does my 2001 QX4 have an EGR valve or system?

[mvmcali]

i am familiar with PCV valve and what it does but not so much about EGR.
I think its a valve / feedback system that takes exhaust gasses and reroutes them under computer control thru a valve back into the intake manifold?

do newer cars NOT have an EGR system. im looking in my service manual and see no mention in index of EGR
sorry for dumb question

[AZhitman]

https://www.nissanpartsdeal.com/parts/n ... 1w601.html

You do have an EGR, yes.

Maybe a better pic here: https://www.nissanpartsdeal.com/parts/n ... 24f10.html

[mdmellott]

I think its a valve / feedback system that takes exhaust gasses and reroutes them under computer control thru a valve back into the intake manifold?

do newer cars NOT have an EGR system. im looking in my service manual and see no mention in index of EGR
sorry for dumb question

Yes and No - Not a dumb question at all
2001 QX4 with 3.3L VG33E engine - Yes
2001 QX4 with 3.5L VG35DE engine - No

This same result in cars without an EGR valve is accomplished on many newer and older gasoline engines through the use of variable camshaft timing. By altering the length of the overlap period , varying amounts of exhaust gas can be used to affect the next intake cycle. Overlap refers to the period when the intake and exhaust valves on a given cylinder are partly open at the same time.

[AZhitman]

Good catch, MD - I didn't realize 2001 was a crossover engine year. Thanks for clarifying!

[Mike W.]

i am familiar with PCV valve and what it does but not so much about EGR.
I think its a valve / feedback system that takes exhaust gasses and reroutes them under computer control thru a valve back into the intake manifold?

do newer cars NOT have an EGR system. im looking in my service manual and see no mention in index of EGR
sorry for dumb question

EGR got a bad rap early, for a variety of reasons, some real, some imagined. By injecting burned, inert gasses, it lowers combustion chamber temps, reducing Nox. Often it's disabled at idle and full throttle, which means it has no effect on performance. But the concept suggests a loss of performance, and especially with carbs, it wasn't well controlled often resulting in poor drivability. So if done well it's not a bad thing, but if done poorly, disconnecting it can make the car run better.

[VStar650CL]

This same result in cars without an EGR valve is accomplished on many newer and older gasoline engines through the use of variable camshaft timing. By altering the length of the overlap period , varying amounts of exhaust gas can be used to affect the next intake cycle. Overlap refers to the period when the intake and exhaust valves on a given cylinder are partly open at the same time.

What Md explained is called "Miller cycling", and it's also why you should never drive around in a Nissan with a dying catalytic converter. If the cat melts, the Miller cycle will cause the engine to inhale the 2000 degree debris. That's bye-bye engine just about 100% of the time.

[mvmcali]

Yes and No - Not a dumb question at all
2001 QX4 with 3.3L VG33E engine - Yes
2001 QX4 with 3.5L VG35DE engine - No

This same result in cars without an EGR valve is accomplished on many newer and older gasoline engines through the use of variable camshaft timing. By altering the length of the overlap period , varying amounts of exhaust gas can be used to affect the next intake cycle. Overlap refers to the period when the intake and exhaust valves on a given cylinder are partly open at the same time.

@MD... thanks ... i assume that means the DE engine has variable timing? im surprised the govt (especially here in the peoples republic of california allows the auto makers to address the emmissions issue on their own , ie solve it with egr or variable timing. that is.. im surprised they dont say everyone needs the egr valve/system period.

[mvmcali]

What Md explained is called "Miller cycling", and it's also why you should never drive around in a Nissan with a dying catalytic converter. If the cat melts, the Miller cycle will cause the engine to inhale the 2000 degree debris. That's bye-bye engine just about 100% of the time.

@Vstar thanks. but just to clarify.. is the EGR control looking at the output of front o2 sensor or rear o2 sensor to know how much exhaust to inject back into engine? Also..whether or notthe cat fails... isnt the exhaust being injected back into the engine coming from the same place ? (ie same temp gas).. so it would be a question of how often that "valve" is open?

[VStar650CL]

On Miller cycle engines the ECM just has a "map" for the IVT based on RPM and power demand. Most later Nissans have an EGR valve that's variable and have a similar map of how far to crack the valve under given circumstances. The earliest systems didn't have computer controls and really sapped power because of it.

[Mike W.]

@MD... thanks ... i assume that means the DE engine has variable timing? im surprised the govt (especially here in the peoples republic of california allows the auto makers to address the emmissions issue on their own , ie solve it with egr or variable timing. that is.. im surprised they dont say everyone needs the egr valve/system period.

Yes the VG35DE has variable valve timing.

They do to some degree dictate controls, the ability to drive in HOV lanes given the technology on certain cars, regardless of their or others performance. But even at worst, I think there's an awareness that there are different engine designs, for a variety of reasons and one size fits all in terms of controls doesn't work so they mostly focus on tailpipe.