dwightlooi

The Duramax head is not particularly good for airflow (the intake and exhaust ports run into one valve first then the other since the valves are tandem not side by side). Also, it is also possible only in a diesel because the Diesel engine uses a a completely flat combustion chamber roof and all four valves are parallel. The approach -- using one rocker to push down on two parallel valves connected by a bridge is not feasible for a gasoline engine. Kinda central, but not quite. It is very much like the BMW E30 era 2-valve SOHC heads. The valve is between the two opposed valves but displaced slightly to one side. It is not that heavier springs make the engine heavier. I meant the spring force is significantly heavier because it has to actuate the much heavier total inertial of the lifter, push rod, rocker and relatively large valve. In a simplest OHC design (tappets) the spring only as to actuate the valve and the shim (or shimless) buckets. Even for the popular roller follower designs the total mass of the roller followers and the valve is significantly lighter (~1/2 to 1/3 the mass) of the driven mass of typical push rod linkage set. Low spring force is directly related to low startup wear. The main problem with 3-valve, twin in-block cam designs such as those proposed by GM a few years ago is that the rods themselves compete for space with the intake runners and ports. It is impossible to have straight, unobstructed runners and intake ports. Perhaps the reason these designs did not make it to production is because the intake port issues limits flow improvements to a point where improvements over 2-valve designs become intangible. Actually, the push rod setup has A LOT to do with the noisy racket push rod motors tend to make at higher revs. Let me explain... Basically, valve train racket comes from valve float. In general, all valve trains "float" to a tiny degree at higher revs. Just like with suspension systems, when rebounding from a compressed state it the spring is unable to keep everything fully loaded and in contact. Higher spring rates help, but spring rates high enough to eliminate all slop will also cause excessive wear due to friction and hurt economy. I tiny amount of "float" during those small periods of time where the engine is actually reving at the upper 1/4 of its rev range does not hurt the engine. The difference between push rod engines and OHV designs is that the actuated mass of each valve element is very high. There is the lifter, the rod, the rocker and finally the valve itself. The heavier the actuated mass the higher the impact momentum when the valve train elements floating a tiny bit at higher revs remakes contact. This creates louder noise and more notable vibrations. On top of that, the OHV design also has more interface layers than the OHC designs. In a typical DOHC design there is one to two interface layers. With bucket tappets there is basically just one interface -- between the cam lobe and the tappet. In roller follower designs there is two -- cam to follower and follower to valve. In push rod designs you have four -- cam to lifter, lifter to rod, rod to rocker and finally rocker to valve. Hence, there are four locations where you'll have slop during high rev operations and a lot more noise making locations. Its like an anchor chain with five links makes more noise when you rattle it than one with three links. Things like firing order (whether the V8 is flat or cross plane for instance; whether it is an even fire design), 1st and 2nd order vibrations due to engine configuration (I4s and 90 degree V8s have 2nd order vibrations at 2 x crank speed; I3s, 60 and 90 degree V6es have 1st order vibrations at crank speed; I6s, 60degree V12s and horizontally oppose designs are perfectly balanced, etc), and vibrations due to imperfect crank balancing and variance in rod and piston weights across each cylinder are completely independent of the valve train design. NP. I am happy to discuss these things.

In terms of styling, performance and quality, I am sure GM can correct their past mistakes relatively briskly if they continue down their current path without reverting back to heaping out ugly cars while heeding every advice from the bean counters. However, even if GM builds cars that are every bit as good or better than Honda or Toyota, it'll take years before the car buying public changes their pre-conception of GM vehicles. The negative pre-conceptions out there are pretty deeply rooted from decades of churning out junk.

Well, GM has a downright crappy reputation. If we look at what they build in the 80s, 90s and as recent as the last generation Malibu and Grand Am, much of it is well deserved. Let's face it. GM built extremely low quality, poorly engineered and horribly ugly cars for decades. Not only that but cars whose reliability and dependability record had been leagues behind not only Toyota and Honda, but Hyundai and Kia as well!. For years, GM had been playing the bean counting game trying to retain market share through under pricing the competition rather than putting out good products. They do not seem to realize the painfully obvious fact that the USA is a high cost country and there is no way a US manufacturer can discount its way past the Koreans and soon the Chinese and Indians. Sure, it appears to us enthusiasts that GM has finally turned the corner with cars like the new Malibu, Aura, Solstice, Sky, GMT900, etc. But the GM is going to need a few generations of great products and perhaps a decade or more to win back the hearts and minds of the car buying public. If Wagoner-Lutz & Company wants to speed up the process the new GM products must not only be as good or better than the Japanese competition. They have to be significantly and conspicuously better.

