Exhaust Gas Recirculation Emission Requirement

[philip]

Just a question thats sorta related to headers but has nothing to do with the SD22, Do I have to run a EGR valve with headers to pass inspection (headers for the maxi)? Can I take it off or do I have to weld up a bung to connect the tube? If I do thats going to be a pain to do. Think I can just run the tube under the intake manifold and itll look like its connected and ill pass?

ANY emission control component is illegal to remove or disable these days. So headers having no EGR provision installed on a vehicle that had EGR originally is "illegal."

Back to diesels, certainly the applied legality hinges on whether or not diesel passenger cars in your area/state are being checked periodically for exhaust emissions. Visual and operational checks are made so when the specs say the vehicle was originally sold with EGR, the EGR system has to be in place AND pass a functional test.

I have tried running my SD22 (bosch inline pump) with and without EGR and with some different injection timing settings. So long as the timing is stock or a couple degrees over advanced, EGR makes no difference in power or fuel mileage. But with timing retarded a bit and EGR operative, the throttle response is not as crisp. Slight drop in fuel mileage.

Also on my SD powered pickup, the vacuum amplifier's calibration will modulate the EGR valve when intake manifold vacuum is extra high (coasting condition)(remember, the inline pump uses a air throttle body). This has the effect of slightly extending the time the engine takes to return to idle. This effect is most noticable when quick shifting 1-2 and 2-3.

[philip]

The newest generation of USA diesel spec'd diesel engines will be using more EGR than ever before.

" The EGR capacities of all the engines are being increased. An EGR system takes some of the exhaust gases, cools them and reroutes it back into the combustion cycle. This cooled exhaust gas is still hotter than fresh intake air but the effect of diluting fresh air with recirculated exhaust gas is a reduction in peak combustion chamber temperature. This in turn reduces NOx emissions.

Current EGR systems recirculate about 10% of the exhaust; but the 2007 systems will increase that to about 20% to 35%, depending on the engine model and engine load at any given moment.

The "enhanced" EGR, as some suppliers call the updated system, requires slightly larger radiators and cooling hardware.

Another change for 2007 is that all emissions will count toward an engine's total emission output, so no longer will there will any unfiltered crankcase ventilation into the outside air. That may be a small thing, but it will add to maintenance. " (source: Light & Medium Truck June '06)

Related threads:

SD22 & 25 Crankcase Ventilation Systems
SD22 Cam Profile

[asavage]

The cooling of EGR is new. I've never seen a cooled EGR system, though I've heard of them. EGR became common in the US in 1973.

". . . the 2007 systems will increase that to about 20% to 35%, depending on the engine model and engine load at any given moment.

I've read at least one person propose that greater EGR volume in a gasser can have the potential of increased fuel mileage at light to moderate loads. The theory goes something like: one of the inefficiencies of throttled engines is pumping loss, the wasted energy used to create and maintain intake vacuum. By increasing the volume of recirculated exhaust gas, the intake vacuum can be less (ie higher pressure) and thereby some of the pumping loss ameliorated -- I hope I spelled ameliorated correctly, I've never typed it before.

Anyway -- in a gasser/throttled situation, EGR may have the potential to increase engine efficiency in certain modes of operation. So it was said.

Another change for 2007 is that all emissions will count toward an engine's total emission output, so no longer will there will any unfiltered crankcase ventilation into the outside air. That may be a small thing, but it will add to maintenance. "

This is a shocker. What vehicles in 2006 have open crankcase ventilation? I thought that was sealed up long ago, not so much for HC reduction but to keep dirt out of the engine. Road draft tubes are notorious as a source for lube oil contamination. The "positive" in Positive Crankcase Ventilation in a gasser is the positive (ie forced) airflow from filtered air -- usually from downstream of the air filter, but sometimes a separate filter altogether -- through the crankcase and back to the intake manifold via a fixed orifice or a PCV regulation valve -- not too many of those PCV valves in use these days, with FI being able to cope with larger air "leaks".

That flow of air carries at least one of the combustion byproducts -- water -- out of the crankcase, reducing (water + sulfur = sulfuric acid, + other byproducts = ) sludge formation.

For that reason, I've always been a fan of the PCV system. Closed CCV was first mandated in California in about 1960 or '61.

[philip]

The cooling of EGR is new. I've never seen a cooled EGR system, though I've heard of them. EGR became common in the US in 1973.

Cooled EGR is hardly new. First ones I saw using engine coolant to reduce EGR temperatures was in Ford Crown Vics of the late '80's. But know too that California gets ALL the cutting edge smog stuff first.

