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CA smog is out to get us

5 December 2013
Let me start off by saying that CARB, (California Air Resources Board) is on a rampage against us. No one is concerned until it happens to them. I don’t know what we can do to make smog testing our cars fair and honest. CARB is certainly not playing fair.

My story starts with failing my smog test, not because my basically stock 1991 NSX is running poorly, it is running fantastic, but because CARB keeps lowering the allowable PPM threshold numbers. Yes, I got my cats hot before each test.

Back in 1999 the max CARB threshold numbers were:
Lo speed 15mph HC 138 CO .73 NOx 1982
Hi speed 25mph HC 88 CO .61 NOx 1782
Current max numbers at time of test (Nov of 2013)
Lo speed 15mph HC 80 CO .52 NOx 549
Hi speed 25mph HC 62 CO .61 NOx 507

You can see how the numbers have dropped, especially the NOx numbers and the gross polluter level is below what was a passing level 12 years ago.
Forum user mrbythatmuch created a good thread http://www.nsxprime.com/forum/showth...Limits-Changed that shows how the 1991 manual transmission NSX has lower threshold numbers than an 1991 auto or a 1992. Excuse me, how does that make sense. Oh, I forgot we are talking about the government.

In my case I failed on the low speed NOx test, all other tests passed easily including high speed NOx test. My car would have passed if it was an auto or a 1992. Do a study on why a car fails a NOx test and you will see that it will include the EGR system, which lowers combustion chamber temps and lowers NOx. But wait, My car failed low speed but passed high speed. So it sounds that the EGR is working. I went ahead and had Jerry @ Greenlight run some magic formula thru the EGR and intake to clean things up. The result was no improvement in the next smog test. So the next thing I did was replace the spark plugs and the O2 sensors. I went and retested and failed again with no improvement. Feeling discouraged and not wanting to go thru the expense of replacing the catalytic converters I started to analyze. Also, the smog tech stated that he thought the cats were doing their job by looking at the numbers. I started looking up zip codes in San Diego county that have different smog requirements http://smogcheck.ca.gov/pubwebquery/...ZipLookup.aspx. I live in an ENHANCED area which most people do. I have friends in the BASIC area which is a static test and not a dyno test. I needed someone in the CHANGE OF OWNERSHIP area so I would never have to smog the NSX again.

During the second test I observed the smog tech running the 15 mph test in 2[SUP]nd[/SUP] gear. I later asked him why. He stated that CARB requires him to use 2[SUP]nd[/SUP] gear. That is insane, that is only 1500 rpm. This engine is not designed to operate at that level. I asked if he could do it in 1[SUP]st[/SUP] gear. He stated that CARB audits his results and data weekly and the fines are huge, so no. He was definitely nervous of BIG BROTHER watching him. This made me start to think, I need to find a smog test place that would allow me to test in 1[SUP]st[/SUP] gear, highly recommended concept. I wanted to see if I played around with placing a vacuum on the EGR valve how it functioned and saw that the car won’t run with the EGR open at low rpms. This made me start to think, at what rpm will the car open the EGR enough to pass. I knew that the 25mph test was at 2500 rpm and the NOx levels were at 415, a passing number. So I needed the engine rpm to be above 1500 and somewhere below 2500. How do I get the rpms up during a test, then it hit me. The NSX has smaller tires on the front than the rear. So I installed my old set of fronts on the rear of my car, pumped up the tire pressure to 40 psi which lowers rolling resistance. I also manually cleaned the EGR ports that go into the intake manifold by removing the rectangular plastic Honda piece in the top middle of the engine and removed the plate under it exposing the EGR ports and tried to clean up gunk in the ports, there was some and headed to the smog place. I should add that when driving the car with front tires on the rear you have to turn off the traction control, otherwise the TCS system keeps activating. Guess what, it passed with a low speed NOx level of 411 ppm, rpm was 1660. I increased the rpm by 10% which lowered the NOx level by 300ppm.

So my take away from this is the state of California is trying their best to get older cars off the road by imposing stricter and stricter requirements while creating a testing environment that makes it increasing more difficult to pass. Also, save your old 91 rims, they are a life saver. Cars with a 6 speed or different gearing may have an rpm range that will help them thru this stupid exercise.
A few weeks ago, I got a letter from CARB offering me $100 to junk my 92 NSX. :mad:

There will be plenty to follow and plenty of headache for those of us want to pass smog. Simple algorithm is forcing our cars off the street making room for all the Priuses and Teslas. :mad::mad:
that and a more aggressive final. 15mph in second is really easy for my motor since the gear changes. I have yet to see how the smog check will go with the gears because I don't go in for a check until summer of 2015.
that and a more aggressive final. 15mph in second is really easy for my motor since the gear changes. I have yet to see how the smog check will go with the gears because I don't go in for a check until summer of 2015.

