Vortec EGR System?

**Hog** · 05-30-2013

There are some small EVAP differnces between the 96-97 and 98+ intakes, but the 305 and 350 intakes are NOT differnt.

peace
Hog

**pmkls1** · 05-31-2013

Alright, the first pic is of an assembled manifold with a few things pointed out for anyone not familiar with the layout.

**pmkls1** · 05-31-2013

The next pic is of a bare intake in the same orientation.

**pmkls1** · 05-31-2013

Sorry for having to post one pic per post, but I'm having problems with posting. This next pic is a close-up with the EGR passages pointed out.

**pmkls1** · 05-31-2013

This next pic illustrates the difference in distance that the EGR gasses have to travel to reach the runners. The bank 1 ports in the pic are for cylinders 1 & 3 and the bank 2 ports are for cylinders 2 & 4.

**pmkls1** · 05-31-2013

The next few pics show the throttle body and the air diverter on the throttle blade as well as the underside of the upper plenum.

**pmkls1** · 05-31-2013

After looking at how the EGR gasses enter the plenum and everything else it still seems like the EGR gasses are going to feed cylinders # 1 & 3 more than any others. But, you would think that bank #1 would go rich and not lean since cylinders 1 & 3 are getting more exhaust gasses and less fresh air thus requiring less fuel. Either way, I can see how a bank imbalance could easily occur with this setup. On a side note, I am testing some different cleaning solutions for cleaning aluminum and I will be using this manifold as a test-bed. The above pics are of the manifold directly after being removed and will serve as "before" pics. You can see just how nasty it was in there and this is typical of these engines. This particular engine has 19x,xxx miles on it for reference. I'll post the "after" pics after using some different cleaners as well as the name of the cleaners used and what they contain. I'll post in a new thread so as to not interfere with the purpose of this thread.

**EagleMark** · 06-01-2013

Thanks pmkls1 !

That was quite an effort to document the EGR system.

Mans that is disgusting in there....

**Fast355** · 06-02-2013

Originally Posted by EagleMark

Thanks pmkls1 !

That was quite an effort to document the EGR system.

Mans that is disgusting in there....

Aluminum Wheel cleaner works well

Oven cleaner works well

So does an Diesel EGR shaker bath. My TPI setup and runners were spotless after being dipped in that for 30 minutes.

Express runs like crap with the EGR turned on, especially in hot weather and after having cleaned that mess up myself once, I just disabled it.

**EagleMark** · 06-02-2013

Sure runs better with EGR coming on after 25 MPH instead of off idle. MPG around town is up as well. Have to do some more data but not much EGR activity at cruise speeds? Only showing some EGR after 25 MPH to 40 MPH and none at highway speeds? All light throttle... When I'm done with this tank I'm going to do a tank with no EGR at all and see what MPG does.

EFI Live only has 2 paremeters for EGR. On/Off and the spark advance table which only adds 3 degrees tops.

TunerCat has those and the EGR enable/disable speeds as well.

No EGR fueling tables in either.

Pulled the throttle body today and it's near spotless in there so looks like they did a good job when the intake gaskets and spider were replaced.

**pmkls1** · 06-02-2013

I actually snapped a few pics anyway for a visual reference so that I don't have any trouble during reassembly so it was no big deal really. This vehicle was a recent purchase for pulling a camper and it was used as a tow rig before so I assumed it would be pretty nasty in there. Regarding EGR functions I feel that 1project2many has the best theory about EGR and gas mileage. Every engine configuration reacts differently to changes so it would only make sense that EGR operation would be no different. If you take a moment to remember the theory of how EGR is supposed to work it helps to understand when it may be helpful and when not. The function of EGR is a crude way of reducing engine displacement and fuel consumption by pumping a metered amount of inert exhaust gasses into the cylinders under light engine loads when the demand for power is low. Still, different engines are going to respond to when the EGR is enabled and such differently. I personally have always disabled EGR functions on my vehicles for simplicity, but it can be useful. As for my cleaner testing, the cleaners that I am testing are eagle one chrome wheel cleaner and eagle one mag wheel cleaner. I have worked with oven cleaner before too and it is pretty decent too. It is not just the actual brand names that I am looking into rather it is the base chemicals and the combinations. Everybody knows that muriatic acid is excellent for stripping iron and steel, but it literally eats aluminum. Phosphoric acid works on both, but has limitations. Sulphuric acid also works in small quantities. Sodium hydroxide is an excellent cleaning agent and is the main ingredient in oven cleaners as well as aqueous parts washer solutions. All of these chemicals are readily available and they are also the main ingredients in many cleaners out there. The problem is that these over-the-counter cleaners are pretty expensive by volume. My testing is for the purpose of finding which cleaner I like and referencing the main ingredients and percentages listed on their MSDS sheets and then attempting to mix up my own concoction using readily available and inexpensive concentrated solutions of the chemicals.

**EagleMark** · 06-02-2013

Originally Posted by pmkls1

If you take a moment to remember the theory of how EGR is supposed to work it helps to understand when it may be helpful and when not. The function of EGR is a crude way of reducing engine displacement and fuel consumption by pumping a metered amount of inert exhaust gasses into the cylinders under light engine loads when the demand for power is low. Still, different engines are going to respond to when the EGR is enabled and such differently. I personally have always disabled EGR functions on my vehicles for simplicity, but it can be useful.

That is my understanding, but the purpose was only for emissions.

But off idle while accelerating from a stand still is not light load? And it's on?

At light cruise which is light load it is off?

I've never really studied EGR in data, but this is exactly the opposite of what I expected...

**gregs78cam** · 06-02-2013

I can tell you that on our '99 Grand Am with 3.4L, EGR not functioning reduces MPG by 10%.

**EagleMark** · 06-02-2013

Originally Posted by EagleMark

That is my understanding, but the purpose was only for emissions.

But off idle while accelerating from a stand still is not light load? And it's on?

At light cruise which is light load it is off?

I've never really studied EGR in data, but this is exactly the opposite of what I expected...

Rethinking this it's backwards, the EGR is enabled at higher loads for emissions.

Originally Posted by gregs78cam

I can tell you that on our '99 Grand Am with 3.4L, EGR not functioning reduces MPG by 10%.

I've done this before, 3 times, all on stock factory cam engines and results were the same. 10-15% loss in mileage.

But never have I studied the data of what EGR was doing...

I'm an idiot...

**1project2many** · 06-02-2013

Mileage gains, if any, are secondary. EGR reduces combustion chamber temps to keep NOx levels lower. GM must have seen a need for more EGR under higher load on the L31 so that's when it's active.

Be careful not to strip protective coatings / platings from components during cleaning process. Acids and bases are both very capable of doing that. I wonder if the "electrolytic rust removal" process would be effective here. It does a great job removing paint on parts that aren't rusty. I wonder how it will work on carbon?