About rich fuel mixtures - EXCELLENT web site

[TeamGeek6]

Heres an excellent web site that explains one of the biggest Old Wives Tales in automotive - why rich fuel mixtures do not cool engines and are a waste of time and money:

http://www.innovatemotorsports.com/resources/rich.php


Excerpt:

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"Optimum mix with “later” ignition :naughty: :naughty: :naughty: :naughty:
can produce more power because more energy is released from the combustion of gasoline. Here’s why: When hydrocarbons like gasoline combust, the burn process actually happens in multiple stages. First the gasoline molecules are broken up into hydrogen and carbon. The hydrogen combines with oxygen from the air to form H2O (water) and the carbon molecules form CO. This process happens very fast at the front edge of the flame front. The second stage converts CO to CO2. This process is relatively slow and requires water molecules (from the first stage) for completion. If there is no more oxygen available (most of it consumed in the first stage), the second stage can't happen.

But about 2/3 of the energy released from the burning of the carbon is released in the second stage.

[[Did you catch that...??? This is why the typical poorly tuned over jetted engine has a cylinder and spark plug covered with black carbon deposits, its fuel that didnt have any air to burn]] ;)


Therefore a richer mixture releases less energy, lowering peak pressures and temperatures, and produces less power[/*]. A secondary side effect is of course also a lowering of knock probability. It's like closing the throttle a little. A typical engine does not knock when running on part throttle because less energy and therefore lower pressures and temperatures are in the cylinder.

This is why running overly-rich mixtures can not only increase fuel consumption, but also cost power."

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This nonsense of "rich mixtures" and "cooling because of slow burning" that is posted on this BBS violates every law of Physics in the books.

[Dammit!]

I don't recall anyone saying a overly rich mixture "cools" the engine. What has been said is that an overly lean mixture will fry your top end (and it will).

[TeamGeek6]

Yes, understood. The thing about excess fuel is a general belief that in the end, washes lubricating oil off rings and cooks cylinder walls. They "they" wonder why theyre changing piston rings every two or 3 races...

Im running overly lean mixtures and NOT frying the top end, in fact, the leaner it goes the colder it runs. I can start it, let it go to full hot idle temp and lay my hand on the head.

240*F on the pipe and 110* on the side of the head on full hot idle
400 - 500*F on the pipe and 190*F side of head after several full throttle runs.

Lean = hot is the same kind of fantasy thats based on trying to explain an observation (I leaned the engine out and the top end got hot) without any science. "Cause and Effect" is not that simple.

It is physically impossible to burn less quantity of gasoline or any fuel per time and produce more heat. That violates the whole Physics book at once.

The reason(s) it looks like a lean mixture burns cylinders up is:

1.) Too far advanced timing, run lean with advanced timing and too much of the fuel is burned before TDC (negative work) where it does nothing but make heat. That leads to detonation then melted pistons. Burning the charge too early burns oil off the cylinder walls and rings and the friction sends the heat through the roof.

2.) Poor mixture formation and distribution because of a too -large main jet. Using alcohol jets (very large jets) ruins the mixture quality because it tends to spit out large drops of gasoline instead of a fine spray thats easy to burn.


If you's guys would give up on this insanity of "large jets" and learn how to tune properly you'd make enough power to scare the **** out of yourselves. :eek:

The article above states about a 2/3 increase in power IF the burn is correct. Just the opposite, y'all are losing 2/3 of the engine power you could have.

[OldSchoolin86]

Leaner is hotter. It's the combination of air and fuel that make the charge, not the fuel alone. Think of it like this, ever use an acetylene torch? The more you lean out the acetylene with oxygen, the hotter it gets.

[bigredhead]

Forcing gas thru a smaller jet will result in a finer mist of gas.. agreed.

More oil to compensate would mean sufficient lubrication.. oil does not compress as air does during the compression stroke so more oil would bump up the compression some... right ?

Introducing air somehow after ignition to help finish off the burn.. or delaying the spark just after TDC to create optimum burn should result in full or close to complete combustion of the given fuel would make for nice efficiency and a clean cylinder.

how's them statements ?

[Mr. Sandman]

This is why running overly-rich mixtures can not only increase fuel consumption, but also cost power." This nonsense of "rich mixtures" and "cooling because of slow burning" that is posted on this BBS violates every law of Physics in the books.

They "they" wonder why theyre changing piston rings every two or 3 races...If you's guys would give up on this insanity of "large jets" and learn how to tune properly you'd make enough power to scare the **** out of yourselves. :eek:
The article above states about a 2/3 increase in power IF the burn is correct. Just the opposite, y'all are losing 2/3 of the engine power you could have.
Geekster, geekster, geekster...you assume way to damn much!
You assume that 1/2 of everyone that's on this board is burning up pistons and top ends due to way too lean jetting and you assume that the other 1/2 is running way to rich, fouling plugs and not taking advantage of all available power.

While there are those that do have jetting, electrical, or a myriad of other problems, for the most part, their problems are/were solvable and remedied long before you started posting. There are also those here that are young, immature and still learning, and there are a bunch of others that have years & years of knowledge and real world experience.

You do sound like a very intelligent individual, but as long as you keep talking down to everyone on this board and coming across as an arrogant know it all, you will not get any respect or love here.

[Troll 2]

If you's guys would give up on this insanity of "large jets" and learn how to tune properly you'd make enough power to scare the **** out of yourselves. :eek:

The article above states about a 2/3 increase in power IF the burn is correct. Just the opposite, y'all are losing 2/3 of the engine power you could have.