Actually, I don't really mind engine covers per say. The problem is that the ones GM puts on their engines look CHEAPER than $5 garbage can covers and even worse fitting that the one on my Rubbermaid trashcan. Whats more, in many cases they hide relatively good looking intake manifolds. Dress up is supposed to make the engine bay look more upmarket and higher quality. Those sorry ass covers GM puts on their engines do neither!

I don't want to clog up this presentation thread so I am going to be brief... (1) The designs were manually drawn in Adobe Photoshop using a graphics tablet. Mainly the pencil, line, brush, marque and fill tools were used. (2) I did not intend this to be an extravagant "concept" car, but rather something I envision to be as close to production reality as possible. The wheel spacings and other proportions are based on the "real" Cobalt so, it is proportionally and perspectively very accurate for the Delta platform which I believe the 2009 car will use. (3) The styling is, simply put, centered around the sleek, clean and simple elegance of a high level of coherence between understated but highly aligned elements. I deliberately avoided "loud" styling themes, monster grilles and/or exaggerated proportions which are more frequently polarizing and/or offensive than anything else. Personally, I like designs like the A4, E60 5-series, G35, G6 (non-GXP), Solstice, TL and IS250/350. I do not like the G6 GXP, the new Camaro, the Chrysler 300, the Mustang or the Lincoln MKR concept.\ (4) There is a blooper in the instrument cluster animation if you haven't noticed. The speedo space went from 140 to 180 instead of the correct 20 unit step between each numbering. I screwed up, and I realized it AFTER I have already created over 40 of the 50 or so frames of the animation. I was just too lazy to go back and change it and redo the already finished frames, so I let it be.

The big, squarish, aluminum contraption is not the aftercooler. It looks like the intake plenum. In the classic "M" arrangement for a roots type blower, the blower is underneath in the valley of the "Vee". Air goes into the blower horizontally from the front or the rear. It blows upwards through an air-to-water aftercooler and ends up in the squarish manifold plenum on top. The intake runners from the side of the plenum straight down to the intake ports.

That the engine covers have ANY acoustic minimization effect(s) is a complete load of hog wash. I'll tell you why... There is no acoustic material under those covers. If there have been a Dynamat type aluminum-rubber or fibrous rubber mat underneath you may have a case, but there is none. Moreover, those silly covers do not even form a barrier to sound waves escaping because they do not seal off the sides at all. In short, they have the same effect as if you duct taped a sheet of plastic card or cardboard under the hood or on top of the engine. If you are curious as to how much effect that has, I suggest you try it! Every sound wave that goes up is quietened by the acoustic/thermal mat under the hood (in cars that have it). Hence it makes ZERO sense to put any acoustic material on the engine cover itself anyway! You'll be better served putting additional material on the hood liner! At least that way it doesn't get in the way when you work on the engine and it doesn't look CHEAP!