I've had the JDM gearset and Comptech 4.55 R&P for 17+ years and always easily pass smog. With the specs getting tougher it'll be interesting to see how it does when I have to get it checked this coming summer.
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I found a shop that can run first and second gear on my NSX, but the number is still high :confused:

91 Comptech header and exhaust 135k miles
15 MPH..RPM 2550....121...........702
25 MPH..RPM 2244.....86...........645
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Got my 92 smogged a couple of weeks ago. It just barely passed NOX. I made a point of getting the cats hot and leaving the car running while doing the paper work, but then the klutz spent nearly 30 minutes trying to get a tach signal, and ended up removing a cover from the engine!!!. But what really pissed me off is he ran the 25 mph in 3rd gear (1824 rpm).

My NOX levels were 633 and 609. It's amazing I passed.
I want to make it clear. These number is failed!

I found a shop that can run first and second gear on my NSX, but the number is still high :confused:

91 Comptech header and exhaust 135k miles
15 MPH..RPM 2550....121...........702
25 MPH..RPM 2244.....86...........645
I went to the shop that was closest and didn't worry about it. I passed without any issues. I want to say that it was off of Lake Forest Dr.
Anyone had passed CA smog with header and exhaust??

The muffler is not evaluated in SMOG tests and does not have an impact on the results. The way to think about smog legality in CA is "everything from the airbox to the cats, inclusive". Those are the only things that should be checked by a SMOG tech.

From a technical standpoint, headers won't affect the sniffer either, but because they come before the cats, they are controlled by state SMOG laws.


Oh, and to answer your question, yes many have passed with headers and exhaust, myself included. :smile:
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Results for My 1991 NSX 5-speed 61188 miles. Tubi Exhaust & some random intake. With oem NA1 wheels.

15mph___|14.7|______|0.2|______| 80 | 25 | 17 |_____|.052| .03| .02 |______| 549 |233| 298 |
25mph___|14.5|______|0.2|______| 62 | 20 | 15 |_____|.061| .03| .01 |______| 507 |194| 350 |
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I just got a smog the other day. Passed with no issues. The tach signal was layed on the top of the trunk to receive a signal. Did not have any issues getting a reading. Below are my results.

rpm: 2620 HC: 23 CO: .03 NO: 258
rpm: 2359 HC:14 CO:.01 NO: 305

I was required to go to a Star certified test only. Only mods are pride v1 exhaust, 18/19 vs-xx's. I did get the cats hot before taking it in for the smog. I think this really helps. Its a must for BMW's from my experience.
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My 93 NSX manual failed last week so the mechanic suggested cleaning the EGR and adding Seafoam to the gasoline. I didn't clean the EGR but did add the Seafoam and ran the NSX for about 100+ miles. I took it in today and I warmed it up with some spirited driving and highway as well and it still failed on the 15mph NOx. I have 16" fronts and 17" Rears. I read a few threads and will try checking my spark plugs and also cleaning the EGR. Mechanic also said maybe the O2 sensors were bad also?
Car only has 57K miles so any suggestions. I also pulled a 2012 test from the same place and the RPM's were higher.

2012 Results- Pass
rpm: 2708 HC: 85 CO: .14 NO: 398
rpm: 2424 HC: 34 CO: .03 NO: 323

2014 1st Results- Fail with the 15mph NO
rpm: 1579 HC: 57 CO: .09 NO: 909
rpm: 1751 HC: 38 CO: .05 NO: 646

2014 2nd Results- Fail with the 15mph NO which got worst with the Seafoam added to gas
rpm: 1563 HC: 22 CO: .02 NO: 1073
rpm: 1751 HC: 20 CO: .02 NO: 604

Does someone have a set of 15/16 wheels that I can borrow to get my smog test?

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will try checking my spark plugs ...
Car only has 57K miles

Maintenance interval for spark plugs is 60K miles, so maybe just replace them.

- - - Updated - - -

Check/clean your intake air temp sensor. There's a thread about failing smog due to a dirty sensor. Just a few screws to get to the sensor. My original one at 60K was pretty clean though...
Any follow up on this Mike? Please tell us what you did to pass?
I passed smog (3rd attempt) last week with headers, exhaust, and the help of Shad @ Driving Ambitions. Give him a call if you want to pass it legally :)