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      10-25-2014, 05:00 PM   #1
ingenieur
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Diesel 101

The interest in the new generation of diesels in the US is exciting, especially as BMW makes some of the best.

As other markets have had diesels for years there seems to be a lack of understanding as to the complex exhaust after treatment system required now - not only in the US, but ECE and others as well.

The US market with its strict emission requirements started with Selective Catalyst Reduction (SCR) of NOx along with an OxiCAT/DPF, EGR and now with the N47T/N57T incorporates a NSC/DPF and particulate sensor along with EGR, and SCR.

I'd like to start this thread for members to post a few questions that may help invoke a bit of grey matter - but at the same time understand these newer systems better.

Question 1 - fairly basic.
What are all the reasons an controlled throttle valve with feedback is used in the new BMW diesels - DPF regeneration - engine overspeed protection and what else?
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      10-25-2014, 09:37 PM   #2
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Quote:
Originally Posted by ingenieur View Post
... but at the same time understand these newer systems better. ...
I would advise searching out the three main training documents that have been posted before (usually in the e90post M57/N57 forum):
ST810 - Advanced Diesel Technology
Introduction to Diesel Technology
Advanced Diesel with Blue Performance
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      10-27-2014, 06:37 PM   #3
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Quote:
Originally Posted by floydarogers View Post
I would advise searching out the three main training documents that have been posted before (usually in the e90post M57/N57 forum):
ST810 - Advanced Diesel Technology
Introduction to Diesel Technology
Advanced Diesel with Blue Performance
Yes - a decent summary of the basics I agree.
However, I was hoping to generate a discussion beyond that.

Throttle valve also closes on engine shutdown to prevent engine shake or judder.

There is another function in which the throttle valve is closed slightly - why would this be necessary?
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      11-06-2014, 07:50 AM   #4
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Quote:
Originally Posted by ingenieur View Post
Yes - a decent summary of the basics I agree.
However, I was hoping to generate a discussion beyond that.

Throttle valve also closes on engine shutdown to prevent engine shake or judder.

There is another function in which the throttle valve is closed slightly - why would this be necessary?
EGR performance.
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      11-06-2014, 06:56 PM   #5
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Quote:
Originally Posted by Socom View Post
EGR performance.

When the pressure differential is insufficient for the calculate EGR flow rate the throttle can be controlled to close slightly.

Assuming there are no faults and the system is functioning properly, how would the DDE monitor EGR?
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      11-08-2014, 08:55 PM   #6
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Quote:
Originally Posted by ingenieur View Post

When the pressure differential is insufficient for the calculate EGR flow rate the throttle can be controlled to close slightly.

Assuming there are no faults and the system is functioning properly, how would the DDE monitor EGR?
There is a position sensor. That's pretty clear if you read the documents (page 29 ST810) that I referenced earlier.
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      11-16-2014, 10:46 AM   #7
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Quote:
Originally Posted by floydarogers View Post
There is a position sensor. That's pretty clear if you read the documents (page 29 ST810) that I referenced earlier.
Yes - to know the position of the EGR valve, but the HFM and lambda signals are used to monitor the measured air flow vrs. the calculated model to see if the EGR flow rates are correct.
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