BTW, how many people know the function of an EGR valve is to lower engine temperatures? Sounds daft, but because the gas can't be burnt twice, it lowers combustion chamber temperatures and hence emissions.
Yes, it does lower temp in combustion chamber.
Cause 'dead' air from exhaust have no or very little oxygen, so not all of fuel can be burnt = less power
less power = less temperature in combustion chamber
How much less temp in combustion chamber?
Not so much.
I have found some Bosch literature (on Slovakian language and it was REAL problem to translate) about CR diesel technology. And there is, of course, one chapter dedicated to EGR.
Why, how, when...etc
I lost that PDF but as much as I can recall:
NO (WITHOUT x) is nitrogen mono
xide (or nitric oxide).
Goal of this EGR game is to lower or remove completely NO from exhaust gases by lowering temp.
NO is created when temperature is above 1000 degree Celsius.
Biggest natural source is lightning.
But cause increased pressure in combustion chambers, number of degree Celsius required drops.
According to Bosch docs, as much as I can recall, required temperature is around 600 to 800 degree (depending on particular system manufacturer involved).
if there is higher pressure in comb. chamb. lower is temp point when NO is created. So in high pressure sys's it can be as low as 600 degree...
And there are some figures saying:
-for each 1 degree Celsius lower temperature in combustion chamber, 5% less of NO emitted by the system...
Nothing more than this in Bosch documentation.
I don't know if that means if you lower temp by 20 degree C, than you will have 20 x 5 % less = 100 % less
, drop from 600 to 580 degree)
but certainly EGR sys does not lower temp in comb chamber for some enormous figures...therefore...if you remove it (on any way, whatever) temp in comb chamber will not be critically higher than without it...
Please, can someone from Bosch give us real (measured) and accurate data on this case once and for all.