James C. Liu's Weblog

Monday November 08, 2004

Passing less smog

Most of us drivers in California already know about the smog test rules here. Basically, newer cars don't need a smog certificate, but after 4 years, all vehicles less than 30 years old are required to have a bi-annual smog certificate. Don't ask me why the policy makers in Sacramento put in the grandfather clause that allows 30+ year old cars to drive without passing the smog test, because it doesn't make sense. Some studies back in the late 80's and 90's indicated that 8% of all the vehicles (mostly the older ones without any type of smog equipment) produced 90+% of the smog).

How much smog a vehicle has the potential to make is measured as the percentage of allowable NOx, CO, and unburnt hydrocarbons (HCs). That's because these compounds react with moisture in the air and sunlight and create a hazy and obnoxious vapour that sometimes covers large urban areas. California still doesn't seem ready to limit the absolute maximum amounts of these pollutants; Our policy only enforces concentrations of these pollutants as percentage or parts per million in the exhaust stream. This means that an SUV with 10-cylinder, 6 liter montrous engine that's pissing a liter of gasoline per 5km could pontentially be releasing 10 times the pollutants of, say, a hybrid gasoline/electric vehicle with 1.2 liter engine that barely sips a liter of petrol and achieves 25km; they both get the same passing score on the smog test and both get people to work and school conveniently.

Last year, California did change its rule and instead of a low and high RPM smog test, they now require older vehicles to undergo a low speed (15 mph) and moderate speed (25 mph) on a dyno that can simulate the car going up a slight incline at these speeds. The test is tougher for older vehicles to pass because unlike the slow and fast idle test, this puts real load on the pistons and if rings and valves are worn, such a load will reveal a more accurate picture of the pollution released while actually driving. I'm not sure if all cars are required to take this test, but I've noticed the older ones and high mileage vehicles seem to be targets for this test.

I drive a 1992 model year Toyota P/U 2WD with 4-cylinder Fuel Injected 22-RE engine - perhaps the finest and most durable mass production engine ever made in the world, bar none [at least in the eye of this very satisfied owner]. This engine and its carburated predecessor, the 22-R, are legendary for lasting well over 300,000 miles without an overhaul. (Remember the "Oh what a feeling! (Jump) Toyota! Commercials?) The engine is mechanically simple and extremely serviceable and reliable. I bought the truck Dec 1991 while in College for just a hair over $7,400 out the door. It averaged about 24 mpg fuel economy while commuting to Berkeley and this included driving up and over the hills into Tilden Park in the mornings to avoid the gridlock along Hwy 24 and the Caldecott Tunnel. To my surprise, almost 13 years later, an audit of fuel costs and mileage today indicates that my flat-land-Silicon-Valley commute provides me an average of 28 mpg. Part of this no-doubt is due to the terrain difference. But another big factor has been the aerodynamics improvement of a lightweight composite flush-mount camper shell mounted over the truck bed. It streamlines the backside and provides a lockable storage area. Another factor are the improved tires at 33 psi that provide a few more percent mileage over the older tires at 28 psi. And instead of the old resistor spark plugs, the addition of platinum and iridium plugs and even dual prongs seem to improve the combustion.

My truck hasn't been in a shop ever for engine work. I've done all that work myself. It was recently in the shop for new tires and shock absorbers and some wheel bearings and seals. These were long deserved maintenance jobs that my home garage isn't equiped to do. But for a truck that has 174,000 miles on it, I'd say it has been well worth the maintenance. I now have a truck that drives better, I think, than it ever felt when I bought it, and it gets even better gas mileage than ever before.

So what about the smog test?

Two years ago, when I got the truck smogged, it passed with flying colours. But the test was the old slow and fast idle RPM test - not the new load test that went into effect recently. I had a few trepidations about that, so I decided to do some standard things to tune the truck up.

