Spirit R/T failed emissions NOx

[Turbo3Iroc]

My Spirit R/T keeps failing emissions for high NOx. The last 2 tests have been 2-300 ppm above the limit and the change was putting an exhaust on with a converter, which brought it down less than 100 ppm. I just checked the cam timing and it seems to be right on.

First test with no converter:

HC ppm Limit: 136 Test: 110
CO% Limit: 0.73 Test: 0.77 Fail
NOx ppm Limit: 1591 Test: 1544

Second test with no changes:

HC ppm Limit: 136 Test: 98
CO% Limit: 0.73 Test: 0.68
NOx ppm Limit: 1591 Test: 1867 Fail

Third test with 3" exhaust with converter installed:

HC ppm Limit: 136 Test: 82
CO% Limit: 0.73 Test: 0.64
NOx ppm Limit: 1591 Test: 1790 Fail

I'm at a loss now since the cam timing seems to be ok. Other than the 3" exhaust the car is bone stock. What do you guys think?


Kelly
Bristol, CT
92 Daytona IROC R/T
91 Spirit R/T
04 Ram Hemi

[turbovanman²]

Was the converter brand new?

It honestly looks like the converter is dead, it should have cleaned up those readings to almost 0.

[Marcus86GLHS]

ouch what a dirty car.
j/k

yes maybe bad convertor.....my guess would be turn the fuel pressure way down and throw in some super-hot plugs.

arent oxides of nitrogen the result of unburned gasoline/hydrocarbons?

btw your CO levels are very near what my omni tested at in 2005 (new cat, TU cal and 50 psi base fuel pressure w/ cold plugs), i just squeaked by but NOx was only 50% of max allowed.

good luck kelly.

[Turbo3Iroc]

The converter isn't new but I think it only has about 25K on it as it came from the same car as the motor that is in this one now.

I pulled the plugs in it since my last post and it has Autolite 63's in it. I know that's one step colder so should I go back to the 65's

This car is as stock as they get for me, I dont even have an adj fpr on it yet Mark.

[LowSL2]

High NOx is caused by high combustion temps. The catalytic converter should be able to clean this up. What kind of muffler do you have? If the exhaust flows too well the converter doesn't heat up enough and/or doesn't "have enough time" to clean the exhaust gasses going through it. I had the same problem recently with my brother's Saturn failing NOx. He had a 2.5" high flow cat converter and a nice flowing exhaust. We put a stock exhaust on with a 2" cat and 1.6" exhaust and it passed with flying colors.

Also make sure they have a fan blowing on the I/C as well as the radiator. Hell, just have the air blow on the I/C and let the cooling fan do the rest.

My 92 R/T had a NOx output was 794 at 15 mph and 416 at 25 mph with 150K on the clock and a stock exhaust. That's with no fan at all on the I/C and the engine super super hot.

[turbovanman²]

The converter isn't new but I think it only has about 25K on it as it came from the same car as the motor that is in this one now.

I pulled the plugs in it since my last post and it has Autolite 63's in it. I know that's one step colder so should I go back to the 65's

This car is as stock as they get for me, I dont even have an adj fpr on it yet Mark.

Check the oxygen sensor, your a bit rich, the CO should be around .5 before the cat but that should also help the NOx.

You need to buy a good cat, the one you have is no good. Walker Super cats, #15147 is what you need. I use that number all the time for our Smog program. 2nd best cat Walker makes.

High NOx is caused by high combustion temps. The catalytic converter should be able to clean this up. What kind of muffler do you have? If the exhaust flows too well the converter doesn't heat up enough and/or doesn't "have enough time" to clean the exhaust gasses going through it. I had the same problem recently with my brother's Saturn failing NOx. He had a 2.5" high flow cat converter and a nice flowing exhaust. We put a stock exhaust on with a 2" cat and 1.6" exhaust and it passed with flying colors.

And lean mixtures, advanced timing etc.

A high flow exhaust has nothing to do with not heating up the cat. The reason your Saturn failed and then passed with the stock cat is the stock cat is 1000 times better than most aftermarket junk. Why do you think an OE cat is $700 and an aftermarket one is $70?

[Turbo3Iroc]

The cat on the car is a Catco and I have previously had bad luck with them. I actually had one fall apart on me as I was driving down the road on my old Dakota. I replaced it with one of the Walkers you mentioned above and never had a problem again. The heat shields broke off of the Catco in less than 6 months. The muffler is a Walker Ultraflo.

The last 2 tests I got the car as hot as I could before the test but it always ends up sitting for like 10 mins while they finish up the car in the bay and get me in.

[Pat]

I've had trouble with Catco's and emmissions tests also. My brother recently had trouble getting his GLHS through Maryland emmissions for high NOx. We're almost postitive it's the cat since the car runs like a top, everything shows perfectly on the scanner..it has a 3" catco cat that I put on it when I owned it.

[turbovanman²]

Catco equals cheap. I bet you put that Walker number on and it blows 0's,

TIII's rely on the cat for NOx reduction, there are no EGR systems and the timing is advanced alot so it puts a big strain on cheap converters.

[Clay]

And lean mixtures, advanced timing etc.

the cause of NOx is from high heat....... these are things that can cause high heat.

[Turbo3Iroc]

Ok, I guess the converter is next. As you can see I have also had trouble with Catco but I wanted to leave that out of the initial discussion to see what the consensus had to say.

Kelly

[WickedShelby88]

I'm with Simon. When I first started learning about emissions systems in vocational school the teacher brought up NOx alot as being the culprit for greenhouse effect among other things. A good converter is necessary. We would test bone stock cars with factory converters and usual if the NOx was high and the engine was in pristine shape we would replace the the converter and the NOx would fall like a lead balloon.. Good luck with your ride. I'm gonna have to get one of those walker converters myself. Can't go wrong with a ballsy setup and clean emissions

[contraption22]

Some tips to try to reduce NOx on the dyno.

Bump your tire pressure as high as possible to reduce rolling resistance.
Also, try testing in a lower gear (like 2nd instead of 3rd).
Make sure the A/C and defroster is off.
Anything you can do to reduce load on the engine.

[Turbo3Iroc]

Mike, I always bump up the tire pressure when it's emissions time. I haven't had the defrost on either and I thought about having them test it in 2nd but I wasn't sure if that wouldnt make things worse.

[contraption22]

Kelly, do you have adjustable cam sprockets? This is going out on a limb, but what about advancing the intake cam, retarding the exhaust cam for more "overlap" therefore reducing cylinder pressures and maybe somewhat of an "EGR" effect.

[Turbo3Iroc]

No, not on this car atleast.

[tryingbe]

My saturn failed California emission with a brand new catco cat. Put in a walker and it passed good.

GLH passed AZ emission with magaflow 3 inch cat, 3inch system and a front mount IC first try.

[Marcus86GLHS]

"...GLH passed AZ emission with magaflow 3 inch cat....."

same experience here in CT....the magnaflow cats are imo the best high flow units available.

[turbovanman²]

"...GLH passed AZ emission with magaflow 3 inch cat....."

same experience here in CT....the magnaflow cats are imo the best high flow units available.

Nah, the Walker number I posted is the 2nd best cat you can get, tried them all.

[TurboJerry]

Catco's last through about 2 emission tests if you're lucky. Every time I had high NOx, a new cat fixed it. The og cats last forever, too bad no one makes one like that for a decent price.