Your Mileage May Vary

By J.G. Pasterjak
Apr 21, 2008 | Chevrolet, Honda, Mazda, Mini, Volkswagen | Posted in Shop Work | From the Dec. 2006 issue | Never miss an article

We’re gasaholics. It’s that simple. Even more than booze, pills, smack, crack, ice, chip, crunch, ganj, boot, yellow wigglers, screaming sunshine drops and frisco freakouts, we Americans crave that dinosaur juice.

According to some sources, about 40 percent of the world’s produced energy comes from oil in some form. Over half of that crude is refined into gasoline, meaning that a great deal of the energy produced in this world comes from some type of combustion engine.

Worst of all, once the energy is released from that gasoline, it is, for all practical purposes, gone. Every controlled explosion of that atomized mixture of fuel and air throughout the world reduces our finite supply of gasoline that much further. And we’re so hooked on those explosions we can’t stop ourselves.

We’d better make them count.

Despite what the Fox News Channel might say, fossil fuels are a finite resource, and their use can and does affect the world around us, sometimes negatively. So we’re all in favor of developing alternative energy sources. Still, even Al Gore must smile when he hears an uncorked 5.0-liter Mustang roll on the throttle. That powerboat-like burble from the exhausts just can’t help but put a smile on your face.

So what’s a red-blooded enthusiast to do?

Although we as a society may need to wean ourselves from the juice, it’s going to take some time for us to reach that point. In the meantime, gasoline is destined to become more difficult—and more expensive—to come by.

That’s where this great debate really grabs our attention, since we’re all about getting some bang for your buck. And if your bucks are spent on gas, and your bangs include motorsports, then sooner or later you will find yourself developing some sort of interest in fuel-efficient performance cars.

To that end, we collected five cars for a unique test: Drive to the track and do some laps. Sounds simple, right? Well, we wouldn’t just be measuring our performance with a stopwatch, but our wallets as well. This test would consider not only good lap times, but also which cars could produce those times while burning the least amount of fuel. Call it a smiles-per-gallon shootout.

Our contestants came from all over the automotive spectrum. Representing the future was the Honda Civic Hybrid, a “real” Civic that also happens to have an electric engine assist to help it get stellar mileage. The MINI Cooper and Mazda Miata were included as typical examples of sporty enthusiast cars, with one capable of carrying four adults and lots of cargo, while the other can carry a 12 pack of Diet Pepsi and a towel (okay, a small towel). The Chevrolet Corvette C5 made it into our test on the strength of its monstrously tall sixth gear, which helps it get more than 30 mpg on the freeway. Finally, the wild card of the group was a slightly modified, turbocharged diesel VW New Beetle.

Setting Some Ground Rules

We admit that we’re not the EPA, but we still needed a testing matrix for our little fuel efficiency exercise. Fortunately, we found that even though we don’t have lab coats and pocket protectors, we could still look to the EPA for some guidance. (Ironically, their Web page shows a Miata undergoing fuel economy testing.)

The EPA methodology calls for all cars to be tested under controlled conditions in a laboratory. Each test vehicle is mounted on a chassis dyno, allowing a professional driver to follow a prescribed schedule.

The EPA’s “city” route is designed to mimic stop-and-go driving and covers 11 miles in 31 minutes. Twenty-three stops are part of the routine. The “highway” drive covers 10 miles in 121/2 minutes. The average speed during this part of the test is 48 mph, and cars top out at 60 mph.

The EPA notes that all testing is done with the air conditioning turned off. To help the numbers better reflect real-world experiences, the figures gathered are then adjusted downward a bit—10 percent for the city numbers and 22 percent for the highway figures.

While the EPA’s testing procedures allow no room for improvisation, some people are critical of the method. Complaints allege that the highway testing speeds are too low, while the city driving doesn’t include enough time idling. The fact that a car is stationary also doesn’t factor in its aerodynamics, some have noted.

Our own real-world experience supports some of those claims. Some of the cars we have tested fell short of the EPA numbers, while others did much better. For example, the same 1999 Corvette that’s part of our test routinely gets 30-plus mpg on highway trips; the EPA has it rated at 28 mpg.

