Just got home from Performance Solutions :)

[phenix]

Awesome zach!

I couldnt agree more though with you on performance solutions. Dan and Devan know there shit and i honestly feel like they car about my car and arent just going to hack away like 99.9% of the other shops here in az.

Cant wait until my car comes back to me with that 5spd. Today!

-Aaron

[evil04cobra]

The benefits of anti-seize are really two fold, and especially beneficial to an application with four threads in the cylinder heads. Primarily, it is the function of anti-seize to prevent gavanic corrosion or galvanic galling of disimilar metallic components held in close tolerance. However, anti-seize has been proven to work very well as a heat-sink compound where the heat from the plug can be more easily transferred to the cylinder head and cooling passages. Since 4 thread heads do provide limited heat transfer, increasing the capabilty of heat transfer in this application is beneficial to say the least.

Cheers,

PARKER

[Lucafu1]

ok a/s owns all =)

i dont use it cause my plugs come out ever 1k miles. but i do know the benifits to it, and stopping corrosion is the best one.

[Lucafu1]

oh yeah i just thought i would add this. on the engines i used to work on we would have to use a/s on the igniter plugs but no one ever did. and every 50 acft hours they would have to be pulled. no one ever had a problem. and those suckers get hot. on average they run at say 800*C (not *F). if you do the genaric conversion it would be to double it and add 32 you get over 1600*F, now thats some heat.

=)

[evil04cobra]

That is hot, but at 14.7:1 A/F ratio, combustion chamber temperatures hover around 2500 degrees Farenheit.

[Lucafu1]

That is hot, but at 14.7:1 A/F ratio, combustion chamber temperatures hover around 2500 degrees Farenheit.

how is this possible?

aluminum has a melting point of 1217*F
mild steel 2462-2786*F
4130 steel (our rods are made of this i believe) 2550*F

if your statement is correct then we are in a world of hurt.
i could be missing something because i dont know a whole lot on engine temps, combustion, and anti sieze.

Luis

[Lucafu1]

i just did some google research and it said it can even reach 1500*C

yeah thats hot. but i guess only for short periods of time and it is controlled. crazy how close they bring it to the material tolerances.

so now i wonder what is the average cylinder temps of an engine?

because what i was talking about on the other one is a constant and only gets hotter (another 200*c hotter).:)

anyways thanks for the info evil

[evil04cobra]

Kind of like the example of asking what the combustion point of a paper dixie cup is. It is easily achieved with a bic lighter, until you fill the cup with water.

Let's examine the process and dynamics involved from the moment that we open the intake valve. With the piston moving down the bore, cylinder volume increases, cylinder pressure decreases, allowing the higher pressure in the intake tract to push the fuel/air mixture into the cylinder. As the piston starts back up and the intake valve closes, cylinder volume decreases and cylinder pressure increases.

When the crankshaft reaches about 30 degrees before top dead center, the spark jumps the gap between the plug electrodes. The purpose of the spark is to raise the temperature of a very small portion of the fuel/air mixture above its ignition temperature. This is the point where true combustion begins. As the exothermic reaction starts, the mixture directly adjacent to the spark plug is also ignited and the process rapidly progresses out from the plug in a roughly spherical shape.

At about 20 degrees BTDC, the rate of heat release causes the cylinder pressure to rise above the compression line which is what the cylinder pressure would be at a given piston position without ignition. Notice that it has taken 10 degrees of crank rotation to generate this pressure level. This is known as the ignition-delay period.

The rate of pressure rise is a function of the rate of energy release vs. the rate of change of combustion space or cylinder volume. The rate of energy release is directly related to the flame propagation rate and the area of reacting surface. Flame speed is dependant on fuel/air ratio, charge density, charge homogeny, fuel characteristics, charge turbulence and reaction with inert gasses and the metal combustion chamber, cylinder walls, and piston.

In technical terms, the pressure rise is referred to as flagregation. No two combustion cycles progress at the same rate or at a uniform rate. Some start slow and end slow. Some start slow and end fast. Some start fast and slow down. Generally, only the ones that end too fast will lead to knocking as the rapid pressure rise may happen too soon with the cylinder volume still decreasing or not increasing fast enough. Usually, not all cylinders will knock at the same time or on the same cycle because of this.


By the time the crank is at about 5 degrees ATDC, the cylinder pressure is about double that of the compression line. From this point to roughly 15 degrees ATDC the combustion process is very rapid due to the increasing area of inflamed mixture and the high rate of energy release. The peak cylinder pressure (PCP) occurs between 10 and 20 degrees ATDC on most engines and the combustion process is complete by 20 to 25 degrees ATDC. The peak temperature within the combustion gasses will reach somewhere around 5000 degrees Fahrenheit and pressures may be anywhere from 300 to 2500psi depending on the engine.

Obviously it is very important to have the crankpin at an advantageous angle before maximum cylinder pressure is achieved in order that maximum force is applied through the piston and rod to the crankshaft. If the mixture was ignited too early, much of the force would simply try to compress the piston, rod and crank without performing any useful work. In a worst case scenario, the cylinder pressure would be rapidly rising before the piston reached TDC which would have the cylinder volume decreasing at the same time. This will often result in knock or detonation which is counterproductive to maximum power and engine life.

Detonation or knock is defined as a form of combustion which involves too rapid a rate of energy release producing excessive temperatures and pressures, adversely affecting the conversion of chemical energy into useful work.

[Lucafu1]

did you right that?
if so you smart. if not your smart for finding it or all ready knowing about it. i hope one day i can be that smart.

and if you think im being a smart ass............im not.:)

[evil04cobra]

I helped write it. It was put together for one of the AETC conferences in Colorado Springs with an engineering professor at Mississippi State University. The AETC conferences are in Orlando now, so at least it's not as cold. The paper has been plagarized and borrowed over the years, but that's OK, I can always find a copy by googling "flagregation". :???:

Here's a link to the AETC www.aetconline.com