For the past three years, the USCC emissions test was based on hydrocarbon (HC) and carbon monoxide (CO) concentrations. Getting reasonable HC and CO levels was a simple matter of strapping on an el cheapo aftermarket catalytic converter, making sure that it gets good and hot, and idling the car in closed-loop operation. Any car with an oxygen sensor in the exhaust and a cat can score reasonably well on the emissions test.
This year we finally upped the ante on the emissions test to include nitrogen oxide (NOx) concentrations. This required new hardware, a MTS 1000 five-gas analyzer on loan from Vetronix Corporation. NOx emission is a real problem for high-output engines because its formation is highly dependent on elevated combustion temperatures and pressures. EGR is the convention for reducing NOx formation, but you won't find that on any of these cars. All they can rely on is good tuning and a good cat.
We made the USCC emissions rules easy on the big-power dyno junkies. We allowed the use of open-exhaust bypass valves on the dyno and gave them a few minutes to seal it before being sampled. This way they didn't have to deal with power loss caused by exhaust restrictions and also take advantage of a cat for emissions. The drawback was that by running on the dyno with the exhaust bypassed around the cat, the converter doesn't get lit off to its operating temperature.
The smart contestant got his cat really hot prior to getting strapped onto the dyno and only opened the exhaust bypass immediately before the pull. This kept the cat hot enough to still be useful on the emissions test. Tuning changes to the engine management were prohibited during the emissions sampling. We checked the entire exhaust system for leaks prior to hooking up the gas analyzer to take unloaded steady state emissions measurements at idle and 2500 rpm. To be sure no significant leaks were present, we made sure exhaust oxygen concentration was within reasonable limits.
Since gas concentrations are measured on different scales; (parts per million (ppm) for NOx and HCs, and in percentage for CO), each individual measurement was assigned an equivalent numeric value and totaled for each species. These were then totaled and converted into the appropriate point value on the overall points scale.
HPA's bi-turbo R32 Golf came out the cleanest of the bunch while, as expected, the highly tuned rotary was a gross polluter. No surprise there, but we were surprised by the cleanliness of the dyno king Supra and the Skyline, which could have easily passed California smog. - Jay Chen
Test 6 Emissions
| EMISSIONS |
| Rank | Car | Points | Peanut Gallery |
| 1 | VW R32 | 110 | More turbos do clean the car up |
| 2 | Toyota Supra | 103 | Gobs of power, and clean too |
| 3 | Nissan Skyline | 101 | There's a reason why O.E. |
| | | | cats cost $700 |
| 4 | Mitsu Eclipse | 100 | Not bad for a decade-old car |
| 5 | Toyota MR2 | 96 | Which pipe is the real one? |
| 6 | Subaru 2.5RS | 82 | Hope that cat wasn't new |
| 7 | Buschur/RRE EVO | 74 | Cleaner at idle than at 2500 |
| 8 | Mazda Miata | 52 | How does something so small |
| | | | make such a big mess? |
| 9 | Mazda RX-7 | 13 | Idle? What's that? |
| 10 | Sparco EVO | 10 | But it looked clean on the outside |
We were warned not to invite Grannie to the USCC again. It seems she was so excited after the last one it took her hemorrhoids three months to settle down. We called her anyway.
Who better to test the true civility of these street cars? The rest of us want big go-fast, but not grandma. The old girl likes cold A/C, comfy seats, quiet interiors and a smooth ride. Grandma needed to be back at the Fading Daze Retirement Home and Bowling Center by dark, so one ride in each is all she got.
Grandma got into the Supra first and the old bird settled right in. She returned from the dollar store with her wig askew and her teeth in hand but she slid out looking none too worse for the trip.
Next was the Subaru 2.5RS. At nearly stock ride height, ingress/egress was easy for the old wench. She asked to be driven to the scooter store, as Mike Kojima had made a list of things to make Grandma's Lil' Rascal go faster. "I don't want to suck, dear!" On the way back, Grandma fell right to sleep in what turned out to be the second most comfortable car in the field.
Next was the RX-7. It has no radio or A/C and, as most rotaries are, it's loud. "That thing makes more noise out the rear end than your grandfather!" she said.
As soon as Grandma climbed into Marcel Horn's VW, her eyes lit up. "My hoo-hoo dilly is a little hot, dear. Can you turn up the A/C?" she asked as she settled into the comfy seat and began to fondle the fine mouse fur in the glove box. Grandma quickly settled into a nap. Grandma likey. - Tom Paule