[philip]

EGR reduces NOx which is the key component in photochemical SMOG. Conventional diesel EGR systems combined with closed crankcase ventilation systems WILL promote substantial accumulations of oily soot throughout the intake tract ... no argument.

My SD22 with its road draft tube has no sludge or varnish present in the valve train area. All gasoline vehicle service schedules I have ever seen say dusty road conditions warrant the shortest oil service intervals. And gasoline engines have closed crankcase venting systems (no road draft tubes) since the early 1960s.

What evidence do you have that the conditions you mention above reliably result in oil contamination via the road draft tube? How could you be sure any oil contamination occuring under dusty road conditions was not the fault of intake air leaks or poor air filtration?

[Zoltan]

I have tried running my SD22 (bosch inline pump) with and without EGR and with some different injection timing settings. So long as the timing is stock or a couple degrees over advanced, EGR makes no difference in power or fuel mileage. But with timing retarded a bit and EGR operative, the throttle response is not as crisp. Slight drop in fuel mileage.

Would anything warrant the removal of the EGR then? In Hawaii we don't have emission tests and if I can improve the performance of the truck or extend the life of the engine, I could remove the EGR.

[philip]

Would anything warrant the removal of the EGR then? In Hawaii we don't have emission tests and if I can improve the performance of the truck or extend the life of the engine, I could remove the EGR.

You're asking me to opine. Ok

An undesireable side effect of EGR in a diesel is faster engine oil contamination. Along with filtered fresh air, your SD22 is now inhaling some abrasive exhaust ... with an SD23/SD25 you ALSO get blow-by oil which combines over time with exhaust carbon to cake up the intake manifold.

This is also born out in Direct Injection diesels too (SD is Indirect Injection). But recent generation diesel specific oils are formulated to handle better this extra carbon that finds its way into your engine oil compared to available oils back in 1982.

You -could- make the argument that occasional chunks of carbon passing through the EGR valve or separating from the underside of the intake valves -could- wedge between the piston and cylinder causing cylinder damage. Does this really happen? I cannot say with certainty. But I do have photos of an SD22 with suspicious gouging in the upper half of each cylinder.

So long as the ignition timing is set to specs, disconnecting an otherwise correctly functioning EGR system did not make a perceptable difference in the way my engine performed or in fuel mileage when driving very conservatively (for max MPG).

[philip]

SNIP I've read at least one person propose that greater EGR volume in a gasser can have the potential of increased fuel mileage at light to moderate loads. The theory goes something like: one of the inefficiencies of throttled engines is pumping loss, the wasted energy used to create and maintain intake vacuum. By increasing the volume of recirculated exhaust gas, the intake vacuum can be less (ie higher pressure) and thereby some of the pumping loss ameliorated -- I hope I spelled ameliorated correctly, I've never typed it before.

Anyway -- in a gasser/throttled situation, EGR may have the potential to increase engine efficiency in certain modes of operation. So it was said.

For best emissions in a gasoline engine, the goal of EGR is to make combustion time longer BUT within certain limits. The peak combustion chamber pressure for best mechanical advantage still needs to occur between 10-15 degrees ATDC ... AND ... combustion must effectively end before the exhaust valve lifts off seat. Diluting the fresh air/fuel with an unburnable component (exhaust gases) allows ignition timing to be set earlier but maximum combustion pressure must still occur in the optimum 10-15 degree ATDC. EGR systems along with more spark lead delivers a weaker air/fuel mixture and more total burn time before the exhaust valve opens.

Regarding alleged lower manifold vacuum. The vehicle requires a set amount of power to maintain speed. If you reduce the power produced by the engine, the vehicle speed drops. The introduction of EGR displaces fresh air/fuel so .... power output drops as you increase EGR.

The driver reacts by opening the throttle little further in order to maintain vehicle speed. This -reaction- by the driver is what lowers intake manifold vacuum. More EGR delays and lowers peak combustion pressure point in piston travel ATDC which in turn increases fuel consumption. So ... you will find EGR is occompanied by more timing advance at a given rpm and light throttle load compared to non-EGR in order to restore peak combustion pressure to the 10-15 degrees ATDC range.

Now whether or not all this results in better fuel mileage is debateable. You will find an increasing number of late model gasoline engines with variable intake cam timing often have no EGR valve. In these electronic engines, "internal" EGR can be accomplished by grossly increasing valve overlap (by advancing the intake cam timing) at low engine RPM.

