Last week I got stranded in a boring hotel room in a boring and wet Detroit suburb. Did I mention that it was boring? Luckily, I'm a car geek, so I was able to entertain myself without spending my Rally budget on SpankTravision.
Arithmetic CalisthenicsIn a situation like this, the car geek must first seek out a car magazine. Any car magazine. Even DaimlerChrysler's glossy, self-congratulatory "Hightech Report" magazine. Then the geek must look for charts. There was a great one buried in a story about some new piece of vehicle simulation software. It was a real yawner if you aren't designing new cars on a regular basis. But the chart was a fascinating peek into the world of those who know more about cars than we do. It was a simple breakdown of where energy goes during normal driving on the standardized New European Driving Cycle used for emissions testing. Or maybe they use it for gas mileage testing. I don't know. I don't design cars in Europe. The breakdown looked like this:
35.3% exhaust heat30% engine heat8.5% internal friction4.2% charging change6.9% air resistance4.0% rolling resistance6.4% translation losses (acceleration)0.6% rotary losses (acceleration)0.3% axles0.9% transmission0.4% clutch losses1.5% alternator1.0% power steering pump
If you break this down into two parts-energy lost before the crank and energy lost after-you can get a peek at the elusive driveline loss factor horsepower junkies are always trying to add to their dyno numbers for extra bragging rights. The first four factors, exhaust and engine heat, internal friction, and charging change (I don't know what that means either), are all fuel energy lost inside the engine, so they don't show up in crank horsepower. That's 78 percent of the fuel's energy out the window. Pistons suck. Oh, well. Life goes on.
Of the remaining 22 percent that actually comes out as crank power, 37.7 percent (8.3 percent of the total) goes to the rolling resistance, axles, transmission, alternator and power steering pump losses. These are the same losses that should occur on the dyno, so should we be seeing a 37.7-percent difference between crank and wheel horsepower?
Before checking, lets fine-tune that number a bit. The car is an unnamed DaimlerChrysler vehicle, but we know it's a manual transmission, since it has clutch losses (which don't occur on the dyno, since there's no shifting gears, and hence no clutch slipping), and it's a good bet it's two-wheel drive. That means the rolling resistance should only be for two wheels, so let's cut that value in half. Also, crank horsepower is supposed to be measured with the power steering pump and alternator already sapping power, so we'll eliminate those. That gives us 17.3-percent (3.8 percent of the total) driveline losses.
Let's check it: 17.3 percent of 170 hp is 29.4 hp, so we'd expect a 170-hp car to make 140.6 hp at the wheels. The Mazdaspeed Proteg, Ford SVT Focus and the late Integra GS-R were all rated at 170 hp and all made about 150 hp at the wheels, so they're a little more efficient than this chart was. But maybe the mystery DaimlerChrysler is rear-wheel drive. A rear-drive car has more gears, bearings and driveshafts than a front driver, so the driveline loss should be higher. Applying this factor to a 240-hp Honda S2000, it should lose 41.5 hp, for 198.5 hp at the wheels. The last one we tested made 203 hp. Pretty darn close. A 287-hp 350Z should lose 49.7 hp, for 237.3 hp at the wheels. Our last test was 239 hp.
It's amazing when these things work out.
Three-Wheel TurboWith the calculator fingers all limbered up, we move on to the e-mail, wherein we communicate directly with our staggeringly brilliant readers. One such reader, Chris Cavalieri, had an idea. What if, he asked, you used a tank of compressed gas, N2O, CO2, whatever, blowing on an extra turbine, to pre-spool a large turbo. OK, there would be a bit of a problem with thermal shock when the cryogenic gas coming from the tank hit the hot turbo parts (a problem he pointed out himself) and you'd eventually have to refill the tank, but other than that, it didn't seem like a half bad idea.
I forwarded the idea over to one of my Garrett buddies and within hours he handed me a nearly forgotten piece of Garrett history. It was called a three-wheeled turbo, and in addition to the normal turbine and compressor wheels, it had an additional small turbine in the middle, just as Cavalieri had suggested. The second turbine, though, was powered by engine oil, pumped up to 2,000 psi by a two-stage pump. The whole thing looked like a normal T3 turbo with the exception of a slightly wider center housing with a few extra, very large oil fittings.
So what became of this brilliant idea? It was used on a Hino bus and a tugboat, but was abandoned relatively quickly for reasons that have been lost to geek history. It's a good bet that the two-stage pump, it's plumbing and control system, and the extra oil drag from the redundant turbine once the exhaust turbine took over, weren't worth the advantage in throttle response. At least not on a bus or a tugboat. Makes you wonder how it would work on a car, doesn't it?
Eberhard's BreweryDozing off for a few minutes, I return to the magazine to read more about how great DaimlerChrysler thinks it is. There, I stumble upon an interesting bit of good news in the war on cold-start emissions.
With a functioning catalytic converter, modern cars emit virtually none of the hydrocarbons, CO and NOx regulated by just about every first-world country. But in the first 40 seconds or so after a cold engine is started, the catalytic converter isn't hot enough to work. It's this cold-start period, then, that gets all the attention these days.
Since most of a car's emissions during the EPA's certification testing happens immediately after startup, making the cat light off a few seconds earlier can reduce total emissions by a staggering percentage. This is why catalysts keep getting closer and closer to the exhaust ports, and horsepower keeps getting harder and harder to make without relocating them.
Some German guy named Eberhard has come up with a special cold-start fuel that knocks hydrocarbon emissions down to virtually nothing in just a few seconds. DaimlerChrysler is now trying to figure out how to stuff a miniature cold-start-fuel refinery into a car. If such a thing could be made inexpensive and as compact as, say a modern evaporative emissions package, this could be good news for everybody. It's not clear if this fuel just burns cleaner, or if it somehow kick-starts the catalyst, but either way, it would allow the cat to move back down under the car where it belongs, leaving room for headers, turbos and all the stuff we like.
Oh, and the air you breathe would be a little less likely to kill you. That might be nice, too.