Hello, 8800 RPM

A 3.9 liter GT3 RS that claims 500 horsepower meets The Loop — and a 3.8-liter 2010 GT3.

Hello, 8800 RPM 1
January 25, 2010

The noise is familiar enough. Grainier than the sewing song of a current Carrera, it’s more mechanical, more serious. But as the red 2010 GT3’s tach needle swings through 4000 rpm and sprints for 8000, the sound isn’t the only thing that’s serious. Acceleration is even fiercer than it was in the last GT3, a 911 that managed 415 horses from 3.6 liters. Question is, can this 435-hp 3.8 eclipse the slightly larger 3.9 in the green 2007 GT3 RS waiting in the next turnout?

What are 200 cubic centimeters? On 3.6 liters, not much: 5.6 percent — right in line with the 2010 GT3’s 4.8-percent horsepower bump. So another 100 cc shouldn’t be worth much, right? SharkWerks, a Fremont California tuner, begs to differ. Company owners Alex Ross and James Hendry say their 3.9-liter GT3 RS makes 502 horsepower on the way to its 8800-rpm redline. We had the same questions you probably do: 997 Turbo power without turbos? GT3 RSR engine speeds on the street? Won’t it blow up? “Yes, yes, and no,” said Ross, who offered to drop the car off for a 1,000-mile test to prove it. When we asked if he could come up with a stock 2010 GT3 for comparison purposes, he didn’t stutter.

As a result, today marks the first time a 2010 GT3 will hit Excellence’s Secret Test Loop. The U.S. press cars have yet to enter the country due to delayed availability for the optional PDEM active motor mounts —so we’ve been waiting since Summer 2008 to find out if the 2010 GT3 builds on the 2008 GT2’s brilliance. Will the latest edition in Porsche’s high-revving GT3 series delight us on the Loop like the GT2 did? Or will it disappoint us there, like 2007’s GT3 did?

Yes, the first 997 GT3/RS left us a little cold. It was hard to say why. From torque to engine note to road-holding to braking to styling to interior quality, it bested the 996 GT3 on every count. Even so, we felt something was missing. Perhaps it was the 996’s purity, but our biggest beef was the suspension tuning. While we loved its grip and turn-in, we found its Porsche Active Suspension Management more re­active than active. The result was a GT3 that jiggled and wiggled on the Loop as well as Infineon Raceway — in both the Sport and Normal suspension settings.

Then came the 2008 GT2. On the Loop and at Infineon, it earned our highest praise. “Put simply, the best road-going 911 I’ve driven, at least on a track,” wrote ALMS driver and Porsche Cup winner Johannes van Over­beek. My take was similar: “On track and the best roads we know, it’s an animal — one with that ‘work of genius’ finesse only Por­sche’s best cars possess… It feels like a Por­sche that Por­sche sweat over, and we’re sure it is.”

Hello, 8800 RPM 2

Euro­pean Editor Ian Kuah handled our first test of the 2010 GT3 (August 2009) and came away impressed: “The 3.8-liter engine hasn’t lost the previous 3.6’s high-revving charm… Low-end torque was already quite good in the first 997 GT3, but it’s even stronger here, the 3.8’s extra torque making the dash be­tween curves an immediate, effortless affair.” As for handling, he found the ’10 car “tangibly more neutral,” noting “it feels every bit as sharp as the last GT3 but has less of a tail-led feeling at eight-tenths.”

His take only served to increase our curiosity. But while first drives on press trips can be informative, they rarely provide an opportunity to really get to know a car. The Loop does. Hidden in coastal mountains north of San Fran­cis­co, its little-traveled two-laners feature everything from perfect pavement with a diverse mix of turns and elevation changes to rougher sections on which only the best chassis shine. Its tight sections challenge a brake system’s ability to dissipate heat while its long, desolate straights allow fast cars to stretch their legs. Put simply, it’s the best road-test venue we know.

