Emissions / EGR question

[BoostKillsStres]

Since EGR lowers NOX what would happen if you changed the EGR tables to command a higher % DC than normal? Would this possibly be to much inert gas and possibly cause a lean misfire?

I didn't know if anyone messed with the values, guess I'll checkout the chip images on the other site and see.

Thanks

 

[BoostKillsStres]

I was just playing as I noticed the differences between the axca and bbjk chips was a bit of egr changes. I can hear my egr when driving at part throttle and the noise to me sounds just like a cold piston rattle, kinda strange. Last time at the sniff test I forgot and still had a golf tee in the egr line to block it off and passed anyway

 

[bruce]

Originally posted by BoostKillsStres
Since EGR lowers NOX what would happen if you changed the EGR tables to command a higher % DC than normal? Would this possibly be to much inert gas and possibly cause a lean misfire?

I didn't know if anyone messed with the values, guess I'll checkout the chip images on the other site and see.

Poorer performance.
Yes. You have to add extra fuel to properly run EGR.

There are no perfromance related gains to be made, from increasing the EGR. I've at one time spent alot of time with a SBC to see what EGR really did, for a performance car.

 

[BoostKillsStres]

Thanks Bruce but I was actually looking at thi sfrom an emissions chip stand point to possibly lower NOx even more.

 

[gofstbuick]

If you increase the EGR duty cycle, you may encounter a lean misfire situation. But as Bruce says, you may also lower performance. Here is the scenario: the exhaust gases are basically inert, and when the EGR valve opens, it allows some exhaust gases to replace combustable fuel mixture. The EGR gases take up space in the combustion chamber and thereby reduce peak cumbustion temperatures. But if the inert exhaust gases were not in the combustion chamber, it would be replaced by combustable gases, therby creating more energy. The factory fed chips use less EGR duty cycle because most areas (outside CA) have a CO attainment problem, whereas non-attainment areas of CA have problems with excess NOx and CO.

 

[gofstbuick]

Additionally, I noticed GA uses the following emissions test for 1996 and earlier: ASM2525 and no load idle test. If GA requires a specific gear selection during the test (CA requires drive), then by the time the vehicle reaches 25mph, it will be in 3rd gear. The EGR and catalyst are the two emission equipment that will have the greatest affect on NOx. The EGR is commanded on in 3rd gear and the cat only needs heat and no exhaust leaks prior to the cat (especially with a three way cat). Exhaust leaks promote combustion and there is a chamber in the three way cat that tries to put out the completion of the combustion process, in an effort to control NOx. If you have a exhaust leak in front of the cat (where the NOx bed is located), this uncontrolled air may promote combustion, and create a NOx problem. The second bed of the cat is for the control of HC and CO. There is a substrate material in front of the oxidation bed that coated with Cerium, a material that attracts O2. As the HC and CO passes into the oxidation bed (of the three way cat), the O2 is released to convert HC and CO to CO2 and H2O (the byproducts of perfect combustion).

 

[bruce]

Originally posted by BoostKillsStres
Thanks Bruce but I was actually looking at thi sfrom an emissions chip stand point to possibly lower NOx even more.

It's all trading one for another, in this case dropping the NOx if you go a fuzz too far and HC spikes hi, just like a lean miss. And with the increase in timing might raise CO.
Takes ALOT to do better then the oem guys.