Air Care Problems, again. High NOx

[Mike Schmid]

So I ran my car thru for the second time.  Last time I had real low HC, real low CO, but NOx was too high.  From reading the brochure it sounds like high NOx is from high combustion temps, so I thought maybe I was running too lean.  So I put my maf screw back in, put in a colt FPR with a couple more psi of base fuel pressure and tried it again.  I logged before hand and my fuel trims went from almost 140% to 102% on all but the low trim, it's still 12x% I think.  At airecare I logged too and the max throttle was 49% and that was only the one time.  

New results are HC stayed the same at 0.20
CO went up from 1.04 to 2.16
NOx went from 3.26 to 3.20, 1.24 is max.  

Grrrr....  :evil:  The trace graph shows my NOx alternately peaks hugely and drops to zero during the regular driving, then on the highway my NOx goes huge and stays there.  

What I'm thinking now is my EGR isn't working properly, because the EGR should lower the combustion temps by introducing inert waste gasses, right?  Comments?  Anyone had an NOx problem before?  Usually the Talon problems are from running fat rich and spewing HCs, bot not this time, HCs are way under the normal reading even.  Any useful input is appreciated, this will have cost me at least $100 now if I pass next try.

[John Hartman]

as for EGR, I have had mine disabled and blocked off every time I go thru.

Now I know your car is newer and subject to alot harsher restrictions, but still I had well under your NOX readings.

How old is your cat?

[Robin Toor]

If you have an SAFC try richining it up quite a bit. I know Jovan's problem getting through aircare was one day he would be rich and have high HC but Nox would be fine, and then the next day he would be to lean and have to high Nox but HC would be fine. If you richen it up you will have a bit higher HC (which you can sacrifice) and lower Nox, this should help.

If not, take off your wastegate arm. This will prevent you from boosting on the aircare dyno, thus giving less air to the motor and making it run richer, this should help you out majorly. It's mostly playing with the A/F mixture until you get the perfect amount of HC and Nox.

[John Hartman]

yea I agree, take that wastegate arm off.  You have a hugeass turbo on a mostly stock system.  Its trying to ram alot more air thru.

[Mike Schmid]

The problem is I don't have an AFC... hence the maf unhacking and FPR swap.

I could try the wastegate arm trick.  I was thinking the evo 16g shouldn't really be spooling but it probably is helping flow more air than the old 14b.  

The thing I really hate is I'd be all for trying one thing and going thru then trying something else except that everytime you do that it costs a 2/3 of tank of gas for the friggen retest fee.  I hate aircare.  You think I should do something with the EGR too, or just pop off the arm and try it?

As for the cat it's not that old.  It would have went on when Dave did the catback.  With the real low HC and CO I'm thinking the cat must be working.  There's also some small exhuast leaks before and after the cat but I'm thinking they shouldn't hurt should they?  Pre cat or post cat, the exhaust is hot, thin and low pressure and should suck fresh air in to dillute the readings and help me out if anything.

[John Hartman]

if you have a way of monitoring temps, check pre and post cat temps.  An oven thermometer should work if you don't have anything better.

We use a laser remote pyrometer at work.

My cat was a good hundred deg hotter post cat as its supposed to be.

As for EGR, you pull it off and make a plate the same shape as the gasket but with no holes in it, then slap it back togeather.

I'd go back to the factory fpr tho, the NT one is making it richer than it needs to be.  At least for aircare, I'd log it and see for regular driving tho, it might be your answer to stock injectors.

[Mike Schmid]

I know how to block the EGR, just looking for some input on whether or not it'll help my NOx.  

As for the colt FPR it brought the trims back to right aorund 100% from maxed out and the HCs didn't change at all between the stock FPR and the colt one.  

As for the cat I suppose I could find a way to check the temps.  I know it'll be hot because my EGT stays up there, not sure what the differential across the cat is tho.

[Robin Toor]

I know how to block the EGR, just looking for some input on whether or not it'll help my NOx.  

As for the colt FPR it brought the trims back to right aorund 100% from maxed out and the HCs didn't change at all between the stock FPR and the colt one.  

As for the cat I suppose I could find a way to check the temps.  I know it'll be hot because my EGT stays up there, not sure what the differential across the cat is tho.

I think blocking the EGR off will actually make your emissions worse, so I wouldn't do that.

Disconnect the wastegate arm, put in some 94 octane gas with octane booster, and rip it up so the motor/cat get real hot. I'm sure you will pass, you aren't to bad on Nox right now, you just need a little bit less to pass. On Jovan's 14b they hit around 0.6 bar on the driving test, so they do get into boost. If you disconnect the arm it should do enough so you can pass.

[Mike Schmid]

With regards to the EGR I think I might have to take a look at it and make sure it works.  I think disabling it would be counterproductive because it's there to reduce NOx.  A quick google search confirmed that:

http://www.allpar.com/eek/emissions.html

I'll look into that EGR, make sure it works, then pull the arm and try again I think.  Thanks guys.

Another writeup:

http://www.allpar.com/mopar/emissions.html

[Artem Goloubov]

Good cat will solve most of the problems.

Also if you have a mechnic friend with the shop, get your car on an analizer and let him to play with setting to get emmisions inline.

[Kimyee Lai]

Good cat will solve most of the problems.

Also if you have a mechnic friend with the shop, get your car on an analizer and let him to play with setting to get emmisions inline.

Don't bend over if the mechanic comes at you with the "analizer!"

Mike, EGR will help reduce NOx emissions.  The exhaust gases act as a buffer and reduce peak cylinder temperatures.  Thermal NOx comes from combustion at high temperatures, and reducing peak temperatures, either through adding fuel or decreasing oxygen by displacing air with an inert gas, will reduce NOx.  On that note, did you know water injection also decreases peak cylinder temps?  If you already have your system installed you might want to try it with your system at a low boost activation...

Definately look at the cat too...typically, high flow cats = more emissions.  

You might also want to decrease your timing to reduce NOx.  You have lots of room to play with on your CO and HC, which is good.  I'd say that some water injection and reduced timing SHOULD do the trick.

[KevinBuckham]

Have you tried altering your timing?

Advancing or retarding timing will move you around the N0x / Hydrocarbon ramges.

[Mike Schmid]

Update: Last night I took the EGR off, it's fairly clean, the valve works too.  That leaves the vacuum hoses to be suspect, they appeared to be good and the connections were all on, but I can't test for vacuum leaks because I don't have a vacuum pump yet.  So I'm not sure if vacuum is making it to the EGR valve thru the temp switch and the solenoid.  

I also checked the timing and set to 5* BTDC.  This time I pulled the wastegate arm off too.  Tested it this afternoon and no beans.  Same results as last 2 times.  

I did some more research and it looks like, if we have a 3 way cat, that the cat uses one set of compounds to break down HC and CO and a different set of compounds to break down the NOx, so maybe the cat is half dead and won't catalize the NOx.  I've pretty much narrowed it down to half dead cat or no vacuum getting to the EGR.  I need to track down a vacuum tester and do some more tests and then swap on a working cat.  

Fuckin aircare sucks... and it's getting expensive, $100 already + $23 for the next test.   :evil: