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A 911 With 917/10 Power
Eleven Fifty Seven
A street-legal 911 with 917/10 power
STORY AND PHOTOS BY JEFF HARTMAN
With turbo boost set to kill and a tank filled with 117-octane race gas, Eddie Bello revs his engine to 6500 rpm and dumps the clutch. His 1994 Carrera 2s air-cooled flat six bogs a bit as the rear tires hook up. Once they do, the tach needle makes a hard right turn, two turbochargers sing a 29-psi song, and Bellos car explodes off the line.
The Porsche rides out on 1,157 horses to make its bones under a big Texas sky. Bello is competing against some of the worlds fastest street cars in the Texas Mile, a 5,280-foot-long contest on a de*commissioned military airfield in the wilds of South Texas. Whoever crosses the finish line with the highest trap speed wins.
It scares you at first, admits Bello, a 40-something drag racer from New York City. When the cars pushing through 160 mph, youre still in fourth, the motors screaming, the cars accelerating so hard the nose is up in the air like a boat trying to come on plane. For three-fourths of a mile, youre thinkin the worst: Will I make it to the end? Will the tranny or motor break? What if one of them does?
When I first considered doing the Texas Mile, I thought I might be able to hit 200, he says. He reworked a few things on the car until, one day, he was actually doing 200 at the half-mile mark. The fear goes away, he says, when youre in fifth at three-fourths of a mile, when the engines got nothing left and the nose comes down with a quarter-mile to go.
Youll have to take his word for it. At top speed, Bellos 964 is screaming along at Mach 0.3 and 7700 rpm 100 rpm below redline, 600 rpm past peak power, and 1000 rpm north of the redline of a stock 964. Four seconds later, hell fly across the finish line traveling at nearly 350 feet per second. Beyond the finish is a frighteningly short section of runway, followed by dirt, gopher holes, and the odd chunk of cactus.
The first time he made the 3,650-mile round trip from the Bronx to south Texas in 2007, he unleashed his 964 at Goliad Airport and discovered the car had lost a lot of its speed. It was embarrassingly gutless until he revved the hell out of it, at which point it would go wild on boost and spin sideways out of control. The situation was so bad that Bello had to double-clutch just to get from one gear to the next. Even so, with stock suspension and stock ride height, his 964 managed a 219.1-mph run on street tires. That was good enough for fourth.
I had re-ringed the motor right before the trip to Texas, and figured Id break it in on the way, Bello says, shrugging. When the engine wouldnt perform, I didnt know what to think.
Bello went back to the Bronx, disappointed but not defeated. Analysis reveal*ed a snapped crank damper locating pin, a malfunction that resulted in dysfunctional crank triggering and ruined cam timing spark advance fell from 22º to 5º. The result was no real power until 6000 rpm, at which point the turbos managed to eke out a little boost.
When Bello returned to the Lone Star State in Spring of 2008, he pulled straight onto the track and drifted over the finish line on part throttle at 219 mph. In a pedal-to-the-metal encore, the car ripped its rear tires loose at 150 mph and then clawed its way to a 226.863-mph finish. It was a new Texas Mile record for street cars. Bello tried to bump the record further in subsequent runs but was thwarted by intercooler plumbing blowouts, a result of extreme boost pressure and oil mist on the silicon intercooler hoses. Still, he was pretty happy with the results.
There are faster Porsches, claims Bello. But not in a mile. In fact, the fastest street car of the event a gutted, methanol-fueled, parachute-equipped Toyota Supra topped Bellos 227-mph run by less than three miles per hour.
200 mph for Dummies
So what does it take to make a 911 hit 227 mph in the space of a mile? First off, it takes money. And where did that come from? The car was paid for by me, says Bello, who did all of the design work and wrenching. HKS helped out with the wastegates, intercooler, and 3430 turbos. He also had help from exotic car dealer Universal Autosports in Glen Cove, New York; Bello does contract wrenching for the Long Island firm, and he was granted permission to work on his 964 there.
