question about EGR (not how to block it)

[adamros14]

Guys i was going to block my EGR and change around the vacuum line but i came across this posted by nissan.

"In designing the ZD30 engine, Nissan engineers increased the Exhaust Gas Recirculation (EGR) rate. This results in a gradual combustion process in which the mixture does not burn instantaneously following ignition, which keeps the combustion temperature from rising".

"Variable Swirl Mechanism

In the ZD30 engine, Nissan�s variable swirl mechanism consists of the tangential port, helical port and swirl control valve but in normal engine speed range, the swirl valve is closed and air is inducted only through the helical port � which works to generate powerful swirl for stable combustion.

At high engine speeds, the swirl control valve is opened and air is also taken in through the tangential port � increasing the intake air quantity in proportion to the larger amount of injected fuel to achieve thorough combustion characterized by little exhaust soot".

doesn't this mean that the engine was designed to work best with the egr active and the swirl valve closed and opened when needed. therefore we should not block the egr but instead just install a catch can and clean the intake periodically??
what do you guys think?

 

[Dave]

Blocking the EGR lowers the EGT's.

However when hitting a hill it will go up to 400 degrees which is safe. If it hits 550, thats when you back off.

My Nav being intercooled and a upgraded exhaust runs at 280-300 degrees on the pyro at 100km/h on the flats.

Hit a hill and you can see it go up to 400 degrees. Towing 2T, mine wont go past 420 degrees on the pyro.

 

[brendan]

please note i am pretty sure dave runs the sensor AFTER the turbo which temps can fall by 200 degrees
BEFOR the turbo is the only true temp you will get

 

[alphabet]

So if we do the egr mod we should install a pyro?

 

[Dave]

please note i am pretty sure dave runs the sensor AFTER the turbo which temps can fall by 200 degrees
BEFOR the turbo is the only true temp you will get

Indeed mine is.

If you remember it drops 200 degrees through the turbo your on the money.

A pyro is a very worthwhile device.

 

[Old.Tony]

Adamros, the real reason the EGR is included is to reduce nitrogen oxide emissions by dampening the combustion temperature to the point where NOx just isn't produced in such quantities. This allows the CAT to additionally reduce the NOx levels and bring the actual output of NOx to a level below that specified by the government.

Essentially the end result is a less efficient motor. Blocking the EGR allows the engine to produce a little extra power and more completely burn the fuel - it's not 100% though.

There's also EGR from the crankcase ventilation system (PCV) which is fed back into the air intake (along with the oil mist that isn't caught by the oil separator in the top of the engine) and combusted. That's the reason why JASO-FD oil is recommended for our diesels (and particularly for anyone with a D40 auto fitted with a DPF).

I don't believe that blocking the EGR should be justification for fitting an EGT gauge. Anyone with a turbocharger (petrol OR diesel) should have an EGT gauge, so that the turbocharger - and ultimately the engine - can be protected. The problem is that when a turbo is shut down before cooling sufficiently, the oil in the turbo's bearings cooks, forms a hard varnish and ultimately destroys the turbocharger - usually only when the turbocharger is spooled up, which means you're in boost range - high RPM - and the compressor lets go, sending chunks into the combustion chamber (or intercooler).

 

[tweak'e]

Guys i was going to block my EGR and change around the vacuum line but i came across this posted by nissan.

"In designing the ZD30 engine, Nissan engineers increased the Exhaust Gas Recirculation (EGR) rate. This results in a gradual combustion process in which the mixture does not burn instantaneously following ignition, which keeps the combustion temperature from rising".

"Variable Swirl Mechanism

In the ZD30 engine, Nissan�s variable swirl mechanism consists of the tangential port, helical port and swirl control valve but in normal engine speed range, the swirl valve is closed and air is inducted only through the helical port � which works to generate powerful swirl for stable combustion.

