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The Hated EGR Valve Discussion......
- Thread starter Dragonbat13
- Start date
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DaveBonds
Garage Trash
Ditto.
Reason 1-
Carbon. I'm sort of surprised that nobody has mentioned this. Used exhaust gasses are chocked full of carbon, even with good AFR, because of the low percentage of efficiency that an internal combustion engine has. Don't think so? Take the catalytic converter off of your new car and see if it pulls the same numbers at the clinic.
Using Seafoam or some other additive to help remove carbon buildup should be done now and then. Adding unusable carbon to foul things up... Why?
Reason 2-
Inert gas, compressed or ambient is still inert. It does nothing, except work against flame. Throwing intentionally unusable gas and carbon into a machine that needs exactly the opposite to run is counter intuitive.
If you want to help lower combustion temp, do it with colder air charge and ditch stupid ideas, like exhaust crossover.
Using exhaust to power anything, other than a turbocharger or scavenging unburnt fuel (by way of harmonics) is useless.
It looks like a fantastic idea when everything is nice and new, and free of carbon, then it stops working, because exhaust is full of garbage. This is the reason why you LOSE fuel economy and LOSE performance with it!
Quench? ANY of these is a better plan;
- Colder air charge
- Colder fuel charge
- Water injection
- Colder ambient engine bay temp
- Colder oil temp
- Colder water temp
- Checking/ correcting ignition advance
- Better fuel
- Higher flowing exhaust
- Better cylinder heads
- Better pistons
- Better head gaskets
...
These can all be done by doing things like losing E.G.R., losing exhaust crossover, using a better intake manifold, using a better carburetor or even just changing driving habits.
There are so many ways to accomplish the goal of the E.G.R. that don't involve the trash it comes with. E.G.R. falls into the same boat to me as air injection on exhaust or exhaust crossover. I know what it's supposed to do in theory, but what it ends up actually doing on a majority factor, over most of it's life cycle is nonsense.
Reason 1-
Carbon. I'm sort of surprised that nobody has mentioned this. Used exhaust gasses are chocked full of carbon, even with good AFR, because of the low percentage of efficiency that an internal combustion engine has. Don't think so? Take the catalytic converter off of your new car and see if it pulls the same numbers at the clinic.
Using Seafoam or some other additive to help remove carbon buildup should be done now and then. Adding unusable carbon to foul things up... Why?
Reason 2-
Inert gas, compressed or ambient is still inert. It does nothing, except work against flame. Throwing intentionally unusable gas and carbon into a machine that needs exactly the opposite to run is counter intuitive.
If you want to help lower combustion temp, do it with colder air charge and ditch stupid ideas, like exhaust crossover.
Using exhaust to power anything, other than a turbocharger or scavenging unburnt fuel (by way of harmonics) is useless.
It looks like a fantastic idea when everything is nice and new, and free of carbon, then it stops working, because exhaust is full of garbage. This is the reason why you LOSE fuel economy and LOSE performance with it!
Quench? ANY of these is a better plan;
- Colder air charge
- Colder fuel charge
- Water injection
- Colder ambient engine bay temp
- Colder oil temp
- Colder water temp
- Checking/ correcting ignition advance
- Better fuel
- Higher flowing exhaust
- Better cylinder heads
- Better pistons
- Better head gaskets
...
These can all be done by doing things like losing E.G.R., losing exhaust crossover, using a better intake manifold, using a better carburetor or even just changing driving habits.
There are so many ways to accomplish the goal of the E.G.R. that don't involve the trash it comes with. E.G.R. falls into the same boat to me as air injection on exhaust or exhaust crossover. I know what it's supposed to do in theory, but what it ends up actually doing on a majority factor, over most of it's life cycle is nonsense.
Lonewolf3165
Living the Dream!
All well said Dave,
Just to shed a little light on the exhaust crossover just for clarity's sake. It isn't the same as EGR. That's used primarily for heating the intake up for quicker warm ups during cold starts. But no exhaust is reintroduced into the engine.
Air injection is fresh air pumped into the exhaust side of the engine, sometimes directly into the exhaust ports & sometimes downstream but always before the catalytic converters. It's used to improve catalyst efficeincy by increasing the catalyst's temperature. Running air injection without a catalytic converter can lead to burnt valves. So remove it if you're not running a cat.
As for the filling of the volume of the combustion chamber(back to the OP here), the engine is going to draw a given volume into the cylinders regardless, the only way to improve efficiency is to actually introduce something into the cylinder that is going to burn.
