PART 2: AV gas in a turbo 2 stroke:

[mike_s]

To each his own but i know quite a few people including my self running Maxima hitest octane booster and it works no if or ands about it. I cant supply any teck data but it works and is super easy to use no more airport or race for us. Good luck.

Maxima is primarily made up of toluene, which has an average octane rating of 114. So you're basically dumping in 16 ounces of race gas to your full tank of gas. When you read on the label that one ounce per gallon will raise the octane 4 points, the miconception kicks in. That will make 91 octane 91.4....not 95. There is simply nothing with a high enough octane rating to do that at that kind of dilution ratio.

Using toluene you will still be mixing close to 50/50 to get anything around 100 octane.

 

[Hardass]

No arguing from me but it works quite well.

 

[kanedog]

Toluene stinks but it works. Not in small 16 oz bottles tho. More like 30% toluene added to your fuel might bring your 91 octane to 96.

 

[TRS]

There is a huge difference in fuels. I generally run a Sunoco 110 mix.
This winter I ran out of Sunoco and wasn't able to get any for two weeks. I had to buy Turbo Blue. What a mistake. I had to change mix ratios to stop det and build an entirely new fuel map. Bottom end with the TB lost the response that the Sunoco has. Also needed to drop a gram and a half to each fly weight. Fuel is a bigger deal than most realize.

 

[TheBreeze]

Super interesting trs. Sunoco 110 is a unique fuel for sure. It's distillation curve, and property's mimic that of 100 ll far more than most 110 race fuel. It "should" have less response, but better det protection due to its super high 90% and final evap #'s. But I'm not arguing with your real world testing.

 

[mountainhorse]

Looking at the stats for the VP 110 a while back... it seems, on paper, that it would give better throttle response for on-off-on type of throttle use than the Sunoco.


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[mountainhorse]

Heres a great article from Sunoco

“Beyond Octane”

From Sunoco’s website “Tech-Corner”
http://www.racegas.com/article/10

Overheard at the local track:
• “High octane fuels burn slower.”
• “My motor doesn’t need all that octane so that fuel won’t do me any good.”
• “I need the highest octane so I can max out my timing.”

Unfortunately, those statements are not always true. As a matter of fact, those statements only have some merit in the street gas world where 93 octane fuel is king and 87 is used by most. In the world of racing gasolines where higher octane choices abound, sharp engine builders and racers know they need to look beyond octane to find the right fuel.

But before we ignore octane, it’s important to look at how octane is measured in the first place.

Octane numbers are measured using single cylinder engines that look more like something out of a Model T than any modern engine. These so-called “knock” engines are operated by trained technicians in labs under controlled conditions. Two tests are used – one for Research Octane Number (RON) and another for Motor Octane Number (MON). The RON test results in a higher octane value than the MON test.

If you average RON and MON, you get an octane value called AKI, short for Anti-Knock Index. It's often labeled (R+M)/2, reflecting the fact that it is the average, or midpoint, between RON and MON. AKI is used to rate retail pump fuels, and it is the most commonly used octane value for race fuels as well.

For example - Sunoco Ultra 93 typically has a RON of 98 and a MON of 88, thus yielding an AKI of (98+88)/2 = 93. If you look closely at the yellow octane labels at gas stations, you'll see the (R+M)/2 description under the big octane numbers. We provide all the octane numbers for all our race fuels - RON, MON, and AKI. So while we may refer to fuels like SR18 as "118 octane" (that's the AKI value), we also show the RON and MON numbers under "Technical Details". For SR18, that would be 120 and 116 for RON and MON, respectively.

Many times you’ll hear that MON is more important than RON because the MON test is performed under higher temperature and engine speed conditions. While this may be true, the laboratory test conditions are not indicative of what real race engines – heck, even mild street/strip motors for that matter – see at the track. Also, some engines have shown a better correlation between horsepower and RON. So, a word to the wise: don’t get hung up on octane numbers.

For a great example of why octane is not the only fuel parameter to ponder, consider the engines used in Formula 1. These engines have compression ratios exceeding 18:1 and spin at RPMs pushing 20,000. Sounds like a candidate for 116 octane race gas, right? Nope - they use a 96 octane fuel!

It’s hard to find a wider variety of race cars than what shows up at your local drag strip. On any given weekend you can see all sizes and shapes of engines ranging from raspy 4-cylinder motors to booming big blocks, and with all kinds of power adders thrown in the mix. This is where looking beyond octane becomes real important. What works for your buddy’s Pro Stock car may not be the best choice for your other buddy’s turbocharged import.

Naturally aspirated race motors with large combustion chambers spinning at high RPMs really like high-octane, fast burning fuels. They need the octane to prevent uncontrolled combustion, and they need a fast-burning fuel so that the flame front can span the large bore of the combustion chamber quickly. If you’re not sure which fuel burns faster than others, one indicator is specific gravity. “Lighter” fuels – fuels with a lower specific gravity – tend to burn faster because fast burning hydrocarbons are themselves light. Look for a specific gravity close to 0.70 and you’ll likely find a fast burning fuel. Of course, consult with the fuel producer to verify your assumptions. You might be surprised to learn that some of the highest octane fuels may also be some of the fastest burning fuels!

