Tricks to pass the smog test

[pbanders]

Here are a few tricks that may help you get past that next smog test. I'd appreciate any additional tips and corrections to the ones I've posted here.

Assumptions: Two part smog test, at idle and at part-load. Ignition in optimal shape, no faulty FI components. Motor mechanical in decent condition, not totally pooped out.

Idle Tests
----------
Failing CO
1. Use ECU mixture knob to lean out mixture (CCW), adjust idle bleed screw to reset idle. I've run mine as lean as hell just for the purpose of the test, and readjusted after passing.
2. Make sure motor is fully warmed up before taking test (cold motor = rich mixture = high CO). I run my car fairly hard before arriving and keep it idling while waiting in line for the test.

Failing HC
1. Retard the timing by 5 degrees. Adjust idle bleed screw to reset idle. Retarded timing reduces HC and NOx emissions. Readjust to spec after passing test.
2. Readjust your valves to be looser by 0.001 to 0.002". If you've got a non-stock cam, you may have to go to a very loose adjustment (I think John Larson has some suggestions). The idea is that you want to get rid of valve overlap, which causes high HC emissions. It may sound like hell, but you're not getting a clatter test, you're getting a smog test. Readjust after passing.

Failing NOx
1. Retard the timing by 5 degrees. Same reasons as above. Readjust after passing.

Note: Changing the timing has almost no effect on CO emissions.

Part-Load Tests
---------------
Failing CO
1. Try reducing the fuel pressure by 2 psig, readjust the idle bleed screw to reset idle to spec. CO is almost entirely a function of A/F ratio, you can make it leaner by reducing fuel pressure a bit. Be very careful not to run the motor hard under these conditions, lest you burn a valve. Reset to spec immediately after passing test. If you have a faulty MPS that doesn't hold a vacuum, you'll see it here on this test (and at idle, too). I do not recommend jiggering with the MPS mixture adjustment screw to try to reduce CO, you'll likely bugger it and end up worse off.
2. Make sure motor is fully warmed up before taking test (cold motor = rich mixture = high CO). I run my car fairly hard before arriving and keep it idling while waiting in line for the test.

Failing HC
1. If you've got a 1.7 or 2.0 with vacuum advance, try blocking the vacuum advance line (don't make it obvious to the smog inspector by disconnecting the hose!). Elimination of vacuum advance reduces part-load HC and NOx. Reconnect after passing the test.
2. If you don't have a vacuum advance, try retarding the timing by 5 degrees, and adjusting the air bleed screw to reset the idle. Again, retarded timing reduces HC and NOx emissions. Reset after passing the test.
3. Increase your valve clearance, as described above. Reducing effective overlap reduces the HC emissions. Readjust after passing the test.

Failing NOx
1. See #1 in "Failing HC"
2. See #2 in "Failing HC"

I'm sure you sneaky guys out there have some more strategies for passing smog - what are they?

[JWest]

How about "guaranteed to pass" junk you put in the gas? I've never tried it but thought I'd ask.

[seventythree]

One word of caution to California residients is that the smog inspection here calls for measuring ignition timing by the use of a timing gun. I know of several incidents where a car failed the test due to incorrect timing. On a 914 however, the inspector may not know where exactly to check, and therefore, just fudge the report by marking it as checked/passed.

[sammyg2]

Use regular unleaded gasoline instead of premium, add ethanol (small percentage, less than 10%). Those two things can make the emissions go down a little. Probably only work if the engine is borderline.

As soon as the test is over add fresh gasoline to dilute the ethanol beacuse is will make the engine run lean.

[pbanders]

Originally posted by seventythree
One word of caution to California residients is that the smog inspection here calls for measuring ignition timing by the use of a timing gun. I know of several incidents where a car failed the test due to incorrect timing. On a 914 however, the inspector may not know where exactly to check, and therefore, just fudge the report by marking it as checked/passed.

I never endured a SMOGII test in CA, I left before it became effective, so I never had a timing test. Here in AZ, they don't test timing. I'd be surprised if your average SMOG tech would know the exact procedure for checking 1.7 and 2.0 timing, anyway!

[red-beard]

Is there a NOx requirement for the 914? I thought EPA 1 only covered HC, CO, partiulate and lead (Which really is a particulate).

James

[bowlsby]

They do check timing here in CA...I have seen it digitally displayed on their video screen as a BTDC number, so I assume it is fairly accurate. I think the print out also may show the exact timing if the car fails the test. I have not seen a tech attach a timing light, but I have seen a clamp around one of the spark plug wires and of course the sniffer in the rectal area...the cars, not mine.