Here is the VVT-i explanation for my 2003 Corolla.



BTW, have you noticed that only SD engines having the Bosch inline (with the pneumatic governor) ever have an EGR system fitted? Even so, not all of these Bosch RBD/MZ injection pumps have an EGR system fitted. Of course my California SD22 has EGR. I have found no VE equipped SD engines with EGR.

[philip]

The cooling of EGR is new. I've never seen a cooled EGR system, though I've heard of them. SNIP

Al. Yesterday my friend with the '98 Jetta TDI came over with hat in hand. The Check Engine light was ON again. A code P1550 appeared on my scanner which led around to a duty solenoid next to the air filter.

Of relevance is that this '98 TDI has an EGR cooler on it. The thing is located on the intake manifold and either the supply or return hose from the heater core feeds it.

[philip]

SNIP- What vehicles in 2006 have open crankcase ventilation? I thought that was sealed up long ago, ... -SNIP

Al: In looking up info about diesel emissions, I ran across this little tidbit from ISUZU :

No more road draft tubes starting 2007

Click: ENGINES / ENGINE EMISSIONS / CLOSED CRANKCASE

"The 2007 emission regulations require that all engine gas emissions be reduced, including crankcase gas. As a result, we'll be adding a closed crankcase system that reroutes ventilation gases back into the engine for combustion. Some systems will have serviceable filters to collect residual crankcase oil. "

[philip]

{This is a 2 yr old post by Al from the MSN Nissan forum.}


From: al_savage Sent: 12/12/2004 12:18 PM
". . . in order to minimize the amount of unburned diesel . . . "

A diesel in good condition has nearly no unburned fuel at the tailpipe (very very low HC emissions). Even when cold. That's the primary reason why diesel cars were exempt from emissions testing for so many years: they burn so much cleaner (in HC & CO) than their gasoline counterparts.

It was only when gas cars got much cleaner than the EPA came around to diesel emissions testing.

In diesels, the fuel is squirted into the middle of hot air, where it ignites. Very, very little fuel makes it to a cold cylinder wall or combustion chamber, which is the major reason why the HC is so low.

Recirculating exhaust gas, which is oxygen depleted (relative to intake air anyway) reduces peak combustion temperature & pressure by displacing oxygen-rich intake air, and if done accurately can reduce NOx emissions with only minor increase in particulate emissions (sooting).

EGR systems are always inactive at idle, and at cold engine temeratures.

"Also, when the EGR is activated manually, no matter what the engine temperature is, the RPM goes up, which means that more fuel is going to the engine."

Yes & no. You gotta dig that on the SD22, the fuel volume is controlled by the IP which "decides" how much fuel to deliver based upon intake vacuum. When you manualy open the EGR at idle you change the intake vaccum and the IP sends more fuel. It's not fuel in the exhaust that is raising the RPM.

As Philip has said in the past, you can't apply std troubleshooting ideas to the SD22; it's neither a typical diesel nor a typical gas control system.

"activated EGR would increase combustion temperatures."

Adding EGR never increases CC heat. Exhaust gas is a combustion efficiency reducer.

Back to the OP's problem:

Now, theoretically, if the injection system wasn't vacuum feedback controlled, and you manually activated the EGR as far as it would go and propped the fuel feed to compensate, you can get misfire and fuel out the tailpipe. This is actually a fairly common scenario in gas cars with a faulty EGR valve. But you have to have significant EGR on a diesel to misfire, at least the ones I've worked on. Just a little EGR at idel won't cause misfire, because most diesels have way too much air available at idle anyway -- SD22 possibly excepted.

None of the SD22s up this way are equipped with EGR. AFAIK, that was a California-only thing in those days.

Regards,
Al S.

[asavage]

{This is a 2 yr old post by Al from the MSN Nissan forum.}

From: al_savage Sent: 12/12/2004 12:18 PM

Wow! A blast from the past.

The internet never forgets . . .

EGR systems are always inactive at idle, and at cold engine temeratures.

I was mistaken. The LD28 as installed in the Maxima actually runs quite a bit of EGR at idle. I didn't know that at the time I posted the above though.

[philip]

EGR systems are always inactive at idle, and at cold engine temeratures.

I was mistaken. The LD28 as installed in the Maxima actually runs quite a bit of EGR at idle. I didn't know that at the time I posted the above though.

Maybe ... maybe not. When ... you have a defective vacuum amplifier or a condition that produces a weak signal vacuum signal to the amplifier at idle, then the EGR will modulate at idle ... when it should not.