dwightlooi

Well, the way I see it, ATS-V should be a $45k car because The CTS-V is a $60K car and the ATS-V should slot in below it. The Germans are pricing their "entry" level Uber sedans at $60K to their own detriment -- they were selling more them when they were $40K. $45K is adequate to make a very nice car with very little compromises to quality. The interior and finishing is basically the same costs as the regular ATS, the V8 and uprated brakes and suspension pieces are not going to have a $15K marginal cost. The price point also forces the elimination of things like active diffs, active suspension, active steering, etc. and that is not necessarily a bad thing. The ATS-V as proposed does not sport a supercharger or turbocharger. It is a good old pushrod V8, naturally aspirated and fortified with direct injection, variable timing and cylinder deactivation. It makes 76hp/liter or roughly 5.5% higher specific output than already achieved with the Z06's LS7 V8 -- a rather conservative goal if you ask me considering the addition of direct injection, VVT and a 12.3:1 compression, all of which are features the LS7 does without. 3500 lbs is for the V8 powered ATS-V. The base car with a 2.0 Turbo I4 should be about 3300 lbs. An 8A will not necessarily improve mileage or performance. It'll just have more gears and either have a lower torque rating or be heavier. The reason being the beyond 6 speeds you rapidly reach a point of diminishing returns with ratio optimization, while you incur additional drag from the spinning but disengaged gears. Distilled to the basics, you only want enough ratios and ratio spread to attain the lowest usable cruising RPM (say 1600 @ 60mph in top gear) while having a gearing low enough 1st gear to maximize acceleration and "enough" speeds to keep the engine operating within its prime power band as it shifts its way up. A Hydramatic 6L80's 6.1:1 spread and 6 steps is doing a pretty good job here with the top gear being set as tall as desired, the 1st gear is about where it ought to be. Any lower and you are getting additional wheel spin more than anything else unless you are running gumball slicks. An 8A is not necessarily a bad thing down the road if it is down right, but don't see it as a priority.

The I6 is not without its flaws. The I6 is a VERY long engine; Longer than a V8, almost as long as a V-12. It is also heavy due to the long bottom end. This negatively impacts balance and weight. To get to 50/50 weight distribution, the BMWs have to have the front wheels very far forward of the A-pillars and the battery in the trunk. This is bad for torsional rigidity and adds weight (because the stressed load bearing structure is longer. They also had to tuck the I6 very far back and cannot implement an integral cross member between the front strut towers (ala Audi). That the 3-series is not overly heavy and has good dynamics is a testament to BMW's engineering discipline. But that same discipline will produce a lighter, stiffer and similarly balanced car if a shorter engine is employed. If you concede that GM cannot build a car in the same size and weight as the 2000~2006 C-class (3250 lbs for the C230 to 3500 lbs for the C55) then you are also conceding that GM cannot get within 10 years of the competition in engineering and manufacturing. Based on that assumption, they will not build a competitive car, period. Adding weight and engine power doesn't change that. As far as pricing goes, the CTS-V -- one size class up and fitted with a force fed 6.2 V8 -- is already at $60K. The ATS-V will have to be slotted lower. If the run of the mill ATS is to be priced high-20s to high-30s. The ATS-V should come in at $45K or thereabouts. This will be consistent with the premium that the CTS-V commands over the CTS. It is also a good price point to be at. That was where the E36 M3s were (adjusted for inflation). An ATS-V priced at $45K will under cut the $60K European Uber sport compacts by about $15K. It also returns an Uber compact to the price segment which saw their best sales (the E36 was the best selling M3); a price segment the Europeans had gradually priced themselves out of. Why is $45K the magic number? Because it is what a young 25~35 year old making a decent salary can painfully afford. Any higher and they can't afford it even if they dream of owning one every day through their college and internship years. Once you need to pander to the 40 and 50 year olds with more established careers and financials, you start getting push backs like them wanting a bigger car, wives complaining about the ride, etc. When that happens they start looking at the M5s and the E63s and the CTS-Vs and away from the ATS-V or the AMG C-class or the M3. This is exactly the situation where the Europeans find themselves in. My formula for the ATS-V will be very simple -- Keep it simple, keep it light, keep it small and keep it at $45K. 5.5 liter Gen V DI VVT AFM Pushrod V8 making ~420hp Rear mounted 6-Spd Hydramatic Auto with Helical LSD. Hyper Strut fronts, Multi-link rears, free floating calipers all around. No active steering, no active differentials, no active dampers, no air springs, no active headlamps. No power sun shades, no massage chairs, no air conditioned cushions, no moonroofs. All steel construction, 3500 lbs.