We’ve tested two 2007 GT3 RSs here, both in the same searing shade of green. After PCNA’s press RS came this one with SharkWerks’ 3.8. It felt like the factory 3.6, but had more power and torque. Enough “more” to justify a projected $17,000 cost? We weren’t so sure. Turns out Ross wasn’t either. He held customers at bay while he and Hendry worked on something he thought might be: a 3.9. Now it’s time to find out if he’s right, among other things.

After hauling up the freeway in the red 2010 GT3, I decide to stay in it heading into the Loop’s first twisty section. Much of the last GT3’s character remains in the new one. The engine is still a little grainy, feeling slightly unhinged. It’s electrifying, exciting the senses in a way no other current Porsche engine does — even those that make more power. The GT3 experience is all about immediacy and is conveyed in myriad tactile differences. Its shifter is notchy and requires a more determined hand. Its clutch asks for more muscle. Its stiffer chassis transmits more road texture and that, along with the buzzy flat six, sends more sensations through its Alcan­­tara-wrapped steering wheel, grippy shell bucket seats, and pedestrian pedals —sensations that remind you this 911 hasn’t been homogenized.

But for a few surfaces, a new radio, and more Alcantara for those who select full leather, the interior is the same. If only the view out back was. Owners who like the new rear wing will be seeing a lot of it; thicker and positioned higher, its blade is perfectly placed to obscure everything be­tween a bus driver’s gloves and a skateboarder’s shoes. We resort to using the tall side mirrors as rearview mirrors, a practice we abandoned years ago.

Hello, 8800 RPM 3

The road ahead is the Loop at its worst. There’s not a cloud in the sky today, but dampness from rain or fog can stick around for days this time of year and some of the best sections are a treacherous mix of dry pavement with occasional wet spots. Unlike running in the rain, where you build up to an engaging pace and then keep it there, you’ve got to weigh all that dry grip against a few wet sections waiting to exact their punishment. This is, after all, no Carrera 4.

Fortunately, the rear-drive GT3’s original-equipment tires inspire confidence in mixed conditions. It’s our first exposure to Pirelli’s PZero Corsa System, Italy’s answer to Miche­lin’s also-O.E. Pilot Sport Cup. We’ve tested Sport Cups on road and track and, on the Loop at least, prefer Pirelli’s R-compound rubber. While outright grip is similar, the Corsa Systems better mimic normal road tires and thus have more predictable characteristics — especially in the wet.

As a result, we’re able to deploy most of 435 horses. Like the previous 3.6, the 3.8 has a meaty mid-range. This is still very much a horsepower engine that likes to rev, but there’s a nice gain in torque as the largest yellow needle swings up and around to the right. The advantage is dis­cernible, but hardly overwhelming. 20 more horsepower and 18 more lb-ft? Yeah, that sounds about right.

The chassis, meanwhile, has benefitted from lessons learned in the 997 GT2. Cor­ner after corner, the GT3 im­presses. “Roll couple” is a term that has yet to make its way into the greater Por­sche lexicon, but factory engineers use it to describe the way a car’s front and rear ends work together. The new GT3’s suspension tweaks and revised roll centers have worked wonders in that regard. As with the last GT3, there’s loads of front-end grip, yielding immediate turn-in. The boon is that the rear end now feels more in step. Softer anti-roll bars are offset by stiffer springs that minimize body roll as well as brake dive. And, on smooth pavement, the GT3 is as cohesive as the 997 GT2 — but it’s the lighter, sharper tool.

Is it all that we hoped for? Not quite. Rougher pavement throws hair in the cake. While body control is better than in the 997-1 GT3, it’s still not as good as the 997 GT2’s. The new GT3 jiggles over sections that failed to disturb the GT2. While we don’t mind being jostled, some of the vertical motions unload the tires — reducing mechanical grip or at least our perception of it. When that happens, confidence is lost and, with it, part of the thrill.

