Ok this might get confusing. Tech specialist requested.

So, I can understand how an EGR valve can sometimes be a good thing for limiting NOx. Especially for motors designed to run HOT anyway. Running an engine hotter is, in a way, making up for less compression. Because with a high compression motor. The compression is supposed to heat up the air and gas in the combustion chamber for the optimal heat range for maximum horsepower and fuel economy with a cold air intake I hope. With lower compression, everything else needs more heat to act in the same manner and get the best of both worlds. Sure a cold air intake on a low compression motor can give you more power for a few reasons but the main topic here is EGR. The main purpose of EGR is to cool down the combustion chamber. And on the way is where the problems seem to be.

Problem 1, I'm sure its virtually impossible for early computers or a vacuum line to guess at how hot the actual combustion chamber is for a proper cooling affect. For proof that one of my engines wasn't running hot enough for optimal performance in the chamber. I actually made a hot air intake close to the exhaust manifold. The intake air temp increased dramatically and I had no loss of power and my fuel mileage went up from 17 to 19. Maybe that means there is a flaw somewhere. But i doubt it.

Problem 2, Exhaust gas takes up unusable space in the combustion chamber. Less fuel economy when its not needed? On the EGR tech board i seen a section describing that for certain engines, the EGR needs to be open at full throttle and high rpm so that the computer can advance the timing and not have to worry about the chamber getting too hot and misfiring. That may be true, however, most of the vehicles close EGR at full throttle and idle, correct? Why is this? Because it takes away from horsepower with unusable exhaust in the chamber? That's what I would say. So why open it at partial throttle unless the combustion is actually getting too hot.

Problem 3 and last, Carbon buildup. I am sure we have all seen intake plenums and runners or ports bombed with carbon buildup, that cant be good. Regardless of how clean the intake ports are, the more carbon and exhaust that gets sucked into the combustion chamber can get past the rings with blow by and crap. Which then can hurt the oil and cause an increased amount of engine damage. As if running some 3rd gens so hot, wasn't doing enough damage as it is...



Anyway, have at it.
Thanks.

 

Well heck...I'l give it a go

You've misunderstood a few things ni your readings.

EGR is Exhaust Gar Re circulation...

Where Exhaust gasses are reintroduced into the intake, then into the combustion chambers.

Now...the intent of EGR is NOT to cool things down, but that's a good welcomed side effect that allows more timing at cruise, and part throttle and we are driving,

There is no "unusable space" in the CC...what you put in, is added to what is drawn in...think of Nitrous,,,,it's floed in and makes a bigger boom...takaing up un needed space?...naw., just adding to the mix.

Now carbon and exhaust don't get sucked into the combustion chamber...carbon and exhaust are by products of the combustion process...piston go up, gas an sir air in the chamber, spark goes off...boom...explosion occurs, carbon occurs, and hopefully most of the exhasy goes out the heads, and back end of the car.

With or without EGR...same stuff gonna happen.

FFS, get over the typo's...it's late and the Giants won

 

Yep, I probably didn't exactly read or remember everything in the right context.

And adding to the story. For years and years I was told that the main goal of EGR valves is to recirculate some of the unburnt fuel from the exhaust for better MPG's. Even by an ex 20 year veteran GM mechanic. Implementing, that was the main goal. Then find out years later the goal is to reduce Oxides of Nitrogen (NOx) or in other words, SMOG.

-"Now...the intent of EGR is NOT to cool things down, but that's a good welcomed side effect that allows more timing at cruise, and part throttle and we are driving,"

What is the main intent of EGR?

-"Now carbon and exhaust don't get sucked into the combustion chamber...carbon and exhaust are by products of the combustion process...piston go up, gas an sir air in the chamber, spark goes off...boom...explosion occurs, carbon occurs, and hopefully most of the exhasy goes out the heads, and back end of the car."

What is EGR allowing to be recirculated?

And how is the carbon buildup occurring in the intake if EGR doesn't allow it?


I can't find an EGR technical article anymore for some reason.....

 

The main intent of EGR is just that, to recirculate some amount of exhaust into the intake to be burnt again...yes, to reduce smog.

The carbon build up you see in the intake passage is from the combustion process that goes into the exhaust, the EGR opens and then the portion of exhaust is pulled into the intake...I think I may have mis read what you had posted, but in effect, yes it is (via EGR) sucked back into the engine.

 

Exhaust gas does not "burn again". By recycling exhaust gas, it displaces fresh intake (oxygen and fuel), so there is less new air/fuel to burn. The extra heat of the exhaust gases also reduces density, as another factor displacing fresh air/fuel. This lowers peak combustion temperature and pressure, thereby reducing NOx / smog.

This mixture, with less peak potential, can use more timing during EGR use.

Since this is "exhaust" that came from the combustion chamber, EGR does not cause carbon build up in the chamber. But, since it is hot and "dirty", it will cause some build up in the "clean" intake.

 

Well, this is a bit late. Thanks for the input here.

Along with another thread I read somewhere, it seems like in the long run. With EGR or not. The engine as a whole needs to be tuned and set up for each scenario. Either way we can come out pretty good. Hard to be perfect.