Dragonbat13
Well-Known Member
With caution towards seeming as though I am arguing (Im not, I just though about this and decided to throw it into the discussion),
Lets take the fuel and spark out of the situtation for a second.
So we do a compression check, EXCEPT, with the engines throttle closed to the same point they would be at cruising speed. Should have a lower cranking pressure due to the throttle being closed, right?
Now introduce the air (for simplicitys sake, but it would be exhaust gas when running) through the EGR, downstream of that closed, restricting throttle. Why wouldnt the cranking pressure come up?
EDIT: I agree that the EGR is old technology and is more trouble than its worth after reading this thread. But its still an option to try for reducing detonation at cruise on a car that is at the limit on the compression ratio. With the proper tuning, such as changing orifice sizes in the valve, it could be made to work correctly. And I am sure that the factory setups are not the best way to use EGR, theres alot better parts out there to do it with.
Lets take the fuel and spark out of the situtation for a second.
So we do a compression check, EXCEPT, with the engines throttle closed to the same point they would be at cruising speed. Should have a lower cranking pressure due to the throttle being closed, right?
Now introduce the air (for simplicitys sake, but it would be exhaust gas when running) through the EGR, downstream of that closed, restricting throttle. Why wouldnt the cranking pressure come up?
EDIT: I agree that the EGR is old technology and is more trouble than its worth after reading this thread. But its still an option to try for reducing detonation at cruise on a car that is at the limit on the compression ratio. With the proper tuning, such as changing orifice sizes in the valve, it could be made to work correctly. And I am sure that the factory setups are not the best way to use EGR, theres alot better parts out there to do it with.
Lonewolf3165
Living the Dream!
You'd be way better off adjusting your ignition timing or running higher octane fuel to cure detonation than adding EGR. Assuming of course the air fuel ratio is correct & your not detonating because you're too lean or running too hot. Obviously you'd need to correct that 1st. You have to understand this 1st: From a performance standpoint, you want to maximize the efficiency of the combustion & get the most energy released from it. If it were solely about cranking pressure then it would make sense if you added EGR to the engine at idle the speed & power would increase or for that matter throught the whole RPM range. The fact is that is doesn't. It impedes it. Try this on an EGR equipped car. get it warmed up & at idle & then open the EGR valve & see what happens. Even slightly. EGR was at the time the most cost efficient way to reduce NOx emissions.
The EPA throws these standards & regulations on the auto makers long before the technology to attain them is even available to do it. So they come up with something as fast as they can, usually a compromise at performance's expense to satasfy the EPA or get fined.
moper
Well-Known Member
I agree with the reason for EGR - it's NOx control - and it's the technology they had in the 60s to do so - so they used it. It works until the engine falls out of tune or gets worn - then it get's less effective and ultimately will fail as noted due to contaminants.
Adding inert gas and expecting power to go up is not logical. Power being increased as a result of more cylinder pressure relies on that addition volume and pressure being from a source of energy - i.e. fuel and air. The volume you are taking up is with an inert, diluting gas which impedes the energy release of the burn. In the case of EGR it uses inert gas and lessens the energy released - so no more power even if there is an increase of volume and pressure.
A car dies when the EGR is openned at idle because it's a massive vacuum leak and the inert gas replaces power producing mixture.
What happens in the chamber in terms of energy production has nothing to do with oil or water temps. Those are affects, the thermal energy absorbtion into those systems is the cause. Changing them will do nothing for power or emissions as long as the internal components remain within accepted operating temperatures. (A cold engine will be less efficient because it's not sealing the combustion chamber as well)
Will EGR work? Yes - provided the engine is in a good state of tune and wear.
Are there other ways to limit detonation that are more effecive - definately.
Adding inert gas and expecting power to go up is not logical. Power being increased as a result of more cylinder pressure relies on that addition volume and pressure being from a source of energy - i.e. fuel and air. The volume you are taking up is with an inert, diluting gas which impedes the energy release of the burn. In the case of EGR it uses inert gas and lessens the energy released - so no more power even if there is an increase of volume and pressure.
A car dies when the EGR is openned at idle because it's a massive vacuum leak and the inert gas replaces power producing mixture.
