Hey!
Im curious about effects of EGR off on diesel engine. I mean performance, fuel economy, engine work. When we switch off EGR on low
fuel quantity there is excess of air. Example: 10 mg of fuel and 470 mg of air( 1 bar atmosferic pressure) gives AFR = 47! So this probably is not good but maybe my understanding is wrong :roll: So how it is in reality? Have someone some experiences to share?

EGR was introduced as a means to reduce NOx emmisions in internal combustion engines,
especialy on Diesel engines that work on very high compression ratios [and emmit a ****load of NOx]

This system introduces an amount of exhaust gasses in to the cylinders preventing [theoreticaly] at least the same
amount of fresh air (and thus oxygen) from entering there, less oxygen means that less fuel can be burned and less power will be generated, so, EGR = cleaner emmisions and less power

Yes of course. But You know some people say that it is better to have EGR off, some are opposite and they say that EGR is good for engine work and fuel consumption. So.... :crazy:

Fuel consumption on diesel engines is given by DRIVER WISH MAP. You will burn how much you push the pedal.
Idea is that with EGR off you have more air available for less pedal, and Smoke limiter map is bounced rare in lower loads.
On VNT and VGT cars, EGR works toghether with VNT. Variable geometry is closed when you dont need boost(paradox is that closed vanes creates more boost), but in this situation VNT is closed to divert exhaust gases into the EGR.
By blocking EGR and not opemning turbo vanes, will feel a backpressure and maybe engine doesnt breath so good and quality of combustion can be affected.
EGR for diesels is only for emissions, thats it. ON petrol cars, EGR reduces throttle losses and pumping loses being a throttled engine and helps to have an advanced timing without knocking. Is not the case of diesel.
People who tells that EGR helps for economy, they read for sure PETROL EGR ARTICLES NOT DIESEL.

Could you tell me the actual definition for the VNT of open and closed.
I get confused to the difference.
I think.......
closed, the vanes are pointing towards another and this blocks the output, but while opening slightly, the gases propel the outer fins to start the spinning .
open, the vanes are pointing towards the inner spindle and having got that far have spun the turbo from slow to fast and is wide open to allow most gases out quickly.

Or have I got it the wrong way?

I would like to know also, on the n75 maps on ecu16c34 for my xsara 1.6hdi, as I have the Mitsubishi turbo, is it controlled by the n75 maps or does that apply to garret turbo only?

Also does the figure e.g 25% relate the vanes being closed by 25% low down the rev range or does it mean 25% open therefore closed 75%?

On the honda I had had ecuc16 the n75 value was increased to increase boost and lowered to decrease boost pressure. Is the ecu16c34 the same?

@Zaccyboy , find your damos and if you have a N75 map well is controlled by that map..but should be.
For VNT mechanism see
https://www.youtube.com/watch?v=t2GrVS-sGdQ

Idea is :
1) VNT closed - need for boost, closed vanes creates vortex effect for more boost ok ? Closed vanes also are like a shield which diverts the gases back to output..but there is EGR PIPE and all these gases will go with pressure to EGR. By blocking EGR there is a constant pressure.
2) VNT must be open in HIGH power and high rpm because where turbo can make boost almost without vanes, because gases flow is big big. VNT are especially introduced for better transition from low to high rpm and to help EGR flow.
I attached a photo man but i`m not good at paiting..but you`ll understand..
Well in LOW rpm vanes are closed to create boost from nothing and diver EGR...BUT until 15 mg you dont need boost..SDI cars works great without boost. Well you block EGR , gases remain there between exhaust and turbo..they pass into the turbo all the time, they dont have another way to go out to final pipe. Hope i was clear. Big circle is the turbo.
Well block EGR, open vanes where EGR was active with 10 15% but not too much because when you need boost after 20 mg, vanes must close a bit. Good part is that having EGR, vanes are closed even if you dont need boost, THEY ARE PREPARED IN RIGHT POSITION TO MAKE BOOST WHEN YOU NEED MORE THAN 20 MG FUEL. Normally in 1.9 or 2.0 engine you can burn clean 20 mg fuel without boost..not more, thats maximum fuel.

Thanks for the explanation much appreciated.

So to get this correct.......

With egr on the vanes are closed and are in correct position?

With egr off I need to ope the vanes up to a max 0f 15% of the figure quoted so i.e 15% 0f 10 = 1.5 so open from 10 to 11.5 ?

This must be done up to 15mg then?

What rpm we taking up to 3000 rpm?

Thanks

Ian

Zaccyboy wrote:Thanks for the explanation much appreciated.

So to get this correct.......

With egr on the vanes are closed and are in correct position?

With egr off I need to ope the vanes up to a max 0f 15% of the figure quoted so i.e 15% 0f 10 = 1.5 so open from 10 to 11.5 ?

This must be done up to 15mg then?

What rpm we taking up to 3000 rpm?

Thanks

Ian

Yes from 1200 rpm to 2800 i think, check your EGR map where was active.
Make logs while driving light and open until you see the actual boost matching desired boost. Even with this is a good idea to drop requested boost, well in BOOST map, reduce 50 100 mbar from 1500 to 2800 rpm until 15 mg.
With EGR ON, closed vanes are alreay in HIT boost position..but on light load doesnt need boost..well gas go into EGR but put pressure on turbo. You open them a bit, when need boost will close to create boost and you will not feel the lag if you dont open them too much. Try better to open them with 10 units because on my car 95 means closed(10% means 9.5). well from 25 add up to 35 and so on.

Thanks buddy,

You say 95 is closed so 25 is open?

So making the figure larger closes the vanes?

So I need to make the figures smaller to open vanes not increase them?

Does lexia record driver info then?

Thanks Ian