall you car whores doing this last year. Won't be able to make it. Have a blast!