The reason to KEEP EGR if using modern factory EFI

[Brad-ManQ45]

I recently had to replace the intake manifold on my '96 Town Car. The original manifold was replaced at factory expense due to the class action lawsuit over the water crossover cracking. THAT manifold 4 years later developed a crack at the passenger rear and was leaking water near the heater outlet.

 

The people that did the work (I only do minor stuff on daily drivers) said they had cleaned out the EGR tube because it was clogged up.

 

This was last month and I'm here to tell you that in spite of colder weather, I am getting .8 MPG better.

 

This sort of reinforces a few points about modern factory EFI and emissions that has been brought up in the past.

 

Basically, the ability to dial in a bit more advance because EGR is being introduced to lower combustion temperatures causes not only less emissions but better gas mileage.

 

And this doesn't just apply to Ford engines. I remember reading about the LT1 engine when it first came out and Chevrolet basically said the same thing.

 

If any of you are thinking that you are going to be daily driving a car you are building, I would seriously consider using a factory EFI system that you can tune yourself to take advantage of the built in engineering for both emissions and mileage they represent, and avoid ripping out ALL emissions stuff.

[dexter72]

Good Post,

 

I am wondering why the check engine light didn't turn on, or maybe it was on. OBD2 systems will read lack of egr and set a code, Atleast the imports will.

 

I work as a Nissan Certified tech and the light will turn on with a 95 and up model.

The 95 and newer trucks will have an egr code. Pre 95 will have an engine miss at 2000 rpm. Cylinder misfire code, Too much egr at a certain cylinder, means egr tubes in the intake are clogged.

Edited February 1, 2012 by dexter72

[randy 77zt]

I used to work as a ford dealer tech.I have replaced a few of those manifolds.Its actually an easy job.Modrn rfi systems regulate the volume of egr flow better than older carburated/vacuem controlled systems.If there are any questions on the rear air ride I know alot about that to.

[Leon]

And people don't believe me when I tell them that gas mileage goes up with properly functioning EGR...

 

Actually, the reason for better fuel efficiency has nothing to do with spark timing. As far as timing goes, it's not that it can be increased, it's that it needs to be increased when using EGR. EGR increases mixture burn time, thus you need to light the mixture off sooner in order to get back to MBT (Max Brake Torque) timing.

 

Engine efficiency increases when using EGR at cruise mainly because of these two reasons: (1) EGR reduces pumping losses by increasing intake pressure, and (2) the lower combustion temperatures lead to less heat loss through the cylinder walls (better thermal efficiency).

[Tony D]

Someone in this thread has retrofitted a modern Diesel EGR Cooler on his 260Z with functioning EGR and no longer gets spark knock to beat all hell, nor an overheated intake manifold. He can't wait to get the TBI adapters in, and program a megasquirt to control the EGR more precisely.

 

But the car without EGR, and with Round Tops vapor locked so badly on a recent 85 degree day (winter gasoline mix) that it was pushed into it's parking stall...

 

Beware the myths that bleed from the domestic side when applying them to a Datsun. So much stuff interacted on the 73 and 74 cars, it makes it hard to pinpoint what exactly the problem is at the root. But the carbs changed, so they were the culprit.

 

I can tell ya, round tops without EGR vapor locking is not fun. An EGR Cooler does wonders for that early setup!

 

I can't wait to increase orifice size and really lay it in there... Higher Compression? Cheaper Gas? Works for me!

[bradyzq]

I look at EGR as effectively making the engine smaller. If you introduce non-combustible spent exhaust gases into the combustion chamber, there is less room for fresh mixture, so it will require less fuel as a result.

[Leon]

I look at EGR as effectively making the engine smaller. If you introduce non-combustible spent exhaust gases into the combustion chamber, there is less room for fresh mixture, so it will require less fuel as a result.

Brady, with all due respect, it doesn't work that way. If I inject a bunch of Nitrogen into my cylinders, it will not mean that I can use less fuel. I'll reiterate the reasons behind getting better fuel economy at cruise with EGR:

 

Engine efficiency increases when using EGR at cruise mainly because of these two reasons: (1) EGR reduces pumping losses by increasing intake pressure, and (2) the lower combustion temperatures lead to less heat loss through the cylinder walls (better thermal efficiency).

[Tony D]

EGR is not "noncombuatible", close tracking if fueling on Federal and CA ECU fueling shows a decreased fueling component when EGR is active in the CA ECU's.

 

While on the face it may be some other force at work, direct substitution of the CA ECU in place of the FED ECU in a Federal Car shows AFR's 0.1-0.2 leaner during the corresponding high EGR (partial throttle, high vacuum) point if operation.

