EGR bypass feedback - smoke test

[pondweed]

noticed that my exhaust opacity was down to 0.6 and had a "fast pass" on the smoke test at recent MOT. Looking back through service history, 30k earlier at 130k it was an average of about 1.8... with a max allowable of 3.0.
interesting results from the EGR bypass addition?

[Keith]

Sort of makes you wonder if the cars should have a recommended min max value and anything else could suggest something is not right

You would think though with the EGR bypass the result would have been higher though!

[SteveWaller]

That is because they check for smoke and not for NOx emissions. Bypassing the EGR valve will provide more air to the engine and hence reduce smoke, but will increase NOx emissions, particularly at low engine loads. Often different emissions have conflicting requirements so reducing overall emissions gives certain compromises. Most diesels will soon have to have particulate filters to enable enough EGR to be used to reduce NOx while avoiding particulates (smoke). This will often result in higher fuel consumption and lower performance as well.

[Roverron]

Originally Posted by SteveWaller

That is because they check for smoke and not for NOx emissions. Bypassing the EGR valve will provide more air to the engine and hence reduce smoke, but will increase NOx emissions, particularly at low engine loads. Often different emissions have conflicting requirements so reducing overall emissions gives certain compromises. Most diesels will soon have to have particulate filters to enable enough EGR to be used to reduce NOx while avoiding particulates (smoke). This will often result in higher fuel consumption and lower performance as well.

Also makes tuning very difficult because however you do it, the particulates will increase and therefore require more frequent cleaning of the (expensive) filter is required. So if its an option - don't have it if you want more performance....

Still its yet another challenge! Where's wingy777 - we might need a particulate filter bypass soon!

Ron

[Kearton]

Originally Posted by Roverron

Also makes tuning very difficult because however you do it, the particulates will increase and therefore require more frequent cleaning of the (expensive) filter is required. So if its an option - don't have it if you want more performance....

Still its yet another challenge! Where's wingy777 - we might need a particulate filter bypass soon!

Ron

Perhaps there is an opportunity here for a cyclone-type element free filter. You could even use a Dyson for the prototype. Then we only need an automatic means to empty it at routine intervals - perhaps leaving little 'sugar cubes' of carbon at the side of the road. The cubes could then be used to fill in some of the potholes.

Kearton