What happens in the chamber in terms of energy production has nothing to do with oil or water temps. Those are affects, the thermal energy absorbtion into those systems is the cause. Changing them will do nothing for power or emissions as long as the internal components remain within accepted operating temperatures. (A cold engine will be less efficient because it's not sealing the combustion chamber as well)
Will EGR work? Yes - provided the engine is in a good state of tune and wear.
Are there other ways to limit detonation that are more effecive - definately.
waggin
moving on ain't easy if you drive a Ford :p
so on a well tuned HEAVY TRUCK engine they are beneficial??? or in my case a DIRECT DRIVE airboat??? I mea'n I'm gonna have to give it a whirl to see for sure...on an airboat with DIRECT DRIVE the gains are seen easily so I guess its time to find out...?????
DaveBonds
Garage Trash
Yeah, I guess I wasn't clear on why I was lumping them into the same category, other than an example of better solutions to design side effects.
Exhaust gas is the quickest way to gain temp on cold start, so it's used to heat the plenum, but no gas is ran into the runners. It works good, but eventually carbons up and depending on the rest of the system's conditions on the engine, can cause overheat or fuel coking issues.
Air injection is also silly. It does increase exhaust temp to help the platinum in the converter do it's job, but it also helps use unburned fuel from increased temp, stoking it like a bellows on a coal or like an afterburner, which is actually how it became. Air pumps were standard equipment on some vehicles, starting back in 1972. Ex girlfriend's '72 472 DeVille had one and my '72 Datsun 240Z has one that will not go back on, with the engine rebuild.
They also throw emissions tests by way of playing a loophole from polutants measured in PPM. Limits aren't so difficult to achieve, when your engine "produces" clean oxygen, as well as exhaust gasses.
That's all I meant by how each device doesn't quite or only do what it's set out to do. haha...
I like an engine that runs it's numbers by good design, without redundancies.
I am a fan of exhaust heat stoves for cold start air, though.
moper
Well-Known Member
The systems were designed for emission control while running the fuels of their time. Period. If the engine was designed to use an egr, and is in that factory state of tune and your running a high-test-non-ethanol supplemented fuel - then an EGR will help you unless and until you mess with the tune up or things wear to the point that oil or soot gum things up. Running 10% ethanol or lower octanes change things dramatically in terms of the tune up and quality of the burn in the chamber.
If you are looking for a more permanent solution to a heavy load, steady state engine (airboat especially) then I'd look at a water injection system. Run a good water filter on a rigged up intake (rahter than a tank) and draw right from the swamp... There are systems that can be scratch built - guys have been doing H2O for decades.
racerhog
RacerHog likes his Mopars
Pishta & Moper Got it Right.... Reduce's NOx. Bottom line....
You keep bringin up tha air boat.....so I gotta ask. Is the prop really that much of a load? School me. I don't know anything about um.
waggin
moving on ain't easy if you drive a Ford :p
yepp it's a constant load and the load increases with rpm's...I run 87 octane with ethanol so looking for anything that makes more low end torque so I can add pitch to the variable pitch carbon fiber prop...I'll just have to try it and see what it does at the tachometer
Ok. Thanks. I understand about the variable pitch. Didn't know air boats had all that. Add more low end torque? A Buick 455?
MopaR&D
Nerd Member
I took an Internal Combustion Engines class this past semester in school (UC-Denver) and we learned a lot about EGR, or more importantly what's called the "residual gas fraction" of the mixture in the cylinder during the compression stroke. This is the fraction of exhaust gases in the chamber either left over from the previous cycle or due to EGR. There is usually 5-10% in a typical engine from "leftovers" and EGR usually bumps it up to a max of 30% in gas engines.
So what are the benefits? You guys pretty much got it, it lowers combustion temps from there being less combustible gases in the unburned mixture. Thinking of emissions it reduces NOx like has been said which is directly related to the burn temps in the cylinders. The reason it can add efficiency at part-throttle is kind of for this same reason. Cruising on the highway for example only requires 10-20 HP but your engine burns way more gas (and pulls in way more air) than needed to make just that amount of power simply because you have to keep the throttle open far enough so the engine will maintain that cruising RPM. This is why having short (3.55+ etc.) gears wrecks highway gas mileage BTW. Adding burned inert exhaust gases takes up some of that volume of intake mixture needed to keep the engine spinning; thus less fuel and fresh air are needed and the "pumping losses" are reduced.
Something to consider this is why diesel engines get such better fuel mileage (and emissions aside from soot), they have no pumping losses because there is no throttle and because of the principles of compression-ignition engines they have as much as a 60:1 air/fuel ratio at cruising and always operate lean of stoichiometric even under full load.