No one here has said running too large of jets will make a engine run better.
Well as i've asked and said before. Are you running a a/f ratio leaner than optimum of 14.7-1 at cruise and richer under power? Why wont you answer a basic question?
Then, no were not loosing two third's of the engine power. Good greif, why would you think that. Wow................................ :rolleyes:

[Jason Hall]

Man all I can say is you are to smart for your own good. If you would leave your timing alone & jet your ride rite, there is no reason to even talk. I have never heard so much bull about timing, & tuning in my life. I have a .010 trx 250-r with a cr ignition & it is ported by me, with a 36mm pj carb It runs like the wind with a 170 main jet. I always run my needle lean, because I love the arm ripping mid range when you roll on the gas. As far as timing I just don't understand why you are making It so dificult & technical when its not even needed. The cr ignition is by far better rite from honda, most definatly better than what you are farming up. I just don't understand what you are gaining by talking all this smack about timing/tuning bring that ride to the closest 250-r you can find on this board & race it, then talk about your physics. A jet is always a jet, & what ever size works to make your ride run best is what you should run. You are trying to confuse every in-experianced tuner on this board. If i were you I would keep your physics in the book, & tune your ride by the seat of your pants, or by the clock. I wonder If this guy is trying to learn from us :wondering :crazy:

[Troll 2]

Im running overly lean mixtures and NOT frying the top end, in fact, the leaner it goes the colder it runs. I can start it, let it go to full hot idle temp and lay my hand on the head.

240*F on the pipe and 110* on the side of the head on full hot idle
400 - 500*F on the pipe and 190*F side of head after several full throttle runs.
.


You say your running "overly lean mixtures". Must be a/f ratio? What is it then if different than" Optimum AFR is 14.7:1"
I let my R idle for five minutes after running around a little. Outside air temp here was 80* when tested today. The side of the head was 127* @ idle, then 212* on the exaust flange on the head. Then I asume the nickel plating on my pipe was causing very low readings, so there n/a.
After four full on 1/4 mile runs threw all the gears. Temps read 156.5 on the side of the cyl. head, flange temp near the outlet at 256*.
Sounds like yours runs hot ........................ :beer
I ran a chassis dyno for sixteen years dialing in fuel and spark curves. I ran 1000's of horsepower tests, with oil temp probes, four gar analizers, and sun equitment scopes. http://mcgeesauto.com/
Just interested in how yours is set-up........................ :D

[KASEY]

seems you have all the answers ,,, ok i won't argue ,, stock 86 250r's produce 39 hp, thats directly from honda.. so if you say your super 3 year long tuning adds so much,,,, lets see a dyno report ,,something to actually back up the claim, arm ripping power means nothing to me i got it everytime i get on my trike,,, i would like to see something real to prove to me that if i spend the $200 your asking i get something more than soldered terminals......................................... ......................................... :) :)

[TimSr]

It is physically impossible to burn less quantity of gasoline or any fuel per time and produce more heat. That violates the whole Physics book at once.



Amusing thread!!!!!!!!! "Combustion" is a fancy word for "burn". If you burn something, and you want to know what more air in there does, just ask any kid who has ever built a campfire, and blown into the coals to get it going. Leaning out a combustion chamber to make it burn cooler makes about as much sense as putting a fan in front of your fire to make it less hot. Apparently chemistry geniuses are not designing fire fighting equipment, thank goodness!

Your statement is technically correct, though, if you understand what "rich" means in relation to a combustion engine. A "rich" condition is caused by supplying a combustion chamber with more fuel than it can burn. If your motor is too rich, you are not burning more fuel. You are blowing it out the exhaust, and leaving it all over the insides of the chamber, including your plug. Without all the techno mumbo jumbo nobody wants to hear, we do plug readings to see how much of the fuel we supply to the chamber is actually being burned, and how completely its being burned. We all know a nice dry, tan plug means fuel burned completely and left a carbon residue. Carbon, too, will burn if hot enough, which is why a white plug indicates it got a lot hotter than a tan one. When it gets hot enough to burn carbon, it also starts getting hot enough to burn off certain metals. If your cure for a chamber that burns metal off the piston is to increase the ratio of oxygen to fuel, you are doing exactly what OS described happens when you increase the oxygen to acetylene ratio on a cutting torch. Im glad it works for you, but others need to know that their results are likely to vary, and not for the better. Can running rich cool an enigine? Of course not. Combustion (burning) is the source of the heat, and will not cool anything. The more we increase the fuel to air (oxygen) ratio, the slower the fuel will burn, and the less heat it will generate, though. We increase air, and it burns faster and hotter. Same thing happens when we slow the burn rate by adding more oil to it. Less of it burns, and it generates less heat, resulting in what looks like a rich condition. Is cooler better? NO. Heat is energy. We want heat. This is why there are no benefits to runing more oil in your gas than you need to lubricate, and no benefits to running rich. You will generate the maximum amount of heat possible without melting the piston to achieve optimium performance. Why do we put so much effort into cooling an engine? We are getting rid of the heat with a cooling system, not preventing its generation. The more heat we can get rid of, the more we are then able to produce without melting anything important. The more fuel we can burn completely, the more power it will produce. Too much fuel reduces heat and power produced. Too little fuel, with too much oxygen usually produces even more power, but also more heat than your piston can stand up to.

I do agree that most machines are jetted way too high, and running way too rich, killing performance. I dont know who ever started the nonsense that every time you get new rubber grips, you have to jet richer, or that bigger jets are some kind of performance modification, but it seems to be a popular notion.