Forced Induction High No Levels At E-check

Just wondering. What is the status of the EGR system? Has it been deleted by chance? Consider cleaning the throttle body EGR passageways.

Any DTC codes?

How about the PCV system? Excessive PCV blow by?

Double check the vacuum lines to/from the DPFE. Also the DPFE sensor fails frequently. Frequently enough that if no other reason can be found, I would consider replacing the DPFE for diagnostic purpose.

dustang50 said:

EGR system has been deleted.
Where is the DPFE sensor located?

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The MAIN purpose of the EGR system is to lower EXHAUST temperatures in order to reduce NO. IMO it's naive to think that the excess NO isn't related to the deleted EGR system.

As for the location of the DPFE sensor, one would expect that you don't have a DPFE sensor since your EGR system has been deleted.

As for why it passed 2 years ago, how about the motor was two years newer.... Less blow by. More efficient combustion in newer motor. Even different blends of gas could have an impact.

Consider switching to a larger super charger pulley. Pulling some timing. Or re-adding the EGR system.

Cats and EGR deal with oxides of nitrogen.

You said it passed in for the last number of years "set up this way." Is everything the same? Did you make any changes (e.g. delete the EGR) since the last emissions test?

Does the car still have the factory midpipe?

How far over the limit is your reading?

How are the other metrics (e.g. CO, HC etc)?

dustang50 said:

Could the cats have gone bad?

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The Cats shouldn't affect the NO levels. So heating up the cats more won't make any difference. Remember that it takes high temperatures in the exhaust to create NO. Once created, NO is fairly stable. Which is why the cats don't have any effect.

EGR works by reducing the overall volume of the fuel/air charge. This reduces the overall power of the charge. So anything that reduces the total fuel charge has the possibility to reduce NO. Other options include lower CR, making the AF ratio slightly richer. Don't over do it because excessive unburnt gas could cause a fail in other parameters. Bottom line, if the AF is too far out of adjustment it will create SMOG issues.

I don't really understand the logic of removing the EGR system in the first place. The PCM locks out EGR during WOT. Therefore the EGR doesn't affect performance at WOT.

dustang50 said:

One more question - is it normal for the supercharger to feel hot to the touch? Not sure if I'm just noticing it now or it's always been like that.

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Check the Supercharger bypass valve. I could see if the bypass valve isn't working like it should that could make the supercharger run hot.

wmburns said:

The Cats shouldn't affect the NO levels. So heating up the cats more won't make any difference. Remember that it takes high temperatures in the exhaust to create NO. Once created, NO is fairly stable. Which is why the cats don't have any effect.

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Correction: Proper three-way catalytic converters take NOx and convert it to oxygen and nitrogen (N2) gas along with the two-way standard of CO to CO2 and HCs to water and CO2. A working converter will reduce NOx although if the engine is producing excessive levels due to high chamber temperatures it can be overwhelmsed.

I will suggest that the "high flow" style of converter used in aftermarket midpipes are of little use for emissions reductions, at least not for long. I saw the same thing with my MRT catted H-pipe: Over time the readings got worse and worse until the car failed emissions tests. Replacing the MRT with the factory midpipe resulted in readings that essentially matched those I saw when the car was a year old and bone stock. Factory cats are very good at what they do.

Bypass e-check... Get on ohio bmv website and submit a package for collector plates. You'll have to send them an application with pics of the car and receipts for your mods totaling over 5k. I have had the plates for about 2 years, it's a lil more of a pain to get your tags (can't do it online), and it's like $5 more a year... but worth not having to mess with e-check.