Emissions Test
Let's face it, emissions testing is probably the least glamorous of our tests. That's not to say it's unimportant. Even if you don't give a hoot about how much these cars pollute our air, a clean-running engine is generally a well-tuned engine. It takes skill to tune a car for low emissions, but this test isn't just about low numbers. It's an indication of each tuner's attention to detail.
That said, the two cars with untouched OEM ECU and catalytic converters predictably took first and second place. OEM engineers spend thousands of hours tweaking their computers and emissions control equipment. Our competitors evidently spent a little less time on their emissions tunes. What's more interesting is how the 'tuned' machines stacked up against each other.
At idle, the Subaru WRX STI was pretty clean, ranking third, behind the Integra and the Atom. It's obvious PDX Tuning put some thought into its emissions tune, running extremely lean. Our exhaust probe showed an air/fuel ratio of around 17:1. As a result, extremely low levels of unburned fuel (hydrocarbons, or HC) and carbon (CO) were emitted. The downside to running really lean with low levels of HC and CO is that a lean mixture burns hotter and increases pressure in the combustion chamber. This increased pressure and temp increases the production of NOx during combustion. And that's just what happened here. The PDX Tuning machine had the second-highest NOx levels at idle. At 2500rpm, the car was so lean it suffered from a lean misfire, sending all the numbers through the roof. Maybe next time, guys.
Groma Fab's 2002 was polluting like an early-60s car should. Billowing clouds of partially burned oil and fuel (that's a slight exaggeration), the BMW was coughing up blue smoke and virtually squirting unburnt fuel from the exhaust. Probably a result of the lumpy camshafts with lots of valve overlap. But who cares about its emissions? The car is smog-exempt, even in the Nazi state of California.
Considering the ungodly amount of power Mattraw's Audi S4 made, it's nothing short of miraculous it was so clean. Using the stock engine management, retuned by GIAC, and a set of new, high-quality cats probably had a lot to do with it. When we saw them installing a set of cats just after rolling off of the dyno, we were worried the converters might not get up to operating temperature in time to make a big difference. But one look at those numbers and it's clear they were hot enough to get the job done. As clean as it was, it still couldn't hold a candle to the OEM tuning of the Integra or Atom.
Low emission levels didn't seem to be on the GT-R team's to-do list. The thing ran so rich at idle, our eyes started watering as it pulled up. It had no cats, not like they'd help anyway. With HC levels that high, a catalytic converter would melt and plug itself up in no time.
If it weren't for the high HC levels at idle, Blacktrax's V8-powered Nissan would have been respectably clean. We suspect the aftermarket cats just weren't up to the job. Most high-performance cats aren't nearly as efficient as OEM items, simply because they don't use as much of the active ingredients platinum and palladium, because of the cost. These cats probably had even less precious metals than most high-flow converters.
-Ryan McKay
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