2009 Chevy Cobalt SS coupe – A Design Study Design Details The 2009 Chevrolet Cobalt design conveys a strong, modern and sporty stance. The lines are uncluttered and flow smoothly from one geometric entity to another. There is no boundary line or curve that does not line up with another feature. The roofline is a swooping all glass green house flanked by uninterrupted front to back arches. The lower ends of both the front and rear windscreens are recessed in a display of solidity and strength. The recessed front windscreen treatment also eliminates the need to expose a big swath of black plastic between the hood and the windscreen. The front fascia is deliberately given long, relatively narrow, openings to widen the apparent stance of the car to counter the somewhat tall and narrow nature of the Delta platform. The headlights firmly anchor corners and are fitted with a projector low beam and complex reflector high beam. The crystal turn signal lights penetrate down into the upper bumper for an added touch of aggressive candor. There is no ornate grille, and chrome makes an appearance only as a thin strip on the lip of the hood. Both the upper and lower grilles have airfoil shaped lower lips to convey a sense of aerodynamic refinement. In the SS model, the lower grille proudly displays the front mounted intercooler. It is also flanked by a pair of integrated fog lamps and the brake cooling intake accommodations whose lines flow into those of the main headlights. The flanks of the car feature a pair of side vents which originate from the part line between the front fender and the door for minimum clutter. A pair of body colored vertical strips serve as a gentle punctuation for these slender but functional excavators and the car proudly wears the GM emblem squares just ahead of the top of these strips. The side view mirrors feature integrated turn signals. But, apart from these subtle touches, the waist of the car is left clean cut and unadorned by extraneous trinkets. The rear of the car preserves some styling heritage from the out going Cobalt in the overall shape of the tail lights. The strong, vertical backup lamps mirror the turn signals in the front of the car in their placement and disposition. Perhaps the most unique feature is the inward facing dual exhaust outlets which vent sideways into the diffuser channel. The car does not don any wings or spoilers as these are not deemed necessary or complimentary for a car that is already conspicuously sporty. The interior of the car retains the GM corporate switchgear, but the center console adopts a 2 tiered layout to improve on knee room -- the lack of which is a problem which current Delta vehicles suffer from. The seats are well bolstered and feature a separate low density cushion for forward thigh support. The steering wheel is an evolution of 3-spoke affair now common on GM vehicles -- paddle shifters are fitted on automatic transmission equipped cars. Following the uncluttered theme of the car's exterior, the cabin is kept simple and sleek with flowing lines that line up various utilitarian features. The cockpit is largely unadorned other than for the single lacquered chrome or walnut strip that wraps around from the doors across the dash. The 2009 Cobalt also debutes GM's new hi-fidelity audio system which is standard on the LTZ and SS models. A total of 9-speakers, an external DAC and an integrated amplifier comprise the new Delco Monsoon Stereo. The dash unit is identical to non-monsoon equipped cars, but a little red symbol indicates the presence of this premium audio setup. Hi-fidelity sound is delivered via four 1" silk dome tweeters, four 4" polypropylene mid-bass and a single 8" sub-woofer, all using neodymium drivers. Attention was paid to speaker placement and performance. Unlike most cars, both the tweeter and the mid-bass drivers are angled towards the occupants. The door panel also integrates a proper speaker enclosure with acoustically dimensioned speaker housings. In the case of the mid-bass driver, the enclosure is a reflex design with a tuned port in the door pocket area. The low frequency air driver is hidden under the rear shelf in another a reflex type enclosure with two a serpentine reflex ducts spanning the rear shelf and terminating in a pair of trumpeted reflex ports on the C-pillars. The resonant frequencies of this housing and ductwork were carefully measured and neutralized using a trio of Helmholtz resonators attached to the duct work. The entire setup is driven by in integrated 25watts x 4 + 50 watts x 1 channel (RMS) amplifier under the dash console. High quality digital-to-analog conversion is handled by an external DAC integrated with the amplifier receiving undecoded digital output from the standard head unit. This external DAC uses a Burr-Brown PCM1794 Advanced Segment 24-bit 192kHz DAC chip with a signal to noise ratio of 132 dB. Technical Details Despite some early speculation that a rear-drive Cobalt may be created by GM, the lack of an existing compact RWD platform and the 2009 dateline ensured that these remained nothing but unfounded rumors. The 2009 Cobalt is based on an evolution of the Delta architecture that underpins the current Cobalt, G5, and Astra. The enhancements include a die cast magnesium cross beam, tailored thickness/strength sheet steel and increased use of laser welding. Torsion rigidity is up 18% and bending rigidity is up 12%. Quiet steel is employed in the firewall and around the sub-frame mountings. Like before, the car is suspended by struts up front and a twist beam axle in the rear. However, the front suspension now features forged aluminum lower control arms. At 2870 lbs for the base model and 3057 lbs for the turbocharged SS, the new Cobalt is not a fly weight automobile. This is remedied by a choice between pair of very capable engines. The base model through the deluxe LTZ is powered by a direct injected version of the 1.8 liter Ecotec Inline-4 making 150 hp @ 6200 rpm and 135 lb-ft @ 4200 rpm. Thanks to direct injection, this engine is perfectly happy with a diet of 87 octane gasoline despite a lofty compression ratio of 11:1. Driving enthusiasts however will be pleased with the availability of the SS model with a direct injected and turbocharged 2.0 liter engine similar to that used in the Pontiac Solstice GXP. The 2.0 Ecotec SIDI Turbo produces 260 hp @ 6000 rpm and 228 lb-ft from a rock bottom 2000 rpm to an impressive 5950 rpm. For this front-drive application, the torque rating of the engine had been deliberately lowered to minimize torque steer. A revised turbo enables the lower torque output to be maintained up to a higher engine speed to produce the same horsepower as the Solstice engine. Both engines are mated to the new Hydramatic 6T70 6-speed automatic transmission. The Cobalt SS also offers a 6-speed manual as a no cost option. An open differential is employed with the 1.8 liter engine, whereas a Quaife helical automatic torque biasing (ATB) differential is installed in all turbocharged SS models. All Cobalt models are fitted with front and rear disc brakes with ABS. Traction and stability control is standard on the SS and optional on other trim levels. The SS model also feature larger ventilated disc brakes (13.1” front, 12.3” rear) grabbed by beefier 2-piston floating calipers. 16 x 6” rolling stock with 205/55 HR16 Goodyear Assurance TripleTred tires is standard on non-SS models. The SS is fitted with 255/40 WR17 Eagle F1-GSD3 tires on 17x8.5” alloy wheels in front, but carries narrower 225/45 WR17 Eagle F1-GSD3 rubber in the back. 0-60 mph in the SS is estimated at 5.8 seconds with the automatic transmission and 6.2 seconds with the manual. From a drag launch, the ¼ mile mark is expected to be reached in 14.4 seconds at about 96 mph. EPA fuel economy is estimated at 21 mpg City, 28 mpg on the highway.

