I hope your parents did not pay much for your education, you must have been learning about long-chain hydrocarbons the day English 101 covered why you cannot start a sentence with the word however.

Example:

The Petronas Towers each have 88 floors, there was going to be one more, however, that's another story.

 

Yesterday I culdnt spell Enjuneer, today I are one.

 

"By now the muffler on the mower was glowing bright red and the fairing above it was melting. The motor no longer needed a spark plug to run. It was pulling in enough fuel (Hexane) through the carb to keep on going. With the rubber boot on the spark plug catching fire he finally put the mower blade down across a 4" x 4" fence post and it killed the motor.

Later that week he took it in to the small engine shop and they dissected the mower. The cylnder head had started to slump and melt. The valves were charred and the rings were fused to the cylnder walls.".............

 

While I agree with the majority of what you've said here, this statement is false.

Pre-ignition and detonation are not the same thing. Yes, Pre-igntion does occur when the mixture ignites before the spark plug fires. Pre-ignition is caused by a hot spot in the combustion chamber (spark plug thread, carbon deposit, etc) and increasing the octane rating isn't what you need to fix it. Pre-ignition can lead to detonation, just like advancing the timing too far can, but detonation is seperate phenomenon.

Detonation occurs when the mixture in the cylinder auto-ignites. It usually occurs AFTER the plug fires. Under normal combustion, there is a flame front that moves through the cylinder and burns the mixture. When the mixture detonates, it explodes, BOOM, rather than burns. This explosion creates a shock wave inside the cylinder. The knock you hear is this shock wave bouncing around. It isn't two flame fronts colliding. If this were true, dual plug heads would be a disaster.

To address a popular myth, higher octane gas does not control detonation by burning slower. It controls detonation by resisting auto ignition longer under high temp and pressure. At a given temp/pressure, there is a limited amount of time before the mixture explodes on it's own, with no ignition source. If you can burn the mixture normally before this time expires, great. If you can't, it detonates. Higher octane gas gives the mixture more time to burn before it detonates. If you do something to make the mixture burn slower, detonation will get worse, not better.

To whoever was asking if (piston) airplane engines were the same as car engines. No they aren't. Auto engines are more high tech! But seriously, there is no magic in an airplane engine - the same principles apply.

 

Just like all of you other posts, this one is also irrelevent. Your grammar education is as bad as your science. Since you insist on being an A$$HOLE, here are some more reference sites for you to read. These are in addition to the ones posted earlier on the subject of gasoline.

BTW, my parents did pay quite a lot for my education (thanks mom and dad) for which I am eternally grateful.

http://www.bartleby.com/64/C001/032.html
http://www.dianahacker.com/rules/sub...e/however.html
http://www.stpt.usf.edu/pms/semicolon.html (a few paragraphs down)

 

You are correct in that pre-ignition and detonation are two different phenomena. However, they are so closely related that it is almost impossible for non-experts to distinguish them apart. The biggest difference between the two is that detonation often occurs after the spark plug fires. Pre-ignition by definition only occurs before the plug fires. There are other slight differences as well but in an effort to simplify things for moviela, I opted to lump them together.

You are wrong about the origin of the sound. It is definately caused by the collision of the 2 flame fronts. I'm sure the pistons banging around uncontrollably add to the clatter! Dual plug engines have specific combustion chamber designs that prevent this from happening.

The point about airplane engines is right on! They are extremely primative compared to their modern automotive counterparts. While some airplanes can use automotive fuel (with proper approvals and certifications), post 1970 era autombiles cannot use airplane fuel. Even pre 1970's automobiles don't run very well on AVGAS due to different vapor pressures, boiling points, etc. but all that lead sure does make the valves in my 1966 327/350HP Corvette happy!

 

Hmm... I'm still not buying this. Second plugs are added to existing heads relatively often, I find it hard to believe they coincidently have the correct chamber design for this. I also find it hard to believe that there is a design out there that can keep multiple flame fronts from crashing into each other. And finally I'm not grasping how two flame fronts create a pressure spike when they meet each other? Or why this would be different than two parts of the same flame front meeting? Certainly this happens with all the tumble and swirl that gets designed into the intake flow?

BUT.. it doesn't really matter in the scope of this post, so, I'll agree to disagree. I guess I'll have to find another way to avoid doing any real work this afternoon. :p

 

Pressure has to be greatest when the 2 expanding fronts meet or when the single front reaches the other side of the chamber. Pressure continues to increase until there is nothing left for the combustion process to consume. This assumes the piston's descent hasn't already had an impact on the process. Yes, every combustion chamber design has a pressure spike at a certain point in the process. The difference is that it is at a known point and magnatude. With pre-ignition or detonation, the spike occurs at the wrong time.

For years (I'm a relatively old guy here) it was generally accepted that the sound was from the 2 flame fronts colliding. After reading your post again, I did some more reading tonight and see that more and more people are hearing it differently as you do. It appears that current thinking is that the pressure spike is greatest when the 2 fronts collide but that is merely a coincidence and not the actual cause.

Thanks for the correction.
Greg

 

Society also benifits from your parents' funding of your education. Persons of high intellect, when educated, often contribute more to the world than they consume. Kudos to Mom and Dad.

You citations, however, are from woodpeckers who think they are carpenters. One even mentions "Elements of Style" and attempts to marginalize it. That work along with "The AP Style Book" sit on the desk of every serious journalist, and many editors in the English speaking world.

Now for a question I have wondered about, Octane listed on the pump in California is mostly 87, 89, and 91. Other states it can be listed as high as 94 in the majority of stations. Is that California 91 octane the same fuel as the 94 in other states?

 

Absolutely. Everyone gains from education.

The citations were from a google and only to quickly prove my point. I don't have any of my prep school grammar books at hand but I can assure you that more professors allow the use of the word at the beginning of a sentence. You either are very old or were taught by someone who was. I was in HS back in the 70's. My daughter's curent HS (college prep) grammar book does not forbid it either. Oh. well....

California fuel at any octane is not like any other state due to the increased amount of oxygenates out fair state has mandated. The other states get higher octane ratings.

 

I thought the purpose of using a fuel cleaner/additive (Techron for example) periodically was to avoid having the fuel injectors cleaned (typically every 60,000 miles).

Feel free to correct this. Are some people saying that high octane gas is good enough to avoid cleaning the fuel injectors? What are tell-tale signs of needing to clean the fuel injectors?

If you don't use a fuel additive, how often are you supposed to clean the fuel injectors for a 2005 C240 4MATIC. This is not addressed in the maintenance manual...

Opinions? Advice?

Thank you.

 

You are correct about cleaning aditives but they are completely different from octane boosters. I beleive that it is generally accepted that top tier gasoline manufacturer/retailers have enough detergents in their fuels to reduce the need for further cleaning additives.

Tell tale signs? Lower performance and economy but many other things can cause these symptoms as well.

My $.02 is run Shell, Chevron, etc and not worry about it.

 

AMEN! i was about to throw up reading his comments.. he actually thinks he knows a ton about it all!! haha