Enthusiasts always view new emissions laws with suspicion, if not outright hostility. Perhaps it's our collective memory of the pathetic emissions controls of the '70s or the cumbersome fuel injection systems of the '80s. However bad it was then, it's pretty good now. Yes, the aftermarket has had to learn a whole new bag of tricks, but in many cases, those tricks are easier to learn. Picking the right fuel injector is far easier than picking emulsion tubes for your Mikunis.
Modern engines are capable of incredible power output not in spite of, but in many cases because of the tight tolerances demanded by modern emissions laws. Consider the fact the air is actually cleaner than it used to be, and on most days you can actually inhale and not die; perhaps we should gather all our friends at the EPA and CARB (California Air Resources Board), have a big barbecue and celebrate our love for each other.
For every tightening of emissions laws, there is a ripple effect that demands new solutions from not only the powertrain engineers trying to meet their new targets, but also the tuners trying to wring horsepower from these new engines. Tricks that worked a few years ago are hopeless now, and those we are comfortable with today will do us no good tomorrow. With that in mind, let's look in the crystal ball and see what tomorrow's emissions standards are going to mean to tuners.
Evaporative emissions
CARB recently clamped down on evaporative emissions. The reason this has anything to do with enthusiasts is that it has brought about a new fuel delivery strategy that is being adopted almost universally. In the past, fuel was pumped from the tank to the fuel rail and back into the tank. A regulator on the rail controlled fuel pressure by restricting this return line. This strategy was adopted to simplify the electronic side of the fuel injection system. Predicting how much fuel an injector will deliver in a given amount of time requires knowing the pressure drop between the fuel rail and intake manifold. To avoid having to measure manifold pressure and calculate the appropriate pulsewidth every single time the injector opens, the fuel pressure regulator was simply referenced to manifold pressure so that fuel pressure would vary relative to the outside world, but would be constant relative to the manifold.
What does this have to do with evaporative emissions? Simple: Fuel that is pumped into the engine compartment and back to the tank gets heated, and hot gas evaporates more readily than cold gas. Modern, "returnless" fuel injection systems have a pressure regulator in the gas tank that bypasses surplus fuel without pumping it out of the tank. Fuel pressure is fixed relative to the outside world now, but with computing power now cheaper than extra fuel lines, the additional calculations are no big deal.
Now, how does this affect you? Whenever a tuner wants to turbocharge or supercharge an engine, it has to figure out how to get enough extra fuel into the engine to meet with the extra air. By far the most common solution, is to simply add a second fuel pressure regulator. The stock regulator works at a 1:1 ratio, increasing fuel pressure by one psi for every psi of manifold pressure. These extra rising rate fuel pressure regulators increase fuel pressure by three, four, or five psi for every psi of boost above atmospheric pressure.
The real advantage to rising rate fuel pressure regulators is their ubiquity. Until recently, this strategy worked on any fuel injected car. That's all over now. Look no further than this month's Project Miata for an example of how cumbersome "simple" fuel enrichment can be on a returnless system. The solution for the aftermarket will ultimately be the same as the solution for the OE manufacturers: computing power. Stand-alone engine management systems are evolving at an unprecedented pace, with software becoming more useable and prices becoming lower every day. In the end, modified cars will run better, be cleaner and more powerful with stand- alone engine management, but meanwhile, the adjustment will be difficult.
Cold-start emissions
Making the exhaust gases clean on a warm engine is relatively easy, but cold-start emissions are another story. The main problem is the catalytic converter needs to reach its light-off temperature before it will start cleaning the exhaust.
The most common solution is to use a close-coupled catalyst. In English, that's a catalytic converter that's mounted really close to the exhaust ports. The problem here is the catalyst's location doesn't leave enough room for a manifold to be tuned for exhaust scavenging. While most under-floor catalytic converters have a minimal impact on power output, close-coupled cats are almost always a performance bottleneck.
The best solution to this problem is the one used on the Celica GT-S and the new Civic. Instead of moving the cat closer to the heat, they concentrated in moving the heat to the cat. In addition to a stainless-steel manifold that absorbs less heat, both cars use an e-pipe instead of two conventional secondary tubes in the bottom of their tri-y manifolds. An e-pipe is simply one big exhaust pipe with a divider wall down the middle. This keeps the exhaust gases separate, but has far less surface area than two separate exhaust pipes, and therefore less heat is lost to the outside world.
The quest for quick lightoff times would seem to preclude turbochargers, but two of our "Eight Great Rides" winners still have them. A turbocharger is bad for cold start emissions not only because the turbocharger itself absorbs heat as it warms up, but also because the very exhaust energy the turbo uses to drive the compressor wheel is the same exhaust energy needed to light-off the catalyst.
Volkswagen's solution, as seen in all the 1.8T-powered cars, is a tiny turbocharger. By simply keeping heat loss to a minimum, it has been able to get good cold-start light-off with a turbo.
Subaru's solution, as usual, is less conventional. Subaru's flat four layout makes catalyst light-off inherently difficult, since the two cylinder heads are over a foot apart. There is a lot of pipe and a turbo between the first bit of exhaust heat and the catalyst. Subaru's solution was to put a catalytic converter before the turbo! Anyone familiar with turbochargers will wince at the thought, since the catalyst is now stealing exhaust energy that should be making the car faster, but Subaru's solution seems inevitable. It may be unconventional and it may be less-than-ideal, but at least we still have a turbo.
From the tuner's standpoint, there is little that can be done about close-coupled catalysts. You either have to live with the exhaust restriction, or build a race-only engine. Even relocating the catalyst downstream using stainless steel and e-pipes would be technically illegal, our barbecue buddies really frown on moving cats.
Full-throttle testing
Finally, the next emissions hurdle on the horizon is full-throttle emissions testing. Current emissions certification uses a drive cycle with no full throttle. This has allowed a little more freedom to tune aggressively during full throttle. This has also allowed nitrous oxide to be considered CARB legal, along with many other power enhancing bits that don't make a significant difference during light-load driving.
Enjoy it while you can. Full throttle is on its way to the drive cycle, and the result is going to be lower specific output. Optimum power production and optimum catalyst function require different fuel mixtures.
On current cars, when your foot hits the floor, the ECU knows which you care more about, but when full throttle hits the drive cycle, you foot won't have nearly as much authority. The solution will probably be bigger, lower output engines. Our sneak peek at Nissan's newest performance cars may be a hint at what the future will hold. The Z makes 260 hp from 3.5 liters, while the SE-R makes 180 hp from 2.5 liters. While the horsepower numbers are quite strong, the specific output is nothing to get excited about. Get used to it.
Along the way we can also expect to see faster-acting, wideband O2 sensors that know not just whether the fuel mixture is rich or lean, but how rich or how lean. As these parts get cheaper through the magic of mass production, tuning our new, low-buck engine management systems will get much easier, and since we'll have big engines to work with, there should be plenty of power to go around.
I have seen the future, and it ain't all bad.