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Message-ID: <5962668.1103577901125.JavaMail.ratwell_at_mac_dot_com>
Date: Mon, 20 Dec 2004 13:25:01 -0800
From: Richard Atwell <ratwell_at_mac_dot_com>
To: Type2 <type2_at_type2_dot_com>
Mime-Version: 1.0
Subject: Smog test: VW 1, Gubernator 0

I went for my biennial smog test today. This is a long story but hopefully helpful to others...

Figuring out the right air fuel ratio to set the bus to in hindsight didn't seems as difficult as I thought it would be in order to pass but I did have the benefit of driving around for several days with a CHT sensor I whipped up and a wide band oxygen meter which is hooked up to the #1/2 afterburner on my exhaust:

http://homepage.mac_dot_com/ratwell/.Pictures/Maintenance3/253-WidebandBung.jpg

I've learned a lot from watching the readings, driving the bus and adjusting the mixture. Being able to do this while driving is a real help. I can't raved enough about it. The idle mixture does have an inpact on the overall mixture but what surprised me most was how well the FI runs under a large range of AFR settings. You set it and forget it! (sorry).

With my EGR hooked up, the day before I performed a minor tuneup (new plugs, new wires, new cap, new rotor) and left the valves as is because of my leakdown tests and valve adjustment were only done a short while ago. With the new rotor I had to retard the timing slightly because the electrode pits. I also reset the idle speed. I've got a pertronix so I didn't need to swap in fresh points. I also changed the oil and filter because I've been doing a lot of short trips and didn't want contaminated oil jinxing otherwise good results. My charcoal filter is the factory original with vintage activated charcoal inside.

I set the AFR at idle to about 2% CO and went driving on Sunday. I always use 87 octane from the same station and forgot to fill up with 89 in anticipation of the test so with half a tank I filled the rest with 91 to approximate 89 with my own brew. As I left the station the AFR changed to 1.3% and held that value after the car got up to operating temperature again. Whoa, it's not bunk: they really are selling cleaner burning fuel!

Time travel back two years ago when I had my last test. Back then it was the TSI (two speed idle test, no dyno) and the limits were 2.5% CO (low speed) and 3.5% CO (higher speed). After looking at the 2003 cutpoints tables for the dyno (ASM) test I decided to tune it on the lean side knowing these values while for a different test would fail me. My bus has always run richer than spec but it's in good shape because of it. Keep in mind the bus is subjected to truck smog limits, not the stricter ones for a passenger car.

I set the idle for 0.7% CO (which I thought would pass me) and the factory setting is 0.5% to 1.5% CO anyway. This produced the following results:

temp: 60F
head temp: 315F at 50mph, 390F at 70mph
AFR idle: 0.7%
AFR light throttle: 0.1%
AFR half throttle: 2.5%
AFR WOT: 5%

With my deadline approaching I decided to risk the test rather than go for a pre-test. Since you can re-register with a smog failure and get an extension it seemed worth the risk. If I'd paid for a pre-test I'd be out that money anyway if I had to make some adjustments. If I failed on the real test, I could retune and get a free retest. Luckily I have some equipment so I'm not doing this blindly.

The testing cost has gone up because I had to get smogged at a test only center (the bus is categorized as high emitter profile). The prices at those stations are high because they can't recoop any money for the testing equipment through repairs. Those setups (dyno, sniffer, computer) costs about $40k and a test only stations expects to recover the costs in only a couple of years. Kaching.

I woke up this morning and went for a drive to warm up the bus before the test. The humidity is terrible today (not raining yet). It's about 50F and 95% humidity. Sure enough with the bus warmed up the AFR was reading richer (1.5%) than last night so I turned out the screw on the AFR half a turn and this seemed to reset the mixture to last night's setting. I've read many times about jetting carbs on race day for the humidity but it almost completely escaped me. The FI system works so well you tend to forget about it.

I'd been through the test before with my wife's car but had to use a different station. EZ Smog at Reed & Lawrence in Santa Clara had the best price and no lineups that last few days so I went there.

Even though the engine was warm they kept it idling for 10 min while they configured the computer. I wasn't worried about overheating because it's so cold out today but I wondered how it would affect the test. They said they do it as a matter or practice to help the cars pass. They said if the cars is turned off for only 5 minutes it may easily fail.

The first step is mostly paperwork and setting up the computer. They look for the BAR sticker but relied on the computer records to provide the VIN, my address, model year, etc.

The second step is the actual emissions test. The first dyno run was aborted because the computer didn't like the way the engine was accelerated. The second test was completed but they didn't configure the tester to read my BAR sticker so it was aborted and logged with the DMV that way. The third test was started over from scratch and was more eventful...

With the sniffer in the tailpipe and a rpm coupler reading #4 spark plug wire they began the test on the dyno. The computer automates the testing and the smog tech simply uses a remote control to communicate with the computer. The first stage revs the engine to 15 mph and they hold it there while the sniffer does it's job. The tech had to shift the bus into 2nd gear to accomplish this. The computer then cued the tech to bring the engine to rest then the second run began. It repeats the same steps until the computer requests the speed be raised to 25mph for a few moments. I didn't pay complete attention because I was interrupted by another customer but judging by the results he must have shifted into 3rd because the rpm at 25 mph was recorded as 2000rpm again.

After the dyno testing, they did a visual inspection. The tech seemed mystified by the bus engine having never seen one before and he didn't test the EGR valve or even check the timing. Yipee. They used to do the visual test first but it's now done last I guess so they can charge you full price for the test and so the DMV can collect more smog test results.

The last thing they check is the gas cap to see if it seals. If you have a CA bus they might also check for a fuel restrictor but since my bus is Federal I require neither the restrictor or a CAT.

You are waiting on baited breath you say? I passed. Here are the results (number are read as MEAS/MAX):

15 mph - RPM 1990
%CO2 13.9 - %O2 1.2 - PPM HC 48/204 - %CO 0.19/1.66 - PPM NO 652/1534 - PASS

25 mph - RPM 2018
%CO2 13.8 - %O2 1.5 - PPM HC 31/169 - %CO 0.11/1.46 - PPM NO 563/1294 - PASS

The %CO limits didn't jive with the ASM cutpoints...

http://159.145.15.175/ftp/pdfdocs/asm_ph43.pdf

...but since they are higher who cares. It's as if the limits bracket the factory limit of 1.5% CO. Hmmm.

The smog tech was truly shocked the bus passed so well. It was certainly a relief for me. He was a very nice guy and professional but when he used his cellphone and I asked if he was calling the Gubernator to give him my results he didn't get the joke.

I'll scan the report later and put it online. It looks basically the same as the one from two years ago except they are now checking for liquid fuel leaks at the time of the visual inspection.

I did chat up the tech about the testing machine. They calibrate the sniffer with three bottles of gas every 3 days. The tester seemed in line with my oxygen sensor so that made me happy. The test was done at light throttle and that's also where I checked my own adjustment.

Remember, humidity and fuel grade will affect the results. At least it did for me. If you don't have your own equipment, plan ahead and get smogged on a day with weather conditions that are similar to the day you had your mixture set. The smog tech couldn't tell me whether or not his equipment compensated for weather so err on the side of caution.

-- 
Richard, 1978 Westfalia CDN
http://www.ratwell_dot_com/
Cupertino, CA