[TDIwyse]

OK, this is not an EGR "delete", but the data I'm seeing, and intial results from Hooper, show one way to significantly reduce the utilization of EGR on our US 335d's. The other way I was working around EGR (posts 59 on from this thread

http://www.bimmerfest.com/forums/sho....php?p=7691987) was not able to be reproduced by Hooper, and I was only able to do it with the OEM intake and not the AEM homemade intake I'm playing with. So it was a finicky approach.

Pros: Cheap. Easy to install and uninstall. Radical reduction in EGR utilization (~1/3 of stock EGR utilization potential, and maybe more). Not seeing a reduction in peak power/torque output caused by "safe" or "limp" mode.

Cons: Sets "pending codes". Will set an SES/check engine light if you don't clear pending codes each drive. Will require user to have a way to clear codes (I have successfully used Torque and Bavarian Technic tool to do this - Torque is my daily driver gauge cluster so use it 99% of the time and adds ~10 seconds of fussing around at the end of each drive to clear codes).

Unknowns: Have not tried using it through a DPF regen cycle yet to see if it interferres with the OEM particulate mitigation system. Will update info at next DPF cycle.

So basically what's going on is the temp sensor on the EGR is going to be fooled with a simple red LED diode (note, there may be better/more effective ways to do it than this, looking for feedback from the forum to experiment with and explore this) placed in parallel with the sensor to distort the EGR sensed temp and alter the DDE's calculation of how much EGR to use. The lower the impedance on this port the "hotter" the EGR sensor reports to the DDE. The parallel LED makes it look like a nonlinear lower resistance. The DDE is sending out a current to this sensor to measure the resistance. Having the LED in there is creating a voltage just below the LED's "Knee" (in this case with the LED I'm using ~1.5V on my car and a red LED usually has a turn on voltage around 2V) and is just enough to get the LED to start to give off light. You can tell if you have the anode/cathode orientation correct if you see a faint glow (might need to be in a low light area as the glow is very faint) when the DDE wakes up (just open/close a door for example). The partcular LED I'm using at this time is rated for 1.5 mcd at 10mA. Hooper used a different rated LED but got similar results.

The attached picture shows how I'm shaping the LED leads to fit into the female plug of the EGR sensor and fold under the housing of the male connector. This is a simple, easy placement of the parallel connection of the LED. I'm also using a couple zip-ties to physically hold the connection in place so it doesn't work itself loose. There may be better/easier ways to make this connection, but this is a first attempt on my part that doesn't involve cutting/splicing wires.

Doing this will throw some pending codes (see Android Torque generic OBD codes in the attached), and the first time I used it I got the half lit engine symbol and the car did what appeared to be an EGT recalibration procedure where the DDE knew something was wrong, put the EGR utilization to 0, used post injection to raise the EGT's up to ~900 F before going into the "low" EGR utilization mode. Subsequent drives have not shown this "recalibration" procedure, and based on Hooper's email doesn't appear his car did either, and have just been lowered EGR utilization.

The attached pic shows the Torque recorded EGR/EGT/Coolant temp results of the to and from work drives (~14 miles each way) using this mod. Average EGR use for these drives calculates to ~26-27%. Without this mod, looking at historically recorded data from last year for drives to work, shows average EGR use was ~82%. Yesterday afternoon did a 110 mile round trip drive with similar ~27% average EGR. So this little mod seems to be capable of giving a ~300% (82%/27%) difference in EGR utilization. Again, we might be able to do better before triggering a limp mode...

Engine torque and HP output are not measurably affected (based on Android Torque app data for the same stretch of road I use as a quick baseline for my morning drive to work) with this mod. Whereas unplugging the EGR, which will give you 0% EGR, radically reduces peak torque/hp and gives a continuous large engine icon on the display.

Hopefully Hooper will add some of his data and thoughts/experience on this as well. And if others wanted to try this and/or other approaches to reduce EGR that would be great.

[Vreimann]

TDI have you run tests to see if there is a difference in EGR position based on fuel with and without additives? Reason I ask is that with a higher cetane, the combustion temperature should be higher since the timing can be advanced, and if the temperature is higher then the egr should be closed more.

I like the idea of getting the egr to close more, but there has to be another way to get the temperature up without fooling the computer to think the temperature is up.

I was reading this and thinking that BMW should have programmed our cars for use of 40 cetane fuel instead of selling a car which suggests having a minimum cetane of 50.

[DieselDiner]

TDI, the link to the other forum is not working for me. Can you tell us the name of the thread instead?

[TDIwyse]

Originally Posted by Vreimann

TDI have you run tests to see if there is a difference in EGR position based on fuel with and without additives? Reason I ask is that with a higher cetane, the combustion temperature should be higher since the timing can be advanced, and if the temperature is higher then the egr should be closed more.

I like the idea of getting the egr to close more, but there has to be another way to get the temperature up without fooling the computer to think the temperature is up.

I was reading this and thinking that BMW should have programmed our cars for use of 40 cetane fuel instead of selling a car which suggests having a minimum cetane of 50.

I have not. I run additives all the time and they include cetane boosters, so all my data would be at well above 40 cetane fuel.

One thing to note, the in cylinder combustion temperature is not the same as the exhaust gas temperature (EGT). I'm not sure I would expect much of a difference in EGT's and EGR use for a low load/boost condition (steady state cruising) with a 40 vs 50 cetane fuel in a modern HPCR engine. If anyone has a link to a paper that compares something like that I'd like to give it a read and learn more about it.

[TDIwyse]

Originally Posted by DieselDiner

TDI, the link to the other forum is not working for me. Can you tell us the name of the thread instead?

Thanks for pointing that out. My bad.

http://www.bimmerfest.com/forums/sho....php?p=7691987

Posts 59/60 on page 3 of "Houston (Munich) I think we have a problem"