So we decided to come up with a testing matrix that would determine a GRM Performance Index of Efficiency. This test format would duplicate our driving manners, covering both highway, city and even track use. It might not be 100 percent scientific, but it should still provide some useful data.

We started by gathering all of our test vehicles together at a gas station here in Ormond Beach, Fla., for a final top-off and tire pressure check. Then we caravanned to Central Florida’s Ocala Grand Prix kart track. The instructions for each driver were simple: windows up, air conditioning on, no skipping shifts and use cruise control if available.

Our drivers traveled as a group to the track, with each individual doing his best to match the pace of the convoy. The 76-mile journey covered a lot of open road, but it did include some stop-and-go driving, a bit of morning congestion and a few construction zones.

Once at the track, each driver got one familiarization run followed by 10 spirited laps. The goal here was to duplicate an enthusiastic country drive in a more or less controlled environment. After those 11 laps, the stop watches came out as Tech Editor Per Schroeder hopped in the driver’s seat and clicked off three consecutive hot laps in each car. After all of this track work was completed, the drivers climbed back into the cars and the group headed out onto the interstate for a quick 4-mile trip to lunch.

Before anyone could chow down on their tasty sandwiches at the Ocala Whataburger, all of the cars were refueled at the same gas station. Since we knew how far each car had gone as well as how much fuel was used—and yes, we did a little math to compensate for non-stock tire sizes—we were able to compute some real-world mpg figures.

Finally, to make sure we had the complete story on each car, we added one more measurement to our test. In addition to lap times, we also wanted to evaluate performance potential by seeing how much power each car was producing. To get those figures, we ran each of our test candidates on Projekt 7 Tuning’s Dynojet chassis dynamometer.

Once all of the testing was completed, we divided each car’s fuel economy by its best lap time to get what we call the GRM Performance Index of Efficiency.

By the way, the idea for creating a performance index of efficiency came from pro driver Randy Pobst. “Ever since I started driving, I have compared performance potential and fuel efficiency,” he says. “My 240Z was a good one back in the college days. I remember when fuel went to 75 cents a gallon, and we all thought we were gonna die.” Randy’s daily driver is a veggie-fueled VW Jetta.

Reviewing the Data

Well, we learned a lot of stuff from this test, and confirmed a few suspicions. First off, it doesn’t take much horsepower to get most modern cars down the road. The Corvette is an excellent example of this: On the drive to the test track, it got more than 34 mpg. Once all the power of that big V8 was unleashed, however, any mileage advantage disappeared as the engine was let loose to drink like a vampire.

Second, most modern cars are pretty well composed when pushed hard. Yes, the Vette was fastest around the test course, but all of the other fuel-powered cars were well within a second of its time.

Third, hybrid technology may not be perfect yet, but it’s a huge step in the right direction. The Civic Hybrid delivered twice the fuel economy of its closest competitor, and while it was a few seconds behind the pack on the test course, much of that differential could easily be negated with some better tires instead of the skinny, high-pressure gas savers that come stock on the car. After all, it is a Civic, which means it has an inherently good chassis, and the hybrid engine did roll up over 90 horsepower on the dyno. There’s very little separating that from “real car” status.

The MINI and Miata were known quantities and performed as such, both getting excellent mileage and performing well at the track. It’s no surprise that these cars are favorites of cost-conscious enthusiasts everywhere.

The wild card in the test also performed better than expected. Although this particular TDI-powered VW New Beetle had been modified to handle a little better, there was no denying that it was as fun to drive as anything else at the test, and the 38-plus combined miles per gallon made us think long and hard about the viability of diesel-powered cars as something more than novelties.

Our Test Subjects

We could have done this exercise with any group of cars, but to keep it manageable and somewhat relevant, we chose a few that represent the cars driven by our readers.

The first three on the list were the MINI Cooper, C5 Corvette and early Miata. The Vette was bone-stock, the MINI was prepped for national-level Stock class autocross, and the Miata was just a neat street car. (Conveniently enough, these all came from our own fleet.)

VW’s turbo diesel cars have become legendary for the economy they deliver, so we needed one of those, too. Ideally, we wanted one that was prepped for motorsports, since we wanted to see if it was possible to marry performance and economy. Lucas Webb’s 2002 New Beetle perfectly fit the bill: Even though it’s a daily driver, it has been prepped for track work.