 

When placed in the opposite vehicles, AFR's track identically.

 

This would tend to indicate the CA ECU was somewhat leaned to compensate for SOME fueling capability provided by "noncombuatible" EGR.

 

As someone who made a C10 Chevy Truck run on wood smoke, the thought that combustion byproducts are entirely "spent" is a fallacy. There are fueling properties in there. Conventional teaching says it's "inert" but practical application shows otherwise.

 

Splitting hairs? Maybe. But it's "displacement loss" can be made up by ignition timing for better peak pressure point due to poor fuel, or simply by allowing higher compression on a given fuel without "knock"...

 

The pumping losses mentioned also comes into play counterintuitively as you "take in more" in reality than you did previously so that internal loss being eliminated adds to the output side if the equation as well.

[bradyzq]

I fully admit that EGR is not my area of expertise, and "non-combustible" should perhaps be replaced with "much less combustible." Other than that, aren't we saying the same thing?

 

With EGR active, the percentage of oxygen available for combustion within the overall mixture is lower than when the EGR is not active, therefore, for a given mass of "air," requiring less fuel to maintain a given AFR. Is this not what Tony described in his ECU swapping example?

 

With the "much less combustible" EGR component of the overall mixture diluting the rest of the mixture, it causes the burn rate to slow because of lower combustible mixture density. The resulting slower burn rate now requires more ignition advance to attain MBT.

[Tony D]

Or one can look at it as "allows maintaining the current ignition advance"...instead of retarding the timing and loosing power without the EGR...

[bjhines]

EGR only works at part throttle. It will not "IMPROVE" performance to remove it because it only affects part throttle operation. People removed EGR when it was malfunctioning or when the carby was retuned or replaced with a "performance" model. Some people naturally assumed that EGR/.emissions systems must be bad because the American auto industry made a disastrous mess of EPA conformance in the 1970s and 1980s. Folks have made all sorts of associations with emissions being BAD for performance because of the total crap US car-makers tried to sell us for decades. How much power did the 1982 corvette have?...i think less than an modern L4 with 1/4 the displacement. Those anemic 1980s V8s are a fricking JOKE!!! No wonder folks have a bad memory of emissions systems.

 

Tony... The wood smoke truck ran on the volatile, combustible fumes that wood gives off when "cooked" in an oxygen free tank. Those fumes can replace gasoline and have been used in remote locations as a frustrating and dirty fuel source to run engines designed for spark ignition operation. You have to regularly shut down to clean out the wood remains and clean the pipes of condensates from the wide range of stuff that comes from cooking wood. The wood chips used must be bone dry or the steam will form varnish in the plumbing.

.

[Leon]

I fully admit that EGR is not my area of expertise, and "non-combustible" should perhaps be replaced with "much less combustible." Other than that, aren't we saying the same thing?

 

With EGR active, the percentage of oxygen available for combustion within the overall mixture is lower than when the EGR is not active, therefore, for a given mass of "air," requiring less fuel to maintain a given AFR. Is this not what Tony described in his ECU swapping example?

Yes, EGR dilutes the mixture and thus you have less combusibles in the cylinder. Think about it though, if you are putting in less fuel, that means you are losing power compared to 0% EGR. You require less fuel to maintain the same AFR, but that also means you also have less fuel to burn. When thinking along these lines, it would seem as though EGR will have a negative effect on cruise performance.

 

This is where those 2 factors I mentioned come in (less pumping and heat losses). Because of improved thermal efficiency and lower pumping requirements, the engine doesn't need as much power to maintain operation. You're making less power at part-throttle cruise, but because of EGR, you don't need as much power (fuel) to keep going, hence the mpg benefit at steady cruise.

 

With the "much less combustible" EGR component of the overall mixture diluting the rest of the mixture, it causes the burn rate to slow because of lower combustible mixture density. The resulting slower burn rate now requires more ignition advance to attain MBT.

Bingo!

[Brad-ManQ45]

Dexter:

 

The pipe wasn't completely blocked, but almost.

 

Randy:

 

I've already replaced my bags a few years ago, but now I'm gonna hafta start investigating why the light comes on after about 10 minutes of driveing - I might take you up on your offer.

 

My brother-in-law has an '03 Navigator with ~0 compression on #7 cylinder and is looking at ~$4500 to replace the POS original driver's side head with the new and improved (read re-engineered after realizing they screwed up and won't cover it by recall) head....

Edited February 6, 2012 by Brad-ManQ45

[Victor_Zedman]

EGR sucks! get an no egr n42 and there you go.

[Leon]

EGR sucks! get an no egr n42 and there you go.

Looks like somebody didn't read the thread...

[Tony D]

"Running up post count to post in classifieds"