Of course, you need the right raw material. For a car capable of more than 200 mph, aerodynamic drag is no small concern. The resistance due to parasitic losses and aerodynamic drag increases exponentially: If you can go 100 mph on 100 horsepower, you need 300 more horses to reach 200 mph. Each additional mile per hour requires more power than the last and thats ignoring the torque required to accelerate hard enough to do it within a single mile.
When Bello kicked off his 964 project, he wasnt planning on heading to Texas; he just wanted to go faster at the drag strip than he had in his slant-nose 1983 911 SC. That car was built to be as fast as the Yellow Bird, the 469-horse Ruf CTR that gained its nickname during a test where Road & Track proved the 3.4-liter twin-turbo 911 was capable of 211 mph and a quarter-mile time of 11.7 at 133 mph. In time, Bellos SC proved capable of an 11.0 at 142 mph in West*hampton, New York on a Long Island drag strip that has since been replaced by condos.
With a goal of maximizing quarter-mile speed, he decided that the best drag-racing 911 would be a narrow-body 964 due to its low drag and minimal frontal area. The models heft didnt bother him. Says Bello: Yes, earlier 911s can weigh 600800 pounds less than a 964, but for the 964s extra weight, you get air-conditioning that works, better sound deadening, and a really nice interior. You get a much better street car.
Bello acquired a 1994 964, removed its engine, and started to lay out a radical street powerplant. I never cared much about elapsed time, he says, just miles per hour. With that in mind, he planned his 964 build with an eye toward besting his 83 SCs 211-mph top speed.
He knew he would need mountains of power to win in high-speed super-stock drag racing. He figured hed need at least 1,000 hp. But how do you get that from an air-cooled 3.6 while keeping it alive? Bello says you make the power with tons of boost, a super-efficient intake, and as many revs as possible. He says you keep it alive with the best reciprocating parts, cool oil, race gas, and reasonable rpm.
Seem like a contradiction? Adding boost is far easier than increasing engine speed, because the next problem in a four-stroke engine is rarely the compression forces pushing down the connecting rods, even when turbocharging takes power output to stratospheric levels. Turbocharging typically increases peak cylinder pressure only modestly. On the other hand, reciprocating forces from increased redline go up exponentially as crankshaft speed increases, which adds to the loadings on the rods, pistons, bearings, and crankshaft immensely.
Bello disassembled the 3.6-liter, normally-aspirated flat six and began to build a twin-turbo engine, targeting max torque just past 5000 rpm, max power around 7200, and redline at 7800. The initial goal was simply to build a street/strip 911 that was insanely powerful by leveraging the expertise he gained in drag racing.
Bello decided to maintain the stock rod-stroke geometry with an eye toward controlling piston speed at engine speeds approaching 8000 rpm. Por*sche never changed the rod stroke for the water-cooled engines, says Bello with a smile. They just installed skinnier rods. He installed the best reciprocating parts he could find: a rebalanced stock 964 crank: Carrillo rods, 993 pistons with moly rings, and 993 Turbo cylinders with custom spacers. He paid a lot of attention to crankcase windage, modifying the case and crankshaft accordingly.
He also paid close attention to oil temperature, and more so once he decided to run the Texas Mile. A mile is a lot longer and faster than a drag race, and it works the engine far harder. By the time his 964 arrived in Texas, it would have two coolers fed a steady stream of oil by a factory GT2 oil pump. Adding a second cooler makes a huge difference, he says. Run*ning just 50-percent throttle in the 4000
5000-rpm range, I knew Id see engine temperature going up with one cooler and an air-cooled motor is counting on the oil to keep it cool.
With the twin-cooler setup, oil temperatures remain stable all the way to 226 mph. The lifeblood of this 964 is 0W-40 Mobil 1 with Lucas synthetic oil treatment. Says Bello: In the past I ran 20W-50 with anti-wear additives, but you sometimes see weird cylinder coating going on, and the rings might not seal correctly.
