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fuel question?

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fuel question
6K views 56 replies 19 participants last post by  Wicked Performance Boats 
#1 ·
can anyone tell me what 100 octane leaded is.. exactly.. thanks:D
 
#4 ·
Just kidding around on the previous post ... it was the obvious answer :D If you're asking what 100 octane leaded is used for there are numerous types and uses

100av is a low lead 100 octane used for aviation.

there are 100 octane leaded race fuels on the market as well that are used for spec fuels in different kinds of racing and high compression dirt bikes, etc.
 
#7 ·
the fuel at Terribles is a 100 race fuel made by Torco Racing Fuels for the Herbst Stations, I should know as I sell it to the Herbst.

Av Gas is a aviation fuel that has a higher octane rating than pump gas that people use in their boats to avoid the higher cost of race gas.
 
#10 ·
Thats what I run in mine. Avgas, 100LL, whatever you call it, its the same. LL being low lead. Stable for longer periods than "pump" gas, more pure, and higher octane. I'll blend it with 93 also. Obtaining may be an issue, but once you get the hookup on it, stay with it. The cost is minimally higher than pump gas right now.
 
#25 ·
Hey Milkmoney what ya lookin at? What compression ratio does he claim it is? I'm going to pm busby on the 100 octaine dealio, thats about where I need to be. I've been mixing 110 and 91 to get there. Tittyman I haven't been able to get hooked up with av fuel here but the last batch of 110 I bought was a hair over $6.00.
 
#26 ·
hey h20, the many few i am looking at is this one. located on craigslist, city would be san francisco, but the boat is in san jose. 86 bahner with 13 1/2 to 1 date posted would be 5-3-2008, hope this helps you.. let me know what you think.. thanks..:D
 
#39 ·
avgas mon #'s

"The 100LL is blue and the 100/130 grade is green. Both of these have much lower Motor Octane Numbers than most racing gasolines and will detonate when the engine octane demand is greater than the octane number of the gasoline".

Busby do you have actual test #'s to back this up ? not looking for a pissing match on this as i'm sure with so many choices for race gas that the best brands have done the research to formalate grades for specific performance applications , BUT i have always read and heard that avgas had high motor octane #'s and that the green 100-130 ( haven't seen here in Canada for years) had very high lead content and a RM/2 # of 115 and that LL100 a RM/2 # of 105 . and although planes do cruise at high alt. at a low rpm they have to take off from the airport and under a very heavy load . not legal to use here but if you can get it works fine for most sportsman or performance use up to 12.5 :1 .
 
#40 ·
"The 100LL is blue and the 100/130 grade is green. Both of these have much lower Motor Octane Numbers than most racing gasolines and will detonate when the engine octane demand is greater than the octane number of the gasoline".

Busby do you have actual test #'s to back this up ? not looking for a pissing match on this as i'm sure with so many choices for race gas that the best brands have done the research to formalate grades for specific performance applications , BUT i have always read and heard that avgas had high motor octane #'s and that the green 100-130 ( haven't seen here in Canada for years) had very high lead content and a RM/2 # of 115 and that LL100 a RM/2 # of 105 . and although planes do cruise at high alt. at a low rpm they have to take off from the airport and under a very heavy load . not legal to use here but if you can get it works fine for most sportsman or performance use up to 12.5 :1 .
yes ... but if you look at what I said about 100LL and 100/130 ... Both of these have much lower Motor Octane Numbers than most racing gasolines ... this is true & will detonate if the demand is higher than the octane provides resistance for

More info:

Aviation gasolines are all highly leaded and graded using two numbers, with common grades being 80/87, 100/130, and 115/145 [109,110]. The first number is the Aviation rating (aka Lean mixture rating), and the second number is the Supercharge rating (aka Rich Mixture rating). In the 1970s a new grade,100LL (low lead = 0.53mlTEL/L instead of 1.06mlTEL/L) was introduced to replace the 80/87 and 100/130.

