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Old 03-06-2017, 11:50 AM   #26 (permalink)
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Originally Posted by [email protected] View Post
I wasn't aware of the PCV problems but that sounds feasible that it's a contributing factor. Screw up something you had working fine for many years. Oil vapor in the intake also causes knock, furthering driving the need for a good PCV system.

I'm not sure why you brought up EGR, but you should know that GM has EGR "systems" on every motor they make in the US and have since the 70's. Most EGR is done internally now with VVT.
GM (and most everyone else with a vvt engine nowadays) uses cam phasing to provide EGR internally. In certain modes early intake valve opening blows exhaust back into the intake tract before the piston starts down again, drawing the exhaust residuals back into the cylinder.

If you've ever had a modern GDI engine apart you would be amazed at how much dirtier everything is on them except for the holes in the tip of the injector. Combustion chamber, exhaust manifolds, turbo, exhaust pipe, exhaust/intake valves, intake manifold, everything on them looks like a chinese diesel engine.

FYI-GM gas engines have had EGR valves later than 2003, not sure where you got that year from. I think external EGR in gas trucks ended with the start of the GMT900 in 2007 but don't quote me.
So this can be tuned out with HP tuners? This does seem more elegant than EGR valves and coolers and such. If electronic tuning can get rid of the cylinder deactivation and EGR cam phasing all that is left is the PCV system. I've seen some well thought out PCV filters on some commercial diesel trucks. That would be pretty easy to retrofit. All this stuff would be easy to undue if it needed warranty repair...well maybe the computer hacks are detectable. Not sure.

Last edited by dpaqu; 03-06-2017 at 12:04 PM.
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Old 03-06-2017, 12:17 PM   #27 (permalink)
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I'm getting off topic in my own thread

Check here
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Old 03-06-2017, 07:34 PM   #28 (permalink)
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Quote:
Originally Posted by [email protected] View Post
I'm not sure why you brought up EGR, but you should know that GM has EGR "systems" on every motor they make in the US and have since the 70's. Most EGR is done internally now with VVT.
GM (and most everyone else with a vvt engine nowadays) uses cam phasing to provide EGR internally. In certain modes early intake valve opening blows exhaust back into the intake tract before the piston starts down again, drawing the exhaust residuals back into the cylinder.

If you've ever had a modern GDI engine apart you would be amazed at how much dirtier everything is on them except for the holes in the tip of the injector. Combustion chamber, exhaust manifolds, turbo, exhaust pipe, exhaust/intake valves, intake manifold, everything on them looks like a chinese diesel engine.

FYI-GM gas engines have had EGR valves later than 2003, not sure where you got that year from. I think external EGR in gas trucks ended with the start of the GMT900 in 2007 but don't quote me.
Its not a random year, GM removed external EGR systems in starting in MY 2003 on GM800 trucks and cars around that time as well they lack an EGR system period. What changed in the 4.8/5.3 was the PCM calibrations, and the catalyst on the cars the cam was respec LSA wise to use the EGR effect of it. The Gen III is a non VVT motor. The Gen IV have VVT some apps and all Gen V are VVT as well.


Here is the Ref from GM for MY2003 EGR removal as proof listed is LR4 but rest of the RPO's read the same.
https://archives.media.gm.com/divisi.../lr4lm7l59.doc
Quote:
Originally Posted by GM
EXHAUST GAS RECIRCULATION REMOVED (RPO LR4)
The EGR control valve and plumbing have been removed from the heavy-duty variant of 4.8L LR4. The EGR system was used to recycle some exhaust gas back into the intake stream to cool combustion and reduce oxides of nitrogen (NOx) emissions. Software refinements in the PCM, and the engine’s overall efficiency, allow the LR4 and 5.3L LM7 to meet all 2003 North American exhaust emissions standards without EGR. Removing EGR reduces cost and complexity, improving both assembly efficiency and reliability. The LR4 was the last Vortec 4800 or 5300 built for North America with EGR
Note the vans still used EGR as well as DBC.
Quote:
Originally Posted by GM
EXHAUST GAS RECIRCULATION REMOVED
The EGR control valve and plumbing have been removed from most 6.0L LQ4s. The EGR system was used to recycle some exhaust gas back into the intake stream to cool combustion and reduce oxides of nitrogen (NOx) emissions. Software refinements in the PCM, and the engine’s overall efficiency, allow the standard LQ4 to meet all 2003 North American exhaust emissions standards without EGR. Removing EGR reduces cost and complexity, improving both assembly efficiency and reliability. The LQ4 built for the Chevrolet Express and Savana retains EGR in 2003.

So again adding a catch can to the Gen V motors and cleaning the intake valves often will help with intake carbon issues as it helps keep oil out of the intake. Cheap insurance. And yes have seen the DI GM V6's and the carbon issues they have had over the years.
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Last edited by Bo185; 03-06-2017 at 07:52 PM.
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