Ultimate Street Car Challenge - 8 Emissions

We'd all like to build killer street/track machines without sweating draconian smog laws, but that's a pipe dream. To legally run the highways of California, we've all got to somehow circumvent the biannual nightmare of smogging our 'street cars'. To spread the joy, we make the USCC competitors do the same. If we can't get away with showing Johnny Law the middle digit, why should they?

In California, a smog test consists of two parts: a visual inspection and actual emissions testing on a loaded dyno. The dyno simulates the load of the car driving down the road at 15 and 25mph. This provides an accurate reading of the level of pollutants each car emits during normal driving.

Thankfully for the competitors, we don't have the equipment or the time to do this, so we're reverting to the old-school way of measuring emissions-at idle and at 2500rpm. While this is in no way a precise indication of actual emissions during driving, it's a level playing field. That said, not a single competitor would have passed California's real emissions test.

To ensure consistent results, each car was tested just after its last dyno pull. We measured three gasses, hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxides (NOx). The results should be taken with a grain of salt, however. While we did our best to make it fair, we're only as good as the equipment we use. If we can trust the sticker on top, our emissions analyzer was last calibrated about 10 years ago, making it about 9 years overdue for a service.

With a gas analyzer that would spontaneously (and infuriatingly) shut down mid-test with increasing frequency throughout the day, we were lucky to even finish. But we did, and the results were enlightening.

The biggest pig of the bunch was the RX-7. Sporting a spankin' new engine and gnarly camshafts with loads of valve overlap, the Mazvy/Chevda bastard virtually spit raw fuel from the exhaust. At idle, the FD maxed out the HC meter, measuring an indicated 4600 parts per million (PPM) at idle (which makes it as dirty as about 500 Toyota Corollas).

The next highest idle HC was recorded by the R32, which saw 900ppm. So the next time visibility is reduced to 30 feet because of smog, look for these guys.

At the opposite end of the spectrum were the NSX and 350Z. At idle, the 350Z emitted a paltry 20ppm HC. Both the 350 and NSX had emissions levels that were nearly low enough to pass a smog check, but neither would pass the visual inspection. The key to their low emissions was a lot of tuning. While both cars were surprisingly clean, their tuning methods were a little different. The 350Z recorded the lowest HC levels at idle (20ppm), and the lowest CO (0.1) at idle and 2500rpm. The low CO levels tells us the car was running lean and helps explain why it had slightly higher NOx levels, which ultimately cost it the top spot.

Future USCC competitors take note: given the lackluster results of most the cars, this portion seems like an easy place to pick up a few points. Seems like only a few people are really trying.-Ryan McKay

The Big PictureIt's almost 2pm. Many of the contestants are nearly done and still no Joe, still no Prototype Racing Elise. Some of the contestants are grumbling for us to cut them from the competition, but we can't do that, not only because we can't get hold of him, but because he had less than a week to prepare. We decide to give him until the hour, then, with 15 minutes to spare, he pulls up, having driven around for an hour completely lost. Joe-it's time to get a cellphone.