I have retrofitted a dual port 73 TB onto my 74 2.0 car. The off-the-line seems to be improved but it is subtle. It still is no rocket ship FWIW. Don't know how it affected the smog test results.

[LateApex]

I just slip the guy a few more $$'s and I'll pass.

[kena]

They do attach and use timing light after they figure out where the engine is. Always just stand there and smile first though to intimidate them a bit as macho inspector looks for engine. I had to sneak a catalytic converter unto my 2.0 car to get it to pass. My 76 was a 49 state model that doesn't use one. At one test station (pre-test) I got busted when the inspector noticed it and failed me(after consulting his manuals and realizing it also didn't need an EGR nor cat converter)

The most important thing to do is never go initially for the actual test...if it fails and you get labeled as a Gross Polluter automatically during the test you are now in smog hell. Always ask for the pre-test and if it passes just continue right into the actual test. Mine passed pre-test, then immediately failed first actual reading and then thankfully passed on the second attempt. The inspector never saw the cat installed up under the rear of the car.

[Brad Roberts]

Most of the 914's I see fail the test have a problem with holding a steady state RPM. The car surges while they are trying to do the test. Most of them burn clean and will pass visually if semi maintained.

B

[anthony]

You don't have to tell me how hard it is to make your 914 run at 2500 rpms for a full 30 seconds straight. I had to sit in the car and keep it at 2500 rpms for the guy with my foot.

Here are some notes from my last CA smog check (non-dyno style):

at first they didn't even want to work on my car (I had to convince them that it was all legal and it had the sticker)

the tech checked for the evap canister

he measured the seal of the gas cap

he checked the timing by hand after I showed him how

he hooked up a vacuum gauge and check the vacuum advance unit so I'd be careful about blocking that line.

[bowlsby]

As an aside for California 914 owners:

1 Jan 2004 - the 1974 cars are smog exempt

1 Jan 2005 - the 1975 cars are smog exempt

1 Jan 2006 - the 1976 cars are smog exempt

Its not that much longer.

[pbanders]

Originally posted by anthony

he hooked up a vacuum gauge and check the vacuum advance unit so I'd be careful about blocking that line.

Jeez, things have gotten worse in CA since I left! OK, don't block the advance line in CA. Do you have a NOx limit? If not, open up the valve clearance to reduce HC instead of futzing with the timing. I'm pretty sure that as anal as the CA smog techs are, they're not going to check THAT!

[anthony]

No NOx limit for '74 914s in CA - not sure about . They just test CO and HC.

[914GT]

Would anyone care to comment on emissions regarding SBC V8 conversions? Here in Arizona I'll have to pass CO and HC on my 74. I'm currently restoring mine and need to make a decision as to go with the V8 or rebuild the original 2.0. If I go V8, should I plan on adding an air pump, EGR or Cat even though they weren't originally required? My 68 Chevelle w/350 and only PCV easily meets the limits for a 74 model here. Thanks for any suggestions.

Guy

[kena]

When we say smog nazi's and other bad things about Cal. smog reqmn'ts we aren't kidding. In Cal. you can't put that 68 SBC in a 74 anything. You must put a 74 or later SBC which meets the original 74 Cal. SBC smog requirements.

[914GT]

What I was trying to say was a good condition properly-tuned 350 without any emissions controls will easily meet the smog limits specified for a 74 model year car in AZ. The engine I have planned for my 914 is from an 80-84 model. I'm glad AZ isn't as strict as CA for checking engine date codes or whatever but I'm sure they are getting there. I wasn't planning on putting any smog controls on since the original 2.0 didn't have any besides the vapor recovery canister. They only do a gas cap check and exhaust test so maybe I am OK - hopefully.
Guy

Originally posted by kena
When we say smog nazi's and other bad things about Cal. smog reqmn'ts we aren't kidding. In Cal. you can't put that 68 SBC in a 74 anything. You must put a 74 or later SBC which meets the original 74 Cal. SBC smog requirements.

[anthony]

They wouldn't pass the "visual inspection" in CA. The engine/smog equipment must match the official sticker in the engine compartment. In CA they would make you comply to the 80-84 smog spec for the engine you put in and it would have to have all the smog equipment for an 80-84 Chevy.

I'd personally do it legal so you're not hassled in the future. I wouldn't want to do all the work of a conversion and then hope I'd be ok. They could easily tighten up the smog check in AZ and then you might be screwed.

[JWest]

I'm not real familiar with the California laws - what happens if the sticker is gone from the engine compartment?

[Dave at Pelican Parts]

They have a book that lists the requirements for just about every car made since testing was required.

--DD