Managing EGR for MPG

[DRW]

Carlos, thanks for the visuals. It looks more cohesive that way.

I was tempted to simply add egr to a section that had none, and raise egr where duty cycle was less than 100%. I guess I'll just try it and see.

Today on my commute I set the logger to show EGR temp. I could deduce when egr was open or closed because the temp would go up or down. It dawned on me that I typically cruise on the freeway around 2000 rpm, and at light throttle I saw egr temp go down, so I guess I'm on the section of the egr map where egr is low or reduced.

I also checked and found that the egr passage goes through the engine coolant jacket in the head, so it gets cooled slightly. EGR temp is read after going through the coolant jacket. After cruising on the freeway for 10 minutes egr temp leveled off at about 360 F. so the coolant also gets heated by egr. I'm already running around 197-203 F coolant temps on the freeway, so I'll have to watch temps after I make some changes just to make sure the motor doesn't overheat. I hope that's the only side effect.

I'm also wondering if increasing egr at the 125 degree coolant temp point might hasten warmup? Or will the reduced combustion temp slow warmup?
I know, I know, 'test it and see'. I wish the answers were easy!

[ZugyNA]

Originally Posted by omgwtfbyobbq

It's also why EGR coolers (pg.7) are being considered. They allow a cooler intake charge that reduces the octane requirements needed to run an engine, effectively reducing one of the limits to the percentage of EGR, the other being spark retardation. Essentially, diesel efficiency and characteristics from a low octane gasoline powered SI engine.

One method to cool EGR gases is to use the EGR tube to inject minor amounts of water...some claim HP and mileage gains.

[DRW]

Originally Posted by ZugyNA

One method to cool EGR gases is to use the EGR tube to inject minor amounts of water...some claim HP and mileage gains.

Interesting idea. On my car the EGR passage is cast into the head and intake manifold. The EGR valve is bolted on, so I might be able to rig some sort of adapter in it's place that re-routes EGR gasses to some sort of heat exchanger, then mount the EGR control valve elsewhere. Maybe I could use a spare EGR valve from a junked car and thread some 1/2"NPT fittings. Hmmmm.. OK I have some ideas to work out.

Ironically, if I do this the smog tech personnell might fail me for a modified EGR valve.

[red91sit]

Originally Posted by omgwtfbyobbq

I saw a story on the new behind-the-counter law, and they stated that most meth comes from out of country because it's cheaper to make it and ship it. Honestly, even if they suspect you of using it for illegal pruposes, the most they may do is have a heli buzz your place every now and then. My mom used to put up shade cloth for our dogs during the summer, and the police heli would buzz us once or twice a month, because dogs are weed.

As a member of the Northern States I thought I'd share, meth is HUGE up here, annhydrois (sp) ammonia was getting stolen more often then kids 18" wheeled bikes!! not too long ago we went through a ton of changes, certain medications formulas changed, stores could only have 2 on the shelf at any given time. This was accompanied by more school presentations than i could count. Then the helicopters started in on the busts, we had thermal imaging ones though, they could detect large amounts of heat (in the woods, basements, kitchens) from cook's cooking it. But back on topic,

I noticed some one mentioned using methanol, it should be noted this stuff is real nasty, and even if its' $2 a gallon, It's stoichometric ratio is ridiculously low, to the point gas would still probbly be cheaper at $3 a galloon.

What about running exhaust through an intercooler? from a performance aspect, this makes me cringe, but for efficiency...

I noticed a mention of more horsepower with water injected into the EGR? this doesnt' make sense, we want the egr to reduce horsepower at a given throttle position, and if this was W.O.T. the egr shoudl be shut tighty anyways :S

The reason there is no EGR at idle is not detonatoin, the motor just dies. I opened my egr one time, motor died haha that simple, If i was idleing too high, it would be fine, but it's much better to just lower the idle.

One of these links mentions applying vaccuum to the crank-case, NASCAR actually did this (with an electric pump) and experienced a small improvement in power, even with the extra power required for the pump! I dont' knwo why they don't use them, rules perhaps?

[onegammyleg]

Originally Posted by red91sit

One of these links mentions applying vaccuum to the crank-case, NASCAR actually did this (with an electric pump) and experienced a small improvement in power, even with the extra power required for the pump! I dont' knwo why they don't use them, rules perhaps?

A mechanical racing vac pump..


This is related to reducing windage effects.
Most racing engines are equipped with breathers in order to help reduce crankcase pressure which can cause oil leaks and adversely affect the way an engine performs.

By further reducing this pressure in the crankcase with the help of a vacuum pump, a number of improvements can occur.
Theoretically a piston on the downward compression stroke has less resistance to impede its progress, allowing it to accelerate faster.

Sump vacuum helps to draw oil from the engines internal rotating parts as well., which reduces rotating weight and returns the oil to the pan for cooling faster.
The oil vapour in the crankcase is reduced , captured and drained into a vomit tank for later disposal.

An example of a 555ci big block chevy drag engine gave a 30hp improvement with an air pump compared to when fitted with normal PCV breathers.

