I needn't re-read it to know you totally missed what I was saying.

less fuel injected at the injector with the introduction of exhaust gasses into the intake would slow you down.

I don't mind talking about any of it

 

I know what you were saying, you reiterated my point, again, in depth, in your recent long breakdown of lead heads comments.

 

And your point is that there is less fuel at the injectors with an increase in egr duty cycle? This would not be accurate.

 

I'm not taking the bait, if you get it you get it, if you don't you don't. But the answers are in your comments.

 

i did it because my truck would have a slight surging at speed, i bought a new one and it did the same, so i plugged the vacuum line.been years now.

 

There is no bait, and yes the answers are in my comments.

 

The AFR remains constant when the EGR opens, and fueling is certainly not increased.
Yes it does. The more EGR added at a given throttle position, the less fuel that is injected.
Here's where your thought experiment falls apart. The A/F ratio is never, ever 16:1 on an EEC-IV system. Unless in the throttle, it spends most of its time at 14.7:1 in closed loop operation - with the EGR open or closed. You try and claim the computer doesn't compensate for EGR flow, but it does.

There is no such thing as "Exhaust Air Fuel Ratio". When crusing the computer operates the engine as close it can to stoich. When the A/F ratio is at 14.7:1 or richer than 14.7:1, there is no oxygen in the exhaust stream. It is completely inert and not combustible. As far as the engine is concerned you might as well being throwing a noble gas right into the intake - it would have the same affect. The only time there would ever be a significant amount of free oxygen in the exhaust is during deceleration when the injectors turn off. Even running very lean (16:1) would not have a significant amount of oxygen in the exhaust.

So let's reiterate how the EGR system actually works:

- Vehicle is cruising and computer commands a certain amount of EGR given the current driving conditions
- EGR Valve opens and exhaust gas begins to flow. The exhaust gas is completely oxygen free because the engine is running at 14.7:1 or richer. It's effectively completely inert.
- Desired EGR flow is based on a table where the desired EGR flow is in terms of percentage of total mass of air going into the engine. So 10% means the computer wants 10% of the total amount of air going into the engine to be exhaust gas
- The computer then takes that %, looks at the current engine mass-air flow rate, and then calculates how much EGR flow in lbs/minute is necessary for EGR to represent 10% of the total air charge
- It then compares that desired flow to the EGR flow vs. position curve, and opens the valve the desired amount.
- The EGR flow reduces the amount of combustible air in the manifold, reducing power and cooling the flame front down. The computer reduces fuel based on the EGR mass flow and advances timing. A/F ratio is still 14.7:1 and the O2 sensor will trim any error back to stoich.
- Driver increases throttle slightly to make up for slight reduction in power due to there being less power being generated.

I have access to the inner workings of the computer. I know how it works, and I know what happens when the EGR valve opens, and what the computer does to compensate. EGR Valve gets commanded open, spark gets advanced and you see a slight reduction in injection pulse-width.

Here are all the 35 parameters related to "simple" EGR in these trucks:

Here's the table that directly relates EGR position to EGR mass flow

 

The word thermal could be thrown out there, and with a couple more details, efficiency of, could be noted, then a theory of how improved mpg and egr could develop but theory being the key. I'm sure others could perceive my comments up to this point, as defending egr and improved economy but I'm not, it's more of an, it coulda, in theory. I was just expressing earlier, that if you pay attention to what's being said, by everyone, the same info presented, could be used to defend an argument, regardless of stance, it's happened since I can remember.
But in the real world, theory goes out the window. My current 5.8, pretty much stock roller engine, emissions delete, gets a couple more mpg under mixed driving, than what Ford rated for hwy. I use the same pump, even go as far as to pay attention to weather temperature and conditions.

 

Lets use some stats you provided in your last response

Even if it reads the same, the AFR is not the same....if the AFR was 14.7:1 under all conditions (disregarding reality), with no EGR, the moment you inject exhaust with a 14.7:1 AFR into the intake, the o2 sensor is no longer reading the actual AF/R going into the engine because it's no longer air and fuel. It is air, fuel, and 10% gasses that are no longer "air or fuel" but will still read 14.7 at the o2 sensor... Like I said, if you took 100% of the exhaust and sent it right back through the intake, it would still read 14.7 even though there was no air/fuel entering the intake. Of course, it wouldn't run.

I never disputed this statement in absolute fashion, in fact, I agree that less fuel has to be injected at a particular throttle position, but in order to maintain the real world demand of the operator, i.e. power production, additional throttle must be applied OR fueling must be increased. I wasn't debating operating laws, I was stating what needs to happen. "trimming" fuel with EGR per a particular throttle position I don't dispute, "trimming" fuel altogether as a result of EGR is completely inaccurate, which is what I was indicating. The more EGR that is introduced, the more air/fuel it will require to produce the same power.