Last, we needed a true fuel economy benchmark. Honda was the first company to offer a hybrid to the public, so we borrowed a brand-new Civic Hybrid from their test fleet.

Our test subjects are listed ranked by the GRM Performance Index of Efficiency, from worst to best.

1999 Chevy Corvette Fixed Roof Coupe

  • EPA figures: 18 city/28 hwy
  • Engine: 8 cyl., 5.7 liters, six-speed manual
  • Owner: J.G. Pasterjak Jr., production manager
  • Basic setup: stock
  • Dyno: 301 horsepower, 311 lb.-ft. torque
  • Cruise control: yes
  • Distance covered: 87.0 miles
  • Fuel used: 3.47 gallons
  • Test mpg: 25.07 mpg
  • Best lap: 40.182 sec.
  • GRM Performance Index of Efficiency: 0.62

Owner thoughts: The C5 has a couple of things going for it in this challenge. First, it has decent aerodynamics and a monster overdrive sixth gear that should help it get over 30 mpg on the highway. Second, it’s probably going to post about the fastest lap time, which is good, because once it gets on track and all 345 horsepower are unleashed, the gas starts to go quickly.

Track impressions: The Corvette is blessed with great amounts of power and a sturdy chassis that can be wielded like a short-handled sledge. Disappointingly, the car’s O.E. Goodyear Eagle EMT tires are simply abysmal. Tires this bad are an absurd choice for a car with this much potential. I’m surprised that more Corvettes haven’t left the road in a flaming trail of debris. They contribute to wild swings between understeer and oversteer with no real provocation. We found ourselves understeering out of slow corners, pressing the throttle down to rotate the rear, easing off to allow the rear to hook up, then slowly increasing throttle to accelerate out. Unfortunately, as the engine came onto its cam, the rear end would break loose again—except now at a much higher speed. I can’t wait until J.G. upgrades the rubber. Until then, it’s just spooky.—Per Schroeder

2005 MINI Cooper

  • EPA figures: 28 city/36 hwy
  • Drivetrain: 4 cyl., 1.6 liters, five-speed manual
  • Owner: Per Schroeder, tech editor
  • Basic setup: Milltek exhaust, Koni FSD shocks, 16x6.5-inch Rota Slipstream wheels, 205/50R16 Goodyear Eagle F1 GS-D3 tires
  • Dyno figures: 108 horsepower, 105 lb.-ft. torque
  • Cruise control: yes
  • Distance covered: 86.3 miles
  • Fuel used: 3.03 gallons
  • Test mpg: 28.48 mpg
  • Best lap: 40.961 sec.
  • GRM Performance Index of Efficiency: 0.70

Owner thoughts: The MINI’s gas gauge is extremely optimistic. We left Ormond with the needle a full width above the Full mark; by the time we got to Ocala and ran our laps, the needle was still on Full. Yet when we filled up the tank, the car took nearly three gallons! For higher mileage, I think the car would have been better off on its base-model 175/65R15 tires instead of the optional 16s, although the track times would have suffered as well. It’s a tradeoff.

Track impressions: Running the MINI on a track like Ocala is almost boring. Almost. It simply does exactly what you want and the only real shortcoming is its lack of power down the straights. I started pushing the car so hard in Turn 1 and into the chicane that I started to run out of track as the car settled into a four-wheel drift. The car’s lack of power urges the driver to try to extend straights wherever possible, to the point where you start trying really stupid things to get the car to go faster. In the end, its ease and composure allowed it to click off a series of extremely consistent laps.—Per Schroeder

1992 Mazda Miata

  • EPA figures: 24 city/30 hwy
  • Drivetrain: 4 cyl., 1.6 liters, five-speed manual
  • Owner: David S. Wallens, managing editor
  • Basic setup: Link ECU, Jackson Racing header and intake, Koni/Ground Control suspension, 15x7-inch American Racing Silverstone wheels, 205/50VR15 Kumho ECSTA SPT tires
  • Dyno: 113 horsepower, 101 lb.-ft. torque
  • Cruise control: no
  • Distance covered: 85.4 miles
  • Fuel used: 2.74 gallons
  • Test mpg: 31.17
  • Best lap: 40.419 sec.
  • GRM Performance Index of Efficiency: 0.77

Owner thoughts: By the time we got to Ocala, I was pretty worried. The Miata had used almost a quarter of a tank of fuel—it doesn’t have cruise—yet Per said the MINI’s gauge was above the full mark, and J.G. said the Vette was averaging 30-plus mpg. At this point, I figured the Miata was going to finish last. Well, at least the top goes down.