The refinement issue is actually a little more complicated than that. (1) Power Pulse Frequency -- For any given displacement, an engine with more cylinders fire more frequently and in smaller installments than a engine with fewer cylinders. However, this is actually a relatively minor contributor to engine refinement. Just look at it this way. Does your engine feel much "smoother" at 3000 rpm vs 2000 rpm, or 1500 rpm vs 1000 rpm? Because that is exactly the pulse proximity improvement you'll see when you go from a four to a six. (2) Balance -- A bigger contributor to refinement is engine balance. Reciprocating engines have a tendency to have a dynamically shifting center of gravity in operation. This causes the engine to shake. This shake, if not absorbed by the engine mounts ultimately transmits to the vibrations you can feel while driving the car and gives an impression of crudeness. Here, more cylinders is not always better. In fact, vibrations have nothing to do with cylinder count but rather the engine configuration. Horizontally opposed engines, the I6 and the V12 are the only naturally balanced layouts. Everything else vibrates* The magnitude of the vibration gets worse as engine displacement (actually mostly engine stroke) increases. The key here is how it is dealt with. Smaller I4s (up to 1.8 liters) generally do not employ balancers because the the vibrations aren't too bad, most 2.2 and 2.4 engines use contra-rotating (lancester) balancers at twice the engine speed and can achieve near perfect balance. A 2 liter usually don't need balancers, but some of them -- including the GM 2.0T -- have them. A V6 is a different story. A 90 deg six uses a single balancer at crank speed but in the opposite direction. A 60 degree six usually does not because its vibration characteristics are not as bad as the 90 deg engine and because there is usually no room in the narrow Vee for a balance shaft. At the end of the day, many 60 degree V6es of larger displacements (eg 3.5~4.0 liters) can actually have worse vibrations than a 2.0 liter with balance shafts (like the LNF) and be roughly equivalent to a balancer equipped 2.4 liter I4 residual vibes. (3) Block and accessory noise -- An engine block flexes and vibrates as it is stressed by the combustion pulses. Accessories and their serpentine drives make noise and shakes of their own. These affect the overal refinement of an engine, but has nothing to do with the engine layout or cylinder count. At the end of the day, a good 4-potter of 2-liters can actually be more refined than many sixes out there, especially the bigger ones. The LNF (2.0T) is plenty refined, the Mitsubishi 4G63 (2nd Gen Eclipse GS-T/GS-X) is buttery smooth. Personally I feel that the LNF engine in the Solstice GXP is smoother than the 3.6 in the Malibu when I drove them back to back. * A 1-cylinder has significant 1st order up-down vibrations. A three has a 1st order end-to-end rock. A four becomes 1st order balanced thanks to an equivalent number of pistons going up and down, but picks up 2nd order up down shake because the acceleration of the pistons going up and those coming down are not equal except at mid stroke. A V6 picks up the three cylinders end to end rock again -- 60 deg sixes being milder than 90 deg ones. A V8 has again end to end rock. The key here is how you deal with it. In a 4-cylinder, contra rotating balancers at twice the engine speed can achieve near perfect balance. In a V8, a cross plane crank can mitigate vibrations through the use of heavy counterweights. In a 90 deg V6, a single balancer a crank speed can do the same. A 60 deg six usually do not employ a balancer because the vibrations are relatively mild. As far as power goes, I think 290 hp 2.0T ATS is plenty good enough, especially if they can keep the weight to around 3300 lbs. You don't have to beat the 335i. For those with the budget and inclination for a 335 or an M3, the salesman can always direct him to the ATS-V with its 420+ horsepower small block V8 -- which ought to be in the $40K bracket and right in line with a 335 while offering 2 more cylinders and about 100 more horses.