(Edit) Forgot to mention this works much better if the EGR gases are cooled down first for obvious reasons. The older factory V8 mopar setup feeding off the exhaust crossover is a much less than optimal setup and couldn't have worked that great even when new.
So what are the benefits? You guys pretty much got it, it lowers combustion temps from there being less combustible gases in the unburned mixture. Thinking of emissions it reduces NOx like has been said which is directly related to the burn temps in the cylinders. The reason it can add efficiency at part-throttle is kind of for this same reason. Cruising on the highway for example only requires 10-20 HP but your engine burns way more gas (and pulls in way more air) than needed to make just that amount of power simply because you have to keep the throttle open far enough so the engine will maintain that cruising RPM. This is why having short (3.55+ etc.) gears wrecks highway gas mileage BTW. Adding burned inert exhaust gases takes up some of that volume of intake mixture needed to keep the engine spinning; thus less fuel and fresh air are needed and the "pumping losses" are reduced.
Something to consider this is why diesel engines get such better fuel mileage (and emissions aside from soot), they have no pumping losses because there is no throttle and because of the principles of compression-ignition engines they have as much as a 60:1 air/fuel ratio at cruising and always operate lean of stoichiometric even under full load.
(Edit) Forgot to mention this works much better if the EGR gases are cooled down first for obvious reasons. The older factory V8 mopar setup feeding off the exhaust crossover is a much less than optimal setup and couldn't have worked that great even when new.
DaveBonds
Garage Trash
Right. It does the same thing that an intercooler does, or anything else that changes volume, only with a supplement that the engine is wasting/ already used. Intercoolers on boosted engines or anything else that can be done to increase volume or air density also help fuel economy/ efficiency and power.
The EGR feeding off of crossover is exactly why it's just not a good design. The idea is ok, but with a factory system, it's just heated gas fighting itself. Heating the air charge and attempting to cool it with the exact same inert gas charge at the same temp... I suppose it regulates and does some good in theory, but the stock intakes that use this system aren't doing the engine any favors on an ideal EGR or plenum heating system.
If they were a little more intuitive, they could have set up a water temp regulated plenum behind the thermostat circuit in the bypass and let the radiator tackle high heat when it opens up. The EGR could have used a cooler, similar to the P/S cooler air to air.
Either way, it's complicating things and we're still talking about exhaust gasses that carbon cylinder heads, valves and piston tops.
Water injection is an awesome idea on a constant load situation with that air boat, because of the endless supply.
The EGR feeding off of crossover is exactly why it's just not a good design. The idea is ok, but with a factory system, it's just heated gas fighting itself. Heating the air charge and attempting to cool it with the exact same inert gas charge at the same temp... I suppose it regulates and does some good in theory, but the stock intakes that use this system aren't doing the engine any favors on an ideal EGR or plenum heating system.
If they were a little more intuitive, they could have set up a water temp regulated plenum behind the thermostat circuit in the bypass and let the radiator tackle high heat when it opens up. The EGR could have used a cooler, similar to the P/S cooler air to air.
Either way, it's complicating things and we're still talking about exhaust gasses that carbon cylinder heads, valves and piston tops.
Water injection is an awesome idea on a constant load situation with that air boat, because of the endless supply.
pishta
I know I'm right....
Run your egr through a Small intercooler In front of the radiator. Egr cold air induction! I will continue to run one if i can once its working properly. Really does no harm other than cluttering the engine compartment with 2 more hoses...high lift cams need not apply as their low vacuum may fool egr activation. I noticed my little truck ran about 20 degrees hotter without egr hooked up or plugged. I always thought pcv introduced under the carb was ludicrous too. I think some modern cars dont have egr as they use MAF meterz that cant read egrdilution as it doesnt pass through the meter? I know thats an issue on turbo cars when the blow off valve opens, the motor controller is like " what happened to all that metered air i let in and accountwd for?"
Lonewolf3165
Living the Dream!
You ran 20* hotter because w/o the EGR it runs leaner. As for the "EGR cold air induction" it won't offer any value for performance. You're just cooling down non-combustables.
Many cars have MAF sensor & EGR. The MAF will show a change in the metered air going in when the valve is open. Modern vehicles are using variable valve timing to control NOx gases now instead of EGR valves.
What don't you like about PCV valve connected to manifold vacuum?
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