-- Deleted -- I decided to add interior view, make some minor tweaks to the front view and change the accompanying text somewhat. Please see the new entry.

Here is my predictions concerning how various "high-tech" features can progressively improve the Push Rod V8. The starting point (red line) is the actual torque curve of the 6.0 liter LS2. The subsequent pictures illustrate how various technology can progressively improve performance until a 500hp engine is achieved. Not that I am not trying for ultimate horsepower here but rather an extremely linear and tractable engine which also happens to achieve ~83.3 hp/liter and ~75.8 lb-ft/liter. I am sure even power is possible with the mentioned technologies if emissions, tractability and linearity is sacrificed. However, I for one, believe that these things can be more important than maximum power output. That'll be a pretty darn nice Small Block "Advanced" won't it?

The Push Rod engine has been much maligned for being ancient, inefficient, low tech etc. It has been called “clunkers”, “American Pig Iron” and a whole host of different derogatory nicknames. But is it really the piece of obsolete trash that it is made out to be? I must say I am a DOHC fan and I applaud GM’s move to put the 3.6 DOHC V6 in everything imaginable. I think that the engine from GM’s lineup I’ll most like to have in my car is the LNF 2.0 liter DI turbo. I love the turbo whistle and I don’t really have a taste for the V8 rumble. But, let’s be honest about the whole Push Rod thing and clear up all the myths shall we? Why Push Rods? There were overhead cam engines l before the push rod small blocks came along. Heck, if you want a really old example of a really “high-tech” OHC 4-valve per cylinder, twin spark, direct injection (yes DI), gasoline engine I suggest that you look at a WWII vintage Daimler-Benz DB601/603/605 inverted V-12 engine. These engines even have a continuously variable supercharger drive by means of a hydraulic coupling that automatically adjusts the drive ratio (based on barometric altitude) to provide the right absolute boost pressure. You’ll find these in the Messerschmitt Bf109, Bf110 fighters. The Rolls-Royce Merlin is also a 4-vavle overhead cam design BTW (albeit carbureted) , and the Junkers-Jumo 213 in the Fw190D9 is a SOHC 3-valve, DI, twin spark design very similar in valve layout to contemporary 3.2 liter MB V6es! This is WAYYY before the American muscle car era; way before Impalas, GTOs, Camaros and Corvettes. The pushrod design was invented to do primarily two things – make the V-type engine more compact and make it lighter. By throwing out the tall and bulky SOHC or (especially) DOHC heads, and actuating the valves from a single in-block cam you save three camshafts, lots of head height, lots of head width, lots of parts and yes lots of weight. You also make the cam drive much simpler, more compact and lighter. If we look at the above, you can see that by removing the four overhead camshafts and half of the valves, we can have just eliminated a whole bunch of metal. The heads become roughly 1/3 as wide, about ½ as tall and less than half as heavy. Of course, the pushrod designs also have less parts and lower costs. I think we can see the contrasting difference between that DOHC engine drawing and the naked LS2 below it. See how compact the engine is and how much dieting it accomplished? FYI, the 4.6 liter DOHC 32v Northstar V8 for instance, is actually a larger and heavier engine than the 6.0 liter LS2 V8. Its output is also only roughly comparable to the 5.3 liter LS4 OHV power plant. Why Overhead Cam? Well, one word – Airflow. In contrast to what many people believe, neither displacement nor rpms make any power by themselves. To make a given amount of power you have to burn a given amount of fuel. To burn a given amount of fuel you need roughly 14 to 15 times as much air as the fuel you intend to burn. The overhead cam designs allow for intake and exhaust valves to be set at opposed angles to each other each with straighter shot intake pots. This is good for airflow. You can also actuate four (or rarely five) valves per cylinder to maximize valve area if you so desire. You can also reap auxiliary benefits such as a dead center spark plug location, light actuated mass for each valve to allow for high speed operation without valve float (or excessively heavy springs) and of course in recent years the ability to implement a CVVT design which advances/retards the intake and exhaust cams separately. It has also been argued that high tumble designs (most OHC engines) promote better fuel-air mixing that high swirl designs (most OHV engines) although this has not been demonstrated conclusively. The combination of high rev breathing capacity and light actuated valve train components allow the OHC engines to also have a much more refined character and sound. Today, this is arguably more important than theoretical airflow limits (more on that later). The problem with DOHC 4-vavle designs is that you incur a lot of weight, a lot of bulk in those cylinder heads. Also, none of the airflow benefits actually show up until pretty high up in the rev range. Airflow capacity, you see, is not a free lunch. And more is not always better. At low engine speeds, storm drain sized runners and ports along with big fat valves and/or a lot of valve lift create very low intake velocities which result in poor intake charge mixing, low power output and high emissions. High rpm breathing enhancement techniques like high exhaust/intake valve duration overlap and advancing the valve timings can downright lead to an engine that won’t idle or run right at low engine speeds. In fact, when DOHC engines first saw mainstream use in the early 1980s, they all performed badly at low engine speeds because of intake velocity issues. Various techniques like blocking off half