Failed MA Emissions Retest

[masho95]

Well I just got back from getting the SHO reinspected. Failed for NOx again...

NOx grams per mile Reading = 2.85 Limit = 2.50
* Old NOx reading was 4.49 so it did come down quite a bit with the new O2's.

I've changed the ECT and O2's since the first test, and I have no idea what else to try.

The only thing that I can think that's causing it, is the copper Autolite plugs that I have in the car for the nitrous. They are colder than stock plugs and perhaps it's causing the car to create too hot combustion temperatures.

ANY ideas?

 

[Bizzy]

did you bother to pull the SPOUT connector?

 

[Blank-Disk]

i got those autolite's too, and my SHO passed NM emmisions fine, so i doubt that's it. Try cleaning the intake manifold out with some Motorcraft brake parts cleaner. That stuff eats everything in it's path. I knwo it doesn't seem like it would be the problem, but my Toyota has been having trouble passing emissions, and it seems like the more intake parts I clean, the better the results are.

 

[Xs SHO 1]

Still on the stock Y-Pipe? If so, maybe its time for a new one....

 

[Rockledge]

The colder plugs should be helping with the combustion chamber temps, as they are more able to draw heat away from the chambers.

It's all about getting rid of that heat in the chambers, so what can you do? An upper engine de-carboning procedure might help. Carbon deposits can trap heat and in fact are know to cause "hot spots" within the cylinders, contributing to spark knock and detonation.

Make sure your cooling system is operating up to full potential.

Running on the lean side will also cause higher heat in the chambers. Make sure all vacuum hoses and connections are good, maybe even re-torque the upper intake, think of doing things like that. A new fuel filter, maybe even running some fuel injection cleaner through the system, might help to balance a slightly lean condition.

Retarding the timing (pulling the SPOUT connector) is always an option, too.

 

[masho95]

Thanks for the suggestions. When the nitrous blew apart the throttle body plate I inspected the intake and was fairly clean but I gave it a quick cleaning anyways. With all that pressure that got blown throughout the intake I wouldn't doubt there is a small leak somewhere. And the cooling system is definitely a bit off. I think the waterpump is heading south as there is a small leak from the weep hole (it seems). And it also sounds like some bearings inside the pump or whatnot are going bad (squeal from waterpump). That's on the list to be changed shortly.

And no it's not on the stock y-pipe. I have my SHOShop hi-flow y-pipe on the car.

I'll have to run over a few things again it looks. Thanks.

 

[pjtoledo]

Spark plug heat ranges

Ok guys, you're going to have to re-educate me on this hot-vs-cold plug stuff. In the old days (remember, I'm "the 'ol man in the SHO") a plugs heat range was all about the mass and size of the insulator and it's ability to absorb heat from the center electrode and conduct it to the outer metal casing of the plug. A "hot" plug had a deeper gap between the center insulator and the outer body, thus providing a longer path for the heat transfer which resulted in a higher temperatures at the center electrode and the part of the insulator nearest it. "Colder" plugs had just the opposite, larger center insulator, thus shorter path for the heat, result was a colder center electrode and insulator. Neither of these should affect the temperature of the actual spark, that's what voltage and current do. I don't see where a hot or cold plug could affect the temperature of combustion gases. A/F ratio, the quantity of the A/F mixture, compression, and the ambient temp of the head and walls would play a major role there.

So, when you say the colder plugs draw heat away from the chambers, you mean they keep the center electrode and insulator cooler right? The rest of the combustion chamber should be unaffected.

Since NOx is a by-product of any atmospheric combustion, it will always be there. The temp at which combustion occurs affects the quantity of NOx produced, hotter yields more. It would seem that a colder plug should reduce NOx somewhat, perhaps only affecting the small amounts of gases in extremely close proxomity to the plug tip.

How about the temperature of the spark? Close the gap down a bit and less energy is needed to bridge it. Has anybody noticed a correlation between plug gap and NOx production?

Hey, it's late, this is the best my 'ol brain can do tonight. Further commentary welcome, maybe I can learn something.

Perry

 

[SHO Dude]

Since NOx is a by-product of any atmospheric combustion, it will always be there. The temp at which combustion occurs affects the quantity of NOx produced, hotter yields more. It would seem that a colder plug should reduce NOx somewhat, perhaps only affecting the small amounts of gases in extremely close proxomity to the plug tip.


Perry

NOx stands for Oxides of Nitrogen. NOx is produced when the flame front moving across the piston exceeds 2600 degrees F. When it does, the advancing flame front consumes the nitrogen along with the oxygen and combines them to form NOx (oxides of nitrogen). These are nasty green house gasses and should be controlled. Most of them should be eaten up by the cats, but the best way to reduce them is to keep the combustion temps down.
There are three ways to do this. You can reduce the compression ratio (not a viable option here), increase EGR flow (also not an option in the MTX cars) or reduce the timing advance. When you reduce the timing advance, the combustion temps fall and so does NOx.

So, MASHO95, go back to your emissions tester and pull the spout connector before being tested. It's located under the back passenger's corner of the intake manifold. Be sure to plug it back in after testing or it'll be a toad on the drive home.

 

[Yamaha V6]

Doug, I think Erik's problem is that he's got a vacuum leak after the MAF somewhere, likely around the intake manifold. He's had a nitrous backfire before all this happened, and I'd imagine the additional post-MAF air would likely mean he's running lean & therefore hotter.

Assuming all else is the same, and stock SHOs pass emissions all the time, pulling the SPOUT is a temporary fix to get past the sniffers - not something that should be required on a daily basis, given the 3 items you mentioned. I think he's got a mechanical problem with the car, and all of this is a band-aid. Erik, do you have access to another intake manifold assembly? Try swapping that out with some new intake gaskets, or see if you can identify a vacuum leak in there somewhere.

Edit: Another thought Erik, how are the seals around the fuel injectors? You may have damaged the seals with your backfire.