I could have used any numbers, the numbers aren't what is important. I see cruise AFR's in the high teens every time I get into my truck, throttle applied. Any factory speed density ford I've ever had a wideband on (other peoples cars on dyno included) leveled out at in the mid 13's at WOT, regardless of RPM...mine included with either a 351 computer or a 460 computer.

Yes, there is "Exhaust Air Fuel Ratio", its exactly what goes into the combustion chamber when EGR cycle is applied. o2 sensors are supposed to read air/fuel mixture that enters the combustion chamber, and because it measures after the combustion event, rather than before, it doesn't know what percentage of the "AFR" coming out was in fact exhaust that went in with the air/fuel charge. Anytime EGR is cycling, there is "EAFR".

Bravo, so you should agree with what I'm saying.

 

You have a huge misunderstanding of what exhaust gas and stoichiometry are, and you don't understand how O2 sensors work or measure air fuel ratio.

Wideband oxygen sensors function by reacting the exhaust gasses with external oxygen from outside the sensor in a reaction chamber. The sensor tries to keep the reaction chamber in a constant state by pumping oxygen in or out of the reaction chamber. This oxygen is pumped into the sensor by an ion-pump. If the exhaust is rich (unburnt fuel), the ion pump pushes oxygen molecules into the reaction chamber, if it's lean, the ion pump reverses direction and pumps oxygen out of the chamber. The amount (and direction) of oxygen needed to be pumped determines the air/fuel ratio.

Stoichiometry is the air/fuel ratio where all the available fuel reacts with all the available oxygen in the cylinder. During stoich combustion, In the exhaust stream there will be no fuel, and no oxygen since all the available oxygen and gasoline has reacted together. The majority of the exhaust will be "inert" Nitrogen and CO2 since all the oxygen has been consumed and all the fuel has been consumed. A key point to understand here is that gasoline doesn't react with air to burn. It reacts with oxygen in the air, of which only 21% of the atmosphere is. 78% of the atmosphere is relatively inert Nitrogen, and 1% CO2.

So now that we know what stoichiometry is and how wideband oxygen sensors work - what happens If you feed a stream of air consisting only of nitrogen and CO2 with zero oxygen over a wideband oxygen sensor? It would read 14.7:1. Why? Because there is no oxygen, and no hydrocarbons in the air stream. The ion-pump inside the wideband doesn't have to pump oxygen in or out of the reaction chamber. That is what your exhaust gas is during cruising conditions - nitrogen and CO2.

So what happens when we open the EGR Valve? We displace oxygen. Since the stoich exhaust gas is just nitrogen and CO2, we've changed the "atmosphere" from 79% nitrogen and CO2 to something closer to 87% nitrogen and CO2. The computer knows this, and reduces the amount of fuel being injected accordingly - since gasoline reacts with oxygen, not air.

What does this mean? It means the EGR effectively reduces the displacement of the engine. It now takes more throttle opening to output the same power and maintain the same speed (a point we agree on). This has some advantages though: The cooler burn allows more spark advance, which increases engine efficiency. It also reduces pumping losses, which is one of the major places where gasoline engines loose efficiency. It takes a lot of power to pull air through a mostly closed throttle valve - the more closed the valve is, the more power it takes to pull air through it. Since EGR displaces available oxygen, requiring a larger throttle opening, pumping losses are reduced.

With the EGR on and flowing, you increase spark, decrease pumping losses and increase overall engine efficiency. There are actually quite a few papers published detailing how EGR (especially cooled EGR) can increase engine efficiency. Here's some reading to get you started:
http://www.autospeed.com/cms/article.html?&A=112612
https://www.dieselnet.com/tech/engine_egr.php
http://www.swri.org/3pubs/ttoday/Sum...n-and-Cool.pdf

 

best thing to do is put a plate over the ports on the manifold. But leave the egr and solenoids and stuff in place to keep from throwing a check engine light. If you don't mind doing the extra work, take everything off of the engine and cap off any ports or opening on the engine with a bung or weld a cap on them. Up to you. I had a '93 with the 300 and the previous owner put jb weld or some kind of chemical in the exhaust port on the egr. Basically the same thing as a plate but a little bit rednectified lol

 

I needn't a lesson on how an o2 sensor works, I wouldn't be this far in a discussion such as this if I didn't. Besides, an o2 sensors function doesn't have anything to do with the points I've made about recirculating exhaust through the intake and how the o2 sensor (and in turn the computer) has no way of differentiating between 10% 14.7:1 exhaust mixed with a volume of air/fuel, or just air fuel by itself.