Track impressions: Where the Corvette flipped back and forth between understeer and oversteer in the automotive equivalent of multiple personality disorder, the Miata was simply a joy to balance on the knife edge of adhesion. A poke of the throttle would bring the rear around just enough to point the roadster to the apex with surgical precision. While the car is not powered by overwhelming amounts of thrust, its gearbox and shifter are easy to use—keeping the little engine on boil with little effort. Of course the Miata is fun on track. It’s a Miata. Where have you been for the last 16 years?—Per Schroeder

2002 Volkswagen New Beetle GLS TDI

  • EPA figures: 42 city/49 hwy
  • Drivetrain: turbo diesel 4 cyl., 1.9 liters, five-speed manual
  • Owner: Lucas Webb, MINI technician
  • Basic setup: Boostvalve boost controller, precision-drilled injectors, deleted EGR valve, Koni springs and shocks, 225/45ZR17 Fuzion ZRi tires
  • Dyno figures: 123 horsepower, 412 lb.-ft. torque
  • Cruise control: yes
  • Distance covered: 85.7 miles
  • Fuel used: 2.24 gallons
  • Test mpg: 38.26 mpg
  • Best lap: 40.592 sec.
  • GRM Performance Index of Efficiency: 0.94

Owner thoughts: I was confident in the diesel’s fuel mileage. Once we arrived at the track, my fuel gauge didn’t move much from full. I figured the hybrid was doing the best. I was expecting higher mileage, but due to the a/c being turned on, it suffered slightly. I thought the MINI and the Miata would’ve used less fuel.

Track impressions: I waited to drive the TDI Beetle until last as, frankly, I was looking forward to the experience. I wasn’t disappointed. The Bug is surprisingly fast with massive amounts of torque and a very well-balanced chassis. Lucas has clearly done his homework on this project. The downsides are few and mostly relate to the car’s gearing. The TDI engine has a limited powerband—it’s only really happy from about 2500 to 4500 rpm. It takes quite a bit of rowing to keep the TDI in this happy little window of über-torque. Once you master the shifts, the Beetle can turn some darn quick laps.—Per Schroeder

2006 Honda Civic Hybrid

  • EPA figures: 49 city/51 hwy
  • Drivetrain: 4 cyl., 1.3 liters, electric motor assist, CVT
  • Caretaker: Scott R. Lear, club editor
  • Basic setup: Navi and XM Satellite Radio
  • Dyno figures: 92 horsepower, 95 lb.-ft. torque
  • Cruise control: yes
  • Distance covered: 87.6 miles
  • Fuel used: 1.44 gallons
  • Test mpg: 60.83 mpg
  • Best lap: 44.813
  • GRM Performance Index of Efficiency: 1.36

Caretaker impressions: With a real-time mpg gauge and average fuel economy readouts tied into the trip odometers, it’s not difficult to guess how you’re doing efficiency-wise with the Civic Hybrid. Before we hit the track, the average economy was creeping toward 60 mpg. The engineers are clever to provide the driver with so much information; it encourages you to become an active part of the gas-saving process.

Track impressions: The Honda Civic Hybrid is an amazing car: quiet, civilized and extremely fuel efficient. But it’s a turd out on the track. Most, if not all, of that blame belongs to its super-hard, super-narrow tires. The steering wheel seemed more like the volume control for a stereo system playing the chart-topping hit “Symphony of Squealing Tires” rather than something that actually turned the car. The tires were so hard, and so prone to sliding, that I couldn’t get a handle on what improvements, if any, needed to be made to the chassis. My experience with other late-model Civics would indicate that the addition of a good set of shocks and a stiffer anti-roll bar or two would significantly improve the Hybrid’s cornering ability.—Per Schroeder

Practical Performance: V8 Torque Meets Econobox Efficiency

Perhaps one day enthusiasts will take to hybrids en masse. There may even come a day when an issue of GRM will contain a tech article on hopping-up electric motors, or a lightweight battery shootout. Hey, it could happen. Until then, turbo-diesels currently offer the most potential for hot rodders who want to marry fuel-sipping efficiency with tire-melting performance.

