Increased Peak Pressure on Diesel's with EGR

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

b1377@worldnet.att.net - 18 Jan 2007 03:21 GMT

Question -

How is is it that employing EGR on a diesel increases peak combustion
pressures (per the new Duramax press releases) when it is an
established fact the EGR decreases peak combustion temperature - I
thought they went hand-in-hand.

Just wondering.

Thanks in advance,

Jim

To reply via e-mail, remove the "1" from the reply-to address.

Reply to this Message

Steve - 19 Jan 2007 01:05 GMT

> Question -
>
[quoted text clipped - 10 lines]
>
> To reply via e-mail, remove the "1" from the reply-to address.

The only thing I can think of is that it allows the fuel injection event
to be timed differently so that the pressure peak is higher even though
the temperature peak might be lower.

But you also have to remember that things like press releases are
written by tech writers who get their information second hand from the
real engineers, and sometimes they re-word it incorrectly.

Reply to this Message

Dyno - 19 Jan 2007 05:35 GMT

>> Question -
>>
[quoted text clipped - 18 lines]
> written by tech writers who get their information second hand from the
> real engineers, and sometimes they re-word it incorrectly.

The challenge with newer Diesel emissions standards is to control both
NOx emissions as well as particulate emissions. EGR is an effective
method to control NOx; Diesels can run more that 30% EGR. But, high EGR
rates tend to lead to high particulate emissions. A way to minimize
particulates is to run leaner. Uh oh, running leaner reduces engine
output. To get the output back while staying leaner and running high EGR
means one has to run significantly higher boost levels. And as we all
know, higher boost will lead to higher peak cylinder pressures. QED.

Reply to this Message