What is the EGR mod?

[rabbit-chop]

Since doing the egr and butterfly mods i'v been getting much higher boost levels at lower rpm and part throttle situations, which is great for drivabilty in general, and economy in stop-start driving, but i think its affecting my economy in highway driving, eg, im getting about 10-14 psi cruising 100kmh compared to the 5-8psi before i did the mod.
I was doing alot of city driving for the first few tanks after the mod and economy was better than normal. But fuel economy is sufferring now im doing a fair bit of highway driving.
I dont pretend to understand the mod, i just followed the instructions i printed up off this forum.
Is there a way to control the psi levels in highway cruising situations?

 

[tweak'e]

take your foot off the gas !

 

[rabbit-chop]

lol, yeah, if my right foot was any lighter id roll gently to a standstill! I did put a dump pipe w hi-flo cat in the same day i did egr and butterfly, so that may have something to do with it too?

 

[tweak'e]

on the flat i'm 8-12lb boost at cruise depending on load @ 100kmh. over 100kmh boost goes up quickly. i suspect your probably driving above 100kmh ??

check the airfilter as it will make a big difference.

the other thing worth mentioning is that typically manufactures undersize the turbo to get back some performance lost due to the egr. that means at full noise the turbo is not in a good efficiency range. it doesn't matter to much as your not often at full noise.
however with no egr the turbo may be sitting in a poor efficiency range at lot more.
how exactly that applies to the zd30 i don't know. i don't have the gear here to test it.

we have three navaras and mine is the cheapest (just) to run, despite me being more lead footed than the other two granny drivers who drive completely stock navaras.

 

[Rumpig]

I believe the EGR only works at engine temps below 50c and when the revs are below about 1800 so the mod shouldn't affect anything at highway speeds.

More likely the new dump pipe.

 

[rabbit-chop]

Yeah, i can hold it at about 8psi maintaining 80 in 5th, probly about 10psi at 90 and it really doesnt want to stay below 11 at 100, of course it will rise dramatically with small throttle inputs. The air cleaner is new, i imagine a dirty air cleaner would lower boost levels if anything, maybe its the new dump-pipe, even though the flanges and gaskets between dump and exhaust pipes were only aligned very vaguely by sight, as the bolt holes were much larger than the bolts i was using, and most likely causing restrictions...
The other factor i didnt mention is last tank where i got dissapoining hiway milage i was running 200;1 2t (penrite semi-synth, apart from the mileage runs beautiful), and using the last of it this tank for another 200;1 mix.
Will be driving very carefully this tank to see what happens...

 

[Rumpig]

I sit on 10 psi at 100kmh but have 32"tyres not factory 31"tyres so slightly lower revs around 2700.

I haven't noticed and diffeerence in fuel consumption whenever i run mineral 2T oil at 200-1. Try a bottle of injector cleaner maybe.

 

[rabbit-chop]

ok, myt do that next tank, thanks.

 

[tweak'e]

Yeah, i can hold it at about 8psi maintaining 80 in 5th, probly about 10psi at 90 and it really doesnt want to stay below 11 at 100, of course it will rise dramatically with small throttle inputs. The air cleaner is new, i imagine a dirty air cleaner would lower boost levels if anything,.........

boost at cruise is a reflection of how much fuel is being burnt. a dirty air filter causes turbo to run poorly causing drop in power. so you automatically put foot on gas more to maintain constant speed. more gas = more exhaust = more boost.

see how it goes after the next few tanks of fuel.

 

[mad possum]

i did the EGR mod on my 2011 2.5 d22, i blanked the exhaust side of the EGR pipe, and since then the engine temp has been reading slightly cooler, I'm guessing thats because i'm not using my radiator to cool my exhaust gas now. slightly better economy at the moment, am yet to do a long highway trip since doing the mod.

BTW its only on page 2 of the engine section of the d22 forom where the 2.5 mod has it's own thread. maybe it should be made a sticky?? with more d22 owners every day this question will come up again if it isnt....

 

[tweak'e]

I believe the EGR only works at engine temps below 50c and when the revs are below about 1800 so the mod shouldn't affect anything at highway speeds.

egr runs all the time once engine is up to temp and is not at idle or full throttle. egr is on at all rpms, just the amount varies.

 

[Rumpig]

Glad i blocked it off long ago and fitted a catch can.

Hopefully the water injections cleaned out all the crap that built up beforehand.