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Re: Lead addative fuel [Re: wodniw5] #1182942 Sat Sep 17 2016 12:20 AM
Joined: Oct 2004
Posts: 129
J
john1 Offline
Shop Shark
Iso Octane does exist and it's the standard which helps determine a fuels anti-knock or Octane rating. The most accurate octane test is performed with an octane motor which is fed pure Iso Octane at a controlled ambient temp, and humidity, with a correction factor for atmospheric pressure. The Octane motor has a variable compression ratio and is run at a steady load during calibration and testing. During calibration while running on pure Iso Octane (which has an octane rating of 100) the compression ratio is adjusted to set the engine at the knock threshold by using knock detection sensors. Once calibrated the engine is fed the test fuel to be graded. If the engine detonates or knocks the compression ratio is reduced until knock can no longer be detected. Based on the amount of compression ratio change the fuel is given a number for it's anti-knock value or it's octane rating. In this example since the compression ratio had to be reduced to eliminate the knock the fuel has an octane rating of less than 100, if the compression ratio had to be increased to create a knocking condition then the fuel would be rated at greater than 100 octane. This is also known as the Motor Octane Rating. Based on decades of fuel testing chemists can do a good job of determining what a fuels octane rating will be based on the blend of the fuel (Research Octane) so Motor Octane Testing is rarely done anymore. I got a chance to sit through a Motor Octane test at a refinery years ago. Interesting enough they were performing fuel tests for a competitor which did not have an Octane Motor in their own lab. The motor's are large single cylinders with a threaded cylinder which can literally be screwed up and down to change the compression ratio while the engines running, pretty cool stuff. John

Re: Lead addative fuel [Re: wodniw5] #1182944 Sat Sep 17 2016 01:40 AM
Joined: Feb 2004
Posts: 19,655
H
Hotrod Lincoln Offline
Boltergeist
Combustion chamber shape has a lot to do with how efficiently fuel burns, and whether pre-ignition happens, which is the precursor to detonation. Stovebolt combustion chambers aren't particularly prone to preignition/detonation unless they get heavily carboned up and hot spots develop.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Lead addative fuel [Re: wodniw5] #1182945 Sat Sep 17 2016 01:52 AM
Joined: Dec 2006
Posts: 1,154
W
WHO, ME ? Offline
Shop Shark
You are correct..Octane is a measurement value of combination of specific gasoline base additives. However there is not a substance with the nomenclature of...Octane. Octane it is the added sum of the hydro-carbon based gasoline components. Therefore it is used as a measured rating.


Re: Lead addative fuel [Re: wodniw5] #1182952 Sat Sep 17 2016 02:24 AM
Joined: Oct 2004
Posts: 129
J
john1 Offline
Shop Shark
So C8-H18 doesn't exist.

Re: Lead addative fuel [Re: wodniw5] #1182954 Sat Sep 17 2016 02:29 AM
Joined: Feb 2004
Posts: 19,655
H
Hotrod Lincoln Offline
Boltergeist
Here's a link:

http://alternativefuels.about.com/od/glossary/g/octanerating.htm

Iso-Octane is the fuel with the "100" rating

Heptane knocks in everything- - - -even a Biggs & Stratton lawn mower.

The percentage of Iso-octane that produces a specific knock point is equivalent to the octane rating- - - -the rest of the blend is Heptane. It's been that way as long as I can remember, back into at least the early 1950's.
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: Lead addative fuel [Re: wodniw5] #1182959 Sat Sep 17 2016 03:45 AM
Joined: Feb 2000
Posts: 4,053
J
Joe H Offline
Shop Shark
Based on what I have seen and used, (104 Octane Booster) all I got from it was red fuel and discolored valves. If the engine has a compression ration that will run on 87 octane, adding more will not help. Now if the said engine has hot spots on the head, odd ball pistons, or timing out of whack, then the higher octane could help. My stock 250 has 8.0 to 1 compression, running 87 octane or 93 octane (no corn added), the mileage and performance is always the same. I have run plenty of test for fuel mileage, so I stand by this one. Even my race car didn't show any difference when going up on octane, the engine was happy with what it had. My '85 Dodge 318 used to ping like made on 87 octane, I sold it with 200,000 miles on so I can't say how long it kept going and pinging.

Again, this is my observations, if you get good results, that great, it keeps the old trucks out on the road where they belong!

Joe

Re: Lead addative fuel [Re: wodniw5] #1182972 Sat Sep 17 2016 11:57 AM
Joined: Oct 2006
Posts: 1,841
B
brokenhead Offline
Shop Shark
octane RATING is the measurement of the effectiveness of the various combinations of fuel that are out there. Whereas OCTANE is absolutely a substance that is used to set the guidelines for determining the RATING. The gas doesn't necessarily have to have octane in it, just have an equivalent resistance to knocking, detonation or what have you. So yes, octane does actually exist.

Re: Lead addative fuel [Re: wodniw5] #1182974 Sat Sep 17 2016 12:55 PM
Joined: Aug 2005
Posts: 8,828
Tiny Offline
Global Mod
I think we've beat this dead horse long enough. The discussion has become circular. If the regular forum mods think this subject is worthy of further discussion they can unlock it.


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