Red-Hot Roadster - 2007 Saturn Sky Red Line

The 2007 Sky Red Line brings cutting-edge technology and a bold direction to GM's "different" division

Chris Werner Sep 19, 2006 0 Comment(s)
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Since its inception in 1992, Saturn hasn't exactly flown the performance flag for GM. Not that it was ever meant to. The company has brought its share of design, manufacturing, and sales innovation to the market, and Saturns have a reputation for being well-built and easy to buy. But in terms of actual, get-your-adrenaline-pumping thrills, I suppose there's not much one can expect from a car company named after a Roman god of agriculture. Heck, until recently, presumably the only "rush" Saturn owners got was while viewing an unscathed plastic door after a good whack from a shopping cart.

Glimmers of hope for leadfoot junkies emerged in model year 2004 with the new Ion Red Line. With its supercharged 2.0L engine, the 205hp Ion introduced the Red Line edition of vehicles to Saturn's lineup and the first bit of excitement Saturn drivers had ever known. But it still lacked a lot in the styling department and, perhaps more significantly, a true performance-oriented driveline layout. Plus, 205 hp, while a big improvement over the standard 2.2L motor's 140, didn't exactly create class-leading performance.

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Model year 2007 builds substantially on this slow-to-get-going excitement theme at Saturn with the introduction of the Sky roadster. One of the coolest looking cars introduced in recent years, the Sky--along with its Kappa platform sibling, the Pontiac Solstice--is poised to compete with successful convertibles like the Honda S2000 and the Mazda Miata (come on, nobody calls it the MX-5). With a base price of $23,690, the Sky has been on showroom floors since late spring and is selling well. But its 2.4L, 177hp LE5 engine leaves something to be desired for those of us seeking serious speed. Fortunately, the automotive aftermarket has already started to catch on to these vehicles, with exhaust systems, turbo kits, and the like. But for a car with such a capable chassis and looks to kill, you'd think GM could cook up something a little more impressive under the hood.

Enter the Sky Red Line. Scheduled to be introduced this fall, this car's subtle styling upgrades over the already-gorgeous standard Sky do tasteful justice to the real news for enthusiasts: a turbocharged 2.0L engine with the first example of gasoline direct injection in GM's North American market. The performance industry has been following this vehicle's pending release very closely, and while the 260hp and 260 lb-ft (both coming at 5,300 rpm) originally quoted by GM were "pending certification" with the new, rigorous SAE J2723 engine test, we're happy to report this turbo'd mill passed with flying colors.

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As the Sky is a somewhat larger car, expect significantly more room inside than competitive roadsters. You see a manual stick here, but fear not: a five-speed automatic will be available for the clutch-incompetent.

We're going to introduce you to the amazing engine technology you'll see when this new car debuts, and discuss the vehicle's other improvements over the standard Sky model. We'll also talk a bit about the possibilities for the involvement of the automotive aftermarket, and finally give some predictions--ahem, caveats--for the success of a car that could very well be the next big thing in performance, GM or otherwise.

Ecotec Tech

Over the years, GM's Ecotec line of engines has by and large been seen as nothing more than an economical and reliable underhood offering. But with its "Gen II" revision that debuted with the 2.4L LE5 engine, GM drew upon experience racing the Ecotec engine family and built in strength to handle extra horsepower, with thickness being added to the main bearing bulkheads, cylinder bore walls, and other areas. The stage was set for a badass, forced-induction four-banger, and here we have it with the turbocharged, 260hp 2.0-liter known as the LNF.

Built for toughness, the LNF features a steel crankshaft and forged connecting rods. The pistons, while of a cast aluminum variety, feature a built-in oil galley and nifty jet-spray cooling system. We spoke to GM's Ed Groff, Assistant Chief Engineer for the LNF engine program, about this and other aspects of the design. "During development, we attached thermocouples to the pistons to allow us to analyze temperatures while the engine was in operation. Piston temperatures are a function of power level, and based on what we saw initially we decided that for the 260hp target power level, we were closer to our in-house limit than we wanted to be. This jet spray technology allows us to cool the piston by between 40 and 50 degrees C (104-122 degrees F), opening up a large safety margin for the engine."

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Exterior details for the Red Line include dual exhaust outlets, TURBO badging, and a more aggressive front fascia with revised grille openings.