You might also be surprised to know that fast burning fuels may not need as much timing as their slower burning counterparts. Many times we get calls from individuals who are dialing in new motors on a fast burning fuel but they’re using timing and jetting numbers from their old motor and fuel combo. “Retard the timing a couple degrees and see what happens” is not the suggestion they expect to hear! With high octane, fast burning fuels, it is easy to dial in too much timing. In such cases, the engine is not detonating, but it is past the point of optimum spark advance, so it’s just heating things up and making less power. A little less timing may really wake up the motor.

 

[mountainhorse]

Heres a great article from Sunoco

“Specific Gravity”

From Sunoco’s website “Tech-Corner”
http://www.racegas.com/article/26

Definition: specific gravity (noun) - the ratio of the density of any substance to the density of some other substance taken as standard, water being the standard for liquids and solids, and hydrogen or air being the standard for gases.

For fuels, specific gravity can be determined by dividing the density of the fuel (in units of pounds per gallon) by the density of water (8.325 pounds per gallon). Let’s look at one example.

Sunoco Supreme weighs 5.95 pounds per gallon. Applying some math: 5.95 / 8.325 = 0.715. So Supreme has a specific gravity of 0.715.

If Fuel A has a lower specific gravity than Fuel B, Fuel A is said to be “lighter” than Fuel B. Literally, a gallon of Fuel A weighs less than a gallon of Fuel B. Sunoco Standard has a specific gravity of 0.728, so it is said to be “heavier” than Supreme.

Why does this matter? Well there are two reasons.

First, specific gravity has an impact on fuel metering, especially for carbureted engines. A heavier fuel is of course denser, so the float in a carb’s float bowl will sit higher than if a lighter fuel was used. If the float sits higher, the fuel level will be lower. Fuel level affects fuel metering in a number of ways, so if you’re switching fuels, pay attention to the fuel level in the bowls.

For most race fuels, specific gravity is also an indication of the composition. Note that the words “most” and “indication” were used – there are exceptions. However, for most race fuels, a lower specific gravity suggests a faster-burning fuel, while a higher specific gravity suggests a fuel is slower-burning. This is because most light hydrocarbons used to make a race fuel are faster burning than most heavier hydrocarbons. This matters because faster-burning fuels usually require less spark advance than slower-burning fuels.

So in addition to paying attention to fuel metering changes when switching race fuels, you need to pay attention to ignition timing as well. We’re not talking huge changes here, but these changes are important to the proper tuning and consistent performance of your race engine.

One final thought – there are implications for pump gas as well. The specific gravity of pump gas will typically range from about 0.720 to 0.770. As you can now guess, this wide range is a reflection of the wide ranging composition. Pump gas composition varies by octane, by region, and by season. For these reasons, a race engine that can run on pump gas must be tuned conservatively just to prevent engine failure. You can imagine the consequences of an engine that is tuned to the ragged edge on one batch of pump gas, then another batch is used in a race and the motor runs lean and timing is over-advanced. Not good.

One of the most important attributes of a race fuel is its consistency. Even if you don’t need all the engine protection offered by a high octane race fuel, you may need its consistency. Specific gravity is one of the many parameters we monitor to ensure quality and consistency in all our fuels, batch after batch.

 

[mountainhorse]

Since AV Gas was blended to provide the proper formulation for an engine running at a steady throttle position...... It's fair to say that it is not optimal for running a high performance sled.... other than say a "Chute runner" that take a run at the hill and never lets the flipper off the bars until cresting the hill.

Optimal and acceptable or "decent" are different things.

If staying off the Detonation sensor setting is your ONLY concern... then AV gas IS completely acceptable ... If throttle response AND staying off the DET is a concern... then running a different blend will yield optimal results.

Rarely will you see a airplane pilot, all day, "blipping" his throttle like Matt Entz riding through the trees with his turbo sled.

Food for thought.

All that said... I'm NOT a fan of ethanol in the fuel...nor of some of the newer, oxygenated, race fuels out there that have tiny fuel life windows and strict fuel handling and temperature concerns.

A few years back... I was able to ride a Turbo'd Pro... and the owner had a lot more money than most here... he ran only Oxygenated "hi tech" race gas... and his sled was tuned to run it.... with a MON of about 98 and interesting fuel properties... that was downright wicked-good in terms of throttle response, turbo lag and overall power... but he had one of his ranch hands drive down to the fuel depot every riding weekend and pick up a fresh drum.... to the tune of about $18/gallon. OUCH...

 

[mountainhorse]

Although there are 6 pages to read... IMO...worth reading all the background info from Post #1 in this thread.


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[mountainhorse]

Continued in PART 3 here

Click on this link.
http://www.snowest.com/forum/showthread.php?t=420643







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[mountainhorse]

TTT