the intake tract with butterfly valves (eg, the TVIS system on the Toyota 1.6 4AGe and 2.0 3SGE engines) is commonly used to get them to not stumble off idle and at low engine speeds. What happened in the last 20 years? Well, to put it simply, DOHC engines have mellowed and OHV (Push Rod) engines have really shaped up. You see, the typical street car, even those with sporting pretensions are typically not going to rev to 8000 or 10000 rpms. In fact, most DOHC engines today are optimized to reach their maximum output at between 5500 and 6500 rpm. Over the years manufacturers have also shied away from monster sized intake ports and runners. Narrower runners and smaller ports are intentionally adopted to so the engine operates well in from idle and up. In short, the original reason for which the DOHC 4-vavle designs where coined – airflow maximization – is not longer pursued! At up to about 6500 rpm, the airflow required can be achieved with pushrod OHV designs which are smaller, lighter and less complex! How small are the differences? Well, a good 3.5 liter push rod V6 like the LZ4 is good for about 224 hp on 87 octane. A good 3.5 liter DOHC engine like the Nissan VQ35 is good for 245hp on 87 octane. That’s about a 10% difference. The LZ4 is an iron block engine that is physically much smaller than the VQ35, and had it been an aluminum block powerplant it would be significantly lighter as well! A So the question today should really be why anyone should want to employ DOHC valvetrains in a typical car? The answer comes down to the consumer’s perception. A car equipped with a Push Rod OHV engine is deemed outdated by the consumer. The perceived refinement in terms of vibrations and acoustic signature also heavily favors the DOHC engines. They don’t exhibit much valve clatter at higher RPMs because their reciprocating valve train pieces are lighter, they tend to also not appear to run out of breath as easily in most cases as revs climb past 5000 rpm or so. In most cases, they are also slightly more economical because on the average DOHC designs mix fuel and air better, and have slightly lower pumping losses at cruise, than push rod designs. Part of the reason is that they tend to have better technological content such as VVT, coil-on-park ignitions, etc. The ability to vary intake and exhaust cam separately is also good for emissions control – good enough to eliminate the need for an EGR subsystem. Even though some of these are not necessarily tied to their DOHC design, they are nonetheless associated with DOHC engines because it is true that when you compare the typical DOHC engine to the typical Pushrod engine, you are more likely to find these “high-tech” features on DOHC ones. However, TODAY, if you are after the highest power density with respect to engine dimensions or weight, and you don’t care about perception or refinement or anything else, you’ll find it in a well engineered Push Rod engine like the LS2 or LS7. I’ll tell you this right now. A 400hp 6.0 liter LS2 is probably smaller or at worst the same size as the BMW 4.0 liter DOHC V8 that is going into the next M3. It is probably no heavier as well. It has better low end tractability and it is cheaper than any V8 engine built for 8,000+ rpm duty will ever be. Sure, it’ll sound and feel less refined. But, as far as performance goes it is a better solution. Where do we go from here? Let’s put it this way… a lot of the DOHC 4-valve engines’ advantages come from their technological content, not the design layout. Things like direct injection, VVT, high energy individualized ignition system, advanced intake design, advanced engine control electronics have nothing to do with Push Rods or Overhead cams. No, you typically find them more on DOHC engines, but that is because market forces and manufacturers put them there not because of the choice of valvetrain layout permits or forbids them! Nonetheless, I see the continued dominance of DOHC valvetrains in family sedans and typical cars. It sounds and feels more refined – HONESTLY IT’S TRUE! The consumer expects it. And they will get it. However, I think that if the GM folks are smart about it they will be very successful in pushing HIGH TECH pushrod designs in sporty cars. As far as HIGH TECH goes, I expect the first direct injection pushrod small block within the next five years. I also expect synchronous VVT and AFM (DoD) -- which has already happened. I expect to see at least an attempt to incorporate either variable length or variable resonance volume intakes. If they really want to push it is actually possible to do a VTEC/VVTL-i like cam lobe switching system on a push rod V8 too. All you have to do is chuck the traditional lifter and replace each with a pair of roller rockers in the block. One follows a lower-lift/low-duration cam lobe. The other follows an aggressive high-lift high-duration lobe. The pushrod is connected directly to the low speed cam. The rocker following the high speed lobes bounces on a spring actuating nothing but itself. At a certain RPM, a steel pin, slipper or collar locks the two together. And the valve is then forced to follow the high speed cam. You can still have hydraulic valve lash adjustment – you just have to do it via lash adjusters on the pivoting end of the rocker. If all these features are used, a 500 hp 6.0 liter push rod V8 with a velvety idle is possible. The engine will weigh less and be smaller than any 500hp DOHC engine using the same block and head materials. We they want to go even more, may I suggest a centrifugal blower driven directly from the crank via a Van Doorne type continuously vectoring transmission? The CVT should be able to vary the total supercharger drive ratio from about 24:1 at lower engine speeds to about 6:1 at high engine speeds linearizing the power adding characteristic of the efficient but peaky centrifugal impeller.

