EGR dilution for more MPG?
 

Hello -

While reading this thread :

News: Only 6% of Americans think diesel will succeed as powertrain option
http://ecomodder.com/forum/showthread.php?t=854

I started googling around for research on Diesel NOx solutions, and I found this paper :

Kettering University researchers visualize environmentally friendly combustion engines
http://www.ensight.com/images/storie.../kettering.pdf
Now, here's my question. Can we simulate this process in our cars? As Ecomodders, are we already doing this to some degree without knowing it?!?!?!?

These were the articles that led me to the PDF :

Cleaning up diesel emissions - Oct. 28, 2005
http://www.kettering.edu/visitors/st...p?storynum=351

The greening of diesel - Aug. 03, 2007
http://www.kettering.edu/visitors/st...p?storynum=595


CarloSW2

Hello -

This is beyond our capabilities, but here's a little more from the same professor dude :

Offroad Exhaust
http://www.motorhelmets.com/htm1/bod...le-offroad.htm
CarloSW2

In TDIs, lots of modding folks disable their EGR for getter performance or prevent intake clogging from the mixing of soot from the EGR and intake oil coming from the crankcase vent and turbo seal.

Disabling the EGR have been shown to reduce FE by as much as 10% on TDIs. So it would make sense that increasing EGR could surely increase FE up to a point, but reducing power. The EGR value in the TDIs ECU can be reprogrammed up to a certain point without throwing a code, but I've never heard of anyone tweaking the value UP for better FE. I might give it a try someday but my vag-com cable (kind of an OBDII cable for VWs) is toast.

With diesels the air charge is more or less always maxed out (there's no throttle plate and on TDIs there's a turbo pushing as much as 15 psi), so they pretty much always run lean, we only play with the amount of fuel injected for the desired power output. It is pretty evident in diesels that more EGR means less fresh air charge hence less injected fuel but also less power. So it's merely a question of FE/power balance.

I don't know much yet about gasoline engines so I can't say what increasing EGR would do.

The problem with low load EGR is irregular combustion. An EGR cooler would be a good start IMO, but even if we could avoid pre-ignition stable combustion may still be a problem due to the proportion of exhaust gasses to air/fuel needed to minimize pumping losses at low load with MPFI. If ya g00gl3 GDI you'll likely find some interesting stuff.

Its a good idea in theory. But, its very hard to impliment and work properly and reliably. This is especially the case when you consider designing a system that will run 200,000+ miles. EGR is not only hot, but its also dirty after thousands of miles. This tends to clog up valves and other system components.

Subscribed:
As a TDI driver I have pondered this, but never done anything.

I only know a few things that may be useful
1) TDI's EGR cooler is HUGE, is water cooled, and from the looks of it could flow around %30 of what the intake manifold can flow
2) Just set the EGR to Close at WOT if you are concerned about power.
3) it makes a noticeable difference on gassers as well supra dropped 1~2 mpg when it was off (un-scientific test over about a year)

they are working on it. but its not street good let alone epa good.

my only would be, if this could easily be done with no adverse effects, and harsh CAFE laws in effect, wouldnt manufacturers be taking better advantage of a system that they designed?!?

Is this effectively varing the displacement of the engine? Is the problem that engines are too big for the job most of the time to run efficiently? Why not have two small engines. Or a clutch in the middle of a larger one for trucks. One runs and keeps both warm until needed. For cars a little tiny 3cylinder (5 to 8HP whatever steady state road load is.) diesel running full tilt charging a battery and or running a motor. only need enough battery for a couple mile hill.

diesel john, WalMart is actually working on a project like that for their fleet trucks. Hybrid diesels where the diesel doesn't have much excess power, the extra force comes from batteries and electric motor.

A couple of factors come into play in an ECM while in EGR mode:

Spark timing vs. EGR rate (Injection timing on a diesel)
Rate of EGR vs. engine load
EGR flow diagnostics.

This has been stated already I think, but to clarify: The EGR by itself does not add fuel economy. What does add fuel economy:
-The ability to run advanced timing while in EGR
-The need to open the throttle slightly with EGR, reducing pumping losses.

