EGR: The good, the bad and the ugly??

[Pinger]

If I was determined to reduce throttling losses on a four stroke I'd go straight to the source of the problem and eliminate the throttle valve.
There have been some - but not many - engines that have done that and used valve timing and lift to control air flow. They have been four valve per cylinder engines and to my mind absurdly complex. A simple two valve per cylinder pushrod engine could IMO be configured relatively easily and be a much better solution than EGR.

 

[L31MaxExpress]

If I was determined to reduce throttling losses on a four stroke I'd go straight to the source of the problem and eliminate the throttle valve.
There have been some - but not many - engines that have done that and used valve timing and lift to control air flow. They have been four valve per cylinder engines and to my mind absurdly complex. A simple two valve per cylinder pushrod engine could IMO be configured relatively easily and be a much better solution than EGR.

Nissan did that on their VVEL engines for the most part. 90% of the throttling is done by variable intake cam lift and duration

 

[thinger2]

We considered that fashionable back then.

Thats the truth.
My high school girlfriend called it "Battery Boutique"
We wore acid washed jeans way before they became high fashion.

 

[racprops]

Diesels control their power with how much fuel is injected, I am wondering why at low RPMs and Low Loads why I cannot just cut back on the fuel injection....Perhaps rig up a false throttle position reading, like it is a almost completely closed when it is wide open....

 

[Pinger]

Diesels control their power with how much fuel is injected,

Completely different combustion systems.

I am wondering why at low RPMs and Low Loads why I cannot just cut back on the fuel injection....Perhaps rig up a false throttle position reading, like it is a almost completely closed when it is wide open....

Lean flammability limit.
What you propose requires charge stratification. Good luck with that!

 

[Pinger]

Nissan did that on their VVEL engines for the most part. 90% of the throttling is done by variable intake cam lift and duration

Fiat did the same with its MultiAir system and BMW with Valvetronic. Those two were relatively small engines so working at relatively high loads where the pumping losses are low anyway. The gains with larger engines could be significantly better and on simpler engines (eg pushrod) less complex to implement.

 

[L31MaxExpress]

Fiat did the same with its MultiAir system and BMW with Valvetronic. Those two were relatively small engines so working at relatively high loads where the pumping losses are low anyway. The gains with larger engines could be significantly better and on simpler engines (eg pushrod) less complex to implement.

Nissan does it on their 3.7L and 5.6L. The 5.6L pulls incredibly smooth at very low rpm, with a very broad, flat torque curve.

This is a stock VK56VD dyno pull.

You must be registered for see images attach

 

[wb292]

Ok I’ll throw my 2 cents in here. Introducing exhaust gas is going to displace oxygen. Yes the combustion temperature is lowered because there is less oxygen and therefore a smaller explosion. So you will need to add more throttle to do the same amount of work. Therefore reducing fuel Efficiency. We know more vacuum increases fuel economy because liquids turn to vapor easier under vacuum. This promotes a more even fuel dispersion in the cylinder before the compression stroke. Pumping parasitic loss would change the vacuum on the intake stroke and reduce fuel dispersion. Next exhaust gases are burnt hydrocarbons and abrasive. Promoting piston ring wear. They any foul intake streams. Valves/runners etc. This is a great way to reduce the engine lifespan.I drive 68 miles each way to work and have been on a quest for better mileage for quite some time. My test rig is a 1991 K1500 RCSB with a 350 and a 5speed. The EGR reduced my mileage by 1MPG because light loads at freeway speeds when it was open a lot. I removed everything that the engine didn’t need to function along with small rolling resistance reductions. I consistently get 20 to 21MPG. There are far better ways to increase mileage .

 

[racprops]

Ok I’ll throw my 2 cents in here. Introducing exhaust gas is going to displace oxygen. Yes the combustion temperature is lowered because there is less oxygen and therefore a smaller explosion. So you will need to add more throttle to do the same amount of work. Therefore reducing fuel Efficiency. We know more vacuum increases fuel economy because liquids turn to vapor easier under vacuum. This promotes a more even fuel dispersion in the cylinder before the compression stroke. Pumping parasitic loss would change the vacuum on the intake stroke and reduce fuel dispersion. Next exhaust gases are burnt hydrocarbons and abrasive. Promoting piston ring wear. They any foul intake streams. Valves/runners etc. This is a great way to reduce the engine lifespan.I drive 68 miles each way to work and have been on a quest for better mileage for quite some time. My test rig is a 1991 K1500 RCSB with a 350 and a 5speed. The EGR reduced my mileage by 1MPG because light loads at freeway speeds when it was open a lot. I removed everything that the engine didn’t need to function along with small rolling resistance reductions. I consistently get 20 to 21MPG. There are far better ways to increase mileage .

OMG I forgot the vacuum promotes liquid to vapor fracture....you had me at that point...

The question is does it work in the millisecond of time during the combustion and firing part of the engine power cycle??

Your other points about "

exhaust gases are burnt hydrocarbons and abrasive. Promoting piston ring wear. They any foul intake streams. Valves/runners etc. This is a great way to reduce the engine lifespan."

Is something to think about. Thanks.

Rich

 

[Pinger]

Ok I’ll throw my 2 cents in here. Introducing exhaust gas is going to displace oxygen. Yes the combustion temperature is lowered because there is less oxygen and therefore a smaller explosion. So you will need to add more throttle to do the same amount of work. Therefore reducing fuel Efficiency.

The same amount of fuel/air is required irrespective of the presence of EGR. But, that wider throttle opening reduces throttling losses.

We know more vacuum increases fuel economy because liquids turn to vapor easier under vacuum. This promotes a more even fuel dispersion in the cylinder before the compression stroke. Pumping parasitic loss would change the vacuum on the intake stroke and reduce fuel dispersion.

That old chestnut of best economy at lowest vacuum is just another way of saying keep your foot out of the gas pedal to maximise mpg. The best efficiency will be at the point of maximum torque (with sufficient - but not necessarily WOT - throttle opening) when there is greater power output which overshadows the frictional losses which to some extent are fixed - not dependent on throttle opening (with the exception of throttling losses).
Vapourisation isn't the concern it used to be in the days of carbs. Port injection atomises well. If you want to improve it, ditch the throttle valve and apply control through valve opening. The turbulence at the valve seat will improve atomisation/dispersion and is exactly where it's required - entering the cylinder.