Even the LS7 has silly, sub-standard dress-up covers. Making it bright red doesn't change the cheapness of it!

No not for the valve gear drive. That pretty much have no "rubber banding" whether it is a gear, chain or belt drive. But it is common to put harmonic dampers on the crank pulley of the accessory drive loop. The water pump, alternator, clutchfan and/or A/C compressor does not need to be synchronous with the engine timing. Its like the little spring packs you find on clutches which allows for some give between the shaft driven input and the friction discs. Racing clutches don't have them but every regular factory clutch does. In the case of the accessory drive pulley they are frequently made from some kind of rubber. In both cases they act to cushion shock loads. Yes. It is dead after a mere 2 years. The new Passat is based on the Jetta platform and uses a transverse 3.6 liter DOHC VR6 engine making 280hp. The 3.6 liter is a 10.6 degree V6. The Audi's never used the W8 but rather a series of 90 degree 2.8/3.0/3.2 liter V6es or 4.2 liter V8s. The latest versions being direct injected and making 255hp and 420hp respectively. The Touareg SUV uses the Audi 4.2 liter 90 degree engine or the 3.2 and later 3.6 liter VR6es. The Passat W8 was the only car to use to W8 engine. Now that the B5.5 Passat is gone, the engine is dead. The only remaining W-engine is the 6.0 liter W12 used in the Phaeton and the Audi A8. The 8-cylicner version of these cars use the Audi 4.2 liter 90 deg V8.

In order to appeal to people with "Normal" tastes the hood nostrils need to go. If they are offered as an appearance package for ricers, I can understand. But it'll turn off flocks of people who wants nothing to do with Firebirds of the 90s and 60s GTOs of the past. What GM has done with the G8 is take a perfectly great looking VE Commodore and turn it into a joke. Geez at least offer the customers a option to PAY to delete them. $500 bucks option to get rid of the Nostrils will find many happy takers IMHO. The G8 has a potential to be a BMW E60 5-series for the masses, don't make it into a Firebird. Stuck in the 60s people who want stuck in the 60s looks already have the upcoming Camaro to cater to their tastes. That, and the likes of the Mustang, Chrysler 300 and Dodge charger. And they are entitled to their tastes. But there has to be a car from GM that doesn't look like an American muscle car or worse yet an American Muscle car with a bodykit -- not everyone aspires to tackiness. I was so happy when the G6 came out and the body cladding and ugliness that plagued Pontiac for decades went away. The Solstice was another clean, sleek and uncluttered beauty. Then the G6 GXP came along which was a bad omen I guess. Now it seems that Pontiac is going back to her ugly genes with nostrils and other silliness. Somebody commented that a G8 without nostrils will look like an Acura TL. Well, I take that as a compliment -- thats a seriously nice looking car! If GM doesn't offer the nostril delete, I think somebody should go into making an aftermarket without the nostrils "CLEAN" hood for the car.

The lower car looks terrific compared to the G8 or ANY Pontiac Sedan past or present.

Shielding? I mean we are not talking about a nuclear reactor here! The worst thing that can happen during a crash is a broken fuel line dumping fuel onto hot metal and starting a fire. A piston engine is has exactly the same problem with regard to the hot exhaust manifold. This is why it is common to have a fuel cut off switch which respond to the an impact force and kills the fuel pump or put it on reverse polarity (sucking fuel backwards). If you are worried about the turbine grenading and sending fragments out, that is a non issue. The chances of a centrifugal turbine distintegrating with enough centrifugal force to send the impeller's fragment through the aluminum or Inconel housing is non-existent because operating speeds are relatively low. Even if an axial turbine is used it is also no-existent given the thickness of the turbine's housing and the relatively small diameter of the turbine used in a car. In aviation, they put a Kevlar liner on the inside of the engine pod housing, but that is because the engine walls have to be made as thin and as light as possible for a flight weight powerplant. This is not done for instance in a marine derivative turbine like the LM2500 or the MT30. And it is never done on a centrifugal turbines like the AGT1500 or LV100. Let's put it this way, if you don't have to do it with a turbocharger, you don't have to do it with a turbine. A turbine doesn't turn at significantly (if at all) higher speeds than a turbocharger (80,000~250,000 rpm). A typical turbo that makes about 14.5psi has a pressure ratio of 2 (by definition). The even when lag is not an issue, the limit a single stage compressor can efficiently achieve is a pressure ratio of between 3 to 4 (~ 43.5 to 58 psi absolute pressure). Beyond that you typically fall of the compressor map of even the most advanced and aerodynamically optimized compressors. A General Electric GE90 engine has a high pressure compressor with a 23:1 pressure ratio. A gas turbine with that kind of performance will have a thermal efficiency of about 44% (which is fantastically good). But that is done with 9 stages. We do not and cannot expect that kind of performance in an automotive turbine costing a few thousand dollars. But even with a fraction of that a thermal efficiency of about 25~27% can be achieved using a simple cycle turbine (this is as good as a modern gasoline piston engine). Using a combined cycle (with auxiliary steam turbine) About 35~40% can be expected which beats most of the direct injection turbo diesels.