Meanwhile, the next trick was to make the 3.6 breathe. Says Bello: I experimented with air-cooled Porsche intake system combos no one else had tried. I couldnt understand why. Intake is a big factor. I opened up the head ports but not too crazy in order to create intake velocity. I installed larger 51-mm intake and 43-mm exhaust valves. I looked at the valve angle and seat cuts on Indy motors to create flow and power. A lot of people are running three-angle valves, but my valves are five-angle with a 45º basic cut and a 20º back-cut to get the same smoothness.
He installed DR camshafts designed to create maximum possible airflow in the initial lift in order to increase the average air flow across a wider range. Says Bello: Most people are looking for a really big maximum flow number at 70008000 rpm. Theyve got 310 cubic feet per minute at peak lift, but they make the least power because theyre losing velocity and they have nothing at lower rpm.
The torque on my car comes in at four grand, and really hard at 5200. You shift at 7000 theres no need to rev out, he continues. In the mile, I used torque to pull down the first quarter in four gears to 165 mph and let it wind out in fifth from there to the end. If I had a sixth gear, I could drop back into the powerband. By the end, Im at 7700 Im beyond peak power, which is 70007200. But this is a street car and matching the peak-power rpm for top speed needs to be fixed with gearing and tires not by sacrificing the whole lower end of the powerband.
Bello began thinking about the turbo system next. Making tons of power takes tons of boost, but, as Bello puts it, when you get near the top, the turbos and motor lose efficiency. Each psi of boost adds less and less power. In the end, it would take at least two extra atmospheres of boost a total of 24.9 psi to set a record in Texas. Bello achieved that pressure by installing two large HKS turbochargers with 0.87 turbine nozzles and an HKS GT50 external wastegate.
Charge air pressurized to 2.0 bar leaves the most efficient compressors smoking with adiabatic heat, so a 24-inch-wide, five-inch-thick HKS intercooler was chosen. Bello knew that, at maximum boost, his engine would need race gas with ridiculous octane to stave off detonation, along with rich mixtures to cool the combustion chambers. He was right: By 2008, his high-boost 3.6 would guzzle VP Hydrocarbons C16 a brew of leaded race gas with an octane rating of 117.
With the engine coming together, Bello stripped the car and prepared to modify its shell for high-speed duty. He briefly considered converting to 928/964 Turbo S-style flip-up headlights, but decided against it when he found out the shop that had turned his 911 SC into a Slantnose was no longer in business.
Lacking a wind tunnel and the mega*bucks required to experiment with new bodywork, Bello dropped back and punted. After a bit of thought, he realized he could improve his cars aerodynamics by replacing its front fenders with 997 units. He acquired a set of the latter, then sectioned and butt-welded as needed to create hybrid 964/997 front fenders.
The next challenge would be getting 900 pound-feet of torque to the ground. The 964 was equipped with a Motorsport G50 transmission with a limited-slip differential, steel sliders, and revised ratios. After experimenting with various gear oils, Bello ended up running 75-90 Mobil 1.
Test and Tune
After installing the engine, Bello wired it to a Haltech E11 aftermarket programmable engine-management system running startup calibration. He headed out to tune the system on the road, gradually adding more load. He tuned carefully at low boost with a conservative timing curve and a rich fuel mixture. When the on-road calibration felt good, he moved to a Dyno Dynamics load-bearing, torque-cell chassis dynamometer to optimize his calibrations.
The sintered-iron clutch disc had been okay on the street, where the tires broke loose under power, but it proved problematic on the chassis dyno. With normal strap-down techniques, the tires slipped on the dynos rollers. Alternately, if he clamped the car down as tightly as possible and loaded it with weight, the clutch would slip. Bello says that his car made 1,000 hp on a Dynojet that refused to record torque due to wheel slippage and claims that it later managed 1,157 hp at the rear wheels on a brake-type, torque-cell dyno with careful operation.
Dyno tuning done, Bello headed for the drag strip. Turbocharger issues came next. I needed a lot of load to make enough boost, he says. It was hit or miss every time I went out. The HKS turbos, with their large A/R turbine housings, eventually gave way to hybrid TiAL turbochargers built around Garretts GT3763. The TiALs were equipped with relatively small turbine wheels and relatively large 0.87 A/R turbine housings at first, but Bello eventually settled on larger turbine wheels and smaller, 0.69 A/R housings. At that point, the planets lined up. Not only was the car easier to drive in traffic, it was faster at the strip.