If you think any efi engine has a max AFR of stoich, then you need a lesson on stoich and how it relates to manufacturing practices, as well as power production. Stoich might be the most efficient burn in theory, but it doesn't make the most power and is not accepted as safe max load AFR for any manufacturer, ever, too much heat among other things . It doesn't make the most power because of the imperfections of a reciprocating assembly, and the short amount of time in which each piston has to harness power, especially where it matters most; the top half of the stroke. Anything from the factory runs rich (~12.5-13.5:1) at full load in order to maintain safe temps and generate the most power, sacrificing some efficiency. If you've ever dyno tuned anything, you'll know that engines produce more power when rich (lesser than stoich AFR). I've dyno tuned more than I can remember.

aside from that discussion derail, I've reread everything that I have said and how it pertains to egr, and what I have said is sufficient for me to allow others to read and learn.

The efficiency of the combustion event is by far the single most important aspect of thermal efficiency, if a 351 with e7's could magically be 50% thermally efficient, it'd blow the doors off anything on the streets and get 40 mpg to boot, with poor volumetric efficiency. No way is jamming inert gas into a combustion chamber, increasing throttle position (and reducing pumping losses) increasing efficiency anywhere close to increasing thermal efficiency of the engine via a clean burn. If it did increase efficiency, manufacturers (and racers alike) would use egr not only in cruise, but in WOT. In addition to that, any credible literature wouldn't attach the term "in theory, it could" anytime it mentions the throttle body opening further as a means of increasing volumetric efficiency. It obviously increases volumetric efficiency, but it's marginal when compared to an increase in thermal efficiency.

I don't need this discussion in order to figure out that you have a respectable wealth of knowledge, I've seen it elsewhere. I'm also smart enough to know that neither of us know much in the grand scheme of things, even if we know more than most. I will tell you this; I know enough for you to evaluate what I've said and try to understand it, even if you don't agree...the egr discussion is raw physics, plenty of evidence in my posts supporting my claims.

 

It has no way of differentiating because it doesn't need to. The only things the oxygen sensor cares about are hydrocarbons and oxygen. Everything else in the exhaust stream is irrelevant. You could feed a mixture of 78% Helium, 21% oxygen and 1% Xenon into the manifold and their oxygen sensor would still read accurately. The 14.7:1 number itself isn't even relevant, since the sensor really functions in terms of Lambda where stoich is 1.00.
Stop straw-manning me. No one here is talking about peak power, or what AFR makes peak power. I've explicitly talked about what happens during cruise conditions, which is where EGR is used. I've stated this repeatedly. Where an engine makes it's most power was not part of this discussion, so stop bringing it up.
This statement alone proves you don't understand pumping losses or how EGR functions. If the throttle is WOT, the pumping losses are already reduced as there is no vacuum or throttle blade for the engine to pull against. Adding EGR to an engine at WOT would just decrease power since you can't open the throttle any more to compensate...
...and those papers don't even use those terms at all, they're actually quite straight forward about their claims. Strong indication to me you didn't even read them.

Here's what they actually say, if you're curious.
"EGR is also used in gasoline engines, primarily in order to reduce pumping work and increase engine efficiency"
"At part load conditions, when the engine intake manifold pressure was less than the atmospheric pressure, adding EGR (either internal or external) resulted in a small reduction of pumping losses, with a corresponding slight improvement of fuel consumption."

Here's published SAE papers on the topic of EGR reducing pumping losses and increasing efficiency. I hope these are credible enough.
Exhaust Gas Recirculation for Improved Part and Full Load Fuel Economy in a Turbocharged Gasoline Engine
Effects of EGR Dilution and Fuels on Spark Plug Temperatures in Gasoline Engines

and another from a different journal
Cooled exhaust-gas recirculation for fuel economy and emissions improvement in gasoline engines

You have a lot of reading to do about EGR theory. I suggest you get started.

 

I was done with the last book response. You keep saying I need "lessons", and "better get started on reading"...but you're the one who is picking apart pieces of what I say to use for your benefit. How max power afr, wot pumping losses (or lack thereof via throttle body, which I indicated) are not relevant or I don't understand them, but they are and believe me, I do (proof is in the entirety of my posts). You're the one who said eec is "never, ever 16:1", when it's range includes lean conditions in the high teens (18+) under throttle. Silly me for remembering things said in previous posts.

There's nothing in those articles that I haven't read before.

I can't tell if you're 15 and likes to read books, or 60 and stubborn.

 

Double post