I will whole heartedly support a mainstream ATS strategy based solely on a 2.0T four potter. Personally, I'll prefer it over a V6 3.0. I really don't want the costs and logistics expanded to offer both an I4 and a V6. Both engines can make approximately 270hp, but the turbo four will make more torque than the V6 and be slightly more economical. The downside is a slight lag in throttle response and a moderate loss of linearity (especially at part throttle). How about the following engine lineup? ATS 2.0T - 2.0 DI-VVT Turbo DOHC I4 - 220hp @ 5300 rpm / 258 lb-ft @ 2000 rpm / 6200 rpm Fuel cut - 6L45 6-spd Automatic ATS 2.0T - 2.0 DI-VVT Turbo DOHC I4 - 290 hp @ 5200 rpm / 325 lb-ft @ 3600 rpm - 6L50 6-spd Automatic ATS-V] - 5.5 DI-VVT AFM Pushrod V8 - 420hp @ 6300 rpm / 412 lb-ft @ 4800 rpm - 6L80 6-spd Automatic ATS 1.9TD - 1.9 DI-VVT Turbo DOHC I4 - 170 hp @ 4200 rpm / 258 lb-ft @ 1800 rpm - 6L45 6-spd Automatic (EU Only)

Actually, a better comparison would be a Camaro SS 16/25 with the 6.2 V8 and 6-spd Auto. The Camaro is ~500 lbs lighter, but it also makes do without the Ecoboost engine's direct injection system. The SHO is essentially FWD until the wheels slip and the haldex clutch engages the rear differential and wheels. Another example that lower displacement and cylinder count does not automatically translate to better economy is the W203 2000~2006 Mercedes C-Class AMG cars. The C32 AMG was 14/19 using a 349hp 3.2 liter Supercharged V6. The C55 AMG was 16/22 using a 5.5 liter (5.439 actually) 362hp SOHC-3v V8. Both cars use a 5-spd auto and weigh within 40 lbs of each other. The latter car gets between 17.5 and 19.5 in my daily driving.

A few minor issues here and there. The assumption is that by 2012 they'll be taken care of. The basic premise though is that with two turbocompressions, additional plumbing and an air-to-water aftercooler circuit there are more things on the TT V6 to go wrong with than with the NA V8. Power from both engines are equal. The V6 probably has more torque area under the curve. The V8 is simpler, cheaper, lighter and has more "character". Fuel economy is going to be pretty close -- the DOHC valve train, back pressure from the turbos, reduced compression and increased weights on the V6 hurts economy, but it makes up for it in having two less cylinder walls and a smaller displaced volume. In the end, contemporary engines point to a 1 mpg advantage to a 3.5 liter class TT V6 vs a 6 liter class Pushrod V8 in the urban cycle, and a draw in the extra-urban cycle.

The Identity issue goes both ways. A TT 3.6 puts it in the same class as the BMW, Nissan and Ford TT sixes. That's both a good thing and a bad thing. It is a good thing in that there is certainly certain demographics of the car buying public which subcribe to the Turbo DOHC = sophisticated + refined school of thought. A TT 3.6 hence will win their favor. The flip side is that from a product differentiation standpoint you end up with a less differentiated product because it is "yet another DOHC twin turbo". The product is less unique and less desired by people who either want a more "special" car or simply subscribe to the American V8 traditions.

Actually, I feel that while it is easy to get giddy with horsepower the appropriate positioning of the V-series ought to be:- ATS-V: 420hp / 3500 lbs / compact - 3.6 V6 TT or 5.5 V8 CTS-V: 550hp / 4200 lbs / mid-size - 5.5 V8 Supercharged or turbocharged As far as the C63 is concerned, that is a 3900 lbs car and exactly what the ATS-V should beat it terms of weight. Shooting for 3500 lbs with a pushrod V8 or TT V6 is not unrealistic. It'll put the vehicle in the same size and weight class as the previous (W203) C55 AMG. 420hp in a 3500 lbs car is roughly equivalent to 468hp from a 3900 pounder -- I'll say it is "competitive". Besides, it'll be easier to make a 3500 pounder handle well. I won't consider a 420hp 3.6 twin turbo V6 "topped out". A topped out DI Turbo will make around 150hp/liter or about 540hp for a 3.6 liter powerplant. That's what the Japanese market WRX STis and Lancer Evolutions do. At 116 bhp/liter for 420hp, we are shooting for an engine that has very minimal turbo lag and better response than the 260hp 130hp/liter 2.0T (LNF). 116hp can be done with undersized turbos with very fast spool times and with moderately high compression ratios for improved cruise economy.