For power, this DOHC engine features variable valve timing on both the intake and exhaust, and a "dual-scroll" turbocharger that delivers 20 psi of boost with minimal lag. This is achieved through some pretty badass technology. "We separate the exhaust passages of cylinders 1 and 4 from those of cylinders 2 and 3 all the way from the exhaust ports to where they enter the turbocharger," says Groff. "So you actually have two nozzles feeding the turbine wheel; hence the term dual-scroll. This creates somewhat stronger exhaust pulses as different cylinders are not interfering with one another as the engine goes through its firing order, which helps the turbine. Also, going off of conventional four-cylinder tuning during the valve overlap period, the cylinders are not experiencing pressure pulses coming back from the exhaust. Because of the combination of the dual-scroll and the VVT, we are able to design in a lot of valve overlap at low engine speed, which helps low-end torque."

But the real story on the LNF is gasoline direct injection, the first system of its kind offered in North America by GM. Instead of squirting fuel into the intake port upstream of the intake valves, fuel is instead injected directly into the cylinder during the intake stroke--at an amazing pressure of up to 2,250 psi. This results in superior fuel atomization and a more efficient burn. To accommodate such a SIDI (Spark Ignition Direct Injection) system, a special intake manifold, cylinder head, high-pressure mechanical fuel pump, and variable-pressure fuel rail are used. The SIDI system pays many dividends, including allowing a higher compression ratio as well as a leaner air/fuel mixture.

Also noteworthy for the LNF-equipped Sky is that fuel efficiency is improved over the 2.4L model, with an estimated 21 city/30 highway with the manual tranny versus the standard model's 20/28. Although clearly this difference has to do in part with the 0.4-L decrease in displacement and efficient direct injection system on the Red Line's engine, it probably is also due to the fact that GM engineers cut the final drive ratio from 3.91 to 3.73 for the car's turbo version. The two models share similar axle assemblies borrowed from the Sigma platform (CTS-V), so this is at least encouraging news for Red Line owners looking to swap to a lower final drive ratio for quicker acceleration.This turbocharged 2.0L mill will also be used in the 2007 Solstice GXP and Opel GT. And as if 260 hp isn't enough, look for substantial power increases on this engine in model years to come!

Engine Electronics: High-Tech

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The turbo version shares the same size tires and identical wheels with its slower sibling (though the Red Line rims can reportedly be ordered in polished aluminum instead of chrome). Also clear here is another area GM didn't bother upgrading: the brakes. The Red Line's caliper grabs the same 11.7-inch vented rotor as the regular model (the rears are unchanged too, with their 10.9-inch rotors).

In addition to the advanced electronics needed to run the new SIDI system, the Red Line's new E69 ECM takes charge of other neat powertrain control functions like electronic throttle control. The ECM provides spark signals through a Quick-Sync 58x ignition system, and the cam and crankshaft position sensors are digital. Another cool feature is that despite the forced induction character of the LNF, premium gasoline is recommended, but not required. "We've tested this engine on all lower grade fuels and confirmed that the control system is able to prevent detonation," says Ed Groff. "The two knock sensors on the engine alert the ECM and it will take steps to control it, it's a computerized learning process. We've tested this engine all the way down to the 85 octane fuel you find in high elevations. But to get the full 260 hp, the engine should be operated on premium fuel."

Perhaps most interestingly, the LNF sports something that GMHTP readers know all too well: a wide-ratio (or, as we like to say, wideband) oxygen sensor. We talked to Ed Groff about why the design team chose to go this route over a conventional narrow-band unit. "The wideband is pretty uncommon in a factory application, and we use it because it gives advantages during the high level of scavenging that we use to increase the turbo response. Particularly at low speed with all the valve overlap, there can be a lot of fresh air going through the engine. So the mixture you sense in the exhaust can actually be lean while you are stoichiometric or even rich within the cylinder. We found the accuracy of the wide-ratio oxygen sensor to be beneficial in this particular application."

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Visible is the turbo's exhaust routing. Hidden are the chain-driven camshafts that actuate the engine's 16 valves and also drive a mechanical fuel pump--which, in conjunction with a tank-mounted electric pump, helps achieve the stratospheric fuel pressures needed for SIDI.

Aftermarket Possibilities

Many of you are probably thinking: OK, great engine, but it's still a little inline four! The image of four-bangers being less-than-durable is not without truth. Yeah, we've seen some four-cylinder imports make amazing power, but that power comes at a price: literally and figuratively. The amount of dough that must be pumped into your typical four-cylinder to get it to withstand large amounts of horsepower is very high, and even then, they're still a ticking time bomb of blown head gaskets, bent rods, and catastrophic block failures.

