Increased MPG by 6-13% by cleaning EGR passages!

[Xist]

I started my new job October First doing in-home speech therapy and my first clients were fairly far apart.

Somehow, I am missing two months of fill data! I logged 46.73 MPG in August and my first tank a week and a half after starting my new job was 44.14.

Then 40.4.

Excluding one short trip where I was supposed to follow my girlfriend's father, who seemed determined to lose me, I have filled up ten times since starting the job, achieving 38.72 - 43.96 MPG, averaging about 41.

Then I had a CEL for low EGR flow and cleaned the passages. It would have been pretty quick and easy, but while Eric the Car Guy, Scotty Kilmer, and everyone else say to reuse the old metal gasket, I ended up deciding to replace mine.

What nobody told me is that you need to order a new EGR valve gasket, which is only $3-7, but I needed to order it and drive a rental until it arrived.

How bad would it have been to reattach it without the gasket?

Exhaust leak?

Anyway, I finally finished my first tank after cleaning the passages. I went 40.8 miles further than I had since starting the job, at 46.6 MPG!

That is 2.67 MPG and 6% better than my recent best tank and 5.6 MPG and 13.8% better than my ten-tank average.

[MPGomatic]

Well done! Cleaning those EGR worm tunnels definitely makes a difference. I'm wondering how long they'll stay clean and if there's anything (magic potions or rituals) that that will keep them clean …

[Baltothewolf]

The reason cleaning those EGR passages is so critical on Honda's lean burn engine is that, when in lean burn you run 100% open EGR. I guess honda uses exhaust gas to combat detonation due to low oxygen content in the air (just a theory). Cleaning this allows easier Lean Burn transition, and longer spurs of lean burn itself.

[Xist]

On top is my EGR plate. That drill bit barely fit into the port, but the end with the tape wrapped around it fit into the hole in the plate, so I made a diagram of how the two meet. The parts with the worst carbon seemed to be where the exhaust needed to make ≤ 180° turns and at the ends, where narrow channels opened and the exhaust went into narrow tunnels.

I was curious how the EGR plate evolved over the years, but I mostly only found EGR block-off plates.

No!

I forgot about reading here http://ecomodder.com/forum/showthrea...rts-21032.html that you need to drill into the intake manifold and tap bolts.

Honda, thanks for changing that!

I figure that those spots do not collect carbon because they are larger, they are bigger to compensate for the build-up, which I am guessing is a result of the ninety-degree turn.

The thing is, I keep thinking about the big holes and the small ports. If they are half as wide, three-quarters of the exhaust would bounce off the edges and swirl around before getting through, depositing carbon in the process.

Would beveling the ports allow gas to flow with fewer restrictions, resulting in less build-up?

If this took 195,000 miles to clog, would cleaning it 100k maintain MPG?

[Baltothewolf]

Originally Posted by Xist

On top is my EGR plate. That drill bit barely fit into the port, but the end with the tape wrapped around it fit into the hole in the plate, so I made a diagram of how the two meet. The parts with the worst carbon seemed to be where the exhaust needed to make ≤ 180° turns and at the ends, where narrow channels opened and the exhaust went into narrow tunnels.

I was curious how the EGR plate evolved over the years, but I mostly only found EGR block-off plates.

No!

I forgot about reading here http://ecomodder.com/forum/showthrea...rts-21032.html that you need to drill into the intake manifold and tap bolts.

Honda, thanks for changing that!

I figure that those spots do not collect carbon because they are larger, they are bigger to compensate for the build-up, which I am guessing is a result of the ninety-degree turn.

The thing is, I keep thinking about the big holes and the small ports. If they are half as wide, three-quarters of the exhaust would bounce off the edges and swirl around before getting through, depositing carbon in the process.

Would beveling the ports allow gas to flow with fewer restrictions, resulting in less build-up?

If this took 195,000 miles to clog, would cleaning it 100k maintain MPG?

I would recommend every 50k to clean the EGR plate, I would also recommend a valve adjustment at the same time.

[Chrysler kid]

At 290k on my old y5 the egr passage was clogged all the way from the metal plate, to thr egr, and the egr back to the head. (The egr recirculates exhaust gas from valve overlap back into the intake manifold port)

I re used both gaskets with no problems. I had to use a drill bit that I turned by hand to clean out the ports under the intake plate. So you don't drill, you just use a drill bit

The best modification you can make to the egr system is to remove and clean the intake manifold and clean out all of the passages inside and out. You could port the holes under the plate but it is still going to pull the same amount of vacuum into the intake through the egr valve.

So it would be like running a ported intake manifold behind a stock throttle body. You might get a better intake response initially from the larger diameter holes but it will still restrict air flow from the air inlet opening

http://ecomodder.com/forum/showthrea...ean-30057.html

[Xist]

I believe they recommend wrapping tape around the blunt end of the drill bit.

[Lonesome Trail]

Hi Balto, the reason EGR works to combat detonation is it actually 'cools' the burn inside the combustion chamber because, like you said, less oxygen per volume on a naturally aspirated engine (the cylinders can only fit so much air inside vs forced induction where air is being 'forced' in at higher than surrounding air pressure).

Carrying forward, less oxygen means the computer can add less fuel so as to keep the O2 sensors happy, and eventually the computer reaches a happy place on its internal maps with all the sensor data it's being provided and you reach the best efficiency it knows how.

This is another reason why aftermarket tuners 'can' make engines more efficient with custom tunes, because you can tweak those tables to be leaner, sooner, adjust for higher octane fuel which will let you go leaner without pinging, etc not even getting into modifications that can improve volumetric efficiency... Neat stuff, physics meets video games, lol.

Also why EGR was so unpopular back when first introduced with carburetors, because carbs are dumb and the engines ran like poo most of the time, combined with freakishly low compression and all the other bad things Detroit did in the 70s.

[Baltothewolf]

Originally Posted by Lonesome Trail

Hi Balto, the reason EGR works to combat detonation is it actually 'cools' the burn inside the combustion chamber because, like you said, less oxygen per volume on a naturally aspirated engine (the cylinders can only fit so much air inside vs forced induction where air is being 'forced' in at higher than surrounding air pressure).

Carrying forward, less oxygen means the computer can add less fuel so as to keep the O2 sensors happy, and eventually the computer reaches a happy place on its internal maps with all the sensor data it's being provided and you reach the best efficiency it knows how.

This is another reason why aftermarket tuners 'can' make engines more efficient with custom tunes, because you can tweak those tables to be leaner, sooner, adjust for higher octane fuel which will let you go leaner without pinging, etc not even getting into modifications that can improve volumetric efficiency... Neat stuff, physics meets video games, lol.

Also why EGR was so unpopular back when first introduced with carburetors, because carbs are dumb and the engines ran like poo most of the time, combined with freakishly low compression and all the other bad things Detroit did in the 70s.

Thanks for the enlightenment!

[Lonesome Trail]

Sorry, I ramble. I'm actually worse in person, lmao. I just get over-excited about things that maybe I can help folks with. Go Newb!