I was under the impression that Ford started using PCV valves in 1968. I agree that they aren't really a smog item but for some reason my Chilton's includes it in the emissions section in one of my books...strange.

 

You are correct, it doesn't increase power. It prevents preignition and the formation of NOX. The formation of NOX robs power (it uses up available oxygen and absorbs heat). So rather, it is preventing power loss. The formation of NOX does take away oxygen. This is not a theoretic problem, this is a very real problem and is part of the reason emission controls have proven to be so difficult to implement. The efficiency of a catalyst is dependant upon breaking down the NOX so the oxygen contained in it can be used to break down HC and CO. It is a very real problem. Most race tuners combat this problem with extra fuel under WOT and vehicle computers do it automatically for you.

This would be true if NOX formation wasn't a limiter of power potential. The EGR valve is a compromise. At WOT the EGR isn't opened because yes you want maximum power and emissions are not top priority under those conditions either, so the vehicle injects extra fuel to accomplish the same thing that the EGR valve would do. The EGR valve is helpful under light throttle conditions, and allows a great timing advance without wasting fuel to cool the engine down.

Nothing is perfect, and from a performance standpoint, an EGR is not very useful, but in a world where emissions and fuel economy are important, the EGR is beneficial.

Not to pick anything apart, but you are correct. More heat does equal more work right up to the point where NOX starts forming in excessive amounts. If atmospheric nitrogen could be removed from the equation, then you could get even more power. Also NOX is considered to be a harmful gas, it is acidic when it mixes with water, it burns mucous membranes, can cause or aggravate allergic reactions, and is responsible for most of the visible smog. (It reacts with other compounds in the air and with ozone and sunlight)

Better methods are being developed for controlling NOX emissions while increaseing combustion temperatures and fuel efficiency. Some of these new technologies are already available on some 2007 and 2008 model year vehicles, and are also coming into effect on 2007 and newer diesel vehicles (these new technolgies are less effective on diesel engines than in gasoline applications)

 

From what source are you quoting this? jd

 

Largely from a book titled "Catalytic Converter Theory, Operation, and Testing". I did not quote it exactly, but the book contains the graphs charts, formulas, demonstrates the chemical reactions that take place, and show the relationship between temperature and combustion efficiency.

The main reason race tuners don't care about using EGR to maximize the use of the fuel, is because fuel economy and emissions are not one of their primary concerns. They use a richer mixture instead, which accomplishes the same effect, but without reducing the volumetric efficiency. They also use high octane race fuel. The higher octane fuels do combat NOX formation by preventing ignition from the shockwave and ensuring the fuel in the cylinder only ignites from the flame front.

 

on the EGR issue, I think under the partial throttle condition it in practice does increase power by allowing more timing advance to be run by the computer. The inert gas keeps the mixture burning cooler (and a little less explosively); without it, the mixture gets hotter, detonation (knock) would happen, and the computer would dial-back the timing advance.

 

NOx is a byproduct of combustion, not a hindrance to it. Max power output (and maximum combustion temperature and pressure) is achieved with a slightly rich mixture, not because NOx is "taking away oxygen from combustion." If that were happening and there was less oxygen available for combustion, wouldn't that require less fuel rather than more? EGR is simply an emissions control device used to lower peak combustion temperatures, thereby reducing NOx emissions and nothing more. I'll re-read my IC engines books just to double check, and post back later on.