Hello, 8800 RPM 4

Back on perfect surfaces, we see the 2010 GT3 for what it is: a great 911 and a worthwhile improvement. It’s not a new ball game, but it is a better car, one with more power, more chas­sis refinement, and better handling. As to its bigger standard brakes? We suspect they’ll perform better at the track, but find the first hints of fade just as we did in the last GT3 (a 996) that we tested on the Loop with standard brakes. Whether it’s the stock pads, the stock fluid, or too many tight turns and not enough straights, we’re soon longing for the optional, fade-free PCCBs.

Time to move to the green RS, which has PCCBs and an engine that promises to work them. Its 3.9-liter six is the result of a collaboration between Shark­Werks and Tempe, Ari­zona tuner Evo­lution Motor­sports, with the former handling most of the mechanical aspects and the latter handling the electronics. The additional 300 cc come from a bore increase. While looking to go beyond 3.8 liters, Ross and Hen­dry decided against increasing the stroke early on. Cost was a consideration, but the primary reason was to preserve the GT3’s high-revving nature.

Hendry is no stanger to extreme displacement upgrades, having worked for Devek, a 928 tuner that built 6.5-liter, 600-hp V8s. Thus, he knows that big­ger pistons tend to be heavier pistons, a detriment at high engine speeds. Shark­Werks’ lightweight forged pistons are an exception, weighing 496 grams each with the wrist pin. By comparison, each factory 3.6-liter Mahle piston weighs 519 grams with wrist pin while each Mahle in the 3.8-liter 2010 GT3 weighs 537 grams.

“Por­sche offset the 2010 GT3’s heavier pistons with a lighter, dual-mass flywheel to help it rev,” explains Ross. “Our pistons reduce rotating mass by 120 grams [over 3.6 pistons], which let us not just maintain the 8400-rpm redline but exceed it.”

To prepare the engine for life at nearly 9000 rpm, SharkWerks took one of the quieter pages from Porsche’s RSR playbook. Steel cylinder liners were installed after the aluminum cylinder blocks were bored for the larger pistons. Hendry had to fabricate special tooling to fit the liners, which is one reason the conversion will not be sold as a kit. We suspect another reason has to do with Ross’ admission that he and Hendry spent two years working with suppliers to come up with piston and camshaft specs for their 3.9.

Hello, 8800 RPM 5

While Ross won’t get into the specifics of either, he says the cams are the key and that both the intake and exhaust profiles were altered: “We came up with a profile that takes advantage of more displacement and higher rpm, one that matches piston valve pockets to maximize lift and duration.” He says the cams benefit from experience with 996 and 997 Turbos as well as the 3.8-liter GT3 project. “Unlike cams for a 911 Tur­bo, a car that doesn’t spin past 7000 rpm, we profiled these cams to be able to sustain 8800 rpm. By learning what we did from the 3.8 build, we knew how to set them up without losing performance down low.”

The compression ratio is 13.0:1, a full point up on the stock 3.6’s already high 12.0:1. The 3.9 is assembled with cylinder head studs developed by Evo­lution Motor­sports for high-horsepower Turbo applications. Made from H-11 tool steel, they’re claimed to have 260 KSI tensile strength, 83.3-percent greater thread-surface contact, and 38-percent more clamping force than the factory studs.

As part of the conversion, standard GT3s get an RS flywheel, which cuts 15 pounds from rotating masses. All cars get a GT3 Cup clutch and pressure plate as well as one of two exhaust setups. The first is SharkWerks’ popular muffler by­pass (250 sold and counting — for 911s that are by no means common). No power advantage is claimed, but the bypass lets more sound through while removing 16 pounds. The green RS’s titanium tips save a further two pounds, but Ross says he won’t produce them because Porsche just introduced an identical product.

