Fuel Requirement? - Page 2 - LotusTalk - The Lotus Cars Community
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post #21 of 29 (permalink) Old 03-29-2004, 08:15 AM
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Is the relationship between octane and additives linear? If so, then those little bottles sold at auto parts stores can't have much effect unless they're on the order of 1000 octane.

The idea of adding toluene (one of the 4 most prevalent aromatic components in gas- others are benzene ethylbenzene and xylene) makes sense. But doesn't the salesperson at the paint store think you're running a meth lab? I'd also think your paint job is at high risk in case of a spill.
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post #22 of 29 (permalink) Old 03-29-2004, 09:00 AM
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Ok, I'm confused and in need of some education...don't high octane fuels require a turbo/supercharger to get the compression to do what they do? If that is the case then the yota engine won't be able to 'use' the higher octane. However, reading this thread I get the impression that it is able to change compression/timing and do just that...

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post #23 of 29 (permalink) Old 03-29-2004, 09:14 AM
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I think the general concensus here is:

ECU management can adjust timing based on fuel octane (by sensing pinging). However, there is a max timing setting where higher fuel octane will make no difference. This max octane value will vary by engine/car.

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post #24 of 29 (permalink) Old 03-29-2004, 09:36 AM
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Toluene & tubo/non-turbo demands

Eyelise, are you really adding a gallon of toluene to nine gallons of fuel to raise the octane? That seems a bit much, considering that there are octane boosters on the market that work and they are usually pint or quart (approx.) cans. I'm not an expert on this but have used 104+ octane booster on a '70 AMX that kept the rings intact when unleaded wasn't available in high octane. Prior to that, I turned piston rings into steel confetti one day because I used a mix of unleaded regular and leaded regular. That worked in the early days of unleaded fuel, but I learned recently that at some point in ancient history (pre 90's) additives were changed so the 'additive-effect' on octane no longer made a significant difference.
Babak, again, I am not a fuel industry expert, but have assembled a few engines (the '70 AMX a few times and a G/prod. Spitfire in the late '70's too many times!) and have learned the hard way that not only compression ratio, boosted or not, but spark advance and fuel mixture all affect the octane required to prevent detonation. Once, with the Spitfire, a distributor which had more total advance than I thought possible made the initial advance setting pretty much irrelevant and destroyed the engine in less than three laps. (it ran REAL GOOD for those 2+ laps!). I also learned with the same car, that not having the correct metering jets/needle valves/settings/etc. resulted in excessivley lean mixtures at higher RPM, again building about the same level of heat as a nuclear reactor in the combustion chamber . . . well, at least temperatures at which forged aluminum pistons melt/burn.
The prior posts stating that low performance engines do not benefit or even suffer some power loss is consistent with what I've learned. Most modern high performance engines are designed/computers programmed to deliver slightly more power with higher octane fuel. They vary as to how much effect this has, but generally, using fuel below recommended octane will lower the power output and higher octane will assure full potential is reached.
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post #25 of 29 (permalink) Old 03-29-2004, 05:40 PM
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Yes, I am adding 1 gallon to 9. If you do the math it doesn't raise the Octane all that high 90%@93, 10%@118. The limitation is percent aromatic hydrocarbons and heat build up. I'm pretty sure some race cars run on 100% toluene. The car really runs super at this ratio, others have pushed it even further. You are right that the commercially available additives likely do very little. It's just not possible with such a small volume to efffect a significant change in Octane. If someone can demonstrate otherwise please do. No problem with buying at the paint shops thus far.
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post #26 of 29 (permalink) Old 03-29-2004, 05:48 PM
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Originally posted by Knute
However- Union 76 stations in some areas have been carrying race gas, and the trend appears to be acclerating. In the SF bay area, for example, there are several stations that I know of that do this, one of which in San Jose actually dispenses race gas from the pumps, and others of which will sell it to you from drums or in containers.
Around here, Union 76 stations carry 100 octane racing gas at several stations (maybe all?) in pumps at the regular islands. No hassle to get it there.
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post #27 of 29 (permalink) Old 03-30-2004, 03:47 PM
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Here in North Jersey, our local CAM fuel outlet (the first one I have ever seen) sells 100 octane "racing gasoline". I spoke to the attendant (there is no self-serve in Jersey) who said that people will add two gallons of the 100 octane then fill up the rest with 93. He says they really gain performance. I am rather skeptical. It costs $4.99 per gallon.

At the pumps, they usually note that octane is derived from the (R+M)/3 method or some equation like that. My organic chem from well over 20 years ago is a bit rusty. Does one of you fuel experts have a handle on it?

I have heard that even Porsche has made their cars able to run on lower octane fuels because not all of the markets to which they sell are able to provide optimum fuels. But if I take the point correctly, a sophisticated engine can manipulate valve and spark timing to gain horsepower (? and torque) depending upon the fuel's ability to retard predetonation.
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post #28 of 29 (permalink) Old 03-30-2004, 06:22 PM
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Some reading on mixing Toulene (sounds like Eyelise is already familar with it):

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post #29 of 29 (permalink) Old 03-31-2004, 04:23 AM
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Originally posted by Cale
...At the pumps, they usually note that octane is derived from the (R+M)/3 method or some equation like that....
There are two methods of measuring octane rating. RON (Research Octane Number) and MON (Motor Octane Number). The MON test is more strenous, and results in lower ratings. I think it's usually around 10pts lower.

In the US, octane number at the pumps is given as the average of the two: (R + M) /2.

But overseas it's common to just get just the RON. Which means that 98 octane in Japan or the UK is about equal to 93 in the US.

I expect the racing gas offered is rated via the averaging method (pump octane).
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