Blending fuel - snake oil or reasonable

I've been doing some research and making some calls, but I'm always curious what other folks think about the topic.

Tune car for octane X, run gas with higher than X octane to make sure things don't go boom. HOW to get octane >X if it's higher than best pump gas available is the question.

What do people really do? Buy a barrel of Sunoco 104 and mix with pump gas? Squeeze the blood out of mermaids, add a newt's eye and then mix with pump gas? Has anyone ever done actual testing of this?

I know that real race fuel is just a blend and there are a million calculators out there for x gal of Gas A and y gal of Gas B = Gas C, but what have you guys seen?

Its most likely not worth it, especially mixing with pump gas.

Pump gas has "winter" and "summer" blends, so you'd be varying right there off the bat. Secondly, the blends can differ a bit in pump gas. You'd need to have the same gas from the same batch of the same blend to have an "accurate" recreation.

From my understanding, Race fuels are "always" the same. No matter what month, or where you buy it. Sunoco 104 from A bought in Dec will be the same as Sunoco 104 from B bought in July.

Then there is the whole "How do I measure it all accurately?" bit... Do you go by volume? Weight?


I could see potential benefit mixing race gas types (maybe a higher octane with a lower octane to get something in the middle), but definitely not with pump gas.

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Welcome to the cult of JVL drink the koolaid or be banned.

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Dazed_Driver
Its most likely not worth it, especially mixing with pump gas.

You'd need to have the same gas from the same batch of the same blend to have an "accurate" recreation.

Let me be clear - I'm saying that I'm proposing tune for the WORST (read: NO mixing) and then run a mix of the pump+race. From some reading, unleaded + leaded is generally a bad idea, but unleaded + unleaded is generally not toooo bad?

I'm not looking for accurate - I'm just looking for something that's some generally measurable amount that's better than worst-case (read: pump gas) that's already been tuned for. I know I won't get any more performance gains, but I'm looking for the insurance of the higher octane to help provide some mechanism of reducing potential detonation.

Make sense?

There was a good article on fuel comparisons in Grassroots Motorsports last month. The conclusion was that in most motors premium pump gas with ethanol was best!

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Robert.

"You are way too normal to be on Rally Anarchy." Eddie Fiorelli.

I agree. The issue here is that my motor melted down because the pump gas was not as advertised I'm basically trying to buy insurance.

Tune for 91 and run 93? -> $
Tune for 93 and run a mix of 93 and something else? -> $$$
Tune for 93 and run race gas? $$$$$ and power left on the table
Tune for race gas and run race gas? $$$$$

Step #1 is finding a good tuner, who is knowledgeable about things (not an internet tuner). Someone who is willing to sit down and talk to you about your goals, your intentions etc. Someone who is good has played with all the different fuels you are thinking about.

Now heres my 2 cents. Running a turbo car (particularly a restricted one), on pump fuel in competition is asking for trouble (or you are leaving GOBS of power on the table). It's one thing to be "safe" on a dyno, or on a street tune, but at the end of a 20 mile stage when everything is completely heat soaked is another ball game all together.

For what you've got "invested" in an engine, it's worth some $$ to gain some durability.

From what i remember, you mostly run NASA sanctioned events? If so, give some serious thought to E85. Being in the US, you can probably go to the corner gas station and buy E85 for less than 87 octane. Put yourself together a cheap testing kit, and know when the stations switch over to "summer" e85 (actually 85%). It's worth the little price to pay for some fuel injectors and the little bit extra fuel useage.

If you must run pump fuel...Buy from a station that is close to your home/shop. Have the car tuned on that fuel. Then when going to events, buy fuel from that station again, and carry it with you to event. Don't buy fuel for your race car some "rallytown" USA....I worry enough about running my reece car on "premium" on some of the places we go to.

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Chris

Interesting question. I don't know about turbo cars, but my G2 Golf has a high-comp motor (14:1) and needs about 96 or higher. I usually run it on 100, but for longer events I've blended it down. I can only carry 15 gallons extra in my van, so I usually start with the car full of 100 and then alternate between throwing 5ga of pump gas and 5ga from my cans into it.

The P-Stock Golf was built for pump gas (11:1 or so), so I don't worry about it much.

Both cars have dumb ol' CIS-E with a knock-sensor that'll retard the timing if the ECU hears a ping, so maybe I've been getting pinging and haven't noticed it. Can't hear much with my Peltor on, and I probably wouldn't notice the couple of hp difference anyway.

Can you run multiple maps and switch the tune on as as-needed basis?

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Self-righteous douche canoe

Tell us about your engine.

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Robert.

"You are way too normal to be on Rally Anarchy." Eddie Fiorelli.

Built EJ25 turbo, stock compression.

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EricW
Built EJ25 turbo, stock compression.

Stock 8.2:1 and 99.5-100mm bore

I say mix. All fuel is a blend... start with local 93, add 20% race 110 and reduce progressively..

And to talk to a real nice guy Boris Mohar at Knocksense.com

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I'm not too familiar with the effects of a turbo...so from what I understand, octane requirements are determined by the dynamic compression ratio of the engine. That is static compression (piston and chamber dimensions) plus cam timing (overlap bleeding pressure). The right octane is to prevent detonation.

Higher octane allows more advanced timing also (until it starts pinging), but to what level of power gains? At some point, using a higher octane is just throwing money away.

I am guessing the turbo cramming more air into the motor is seen as an increase in the compression ratio and therefore allows for a higher octane?

Tim.

We ran premium pump gas mixed with toluene in something we owned. There are formulas everywhere online. 10-30% are the numbers usually tossed around. We bought gallon cans at the hardware store.

Varying reports of effectiveness and most people use it as a latch ditch effort as you are considering.

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TronDD
I'm not too familiar with the effects of a turbo...so from what I understand, octane requirements are determined by the dynamic compression ratio of the engine. That is static compression (piston and chamber dimensions) plus cam timing (overlap bleeding pressure). The right octane is to prevent detonation.

Higher octane allows more advanced timing also (until it starts pinging), but to what level of power gains? At some point, using a higher octane is just throwing money away.

I am guessing the turbo cramming more air into the motor is seen as an increase in the compression ratio and therefore allows for a higher octane?

Tim.

Very good. One correction
"the turbo cramming more air into the motor is seen as an increase in the compression ratio and therefore DEMANDS for a higher octane?

Always bear in mind that the higher octanes burn slower (and cooler), its THAT that reduces the uncontrolled burning we call EXPLOSION--which is way hotter and insanely high pressure over an extremely short time...
Ignition advance is good---up to the point that the "newly lit off charge" is building to much pressure as piston approaches TDC--cause then its pushing on the piston while its trying to come up..

Best way is to find peak cylinder pressure ATDC and exactly where that occurs has to be worked out.. But somewhere in the 30-35^{o ATDC} range..

Eric is thinking right tho--he's looking at "some" increased octane as mainly a safety cushion, not for mo powerz....
A stock 2.5 turbo Subie should kick a lotta ass IF the driver actually occasionally puts the foot down.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

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john vanlandingham
Very good. One correction
"the turbo cramming more air into the motor is seen as an increase in the compression ratio and therefore DEMANDS for a higher octane?

I thought about rewording that before submitting.


What does the margin of error protect against? Heat build up? Being so close to detonation or pinging for a given octane, you might cross the line in a high load situation?

And the follow up would be, what would be a good margin of error in octane points, and how do you know it's enough?

Tim.



Edited 1 time(s). Last edit at 12/17/2012 11:59AM by TronDD.

I've heard of people adding toluene anyone ever do it?