110 Leaded Octane fuel

[Michael W.]

Re: 110 Leaded Octane fuel

Dom, you've confused me with someone else. I'll let a real 'fuel engineer' try to explain:

http://www.whitfieldoil.com/www/docs/171.284/vp-racing-fuel-

It is essential to understand that octane number has nothing to do with flame speed of a given fuel. This seems to be the ongoing source of your confusion and misinformation.

This might help too:

http://www.nitrous.info/nitrous-historic/fuels_detonation_preignition.htm

[Duke W.]

Re: 110 Leaded Octane fuel

I read in another post you wrote Duke, that BB's liked 8* timing.

Initial timing depends on how much centrifugal advance the distributor provides. Most big blocks are 30 degrees, and the optimum range for total WOT advance, which is the sum of initial and maximum centrifugal is 36-40, as high in that range as the engine will tolerate without detonation.

The OE spark advance maps including initial timing recommendation are set up very conservative for reasons I explained in my 2012 San Diego National Convention Tuning Seminar.

Duke

[Duke W.]

Re: 110 Leaded Octane fuel

"Flame speed" is measured in the laboratory by igniting a quiescent fuel-air mixture in and instrumented vessel of spherical or cylindrical geometry, and for a wide range of hydrocarbon fuels there is not much difference.

But combustion in an operating engine is different because at the ignition point the mixture is not quiescent. It's highly turbulent!

That's why in my 2012 San Diego National Convention tuning seminar I used the term "combustion propagation", which can be described as mass or mixture consumed per unit time.

The greater the turbulence the greater the rate of combustion propagation, and and the best power spark advance requirement gives a clue. The less it is the greater combustion chamber turbulence and the more thermally efficient the engine because it comes closer to the ideal of heat addition at constant volume.

An example is the Vortec heads that have best power WOT advance of about 32 degrees versus vintage Gen I heads that need about 38.

Duke

[Joe L.]

Re: 110 Leaded Octane fuel

High octane fuel doesn't "burn slower". I just has a higher autoignition temperature and longer ignition lag time. That's why in some cases it can tolerate more spark advance and maybe make a bit more power compared to pump gas, which may have marginal octane rating for the as-built CR.

Duke

Duke------


I think that "burns slower" is the term in the common vernacular for what you describe here.

[Michael W.]

Re: 110 Leaded Octane fuel

Duke------


I think that "burns slower" is the term in the common vernacular for what you describe here.

Joe-

To say that high octane fuel 'burns slower' is misleading and reinforces the myths surrounding detonation and how it is controlled.

[Duke W.]

Re: 110 Leaded Octane fuel

Duke------


I think that "burns slower" is the term in the common vernacular for what you describe here.

It may be a commonly used among those that don't have a solid foundation in what the scientific and engineering communities understand about fuels and combustion, and to reinforce what Michael said, it grossly misrepresents the involved chemistry and physics.

Understanding autoignition temperature and ignition lag time is not that complicated.

Duke

[Joe L.]

Re: 110 Leaded Octane fuel

It may be a commonly used among those that don't have a solid foundation in what the scientific and engineering communities understand about fuels and combustion, and to reinforce what Michael said, it grossly misrepresents the involved chemistry and physics.

Understanding autoignition temperature and ignition lag time is not that complicated.

Duke

Duke and Mike------


There are LOTS of terms in the common vernacular which are mis-characterizations of what they are intended to describe.

[Domenic T.]