SIDE NOTE: The two engine proposals are intended to represent two directions Cadillac can take... Join the bandwagon of the force induced DOHC sixes (eg. Audi 3.0 Supercharged DI V6, BMW turbo straight sixes, Ford Ecoboost 3.5, etc.) Carve out a unique identity with the American tradition of big displacement, push rod V8 albeit one loaded with contemporary technologies. The output will be roughly equal. In this case it is set at 420bhp, which gives the ATS-V a power to weight ratio superior to the C63 or M3 and in the same class as the Nissan GTR. The Turbo V6 has a slight (city) fuel economy advantage. It also has the advantage of incurring lower taxes in countries where new cars are taxed based on the displacement of the engine. The V8 is lower in costs, complexity and weight. It also has the advantage of providing a more direct response due to the absence of turbine induced lag. The pushrod 5.5 V8 and DOHC 3.6 V6 are roughly equivalent in the weight and size of the engine itself. The additional mass (est. 80 lbs) of the V6 setup comes from the two turbochargers, their manifolds, their plumbing, the air-to-water aftercooler, the water-to-air coolant radiator and the associated pumps and accessories.

BTW, the redlines are not the maximum engine speed. That's the fuel cut speed. The redlines are the basically the indicated shift points. When the transmission is being shifted by the driver via paddles or switches on the steering wheel, a shift light comes on at the "redline" indicating that shifting should be inititated then or shortly thereafter for maximum acceleration performance. This should be the purpose of a "redline". The common, but misguided, practice of using the redline to indicate rev limit is flawed because when you bump the rev limiter, it is too late to do anything about it!

Answers:- (1) Turbocharged engines using torque computing electronic boost control generally have a torque plateau as opposed to torque peak. Basically, the torque limit is reached and held until the ECU determines that boost should be reduced gradually to keep the turbocharges "on map" and prevent over spinning them to an early death. (2) The low red line on the 3.6 TT is because there is little to be had from reving beyond 6000 rpm or so. The GT20 series turbo are sized to generate boost fast and early, they start to run against rpm and efficiency limits in the 5000+ rpm range. It is very much like winding an LNF (2.0T) beyond the mid-5000 rpm range simply makes noise and slows down the acceleration times of the car. The transmission will probably shift at 5600~5800 rpm for best acceleration, allowing the motor to wind to 6800 rpm is moot. The unfortunate reality of single stage compressors -- even ones with very modern aerodyanmics -- is that they can keep only about 3000 rpm worth of torque plateau at moderate boost levels (eg. 12 psi). You can size them up to get them to do this through say 3200~6200 rpm, but that costs your lag time and efficiency at low loads. (3) The LS3 makes its peak power and torque at 5900 rpm and 4600 rpm respectively. A de-stroked version displacing 5.5 liters with the same bore with make power slightly higher in the rev range -- hence 6200 and 4800 rpm. This is a reality of the physics of moving air. Same bore + shorter stroke = same amount of air pumping at higher rpms. Direct injection does not change the amount of air you move with each intake stroke. (4) Both engines run on premium to maximize output. The understanding is that anyone forking out cash for a 400+ hp compact sport sedan isn't exactly looking for the lowest fuel tab.

You may assume that the Twin Turbo V6 is ~80 lbs heavier and ~$2500 more costly. Fuel Economy numbers assume a 3,500 lbs curb weight & Hydramatic 6L80 6-speed automatic transmission.