I have added 2-4 degrees of extra timing during EGR event in ECM programming, with adverse effects. Unfortunately I have no evidence of whether or not this change improved fuel economy.

Interestingly, the Duramax diesel usually shows a slight improvement in economy with the EGR completely disabled.

Since this thread has been pulled back from the dead, I'll pull back information from another dead thread to offer a new response. :)

Honda uses this technique in their generation 2 L-series engine in place of traditional lean burn. They refer to the technology as "Valve Pause." It supposedly returns slightly better fuel economy then its older d15z1 ancestor.

Source

- LostCause

I know BMW was experimenting with a throttleless gasoline engine a few years ago that used EGR to extensively reduce O2 to the cylinders. Not sure what ever happened to it, I am not up on new BMW stuff.

Personally I think EGR is one of the worst technologies we have put on gas or diesel engines and that targeting NOx emissions are counter productive. Traditionally we have countered NOx with the following methods:

Richen A/F mixture up to 14.7:1 for a 3-way Cat (lowers FE, raises CO & HC emissions)
Retard ignition timing (lowers FE, raises CO & HC emissions)
Lower Compression ratio (lowers FE, raises CO & HC emissions)
Add EGR, facilitates pinging so CR & timing are further reduced and while neither leaning or richening the mixture (gas engine), it does dilute the quality of burn. In a diesel it does displace O2 which hurts FE.

The only good thing that EGR does is promote faster engine warmup and reduce pumping losses in a gasoline engine but cylinder deactivation, VVT and using small turbocharged engines are a better ways to do this.

As pointed out in the TDIs it also soots up the engine which increases maintenance requirements and soot in the oil increases wear. I can verify that EGR has not been good for the powerstroke diesels either.

What we need is Urea injection or NOx reduction catalysts to come online so engineers can start building efficient engines again instead of clean ones.

After blocking off the EGR pipe at the intake manifold on an 89 volvo fuel economy improved by 2mpg on average over many many tanks. Maybe EGR on newer cars is effective but most older systems are carbage.

Hello,
I'm rather intersted in DIY EGR tuning. None of my cars has got OEM EGR, so I collected some OEM EGR parts (Suzuki Swift, Daihatsu Charade). One day I'll weld in such a 'bypass'. The valve is feed by a vaccum switch typically.

A stupid 'controller' would just switch on/off (just for testing) in passengers cabin.
A more practible way would be to provide a PWM depending on load and rpm (and engien temperature).
I picked up also a Swift ECU which should do this. Should be enough for starting. At least I'll see under which circumstances engine runs leaner (less butterfly pressure losses in manifold) - when I dissable EGR from passengers cabin.
I see no disadvantage in bad exhaust - maybe sporty drivebility suffers - but that's not the main goal for eco modders, isnn't it? :)

»Horst

X2!

BTW, NOx reduction catalysts are already in use in most GM products, including the D-max.

I don't think standalone NOx reduction catalysts exist in the mainstream yet.

NOx adsorption catalysts have been around for awhile, but they operate on a different, less useful cycle. NOx adsorption catalysts accumulate NOx until the engine runs rich, where the three-way catalyst can operate normally.

Urea & Adblue injection have been around awhile, but I didn't think they made it over to the United States yet. Is this the technology GM's using? In any case, it's kind of a bittersweet solution as Urea is derived from ammonia, which is manufactured from the heavily energy-intensive Haber process.

Standalone NOx catalysts are in the works, though, and I think it will be a huge deal when they are available commercially. Brown skies, (mostly) good bye.

- LostCause

Hmmm.... I have from several sources that the TWC that GM uses is in fact a HC+CO catalyst as well as NOx reduction cat, hence the term three-way catalyst. They are very specific that the NOx portion is defined as a NOx reduction. I'll have to go back and look that up to refresh my memory. This TWC will only work efficiently for HC+CO and NOx when it operates around stoich.

At any rate, brown skies do need to go!!!

I may need to doublecheck my statement regarding the cat on the Duramax diesel though...

The ones I was thinking about are not available yet but should be ready around 2010 when the regulations step up again.

Your 05 Duramax will only have a 2 way Cat.