Re: 110 Leaded Octane fuel

I think we all understand each other now and it is a choice of words and different ways it was tested many years ago. The test that I was taught that I mentioned in this ongoing misunderstanding was the 2 long glass tube test that had a small measured amount of high octane in one tube and low octane in another, both lit off one spark plug. The low octane popped the test device first. A layman would see that as slower vs faster. The WWII guys at our Museum will talk about the 145 octane that the 1500 RPM engines had to use to stop detonation. also the fact that it would burn the exhaust valves when it was used in their jeeps. That came from WWII mechanics and crew men. In long Beach City College, the class instructor said the jeep valves burned the valves because it was not completely done burning as it was exiting the exhaust valve under power. I was chosen to teach the power plant class but declined because of the split hours and the year long schedule.
With all due respect to all the experts in the posts here, I think it is the way, and how we look at the way octane was explained and tested. 50 years ago when I was educated in the effects of low VS high the rules were strict and there were 4 choices of octane each with one more letter in the color starting with Red=3, blue= 4, green = 5 and purple = 6 being the highest. Any 2 mixed could be detected because mixing would cause them to turn clear and loose all color. The requirements went both ways, you were not to use a higher octane than required or a lower . There were a few exceptions with limitations. Because of my respect for the people that designed, tested, and wrote the fuel requirments of operation for all gas engine, I sometimes feel that their teachings are discounted. Driving one of these high compression cars is a privilege that we have to now pay for if we want it to operate as designed.

Dom

[Michael W.]

Re: 110 Leaded Octane fuel

I think we all understand each other now and it is a choice of words and different ways it was tested many years ago.

No, we do not understand each other. You wish to believe that high octane gasoline burns slower than low octane despite multiple posts over the years attempting to set the record straight. No one in this discussion agrees with this viewpoint. I have posted probably a half dozen links from various qualified sources which provided plenty of factual information. These appear to have been ignored or dismissed.

[Domenic T.]

Re: 110 Leaded Octane fuel

Joe,
Thanks,
That's what I was trying to say.

Dom

[Domenic T.]

Re: 110 Leaded Octane fuel

Michael,
READ! What was said before you dissagree what anything I say.

[Gene M.]

Re: 110 Leaded Octane fuel

Trying to stay with the topic, I'm assuming the original poster is referring to aviation fuel since he refers to 110 octane but says nothing about aviation. May be not. We have Sunoco blue 100 octane aviation fuel near by. Is not aviation fuel a longer shelf life compared to pump gas?

[Michael W.]

Re: 110 Leaded Octane fuel

Joe,
Thanks,
That's what I was trying to say.

Dom

If you're referring to any sort of words that infer that it 'burns slower', this is categorically incorrect. To think that this is true demonstrates a complete misunderstanding of detonation.

Let's for a second assume that your ides was correct- how would slower burning fuel avoid a detonation event?

[Domenic T.]

Re: 110 Leaded Octane fuel

It would stop the detonation/pinging when using the correct timing, and it was agreed that the higher octane starts it's burn later than the lower.

Example: 2 are drag racing. one starts slower, and one starts faster. The faster reaches the end first and has a faster time.

[Domenic T.]

Re: 110 Leaded Octane fuel

Lawrence,
Sorry for getting off the original question. I find that you need to mix the high with the low, my high compression engines seem to run the best that way. The only caution on running it straight is the exhaust valve if the octane is higher than recomended under high power for long lengths of time. Also will build up high cylinder head temps. At a machinest seminar the recomend lead for the first few hundred miles to impregnate the lead in the valve seats. I rebuild with stainless steel valves (intake & exhause). just to be safe, but it's not necessary.
If I use factory spechs all my engines ping. They will diesel on shut down (using 91). It stops when I add the higher octane at about 50/50 and has much more power. I found that water injection allowed me to use pump gas and I could tell when the water tank ran out as the car started pinging. Water injection required drilling a hole in the air cleaner and mounting the vacume/RPM regulater along with the water tank. The water was regulated with 2 ways, 1 low vacume would start the spray and 2, RPM also would start the spray. About 1 gal per tank is what was normal. Edelbrock made the one I used. Worked great since the late 70's. Most that do not believe have never tried 110 octane as a mix or tried water. I tried the ping under power with a low time 427 /425 and broke a piston skirt on shut down when the engine dieseled. It was a automatic and the only was to shut it down after it was ran for a while was to turn the A/C on, lights, and turn the key to off with it in low.

Dom