These pumps will benifit mostly very large high rpm motors.
In a small 4 FE motor thats not going to spin very fast at all the losses would greatly outweigh the gains.

[molecule]

great thread...
i have some more definitive knowledge on the honda egr...
at least the hardware...

all obd1 or earlier egr systems use a combination of manifold pressure and electrical activation to determine if the egr opens...
where not only is it computed to electrically open...it is also mechanically controlled by vacuum...

my only obd1 egr experience is on the vx (d15z1)
egr is routed through exhaust (behind exaust valve) through a small opening to the egr valve mounted on the intake manifold
it is then distributed to 3 of the intake runners (if open)
there is not a removable egr cover on the vx manifold...it is cast into its structure 100%
they left #1 runner out of the loop i believe to make egr problems easy to sort out by reading spark plugs...
if spark plugs #2,#3 & #4 are different from #1 then its likely an egr issue...

all p2j cast obd2 heads have egr built into the head...
i just bought a y8 head recently and was confused to find it had egr
then realised honda loves simplicity...
so if you own a y8 engine you can add egr simply by using an egr intake manifold
i have seen obd2 egr valves that are actutated by only electrical...
i have also seen them with vacuum (mechanical) ports on them
just received an obd2 hx (d16y5) manifold and it is purely electrically controlled (3-wire)
the obd2 egr distribution on the intake manifold is more developed.
it has an array of mini-runners to each intake runner leading off a center chamber supplied by the egr valve as pictured in my teardown below
and might i add...what a great place for direct port nitrous or hydrogen...
or as mentioned earlier in the thread...a place for cooling the egr charge...
not sure if cooling the charge would outweigh the benefit ratio
that being the air mass ratio to the oxygen content....
where if you are cooling the egr then each cylinder could afford more of it and therefore a greater duty cycle but then affecting the a/f more severely...
and perhaps too great a loss of power...
well then on with the pics

egr cover under the fuel rail :: egr valve is at the other end (gold top)


egr cover removed


sealing gasket removed from inner runners


when i sold my vx i believe the egr valve was not responding and mileage had dropped from 48-52mpg down to 40-44mpg
i couldn't find anything else but thought this loss was too high to just be egr
never know...i guess it could be that significant on a higher mileage motor...
compression was perfect across all 4 cylinders

[omgwtfbyobbq]

Originally Posted by ZugyNA

One method to cool EGR gases is to use the EGR tube to inject minor amounts of water...some claim HP and mileage gains.

Yeah, I've seen plenty of systems, but it seems that manufacturers tend to shy away because of the need for refilling the system with water and the potential for something to screw up and inject a lot of water. Otoh, there's been some stuff about emulsified fuels, which may provide the benefits w/o the complexity.

[DRW]

Yes, my car is OBD1 and it has a vacuum actuated EGR valve. The vacuum is metered through a solenoid which is controlled by the ecu. On my car the EGR port dumps into the manifold through one port just behind the throttle body plate. I suppose the engineers thought there would be enough turbulence in that area to evenly mix the exhaust gasses with fresh air.

To cool EGR I doubt it'll require an intercooler. The passage is about 1" round, so there isn't much volume to cool. I was thinking about using a small oil cooler, maybe a two row power steering oil cooler. I'll see what I can find in the junkyard tomorow.

I had another look into the ecu disassembly and found the EGR map for the auto tranny version of my car. It's slightly different, most notable is the minimum value of 3B. I suppose this is the lower limit that the engineers felt safe using. I think I'll make some changes and see what happens.

FYI the ecu code uses hexidecimal numbers which uses a base of 16, so to count in hex it goes like this:
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F,
10, 11, 12...1A, 1B, 1C, 1D, 1E, 1F,
20...

[MetroMPG]

Originally Posted by DRW

I was thinking about using a small oil cooler, maybe a two row power steering oil cooler. I'll see what I can find in the junkyard tomorow.

Would a cooler cause water vapor to condense out of the exhaust? If so, would you have to have a way to periodically drain it?

---

Noticed another point in the VX article linked in that supports the EGR mod idea, but for a reason not yet raised in this thread:

Honda modified the VX to use exhaust gas recirculation (EGR) instead of excess air to dilute a stoichiometric air/fuel ratio. Using EGR, exhaust gases are recirculated into the combustion chamber to
reduce NOx emissions by lowering combustion temperature. EGR also improves fuel economy by using energy from the waste stream. However, lean burn is more efficient than EGR.

Now that i've got datalogging capability I'll also have to look to see whether EGR control is one of the parameters I can monitor. (I know it's in the list of parameters in the software, but the car doesn't necessarily have all the sensors the software can monitor.)

[MetroMPG]

'Nother question: for the purposes of testing, someone on TeamSwift suggested using bottled CO2 and feeding it into the intake. Not a bad idea, assuming I can get flow rates high enough to work. And where the heck would one get bottled CO2 anyway?

Another plus to that approach: avoids the charge heating issue/pinging.