No, it was a 2 minute job on Photoshop to illustrate how much better the G8 will look without the Nostrils. It is unclear whether the V6 (non-GT) version of the G8 will be without the Nostrils or the rear deck lip spoiler. I certainly hope so because I think the car looks significantly better without them. And if the V6 G8 doesn't have them then it becomes a lot easier (and cheaper) to source a replacement hood and trunk lid without these ugly antics. If you try hard enough you may even be able to find an owner of a V6 G8 on the same exterior color who aspires to the V8 "look", and you can possibly offer to swap hoods and trunk lids with him. If you offer to also pay for all the professional body shop labor to do the swap, it'll be hard for him to refuse.

Just because you have a history of making butt ugly cars that nobody wants to buy doesn't mean you should aspire to that tradition. Sure, I have no problems looking at a Saturn. Unfortunately, there is no Saturn branded Zeta RWD. The only other car more or less confirmed for NA thats based on the Zeta platform is the Camaro... another throw back to the ugly and... uh... best forgotten past. I was hoping that Pontiac would start a new tradition of making sleek, clean, nice looking cars like the G6 (non-GXP) and the Solstice. In this regard I am disappointed. The original Commodore or its luxury siblings the Holden Caprice, Calais and Statesman are all much better looking than the Hippo nostrilled G8. Get rid of the Nostrils and it'll be a much much nicer car. As I have said before... if I ever buy this car, I'll be willing to spend $2000 to get rid of the nostrils. This is a 2 minute job just to illustrate the point...

Well... Pontiac had styling figured out. The G6 was neat and tidy. The Solstice was neat, tidy and beautiful. And then somebody on the team fell in love with her... Sigh...

A few reasons... (1) Because gears are not practical when the driven spool is far away from the driving spool. Eg. with OHC engines you'll need around four gears in series to reach the top of the head. This is why chains are preferred -- chains typically last the lifetime of the engine anyway and are more practical because you can snake them around just like belts. (2) Gears are noisier and so are chains (albeit a little less so). And more importantly they have practically no slop. This is actually bad for the engine. Harmonic dampers are but on the crank pulley for a reason. You don't want to directly couple loads rigidly to the crank or vice versa. Its hard on the accessory and hard on the engine to not have a little "rubber band effect" to cushion the shock loads. (3) Belts are CHEAP. The last time I checked accessory belts costs $5 to $20 a piece at the store. I am sure GM pays less. A gear, chain or gear+chain drive will cost more to manufacture. (4) There have been certain engines with chain and/or gear driven accessories. One example that comes to mind is the somewhat short-lived VW-Audi W8 engine. In this particular engine, I think the A/C compressor was driven via a shaft connected to a gear sprocket on the timing chain at the back of the engine block. This reduces the belt drive for other accessories to ONE thin belt instead of two and allows for tighter packaging.

Nice car overall, but I'll pay $2000 to get rid of those hippopotamus nostrils. Hopefully the V6 car wouldn't have the nostrils so it'll be easy to get a body shop to do a hood swap. Pontiac had it all nice a tight with the G6 and the Solstice. The final G6 GXP was a horrendously ugly thing even though a previous "Orange" rendition was very nice. Now it seems... they want to extend the Nostril stupidity to more cars. Sigh...

Maybe they can put DI on it. It should be relatively easy given that the Pushrod actuated OHV head is much less "crowded" than a DOHC 4-valve design. The pushrods are to one side and the spark goes in on the other side. The DI injector can go straight down through top of the valve cover between the rocker arms. You'll have a kidney shaped chamber with the spark and the injector both nestled between the valves. I think synchronous VVT should be incorporated on the inblock cam since its integration is simple enough. AFM (DOD) should also be on there. If they really want to go overboard, put in a pair of balance shafts in the crankcase on the valley of the Vee driven at twice engine speed. The 90 degree V8, cross plane or not, has residual 2nd order vibrations just like an I4. Quell it and the engine will feel a lot more refined. Another thing to consider is a completely belt free accessory drive. The water pump, alternator and A/C compressor can all be driven via helical gears and/or roller chains in the back of the block. This will make no part replacements for 200,000 miles a reality -- assuming the accessories themselves hold up that is.

