What type of equipment and data do you use? I use ppm's ("pings" per minute) to determine my performance

 

i just write down preformance note, like sounds, noticable power differences, weather, time, area drove, time of run, and miles.

 

I have to dispute you on this statement. When thermal energy is transferred to air, the air molecules become excited and increase movement, causing them to spread further apart, thus reducing air density. Cold air is much more dense than warm air, which is why cold air intakes are used to increase performance. And engine runs at almost the same temperature no matter what the ambient temp, and though combustion chamber temps do fluctuate some with ambient temps, it is not nearly as much as the ambient temp it's self. If 95 degree air is taken in, since it is less dense it will expand less as it reaches combustion temp than 30 degree air will. Plus more dense air pulled into the same cavity, means there are more molecules in the same area, if at a given temperature the "space" between molecules is always the same, more molecules means MUCH more expansion.

I also have to argue with your statement that too much oxygen present in the combusiton chamber will hinder performance. Although in highly concentrated amounts it will reduce performance as you say by increasing the volatility of the fuel vapor present causing pre-detonation, more air in no way means more oxygen relatively speaking. The air we breath is a mixture of gasses, in constant proportion, more air in a given space simply produces pressure, the proportion of the mixture of gasses remains the same. Cooler air performs more efficiently as long as the air/fuel ratio is adjusted correctly, which "theoretically" a fuel injected vehichle should do on it's own...

 

What I said is correct and still agrees with what you are saying. When I say "theoretically", I mean an ideal heat engine in the case of the second law of thermodynamics. I also go on to say that no REAL engine runs theoretically. Sorry, I shouldve clarified.

For your second arguement...I never said anything about more air going into the combustion chamber. I only spoke about O2 (Oxygen). And yes, you are right on your air analysis, mostly. You did forget to account for the EGR system which introduces exhaust gases pre-combustion which contain almost zero oxygen, so the proportion of mixture gases does not remain the same. Basically all I was saying is that the more air you squeeze into the chamber, the more 02 that is present, although yes, in the same proportion as you mentioned. Since you squeeze more air into the chamber, you now not only have more useable oxygen to burn, but also a fuel-air mixture with a high pressure with a corresponding higher temperature(assuming the air acts as an ideal gas: PV=mRT). This does two things which can combine to form problems. First, more usable O2 means a higher combustion temperature which produces a hotter exhaust valve (usually the component in the combustion chamber with the highest temp). Second, since you squeezed more air in, it will give a higher compression ratio and make the fuel air mixture more likely to auto ignite, especially near the hotter exhaust valve. Alot of these problems can be solved with proper EGR and an intercooler used on tubro applications that cools the initial mixture.

But dont quote me word for word on this. Its been a couple years since I took the class. Check out a book or two on IC engines and prepare to do some head scratchin.

 

All I know fellow's, is on a hot humid day, my vehicles feel kinda sluggish, compared to a cool crisp day, they feel peppier. I knew some of you rocket scientist would give us the scoop on why that is, Thanks guys !!

 

Thats usually how it is. It depends alot on the particular engine though. My 3.0 has pinging problems under high loads and so anything that can make it run cooler (high humidity and cool temps) helps. Other engines which run like the factory built them to really come to life on cool, low humidity days.

 

I guess in many ways we are arguing semantics, not science. I think I see the point you are trying to make, that although more dense air (cooler air) will potentially produce more power, it can't produce the full extent of that potential since power is robbed by pre-detonation. My real argument was with the statement you made about an engine producing more power from warm air which contains more energy, since an engine's job is to transfer thermal energy to air and harness the expansion it causes thus the less energy air contains initially the more effective that process is...

 

Right, like I said, that statement is from Thermodynamics. It only holds true in a true Carnot engine. However, Carnot engines are only possible in theory and have never been produced.

"The conceptual value of the Carnot cycle is that it establishes the maximum possible efficiency for an engine cycle operating between TH and TC. It is not a practical engine cycle because the heat transfer into the engine in the isothermal process is too slow to be of practical value. As Schroeder puts it "So don't bother installing a Carnot engine in your car; while it would increase your gas mileage, you would be passed on the highway by pedestrians.""

http://hyperphysics.phy-astr.gsu.edu...mo/carnot.html

 

Well, i'm not installing any Carnot Engine in my truck anytime soon. That Just tell me that my sytem is getting screwed up in the weater(the electronics atleast). Thanks for the help.


BTW: this was turning into another argument post. lol