High NOX reading for 76 912E Ca. smog not passing

[larsz]

I need some help in reducing the NOX on my 76 912E . It was okay when the engine temps were lower but when the check was done at the hotter temp it failed. All the emissions are hooked up except for the thermal reactors. Can anyone chime in on this before I take it in for the actual test.? Thanks in advance.

[the]

Originally Posted by larsz

I need some help in reducing the NOX on my 76 912E .

All the emissions are hooked up except for the thermal reactors.

The purpose of the thermal reactors is to reduce NOX.

I'd be very surprised if your car could even come close to passing current smog in a state like CA with missing/nonfunctional thermal reactors.

[gerrygug]

Originally Posted by the

The purpose of the thermal reactors is to reduce NOX.

I'd be very surprised if your car could even come close to passing current smog in a state like CA with missing/nonfunctional thermal reactors.

+1

You will not pass California smog with out the reactors. Part of the inspection is visual. If all the factory gear is not there it will not pass even if the NOX is ok.

[SC-targa]

I don't know anything about your car, but I assume you can richen the mixture a bit, can't you?

Remembering back 25 years to an IC Engines class, NOX is created in several conditions related to high peak combustion temps. When the combustion temp is high enough, Nitrogen will react with O2.

If you run a richer mixture, the additional fuel will both react with the O2 and absorb some of the heat. Of course it's a two edged sword because richer mixtures can create HC and CO problems for you if you are close to the limits for them.

I can't recall what ignition timing does to this equation. Someone else can chime in.

Exhaust gas recirculation or a cam with lots of overlap will reduce NOX too.

Regards,

Jerry Kroeger

[the]

Originally Posted by SC-targa

If you run a richer mixture, the additional fuel will both react with the O2 and absorb some of the heat. Of course it's a two edged sword because richer mixtures can create HC and CO problems for you if you are close to the limits for them.

I think that's what's going to be the problem. Even with all of the smog equipment in place and functioning, it's pretty touch and go with the mid-70s car in the strict smog areas of the country.

He's going to have to clear NOX, HC and CO. All of them. At idle, AND under load on a dyno. Makes it very difficult for the 70s cars.

[larsz]

The dyno is not used in my area but is checked for the three gasses at idle & at 2500 rpm.
Would a cat. converter ad on work in place of the muffler to lower the emissions?

[HarryD]

Originally Posted by the

The purpose of the thermal reactors is to reduce NOX.

I'd be very surprised if your car could even come close to passing current smog in a state like CA with missing/nonfunctional thermal reactors.

Thermal reactors will not reduce NOx only convert CO to CO2 and HC to water and CO2.

NOx is formed in the cylnders from the Nitrogen and oxygen in the air. Higher temperatures equate to higher NOx.

You can lean out your mixture a bit which to reduce NOx formation but your CO will increase.

The dotted lines on these charts show how mixture affects emissions:



This thread may also be helpful: http://forums.pelicanparts.com/porsche-911-technical-forum/209910-emissions-failed-octane-question-post1796342.html?highlight=emissions+bosch#post1796342

IMHO, You will need to find someone with an exhaust analyzer to help you tune your car. You do NOT want to keep going to the test station and failing. This will raise a huge red flag to the agency and lead to other problems.