We all know that higher temps inside the engine produce more power. But this also produces more NOx. So it's like a balancing act. Too low of a temperature and you have too much unburnt fuel and no power. Too high a temperature and you produce NOx. That's why CA vehicles have EGR (Exhaust Gas Recirculation) valves. These take some of the exhaust and put it back into the engine to complete the burn but also lower the combustion temperature. A lot of things need to work properly to minimize HC, CO and NOx. One of those things is engine ambient temperature. So I flushed and refilled my radiator and replaced with new hoses and thermostat. The last time I actually had done that was at 78,000 miles so it was due at 174,000. I don't use the standard green ethylene glycol stuff that rots radiators, engine blocks, and water pumps after 30,000 miles. Instead, I use some special Pink stuff either from Toyota or some other OEMs. I think it's based on propylene glycol and lasts upto 100,000 miles. It costs about 3 times as much, but I think it's well worth the durability, protection and labour savings of having to flush the fluid more often.

I also did the standard air and oil filter changes, then changed the fan belts too. And then I focused on the ignition wires. Rather than get the standard OEM factory parts, I opted for some cheaper, after-market High-Current, low-resistance cables. I also put in some new Bosch platinum-2 dual-prong plugs. I yanked off the relatively new PCV value and sprayed some Gumout through it to clear it out. And lastly, I took off the intake throttle boot with the car facing down my driveway (so there was a decline) and sprayed copious amounts of gumout into the air inlet while keeping the throttle plate open. A lot of dark solvent flowed back out of the intake, which I intercepted with a lint-free rag. I later sprayed even more gumout inside and used a chopstick with the rag and pushed it into the intake to wipe down the flapper valve, and intake sidewalls. I try to be gentle and not poke around hard with any metal objects. There's some instrumenation in the throttle body to sense the throttle position and this is all hooked into the Electronic fuel injection, the Exhaust Gas Recirculation (EGR) and other emissions/ignition controls. As much as I'm religious about filling up with Chevron gasoline with Techron, I still can't avoid the gumming up of the intake manifold plus all the sensors, so I get paranoid before these smog checks to make sure that vacuum lines are in good shape, that the EGR value works under vacuum, and that the throttle body sensor openings aren't all gummed up and blocked. So I usually try to give the inside of the throttle body and the plate a good soaking and wipe down.

I did check one last thing which are the battery cables. An experience with Fords has taught me that engine electronics are sometimes quite mercurial when battery cables get corroded. So it can sometimes pay to spend the $8 to get a new cable and apply some contact grease to battery posts and clamps if you see a corroded battery cable. Mine were fine, except for some small cathodic deposits which I cleaned and coated with a conducting lubricant/protector to battery terminals. And then I hopped in the truck and drove down to my local Arco Service station.

To my surprise, they could not give me a standard smog test. My truck fit a "High Polluter Profile" and I was then sent to a "Test-Only" place where the folks are not allowed to make any repairs on the vehicle. I asked the Arco station guy why they do this and he doesn't know. He guessed that it was the gov't's way of keeping some of the Testing stations in business and also preventing some stations from cheating by doing certain minor tweaks to help some folks pass the test.

My results? Passed again with flying colours. I produced less than 1/3rd the average rate of unburnt HC, 1/20th (nearly immeasurable) CO, and only 1/8th the average NOx. In fact, the average is about 1/4 the maximum limits for my class of vehicle. Not bad for an old beater truck with 174,000 miles. And my truck's results were even better relative to average on the 25 mph test than the 15 mph one. It only took minor know-how and diligence in keeping the car tuned. But still, I can't be too pround of the crappy gas mileage of 28 mpg. I certainly have the right to gloat over those folks driving around in a big Chevy Suburban with a "Keep Tahoe Blue" sticker on their back window. But with the current VVT Corolla 2004 getting 40 MPG freeway, and the Prius hybrid getting 60 mpg in the City (yes! in the city!) my truck is a gas-guzzler by comparison. So, yeah, I'm feeling relieved that I passed smog, but the fact is, I'm pretty envious of those folks hauling around in those gas-miser hybrids. November 08, 2004 06:55 PM PST Permalink