EGR:

[Stewart G Griffin]

Can you tell me everything you know about EGR?

Can you run with out it?   What's your though on this?

i've read that it helps cool the exhaust valves and helps them last longer.  My theory is that they were designed to take that kind of heat and if it's not hot enough to melt them, and it isn't, then it's ok?

[VileZambonie]

I'm not going to write a book about EGR as you can read the text books for that but EGR (Exhaust Gas Recirculation) is designed to help reduce oxides of nitrogen. It was never designed or conceptualized to provide added engine performance enhancements hence why hot rodders tend to omit these systems. The EGR system helps reduce the production of NOx gasses by lowering combustion temperatures safely below the threshold of the production of NOx gasses. Pollutant Oxides of Nitrogen are produced when combustion temperatures exceed 2500°F. By adding a small amount of inert gas (EGR) back into the combustion chamber during certain modes of operation it can effectively reduce NOx production. Think of it like this, a non-combustible inert gas does not accelerate combustion temperature and pressure and in many ways is kind of like a small dose of fire extinguisher. As engine's age and suffer from lack of maintenance, carbon build up, excessive wear, incorrect A/F ratio's etc can all lead to abnormal combustion temperatures. If an engine is experiencing detonation or pre-ignition the NOx levels will soar through the roof. EGR can help reduce this but think about it, is it fixing the symptom or the problem? When building or designing an engine for maximum performance you need to be cognizant of compression ratios, maximizing ignition timing etc while aiming for good complete combustion utilizing a fuel that is readily available and within your price range. This is why many auto manufacturers have enhanced engine designs that do not utilize EGR. Many manufacturers have used it as a simple fix to their problem and as emissions standards increased the three way catalyst was introduced. So there are many reasons one manufacturer vs another uses EGR in certain platforms but ultimately if the design characteristics of the engine and the tuning produces unacceptable levels of NOx they will most likely be equipped with EGR.

One more thing, EGR is only used during modes of operation where engine load and driver demand are low, at least in modern systems which are controlled by the PCM. Earlier designs used hokey thermostatic vacuum switches and controlled vacuum ports ie these trucks.

[78BIG-TEN]

Yep Vile nailed it,just about sums it up

[bake74]

     Vile answered your question without really answering your question.    You can eliminate the EGR system if you keep your engine running properly, otherwise it can hurt your performance.

[Stewart G Griffin]

Well, my main concern is that i've heard that EGR helps the exhaust valves last longer (supposedly)  because they cool the combustion temp a little?

[78BIG-TEN]

EGR will reduce cylinder temps like Vile said thereby reducing chance of detonation.Detonation can beat the heck out of valves  and seats as well as pistons and actually kind of tulip the valves.If eliminating egr be mindful of detonation and adjust timing and mixtures to help stop it. 

Back in the early 70,s when this came about we were told no detonation,a few years later were told that slight detonation is ok.Personally I don't want any.I have seen pistons burned all the through the oil ring land in extreme cases.

My 78 was bad about it and all it took was to take a little timing out,and it came without egr.245,000 miles later it still ran great with excetion of power being down a little,but that should be expected with that kind of mileage.Only reason I took it apart was it was no longer a work truck and I wanted to do a full restoration

[Sock]

I live in canada and ive reduced some of my vacuum lines. mainly getting rid of some EGR vacuum sources. now when its cold and i try and give it some gas while its in gear it bogs down and dies...is it because the heat riser isn't warm enough to open yet? i have vacuum to that pot where the heatriser is but not sure why its doing this. 86 c10 305.

Sorry if i kinda hijacked this thread but would rather ask here than make a new topic

[VileZambonie]

You need to start a new thread....

[Stewart G Griffin]

Ok, i've gotten to the point where i can take the valve off or leave it on.  i'm wanting to take it off for easier access to the carb.   This is on the "new" 4.3 that i'm going to be using and i'll post a picture soon.  (the egr valve in this case is right in front of the carb and slightly below it.  This is the factory "hi-rise" manifold)

i don't have a problem with egr and what it does, i just think it would be nice to have less clutter.

Would maybe switching to a 180 degree thermostat make these detonation concerns less likely?