When the car was running right and before he ever thought about competing in the Texas Mile Bello made a road trip to Southern California. While he was there, he went out to Pomona Raceway, the birthplace of NHRA. With no suspension changes, little traction, and the wrong gearing, the 964 tore off an 11.0 at 155 mph on drag radials.
I changed the rear suspension settings just before leaving California, he says, and the car finally started to hook up. As he passed through Texas on the way home and approached San Antonio, he saw signs for a local drag strip. He decided to pull off of I-10.
The tank was half-full of 93-octane, so I topped it off with 117-octane event fuel and ran with a full tank. I didnt know anyone, so I raced with my luggage and toolbox in the car. They paired me off against a dragster. The dragster ripped out into the lead and, when I shifted into second, I spun a little and started to slide out of the lane! But I managed to keep it together. At full howl, the 964 romped past the dragster and raged on to a 10.4 at 155 mph on street tires.
Bello simply collected his timing slip and headed back to the Interstate.
On the Road
Bello and I meet up at Universal Autosports so I can use a lift to take pictures of his cars underside. From there, its off to Long Islands Jones Beach. Its 29º F outside and, at low speed, theres a fair amount of noise from various pumps. Pick up speed and the exhaust sounds a bit like its cats and mufflers have fallen off. Thats not far from the truth. The TiAL hybrid Garrett turbines are the only muffling there is, but theyre fairly effective in ordinary driving; the combined noise is nothing a good stereo cant overcome.
The car is fun when theres nothing around, says Bello. But not at maximum boost with these turbos. At full boost, the torque curve is very harsh. And by harsh he means vertical. At 6 pounds of boost on 93-octane pump gas a combination that offers a not-insignificant 515 hp low-rpm passing maneuvers reveal turbo lag. Downshift and floor it, and the back end breaks loose. This is at 6 psi. At 29 psi, Bello says, the tires dont break loose hell does.
Ill take his word for that. With 93-octane fuel, Bellos 964 is already running on the ragged edge of detonation; it really wants another point or two of octane. Anyway, wed have to change the wastegate springs. And anyway, its 29º out. And anyway, cops are everywhere and were here to shoot photographs and drive a car, not go to jail. In any case, what we learn is this: What may be the most potent 964 on the planet is totally streetable, even in heavy traffic. Start, stop, no problem. When theres no traffic and the turbos are cooking, acceleration is savage.
So whats next? For Bello, a return to the Texas Mile is a distinct possibility. It occurs twice every year once in the Spring and once in the Fall and he was all set to rock n roll in the latter half of 2008 until his sponsor bailed. Bello doesnt mind, because no one beat his Spring record. He says that the next time he enters the Mile, hell crank up the boost to 35 psi and run on oxygenated, 120-octane gasoline. What do you get by adding 5.5 psi when youre already making 1,100+ horsepower? Predictably, it depends, but the easy answer is 80
100 hp. With that kind of gain, 230 mph is a distinct possibility in calm air.
Bello says better gearing will help, too, but that he wont find it in tire diameter. He says he already increased his rear tire diameter from 25.5 to 26.0 inches. It worries me going larger than that because youre playing with the sidewalls and if the car gets sideways, higher sidewalls tend make it whip back and forth. On the 227-mph run, running 26s, I dropped fourth [gear], started spinning the tires, and swung sideways. I let off, straightened out, got back in the gas, no problem. The car was stable.
So far, Bellos fastest time at the drags is a 9.0 at 162 mph. He sees that as a work in progress: Id really like to get a 60-foot time of 1.4 second, he says, noting that a higher-ratio first gear he currently runs a 3.5:1 is one of the next steps. He also says a taller first can help with more than just speed: In my SC, I had to rev the engine high and ride the clutch. At one point, I was installing a new Clutchmasters clutch every week, which didnt make Clutchmasters very happy. Now the car leaves with no problems! And how, Eddie. And how.
unless he has some underbody mods done.
