chapstic951

I have been reading that some people are able to beat the emission test without a cat by using a MAF and I am guessing a piggy back system. How is this done without harming the engine?

Bill

The only way I would think that you can actually cheat the emissions test would be to find a crooked test station. It is unlikley that a test station would do this though. They would risk loosing their license and be fined if caught.

To pass the test legally, all you need is to have a mechanically sound engine running the correct Air/Fuel ratio. This can be done, as you say, with a piggy back system. This would only be needed if your stock system can not make the needed adjustments. My car will pass the emissions test without a cat, but that is only because my AFR is dialed in. You must remember that even though you pass the emissions test without a cat, you will fail the visual test. And again, the only way to get around not having a cat, is to have the test station look the other way.

As far as harming the engine,

If the AFR is too rich and you fail the test, you must lean out the AFR.
If the AFR is too lean and you fail the test, you must richen the AFR.

A slightly rich motor will not be harmed. A very rich motor will foul plugs, run bad and eventually dilute the oil and wash oil from the cylinder walls.

A lean motor is the fastest way to harm an engine. The combustion temps get very high with a lean AFR and you can burn your head gasket, burn valves, melt pistons, melt rings.

So the holy grail that we all chase with the 951 (stock or otherwise) is to get a perfect AFR throught the entire RPM range. If this is acheived, you will also pass smog. A win/win situation so to speak.

PuttingThePoorBackInPorsche

As has been said, you can get very complete combustion without a cat, however you'd fail the visual inspection part of the test - at least that's how they do it out here. Seems kind of stupid/counter-intuitive. . . If the goal is clean air, you should be able to use whatever means necessary to meet the clean air standards IMHO - cat, no cat, whatever. The way the CARB does it with such-and-such is "approved" and such-and such "isn't" is ridiculous. It's simply to give themselves more power and authority. It's completely self-serving (big surprise coming from government, I know. . .)

Far as I'm concerned if you can get passing numbers without a cat or with bigger turbo, injectors, chips, MAF/MAP, whatever, that ought to be good enough. Having a provision in the test whereby a person can fail simply because they have a "non-CARB-approved" part is idiotic and undermines the credibility of the test.

Ski

There are many stations, Memphis TN is one, that just stick the probe up the tailpipe. If all is good, you get your slip of paper and out the door, they don't look under the car or open the hood. Although my car is registered at the condo in Germantown, I recently went by a Memphis test station and passed the sniffer. Car was at 14.7 - 14.9 on the WBO2, I had the A/C on, temp gauge was just above the first white mark. I really feel sorry for you guys and gals in CA.

chapstic951

Thank you for the input. I am looking at getting a Zeitroinx WBO2 this month and a MAF with a piggyback later in the year. Here in VA I don't beleive they do a visual. At least at the Goodyear I go to they does not appear to. I could not imagine how they could if they don't lift the car off the ground. I am also going to look into when VA cars become antiques. From my understanding they do not require emissions at that point.

Sometime down the road I would like to remove the restrictive cat. and hear this bad boy scream...

jgporsche

They are doing sniff tests in northern VA? down here all they do is a visual inspection. I wonder why it would be different up there.

Charlotte944

If the enigne is running properly there is no need to cheat to pass emissions. I have had 2 944s (one early, one late) and a 951. The 944s were chipped, and had test pipes installed. The 951 is chipped, has a 3.0 BAR FPR, and a ReliaBoost set at 15 psi. All three cars passed NC emissions with flying colors.

Maybe you should move to Richmond? My 951 passed inspection and they don't check emissions.

Ski

Just depends on the politicians and MONEY. Germantown TN does not sniff, Heber Springs AR does not, Memphis TN does. Germantown is it's own township within Memphis, go figure.

chapstic951

My car gets violated evertime I come due for emissions. This past trip, they put the probe in the tail pipe and that is it, from what I can tell. He told me I was running on the boarder of failing towards the rich side.

chapstic951

Per the VA DMV:
Any gasoline powered passenger or property carrying vehicle with a model year that is more than 25 model years old before January 1 of the current calendar year and with a manufacturer's designated gross vehicle weight rating of 10,000 pounds or more (i.e. on January 1, 2005, vehicles with a model year of 1980 are exempt from emissions; on January 1, 2006, vehicles with a model year of 1981 are exempt from emissions).

These vehicles also fall within the definition of "Antique Motor Vehicles". However, a vehicle that is twenty-five or more model years old does not have to display antique license plates to be exempt from emissions requirements.

This applies to the counties of Arlington, Fairfax, Loudoun, Prince William, or Stafford, or the cities of Alexandria, Fairfax, Falls Church, Manassas or Manassas Park

From the Dept of Environmental Quality for VA: For all vehicles, a visual inspection will be conducted of certain emissions control equipment that was originally installed by the manufacturer.

My garage must be slacking...fine by me.

Charlotte944

OK, here's some info:

My car always passes. I get between 22 and 25 mpg city, and between 29 and 32 mpg highway. I run MidGrade CITGO pump gas with occasional doses of REdline SL-1 Fuel System Cleaner.

I am running a Guru chipset with a 3.0 BAR FPR and a ReliaBoost MBC set at 15 psi.

The spark plugs have a nice orange/brown patina. There are no vacuum or boost leaks.

Since you are close to failing on the rich side (HC and %CO numbers are high), I suspect that the O2 sensor is causing the problem. All you need to do to verify this is to use a Digital Volt Meter and "back probe" the signal wire from the O2 sensor. With the engine running at idle you should see the voltage vary across 0.50 volts DC. If the voltage does not vary, then the sensor may be bad.

You can get a 3 wire heated sensor for around $40.00 at places like Pep Boys, NAPA, and Auto Zone.

skene

When I got mine tested last month they checked to see if I had a cat on there. I failed, replaced the o2 sensor and fixed some vacuum leaks and it got worse, but judging by the ugly plug in my 4th cylender it's not because of a bad cat.

Technicaly I need to have had it pass last month....but for some strange reason my plates say I'm good until november....

Charlotte944

Andrew:

What sort of numbers did you have (%CO, HC, NOX)?

chapstic951

Charlotte944,
I have since replaced the O2 sensor and was concerned with running lean, per my POS NB02. See thread: Running lean tread

Charlotte944

The whole point of CARB certification is to insure that installing a replacement part will not cause any emissions problems. Those states that have visual inspections have them for a reason, namely to keep shade tree "mechanics" from poisoning the air we breath.

IMHO if you want to run your car with no emissions equipment or restrictions, then make it a track car.