My take of CAFE is to simply ignore it. Let me explain... I am not against fuel efficiency. It is prudent to have fuel sipping offerings in a manufacturers line up in case fuel prices sky rocket and consumers flock to such vehicles as a 3~4 year development cycle is too long for an adjust on demand strategy. Having said that, the market should be the mechanism that decides what vehicles are built and in what numbers, not ideologues in Washington DC or some one's theory on "corporate social responsibility". The way the CAFE law is written, there is nothing preventing automakers from completely ignoring it and still manufacture and sell cars. All it stipulates is a $5.50 penalty per 0.1 mpg per car manufactured if the manufacture does not meet CAFE standards. Let's put that into perspective... Let's say the CAFE standard is 36 mpg. And you come up short at a 31 mpg (GM is currently at 31.3 BTW, Ford is at 31.1). What this means is that every car hitting the showrooms will carry a (36-31) x 10 x 5.50 = $275 CAFE "tax". That's all there is to it. Now, what I recommend is that a manufacturer should have a full range of vehicles -- all designed to what they believe each segment of consumers want based on their best market research and understanding. They should then manufacture the vehicles in numbers, again, based solely on consumer demand. As for CAFE? They should let it fall where it may. However, to be fair, I'll amortize the entire CAFE tab only on those vehicles over CAFE mpg ratings. Beyond that, let's allow the market to decide. If you are a Global Warming coolaid drinker, prefer fuel economy over performance or if that couple of hundred dollars make or break your buying decision, buy the cars under CAFE ratings with no surcharge. If you want that Corvette or Tahoe? Well, they are there for you at a few hundred dollars more courtesy of Congress (and clearly marked as such on the sticker). What an automobile manufacturer shouldn't be doing is making cars around the artificial CAFE standard -- performance cars that don't perform as well as they otherwise would, big SUVs that isn't as big as their buyers prefer, trucks that don't tow as much as their owners want, family cars with engines less refined due to reduced cylinder count, or saddle every buyer with "green technology" which they don't care for and don't want to pay for. They should also not gate production volume of various models to meet CAFE and end up with under supplying certain models and oversupplying others (which then leads to an unhealthy combination of heavy premiums and generous discounting). I say the above based on the following premise:- It is perfectly legal to ignore CAFE. The CAFE penalty is small compared to the selling price of vehicles. It may cost more to meet CAFE that pass on the penalty. It is fundamentally unhealthy to the bottom line to meet the ideologies of the political class rather than market demands.

Depends on how the power outtake is done. This would be true if it is a thrust generator + power turbine setup. That is the gas turbine provides jet exhaust thrust against a separate power turbine connected to the output shaft. The turbine can operate at maximum power and speed, while the power turbine is stalled and stationary. This also allows the output shaft speed to be decoupled from the turbine's operating speed. However, it will not be true if the power outtake is directly from the main spool or low pressure spool. In the former instance, if you stall the output shaft the turbine stops and you make no power. In the latter case, you stall the low pressure compressor and it greatly diminishes the output and efficiency of the turbine. Using a power turbine is more flexible, but using a direct drive setup can be more efficient. In large marine engines for instance, the General Electric LM2500 is a power turbine setup. Their larger (57,600hp) LM6000 is direct drive.