While the Audi R10 TDI is quickly rewriting history as far as endurance prototype racers go, diesel performance isn’t limited to factory-backed efforts. For a practical example of a home-brewed diesel with some bite, just check out Lucas Webb’s 2002 VW New Beetle.

We’ll cut to the chase and give you the important figures for this Volkswagen: 50-plus mpg on the highway and a staggering, dyno-verified 412 lb.-ft. of torque at the front wheels. Seriously.

Lucas, a 20-year-old technician at Orlando’s Downtown MINI, didn’t initially set out to build a stump-pulling diesel Bug. Rather, the car kind of fell into his lap. His parents bought the Bug in late 2001 and used it as a daily driver. Lucas learned how to drive a stick on the car, and by 2003 it was his. It’s now a daily driver that also works well for track days and autocrosses.

The modifications started with the basics, as Lucas removed the muffler to increase exhaust flow and beefed up the suspension with Konis and Eibach springs. The stock dual-mass flywheel was also tossed, replaced by a lightweight, 10-pound aftermarket flywheel along with a VR6 pressure plate and friction disc.

Then the real power-adding mods came. An UPsolute Stage II computer chip increased the fuel timing and injection quantity, while a set of precision-drilled Fratelli Bosio Powerplus 520 injector nozzles featured a more efficient spray pattern. (These parts aren’t that expensive, either, as an UPsolute chip costs about $300 while KermaTDI sells the trick injector nozzles for $285 per set.)

The final piece of the puzzle was a Boostvalve boost controller, which helps smooth out the boost spikes, Lucas says. “The stock system would surge to 20 psi and settle back to 16 psi,” he explains. “The boost controller was set up to sharpen the signal to the turbocharger, so there wasn’t any surging.” Where a lot of TDI tuners run 18 to 21 psi of turbo boost, Lucas keeps his Beetle capped at 16 psi. “I believe this is the reason why I’m running such low horsepower and high torque,” he figures.

An HKS Turbo Timer allows the turbo to cool down once the engine has been turned off, thus helping to prevent coking problems. To further prevent coking, which can be a problem with TDI Volkswagens, Lucas runs an EGR delete pipe.

Aside from these bolt-ons, the rest of the engine is as delivered from VW—stock engine internals, stock intercooler, stock turbo and stock injector bodies.

Even though this Beetle is making way more power than stock—its 412 lb.-ft. of torque and 123 horsepower at the ground soundly beat the stock figures of 155 lb.-ft. of torque and 90 horsepower at the crank—fuel economy numbers are still strong. The stock 14.5-gallon tank gives Lucas at least a 700-mile cruising range, and the car usually gets mid-40 economy figures in town.

The big boost in power is nice, but the rest of the car has not been ignored, either. The interior was gutted to help shed some pounds; curb weight quickly dropped from about 3200 pounds to 2660.

The VW New Beetle is based on their popular A4 chassis, so suspension parts were just a phone call away. “I was chewing up tires without camber, so I fixed that with Ground Control camber plates with spherical strut mounts,” Lucas explains. “I also added ball joint sliders to increase my track width and level my control arms—which also helps with my camber curve.” He has also since gone to Koni springs, while his 17x8-inch Flik Ftd wheels are now wrapped with Falken Azenis tires. (The car wore Fuzions when we tested it.)

As far as the two-tone paint, well, that was unintentional. “I was late for a job interview during a good rain, and spun into a guard rail,” he admits. Along with a respray, his future plans include filling in the sunroof and adding a roll bar.

So are diesels the wave of our motorsports future or just a curiosity? After seeing how easily a turbo-diesel can make insane amounts of torque and still remain civilized, we’re sold on the breed.

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