But the Ecotec is different. This particular four-banger really will withstand the abuse true enthusiasts will throw at it. But don't just take GM's--and our --word for it. We had a conversation with someone who knows firsthand: Mr. Bill Hahn Jr. Since the 1970s, this man has been turbocharging everything he can get his hands on, from V-twin motorcycles to airplanes. His company, Hahn Racecraft, was founded in 1988 and provides turbo systems for vehicles ranging from T-Types to Vipers, Miatas to GTOs. But it's GM's Ecotec platform that has really gotten his heart thumping in recent years. "This second-gen Ecotec architecture is really something. Several years back, GM made a promise that they were going to go after the Ecotecs with a vengeance, and I'd have to say they were not exaggerating in the least!" Hahn has worked extensively with this engine platform in all its applications, and already produces turbocharger systems for the LE5-equipped Sky and Solstice.

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Looking more closely at the Borg-Warner dual-scroll turbo, we see where it gets its name: two separate exhaust passages leading from the exhaust manifold to the turbine inlet. "Combined with the VVT on both the intake and exhaust, this is a key element in getting good low-end torque and power at the same time," says GM's Ed Groff. "Typically, if you put a turbocharger on that's large enough to get the power that you want, you would suffer at the bottom end. We have a variety of technologies--the SIDI, the cam phasers, and the dual scroll--that all help the bottom end," says Groff. Thanks to the engineers' efforts, turbo lag is allegedly cut to imperceptible levels, furthered by a lightweight turbine design.

"I'm excited enough about this new Gen II Ecotec engine that I believe in stock form I will be able to push it further--safely and durably--than any engine from any manufacturer that came before. With the Gen II, we're working with an engine that is brutally durable as far as its bottom end design. With a casing that splits in half like a racing or motorcycle engine, these things are just amazingly capable of higher horsepower. It's really encouraging because while other manufacturers have some pretty powerful four-cylinders on the market, a lot of them are working with 10- or 20-year-old technology compared to the all-alloy Ecotec. You have to be really selective with engines these days, and I can honestly say that the Ecotec, which we have been working with for years, has an incredibly durable track record compared to anything else we've ever worked with. I can honestly say that there's nothing out there from any manufacturer that surpasses it."

Exactly how the aftermarket will address the challenges that direct injection, high fuel pressures, and a brand-new, advanced E69 ECM bring is hard to say. But we can tell you that support is already out there for the Ecotec engine line, and these new technologies only add to the possibilities; though in the spirit of a capitalist market, nobody is saying just how such challenges will be addressed. "At this time, I'm not at liberty to discuss the methods we're planning on using on the LNF in any type of detail, but I already have some pretty solid methods planned out," says Hahn. "I do want to emphasize that we are going to be all over this vehicle. We are excited as can be especially because it's turbocharged, and we may be able to push the envelope even further with this engine than any previous Ecotec just because of the strength of the direct injection system."

Other than the altogether different engine that, in factory guise, gives a whopping 83 hp and 94 lb-ft increase over the standard Sky, the Red Line sports chassis upgrades as well. Beside Red Line-specific coil springs, this new go-fast Saturn model also gets thicker anti-roll bars. However, according to GM's press material, these suspension upgrades yield no improvement in skidpad holding, as the Red Line pulls the same maximum of 0.90 g as its non-turbo bro. This is most likely due to tire size being identical for the two cars: 245/45-18s all around. The Red Line does get Goodyear Eagle F1s instead of Eagle RSAs, but we still would like to see some fatter meats to match the Red Line's vastly-increased potential for speed. Fortunately for less experienced drivers, standard on the Red Line is the latest StabiliTrak electronic handling control system, helping keep such folks from using all this power to inadvertently put their gorgeous Saturn roadster into the woods.

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Pictured are the new E69 ECM, cam-driven mechanical fuel pump, high-pressure fuel rail and fuel injectors. These comprise pretty much everything needed for the Red Line's gasoline direct injection system, which GM refers to as SIDI (Spark Ignition Direct Injection, which stands in opposition to spark-less diesel engines, which have featured direct injection for some time).