At high engine speeds, the swirl control valve is opened and air is also taken in through the tangential port � increasing the intake air quantity in proportion to the larger amount of injected fuel to achieve thorough combustion characterized by little exhaust soot".

doesn't this mean that the engine was designed to work best with the egr active and the swirl valve closed and opened when needed. therefore we should not block the egr but instead just install a catch can and clean the intake periodically??
what do you guys think?

the EGR, swirl valve and egr butterfly is simply there to reduce NOx.

his results in a gradual combustion process in which the mixture does not burn instantaneously following ignition,

is a nice PR way of saying it snuffs out the flame.

At high engine speeds, the swirl control valve is opened

high........about 1700rpm...o yeah thats really high LOL.

these motors are one of the early high egr motors ie they use a lot more egr than previous engines. afaik other manufactures use a similar system. same injection system, swirl valve etc.
the main point to the swirl valve is about decreasing the air flow and increasing egr flow. problem is that at low rpm there isn't a large difference between exhaust gas pressure and boost, so little EGR flows. so they use an inlet butterfly to lower the pressure in the manifold so more exhaust gas will flow in. however that butterfly doesn't do a lot at low rpm, so at very low rpm the swirl valve blocks half of the intake system (reduces air by 50%) thereby increasing the amount of egr to air ratio.

 

[pointblank5]

yeah that swirl valve is definatly a gimmick... if you really wanted to increase the velocity of the air going through the inlet valves in the head, you would have to reduce the diameter of the WHOLE inlet tract from the swirl valve to the inlet valves, not just place a restriction half way down.

and if it was so beneficial to have "swirling" air before it reaches the inlet valves why arent we all fitting Hyclones lol

James

 

[Navara09]

I actualy did a dyno tonight on my nav and did two runs; 1 with the EGR open and the 2nd with the EGR blocked. the dyno showed no change in power but a change in the torque curve. basically showing it was more responsive.

 

[adamros14]

thanks for the response guys i guess ill go ahead and block off the EGR and see how she runs..

 

[tweak'e]

yeah that swirl valve is definatly a gimmick... if you really wanted to increase the velocity of the air going through the inlet valves in the head, you would have to reduce the diameter of the WHOLE inlet tract from the swirl valve to the inlet valves, not just place a restriction half way down.

and if it was so beneficial to have "swirling" air before it reaches the inlet valves why arent we all fitting Hyclones lol

James

i don't think you understand how it works.

the engine has two inlet manifolds. the swirl valve completely blocks one of them. this means all the air flows through the 2nd intake which increases the air speed making the air swirl more as it goes into the cylinder.
not a gimmick, it works well. more importantly it helps mix the egr and air together.

but if you have no EGR going in then you don't need it.

 

[Peteyen86]

Alright, so is it safe to do the EGR mod if you don't plan on installing a pyro? Will it increase temps that may cause any concern?

Pete

 

[Old.Tony]

Yes, Pete. The pyro is still recommended.

At full throttle - when your car is producing the most heat anyway - the EGR valve is closed. The increase in heat production is during the mid-range and the engine will cope with that anyway.

 

[Peteyen86]

Sorry mate, im having a dumb day. So the pyro is a good thing to have, but going by what you just said, the EGR Mod wont change anything in the way of more heat compared to leaving it standard, as like you said, its closed normally when the most heat is created anyhow, so blocking it off permanently wont worry anything. In mid range acceleration, the temps will go up (with the mod) but not as much as full throttle when its blocked normally?

 

[Old.Tony]

That's right.

The pyrometer is best used to make sure the turbocharger is cool enough to turn off the engine - turning off the engine stops oil flowing through the turbocharger and a hot turbo cooks the oil inside its bearings = failed bearings.

The need for the pyrometer isn't directly related to the EGR mod. It's just an interesting note, that the temps do rise a little because there is no EGR.

 

[Peteyen86]

Great, thanks for your help mate.

 

[tweak'e]

It's just an interesting note, that the temps do rise a little because there is no EGR.

depends on engine. those with hot EGR (eg ZD30) blocking EGR will decrease temps. those engines with cooled EGR may find temps increase slightly.