Well, you are talking about a direct drive, simple cycle turbine. Recuperated turbines respond more slowly. The recurperator is a big heat exchanger. The exhaust is used to heat the recuperator before exiting the engine. The recuperator transfer's the heat to the high pressure compressor output before it is introduced to the combustion chamber. This way you recapture a good portion of the heat otherwise wasted in the exhaust. A simple cycle gas turbine with 2 centrifugal stages typically gets to about 25~30% thermal efficiency. Adding a recuperator raises that to the 30~40% range. Complexities aside, the recuperator is also voluminous device. This means that the compressor has to pressurize a much bigger air volume in the recuperator instead of just the minute little air space between the compressor outlet and the combustor. Imagine inserting an intercooler the size of a room between a turbocharger and the intake manifold and you'll get the idea; the turbo will take a long time to pressurize this volume before the engine sees a boost pressure and subsequent power increase. This reduces throttle response. That said, throttle response is completely irrelevant however in stationary power generation or in a turbo electric setup since instantaneous power delivery is provided not by the turbine but by a separate electric motor drawing from stored electrical energy in the batteries. As far as costs are concerned, yes, the materials and high temp alloys used in turbines are more expensive than the metals used in a piston engine. But the turbine is also much less complex, so once the industrial base for volume production develops it is unlikely to be more expensive. Simplicity also means reliability and reduced maintenance. In the aviation world, aircrafts used to be powered by inline and radial piston engines with 4 to 24 cylinders outfitted with a a plethora of overhead or sleeve valves. The advent of jet propulsion dramatically increased dispatch reliability and reduced maintenance requirements. For the most parts, aircrafts now fly 1 hour turn arounds day after day with nearly no maintenance on the engines except for toping off the Mobil Jet Oil II reservoirs. The engines endures daily use for 15000 hours between scheduled overhauls. This is about 3000 cross country flights. And this is because avaiation regulations stipulate rated time between refurbishments. In automotive applications, people usually drive the car until it breaks before doing an engine rebuild.

If you are going turbo-electric you may want to ditch the piston engine completely. A dual spool gas turbine has only two moving parts, no coolant loop, no radiator, no valves, no cams, no rods, no reciprocating parts, no vibrations. A simple cycle 150hp unit is about the size of a 100pcs stack of CDs. Add a recuperator and it's that plus the equivalent of an intercooler. It produces a thermal efficiency between 30~40% at optimal speeds, which is as good as the best diesels. It burns gasoline, ethanol, diesel or all of the above at the flick of a FADEC switch. A turbine is not without it's problems. It takes almost a minute to start up, it takes about as much time to go from idle to full power as a car typically takes to go from 0-60 mph and efficiency falls off quite dramatically as you deviate from its optimal operating speed. In addition, because the operating speeds are pretty darn high (approximately 60,000~120,000 rpms) the gearbox to take it down to wheel speeds will be extremely challenging. However, none of that matters, not if your final drive is electric. You'll simply connect it to a high speed generator and run it at optimal speeds or not at all. Excess power is buffered in a battery, ultra capacitors or both. And, you'll simply parcel it out to throttle request via an electric motor. Generation loss is about 5~10%, motor loss is another 10~15%. That's about the same as a typical mechancial transmissions used in today's cars.

No, a Cadillac should be designed to a standard of excellence, not a cost ceiling. However, designing an engine to be costly and complex for the sake of being being costly and complex achieves nothing. The CTS-V has a blown V8 of the same approximate displacement as the E63 AMG's (6162 vs 6208cc). A supercharger incurs parasitic losses to drive. More importantly, the E63 has a 7-speed automatic transmission (one speed more than the CTS-V) which has ditched the torque converter in favor of an automated clutch pack. Just think of it as an SMG with planetary gearsets. If you compare a normally aspirated Pushrod engine with a normally aspirated DOHC powerplant of a similar output with similar transmissions, aerodynamics and vehicular weights, you'll find that the Pushrod engine delivers better fuel economy. A good example will be the Camaro SS vs the C63. The cars are of a similar weights, deliver within 50hp of each other and both pack automatic tranmissions. While the C63 has 7-speeds vs the Camaro's 6-speed, it still has a conventional torque converter unlike the E63 and SLS. In fact, the Camaro beats out the lighter and smaller displacement C55 AMG (which I own). Camaro SS -- 6162 cc - 6-speed Auto - 400hp @ 5900 - 410lb-ft @ 4300 - 3860 lbs - 16/25 MPG C63 AMG ---- 6204 cc - 7-speed Auto - 451hp @ 6800 - 443lb-ft @ 5250 - 3924 lbs - 12/19 MPG C55 AMG ---- 5439 cc - 5-speed Auto - 362hp @ 5750 - 376lb-ft @ 4000 - 3580 lbs - 16/22 MPG* * (Pre-2008 EPA rating; approx 15/20 under new testing program) As you can see, the Pushrod powered car not only has a fuel economy advantage, it is a SIGNIFICANT one. In case you are wondering, the Corvette does a mere 1mpg better than the Camaro when outfitted with the 6.2liter V8 engine (16/26). And, if you up the ante to the Z06 with 7.0 liters, 505hp and more aggressive gearing, the numbers drop to 15/24mpg.