Soon after the introduction, there was a spate of plug fouling, and high cylinder head temperatures resulting in cracked cylinder heads. The old 80/87 grade was reintroduced on a limited scale.

The Aviation Rating is determined using the automotive Motor Octane test procedure, and then converted to an Aviation Number using a table in the method. Aviation Numbers below 100 are Octane numbers, while numbers above 100 are Performance numbers. There is usually only 1 - 2 Octane units different to the Motor value up to 100, but Performance numbers varies significantly above that eg: 110 MON = 128 Performance number.

The second Avgas number is the Rich Mixture method Performance Number (PN - they are not commonly called octane numbers when they are above 100), and is determined on a supercharged version of the CFR engine which has a fixed compression ratio. The method determines the dependence of the highest permissible power (in terms of indicated mean effective pressure) on mixture strength and boost for a specific light knocking setting.

The Performance Number indicates the maximum knock-free power obtainable from a fuel compared to iso-octane = 100. Thus, a PN = 150 indicates that an engine designed to utilize the fuel can obtain 150% of the knock-limited power of iso-octane at the same mixture ratio. This is an arbitrary scale based on iso-octane + varying amounts of TEL (tetra ethyl lead), derived from a survey of engines performed decades ago. Aviation gasoline PNs are rated using variations of mixture strength to obtain the maximum knock-limited power in a supercharged engine. This can be extended to provide mixture response curves which define the maximum boost (rich - about 11:1 stoichiometry) and minimum boost (weak about 16:1 stoichiometry) before knock
 
#42 ·
ok i would like to know excatly what do i run in a 13.5 to 1 and the boat will be stored in parker, running on the river and what are the disadvantages to this over running pump gas.. like avaliabilty and the engine being touch or less dependable.. :D
 
#44 ·
I'd say run 110, the disadvantage is race fuel costs more, the advantage is you won't blow your motor up. I have to admit running race fuel is a way larger pain in the ass than I thought it would be. But if the sell it at the pump right where you boat, then you are more fortunate than I.
 
#54 ·
So did Terribles stop offering 100 Octane made by Torco Racing Fuels? It's not here at the Bullhead City Terribles anymore.

Also, what's the difference between running the Sunoco 100 Octane Leaded compared to running the VP 100 Octane Unleaded in a blower engine with a 91 Octane tune on it. Does it really matter if you mix the 91 with 100 Leaded or Unleaded if you're not running any sensors? This is just a boat engine that I want to mix the 91 with 100 when it sits for a couple of months.
 
#55 · (Edited)
You guys really need to re-read Busby's posts. He knows what he's talking about. 100LL does NOT meet the octane needs of a automotive or high performance boat motor. It has ingredients that let the fuel be stored for longer periods of time (a good thing) and it evaporates at a different rate than automotive fuels (which means that it has a lighter specific gravity and that means that it acts leaner through the same jet because it's designed to be able to run at a higher less dense altitude).
Also, no one has addressed this yet, but static compression is not the same as dynamic compression. An engines dynamic compression is always lower because of valve over lap at lower RPMS. The bigger the cam and overlap the lower the cranking and low RPM cylinder pressure will be. Just because you have a static compression ratio of 13:1 you can have cranking cylinder pressures of 180LBS with a big enough cam. Lower engine temps of lake boats that run an open cooling system will be more detonation tolerant than higher automotive engine temps. Lake boats also mostly see cooler and moister air, also bringing the detonation factor down. Aluminum heads that tend to cast off combustion chamber heat help also (apples to apples).
Detonation is just lurking around the corner when an engine is under load.....and Jets and V-drives are CONSTANTLY under load unless they are shut off or idling.
It's your engines, so put what you want in them. IMHO, if it's not a purpose built pump gas engine then you'd better be putting some higher octane leaded racing fuel in them.
I can show you all some pics of some really cool melted aluminum ash trays (that used to be pistons) if you don't believe me lol.
Rob
 
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