Those after more noise and even less weight can pick the “race” exhaust, which Ross says is too loud for street use but deletes 57 pounds while adding a little top-end power (8–10 hp). The latter features two lightweight stainless-steel mufflers and weighs 11 pounds. “It comes with ear plugs and requires proof of helmet,” chuckles Ross. The 3.9 still utilizes the factory headers and catalytic converters, which Ross feels are well designed. The same goes for the factory airbox, which means the 3.9 looks identical to the 3.6 when you pop the engine lid.

The final and most complicated piece of the puzzle was the engine management. Evolution Motor­sports has brought ECU tuning in-house and uses an emulator that allows live tuning in three-dimensional maps for fuel, ignition, cam timing, throttle, and more. When the tuning on its Mus­­tang chassis dyno was complete, Ross says the 3.9 moved from 385 rear-wheel-hp to 458 rwhp, which he estimates is 502 hp at the crank. Torque moved from 274 to 326 lb-ft, for an estimated 355 lb-ft of torque at the crank. For the record, Por­sche claims 415 hp and 300 lb-ft, figures that are probably conservative.

Hello, 8800 RPM 6

The best numbers were generated on 93-octane pump gas, but a separate map for 91-octane gas made only a little less power while a map for the “race” exhaust made a little more. Criti­cally, the 3.9’s gains don’t come at the peaks alone. Its power and torque curves mimic the stock ones but add 70+ rwhp at high rpm and 50+ lb-ft throughout the lower range.

“There’s a big jump in horsepower and torque down low compared to the already good 3.6,” opines Ross. “Where the factory cam­shafts and tuning begin to fall off, this motor continues to make power to 8800 rpm — where it’s just five horses down from its peak.”

Those ponies don’t come cheap. The 3.9 conversion runs $25,000 on a GT3 RS and $26,000 on a stan­dard GT3 (to cover the RS lightweight flywheel). The build takes four weeks, with the shop handling initial break-in. Ross says that the job can stretch to six weeks and cost more if additional work is required. The first customer car, for instance, had 35,000 miles and wanted (but did not need) new rod bearings and connecting-rod bolts.

This RS’s chassis is largely stock. It’s running the same aggressive alignment we liked the last time we drove it, but a TechArt hydraulic front-end lift sys­tem has been added. It raises the front end by about two inches at the touch of a button and lowers it automatically at 37 mph. The kit adds stiffer front and rear springs and costs $5,999 against Por­sche’s Front Axle Lifting System, a $3,490 option on the 2010 GT3. We’ve heard owners note that dozens of spoiler lips cost less — a financially sound philosophy but one that requires a stomach for scarred spoilers. For our part, we found TechArt’s system quick, quiet, and helpful. It reduced the hassle factor around town, while the stock, electronically-variable PASM dampers took the stiffer springs in stride.

The only other chassis change is a set of forged-magnesium one-piece wheels wearing Pirelli PZero Corsa Systems. The Champion Motor­­sport Monolite MS 171’s “split-five-spoke” design is similar to the stock GT3’s wheel, but the MS 171s weigh 18 pounds front and 19 pounds rear, for a savings of six and seven pounds per rim, respectively. Altogether, they shave 26 pounds of unsprung, rotating mass.

Hello, 8800 RPM 7

If it looks like this RS is missing something, it is. Its trademark black side stripes have been swapped for ghosted green stripes that no longer interrupt the flow of its lines. Inside, a Brey Krause harness bar locates Schroth harnesses that thread through Euro­pean one-piece GT3 shell bucket seats. Along with the lighter wheels and exhaust, the seats help save more than 100 pounds.

So how’s it drive? Twist the ignition key and you’re greeted by the GT3’s characteristic instant-on spin-up and easy revs, but there’s a slightly gruffer bark from the twin tail­pipes. Let the clutch out and the difference in power is anything but subtle. As the 3.9 pulls through second gear and then third, any initial skepticism about the claimed 500 horsepower fades.

