Quote:
Originally Posted by Hoooper
What? I guess if you move the goalposts to a totally different version of CBU you *might* be right. But you're way off base with respect to CBU as we know it here.
EGR is not an efficiency benefit or improvement. That's actually the whole reason it works. EGR lessens the volume of available oxygen in the cylinder, slowing down the burn and lowering chamber temperatures. Since NOx is only formed at high temperatures, lowering chamber temperatures drastically reduces NOx. Its not an efficiency improvement to load the combustion chamber up with noncombustible material.
I don't mind playing within the rules, but when it means a choice between slightly lower emissions and several thousand dollar repairs vs $10 in material, better mileage, better performance, and no repairs, the choice is incredibly clear.
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You are correct when you consider old technology EGR.
However with all actuators in the engine being controlled by software, EGR can improve the efficiency of combustion engines. Below is how:
1- Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses. (Gasoline engines only as diesels are not throttled)
2- Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces;
3- Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC (Top Dead-Center), rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is minor compared to the first two.
4- In a closed loop injection system, with EGR open, software is calibrated to inject less fuel in the cylinders
On diesel engines the improvement is smaller then on gas, but also occurs. .
I do not debate that blocking EGR reduces CBU. Therefore I do not judge as irrational your assessment on paying 10 bucks on a blocking plate instead of mantaining a clean intake via other measures. I just think the best economical decision would be buying a PFI gas car instead of a DI. Much cheaper engines and zero CBU!
If you have a solution for the emissions puzzle that eliminates EGR without negative collateral effects, start making money on it. All OEM's are desperate for a cheaper solution and removing parts will help