This engine looks like it has a beautifully sculpted intake plenum underneath that plastic cover. Looks like a variable resonance intake based on similar principles to that found on the VRIS equipped Mazda K-series V6es (Mazda MX6/Ford Probe) and the Ford Duratec 2.5 DOHC. GM really needs to get rid of the completely stupid cover that they put on it. The 3.6VVT, 2.0 LNF and most of the recent engines have completely moronic dress-up treatments. I mean if you are going to play dress up, do it like the 1998~2005 VW Passat. If you are just going to slap on a black, amorphous piece of plastic that looks like it came off a Rubbermaid trash can, you are better off leaving the engine undressed. This is especially true when you have a nice head and plenum underneath -- which this DI 3.6 HF looks like it has. This is a disgrace. Whats that black cover hiding? I have seen $5 garbage cans with nicer lids. Another stupid garbage can lid which doesn't even fit! This one is just as bad, only its in cheap looking silver plasticinum. Even Hyundai does a MUCH better job at engine bay dress up! If you are not going to do it like this, don't bother. Please!

I think that overall its a good idea to spin off units that are not part of the company's core business. For one thing it will probably make Allison more competitive as they can no longer count on unconditional GM consumption of their products and they have to compete on equal footing with other suppliers in terms of product superiority and value. It is also good for GM because it is not tied down to using Allison transmissions. Instead she should use whatever is the best or which offers the best combination of product strengths and value. In other words, instead of the best from GM, the transmission can and should be the best in the world -- be it Borg Warner, ZF, Allison, Aisin, or whatever. Generally speaking spinning off supporting subsidiaries makes both the parent company and the subsidiary more competitive. This is the strategy pursued by Boeing for instance. One example being the spin of Spirit Aeros ystems. Instead of being a boeing internal division supplying wings and fuselages to the parent company with little competitive incentive, Spirit now has to compete or perish. As a result they have really shaped up and are now the world's leading manufacturer of large Composite structures. Boeing uses them to supply the nose and forward fuselages for the carbon fiber Boeing 787 -- not because they have to, but because they are the best. BTW, Toyota doesn't really do their own transmissions. Toyota by and large uses Aisin Transmissions. But they also occasionally use other suppliers like Getrag and others. Aisin has a close working relationship with Toyota, but it is not a subsidiary and Toyota is not obligated to buy their stuff instead of say ZF boxes or whatever. Hence, Aisin has to try doubly hard to keep Toyota's patronage. Its a good business model. BMW does the same thing too. They use ZFs most of the time, but they also use GM Hydramatics for instance (the X5, X3 and 330xi AWD 6-speeds are, believe it or not, GM 6L80Es). Again, ZF and GM have to compete hard for BMW's business. This puts better products into BMW's hands.

Do you mean the Vortec 4200 DOHC I6? I have always been a big fan of this motor and I see it as a superior alternative to 5~6 liter class V8s in terms of smoothness and refinement. The 4200 currently makes 291 hp with VVT on the exhaust cam, port injection and 10.3:1 compressoion running on 87 octane. This is by far the SMOOTHEST engine in GM's stables. It puts to shame even the 4.6 liter Northstar; revs and sounds like a mid-90s BMW M50 2.5 inline six which is to say fabulously turbine like and velvety smooth. The Vortec 4200 has also given birth to a 2.8 I-4 and 3.5 l-5. These two engines recently got a displacement bump to 2.9 and 3.7 liters respectively. If equipped with dual cam VVT and direct injection, with or without a displacement bump to 4.5 liters, tis "BIG SIX" should be a 375hp class motor. And a car so powered will have an interesting aspect to it that differentiates it from the rest of the pack. The engine really isn't all that tall. Move the overhead intake manifold to the side and use a more car like oil pan and it should fit under the hood of a Zeta/Sigma platform RWD sedans or coupes. The 4200/3500/2800 engines are 93 x 102 mm (bore x stroke). The displacement bumped 3700/2900 engines are 95.5 x 102 mm. If you really want to reduce the displacement and increase its revability, a 95.5 x 74.8 Inline-6 (same stroke length as the 2.8 High Feature in the base CTS) will yield a 3.2 liter engine. It will also lop about a little over an inch off the block's height. Assuming that you adhering to the same piston speed limits of the 4200 (1285 m/min) you'll also have an engine that revs to 8600 rpm with roughly the same stress level. Even at a very modest 65 lb-ft/liter torque yield (~208 lb-ft for a 3.2 which is really extremely conservative), that translates roughly to 337hp @ 8500 rpm.