But the question remains whether the Kappa platform's chassis is really up to the challenge of handling the LNF's current 260 hp, not to mention the power increases sure to come not only from the aftermarket, but from GM itself in the years to come. Indications are that the answer to this interrogatory is a resounding yes. Bill Hahn Jr., who has been testing the Sky/Solstice platform since its debut last year, explains. "In terms of chassis and driveline, it's already an outstanding piece in terms of architecture. Here you have a four-cylinder, two-seat car, but the reason it weighs as much as it does is because the chassis is so strong. It's a true performance-bred piece, with unequal length A-arms at all four corners and coil-over shocks; this isn't just some warmed-over, parts-bin car with a pretty body on it. The Sky is a real performance car. There's a lot to be said for that, because while there have been similar cars brought to market previously, there has been nothing quite as brutally capable."

"Our testing with our turbo vehicles has shown that the car's ability to put down extra power is actually pretty awesome," states Hahn. "We are not experiencing excessive wheelspin or wheelhop, or some of the other things we see with some vehicles as we turn up the power. This car's dynamics put power down extremely well and without a lot of drama." And even if super-high power levels were to overwhelm this current chassis structure and driveline, rest assured that the aftermarket will step in to take up the slack. For example, extreme-duty axles are in the works, and Hahn Racecraft has already come up with a higher-capacity clutch. So if you've got a hankering to turn up the wick way past GM's design intentions, fear not: all indications point to the aftermarket addressing any problem areas as they become apparent.

Will it Succeed?

The Saturn Sky is a niche vehicle, and the Red Line version appeals to an even narrower range of buyers. As a two-seater with limited trunk space, practicality is far from optimal; but that's beside the point. The current 2.4L Sky is being bought by open-air aficionados on a relative budget who want to drive one heck of a cool-looking car. The Red Line will appeal to the rarer few of these same folks who care not just about looking good and a tight driving experience, but who want to blow the doors off of Miatas and S2000s--not to mention a lot of other so-called sports cars on the road. And many of these buyers will probably want to mod up their Red Lines to take full advantage of this amazing car's as-yet-untapped potential in both powertrain and chassis.

At an estimated base MSRP of under $30,000, the Sky Red Line is still quite affordable for a large percentage of us enthusiasts. The only problem we foresee is Saturn dealerships starting to charge a markup for these limited-edition cars. After all, a big reason the buying public has been attracted to Saturn dealerships since the brand was introduced is the pay-what's-on-the-sticker, no-harassment-from-salesmen policy. Word is that Saturn has issued an advisory letter to all dealerships asking them not to charge extra for the Sky Red Line when it arrives, but apparently the no-haggle pricing situation at Saturn is more of a policy than any sort of contractual agreement between GM and its independent franchisees. We can only hope dealerships don't hurt sales of this car the same way Pontiac dealers did grave damage at the introduction of the 2004 GTO, creating some very upset enthusiasts and setting themselves up for the car's eventual cancellation.

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Though the 2.4L Sky is only able to traverse the standing quarter in a ho-hum 15.7 seconds at 89 mph, GM is saying the 2,990-pound, manual-equipped Red Line will pull a 13.9 at 100 mph. Expect to get to 60 mph in only 5.5 seconds (versus the standard Sky's 7.2).


There's a lot more to talk about with respect to this vehicle, but needless to say, GM has the potential here for a sales and image slam-dunk.With the turbo Sky, GM further solidifies its commitment to not just performance, but advanced, responsible performance technology that simultaneously improves power production, fuel efficiency, and tailpipe emissions. With more SIDI applications in the coming years--the first being a 2008 3.6L V-6 for an as-yet-unnamed vehicle--things will only continue to get more exciting with GM. In fact, by 2010, GM says 1 out of every 6 cars the company sells will feature direct injection. How many of those cars will feature kickass turbocharger systems like the one seen on the Red Line is anyone's guess, but we're hoping it's at least a few.

Though there haven't been many whispers about future rear-drive Saturns to come, we'd be shocked if the Red Line emblem didn't grace more than a couple worth-drooling-over vehicles in the future--regardless of drivetrain layout. If nothing else, the Sky and the soon-to-be-released Aura demonstrate designers' intentions that Saturn cars look the part of a very sophisticated automobile brand, even if it turns out that the Sky Red Line is the only car of theirs that truly walks the walk. And with insiders strongly hinting that 260 hp is only the beginning for this 2.0L motor, things will only get better for the Sky Red Line.

Until now, admitting that you owned a Saturn in front of other performance enthusiasts was a bad move for your social popularity. Let me be the first to declare those days are over.

Read about the new 2007 Saturn Sky Red Line in GM High-Tech Performance Magazine
Chris Werner Sep 19, 2006


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