EGR valves in engines

[Lincsman]

Some modern stuff is better off keeping its egr in working order as it helps to bring down combustion temps during hard work.

Thats what EGR's were for, it was a way to reduce the oxygen level of the intake air and reduce the efficiency of the burn so it didnt get hot and emit Nox2

 

[Timbo]

Thats what EGR's were for, it was a way to reduce the oxygen level of the intake air and reduce the efficiency of the burn so it didnt get hot and emit Nox2

Exactly. The theory is -

a) use a relatively small injector with a delayed SOI and a long duration injecting fuel upto ~25 deg after TDC.
b) use an amount of EGR of inert gasses to cool off the burn and limit exhaust temps to keep the exhaust valves / manifold & turbo from melting.
c) Limit the the extra created particulate matter from a) & b) with extra turbo boost pressure and limited fuelling at lower revs creating a very sluggish and unresponsive engine with lower bottom end torque, that has higher pumping losses, low thermal efficiency and high(er) specific fuel consumption due to a) b) & c).

The soot from the EGR eventually restricts the intake and builds up on the back of the intake valves further restricting breathing, leading to even greater soot production...

It's a ridiculous situation, but does work, ish, upto a point.

 

[RHFW]

Exactly. The theory is -

a) use a relatively small injector with a delayed SOI and a long duration injecting fuel upto ~25 deg after TDC.
b) use an amount of EGR of inert gasses to cool off the burn and limit exhaust temps to keep the exhaust valves / manifold & turbo from melting.
c) Limit the the extra created particulate matter from a) & b) with extra turbo boost pressure and limited fuelling at lower revs creating a very sluggish and unresponsive engine with lower bottom end torque, that has higher pumping losses, low thermal efficiency and high(er) specific fuel consumption due to a) b) & c).

The soot from the EGR eventually restricts the intake and builds up on the back of the intake valves further restricting breathing, leading to even greater soot production...

It's a ridiculous situation, but does work, ish, upto a point.

Thanks for all the replies, clearly I live a sheltered life! So.... does the idea still work on Add Blue engines? I guess the AB system won't allow it?

 

[Lakesdigger]

Thanks for all the replies, clearly I live a sheltered life! So.... does the idea still work on Add Blue engines? I guess the AB system won't allow it?

Adblue and egr are/were two different methods of achieving the same result. Adblue has taken longer than egr to become the norm as earlier emissions regs were quite easily met with mild egr systems. Adblue differs in that where egr restricts the operation of the engine to stop nox production adblue is an aftertreatment of nox. So engine happily operates where it wants though producing nox but this is neutralised with adblue in the exhaust. Most now run both egr and adblue.

 

[Wellytrack]

Adblue and egr are/were two different methods of achieving the same result. Adblue has taken longer than egr to become the norm as earlier emissions regs were quite easily met with mild egr systems. Adblue differs in that where egr restricts the operation of the engine to stop nox production adblue is an aftertreatment of nox. So engine happily operates where it wants though producing nox but this is neutralised with adblue in the exhaust. Most now run both egr and adblue.

Although John Deere did briefly balls that up by insisting they wouldn’t need ad blue.

 

[Lakesdigger]

Although John Deere did briefly balls that up by insisting they wouldn’t need ad blue.

Ah but was that to appeal to people who didn't want to have to put anything other than diesel in a tractor. Same thing happened with trucks before. I think JD still use a more egr biased system than NH for example who went adblue for a start and i think only have egr as the regs required it.

 

[Lincsman]

Adblue and egr are/were two different methods of achieving the same result. Adblue has taken longer than egr to become the norm as earlier emissions regs were quite easily met with mild egr systems. Adblue differs in that where egr restricts the operation of the engine to stop nox production adblue is an aftertreatment of nox. So engine happily operates where it wants though producing nox but this is neutralised with adblue in the exhaust. Most now run both egr and adblue.

Do latest NH have EGR with ad-blue?.. they claimed they could do it without.

 

[Timbo]

Do latest NH have EGR with ad-blue?.. they claimed they could do it without.

External EGR free still, but been using some element of internal EGR though zero cam overlap on the exhaust valves

 

[Lincsman]

External EGR free still, but been using some element of internal EGR though zero cam overlap on the exhaust valves

Interesting... so replace cam more power and everyone non the wiser?

 

[Timbo]

Interesting... so replace cam more power and everyone non the wiser?

Basically, close the exhaust valve before the piston reaches TDC so some exhaust gas remains in the cylinder to be mixed with incoming fresh air when intake opens...

 

[Lincsman]

Basically, close the exhaust valve before the piston reaches TDC so some exhaust gas remains in the cylinder to be mixed with incoming fresh air when intake opens...

Yes i get that, but if the cam is replaced with a "conventional" one you could get more power?

 

[Timbo]

Yes i get that, but if the cam is replaced with a "conventional" one you could get more power?

All things being equal, yes you would.

 

[Lakesdigger]

Do latest NH have EGR with ad-blue?.. they claimed they could do it without.

I'm fairly sure to meet the higher emissions tier they had to have egr whether it was needed or not.