This is a ridiculously fast 911. We’ve driven faster turbocharged 911s, but this is the fastest normally-aspirated street 911 we’ve tested. By a mile. It’s Turbo fast without Turbo torque. Instead, big speed comes with big revs. As a result, it feels manic. May­be too manic, because you feel like you’re getting away with something whenever the tach hits 8800 rpm. Whether it’s a rod, wrist pin, or your driver’s license, you’re sure something’s got to give. Then you do it again. And again…

That’s not the 3.9’s best party trick, however. No, the shocker is this: It’s actually smoother than the stock 3.6, and not just a little. Where the factory 3.6 is grainy — some go so far as to call it rough-running — the 3.9 isn’t. Ross says that a few tricks help here, the most surprising among them being different spark plugs.

Ten miles in, I’m hooked. The soundtrack is incredible, with a demonic shriek underpinned by lower frequencies normally associated with air-cooled 911s. But it’s the way that the 3.9 pulls smoothly from 3000 rpm to 8800 rpm that’s intoxicating. Second gear is good for more than 90 mph while third will take you to the far side of 120 — and there are three more gears to go. In practice, there’s no need to shift out of second on a back road anymore, which gets us thinking about lower ratios in second through fifth to multiply the torque. The grip to use it is there. Then again, this thing is fast enough.

Too bad the chassis isn’t quite as magical. While the alignment helps, the RS’s first-gen PASM dampers still disappoint. The 2010 GT3’s chassis is noticeably better, but we barely remember it because the 3.9 is a scene stealer. When we get back in the red GT3, it feels like someone has hit the Mute button and muted more than noise. The 3.8, while fantastic, can’t hold a candle to the 3.9. Yes, it’s that big of a difference. The 3.9 feels far more alive, far more willing, and far more thrilling.

Does it feel like 500 horsepower? Yes. Does it spin like a GT3 RSR? It does. Will it blow up? We can’t say, but the car will go on to run over a thousand miles in our care on 91-octane gas without a single hiccup. Particularly impressive is the EVOMSit software tuning. Partial-throttle response, often a weak spot with aftermarket tunes, is every bit as good as a factory GT3’s. It’s the final piece in that rarest of puzzles: an aftermarket engine that outshines its factory basis.

There are caveats, of course. We can’t speak to longterm reliability, and such a conversion voids any re­maining warranty coverage on the powertrain. Then there’s the not-so-small matter of the 13:1 compression ratio. That said, the engine management seemed able to compensate, as the 3.9 never pinged in our time with it. Finally, there’s this: While the engine looks stock, emissions legality is another matter — though Ross says it passes the sniffer test with flying colors.

All serious considerations, but they’re not what’s on my mind weeks after the RS leaves. What’s on my mind is the winner of this matchup, and it’s not a car. It’s an engine, and I’m a handling guy. As that sinks in, I realize something else.

Much as I love short-stroke 2.5s and 2.8s, today’s GT3 engines eclipse them. But this 3.9 vanquishes every GT3 flat six I’ve tried. Including the ones in the 997 GT3 Cup and RSR? In a word, yes —in part because they’re overshadowed by a sequential transmission that makes F1 noises and in part because they’re not built to be enjoyable — they’re built to be raced. The 3.9 feels RSR strong but more refined than the production 2010 GT3’s 3.8. Put simply, it’s the best normally-aspirated flat six I’ve tried.

That ranks it up there with my top two Porsche engines of all time: the 469+hp, twin-turbo flat six in 1988’s Ruf CTR and the 605-hp, 5.7-liter V10 in 2004’s Carrera GT. It’s hard to see how a flat six can get any better, but perhaps Porsche under Ferdi­nand Piëch will show us.

Also from Issue 181

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  • 1957 356A with a 2.7 RS Powerplant
  • One-Off 993 Speedster
  • Falken Tire: Racing Against Goliath
  • Early 911T Tastefully Modified
  • 550-horsepower 914 V8
  • 986 Boxster with 3.4-liter 996 six
  • Market Update: 924, 944, 968
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