It matters because space in under the hood not taken up by the engine can be used to house a more efficient intake system, or you can have a lower hood line. Also, if a Pushrod engine is cheaper, lighter and more fuel efficient than a DOHC engine of equivalent power output, why do you want a DOHC engine? The ONLY reasonable justification is the real or perceived civility advantageous, and that has been quite thoroughly discussed elsewhere in this thread.

Rule changes dictate a lot of stuff in ALMS. Basically, DI is forbidden for another season, so they had to take it out.

I don't know if it is finished. But, even if it is, there is a huge chasm of investment difference between building an engine and vesting it for mass production. Creating a one off prototype or even a race engine is one thing. Getting it through qualification and investing in the tooling for mass production is another. Personally, I won't try to build a DOHC V8. Instead, I think GM will be best served with DOHC I4s, DOHC V6es and Pushrod V8s -- all fortified with VVT and DI. I4s for displacement sensitive markets and simple single-turbo solutions. DOHC V6es for mainstream luxury. Pushrod V8s for maximum power density applications -- sport luxury and other performance cars. DOHC V8s are a waste of resources because it offers neither better performance, nor better economy, nor differentiation from the competition.

You can, but it usually does not amount to an optimized design. In particular, the cam drive section will be kinda messy. You'll probably end up with having to use an intermediate sprocket in the SBC's location. You then have try to enclose the rest of the chain drive to the heads or resort to belts. Given that the most complex and costly parts an engine design effort is in the heads and combustion control systems, the very act of reusing the block casting may not be worthwhile from a savings standpoint.

Thanks for the clarification. I use the term loosely because it has become synonymous in popular usage to refer to the 111.76 bore center GM pushrods of yore and contemporary times. But, yes, you are right.

The Northstar is not a Small Block to begin with. In general, the term "Small Block" applies to GM Pushrod V8 engines with an 111.76 bore center spacing. The Northstar is 102mm. Despite the ~10mm narrower spacing, the Northstar is a longer, wider, taller engine which weighs more than the Small Blocks due to it's DOHC design. It also has worse reliability record, especially with head bolts that pull off causing the gaskets to fail. IMHO, I don't think the Northstar will be missed.

Collectively, the contemporary Small Blocks are called the "Gen IV" Small Block V8s. The LS series RPO is part of the Gen IV Small Block family, but the Gen IV includes more than the LS engines. They include:- LS-series (cars): LS1, LS2, LS3, LS4, LS6, LS7, LS9, LSA, etc. L + "Not S" + Number series (branded Vortec; for trucks): L96, LY6, LZ1, L20, LC9, LH9, LMF, LMG, L94, L9H, etc. A few stragglers without "LS" RPO, but used in cars: L76, L99 Point of Note: All the RPOs in Red has VVT. As you can see, ALL of the truck engines -- the Vortecs -- have VVT. However, only one car engine (the L99) used in the Camaro SS has VVT. If you ask me, that's WAY TOO MANY V8s (and we haven't counted the Northstars yet), I'll like to see the variants cut down to one architecture, two displacements and maybe four variants in all. Perhaps these (all sharing the 103.25mm bore, but with either 82 or 92 mm strokes):- 5.5 (420~432 hp, power optimized; DI/VVT/AFM) for performance cars 5.5 (550~580 hp, Supercharged; DI/VVT) for really fast cars 5.5 (375~385hp, torque optimized; DI/VVT/AFM) for big trucks 6.2 (425~435hp, torque optimized; DI/VVT/AFM for bigger trucks

Yes, there were concepts of an over-under Dual In-Block Cam arrangement. The idea is to separate intake and exhaust valve control into two discrete camshafts. This involves a mess of pushrods and rockers at two different angles, but it permits dual independent VVT. Personally, I am not impressed with the idea. It'll be much simpler and neater to simply use co-axial camshafts to achieve Dual VVT. Actually, this has already been implemented in the 2008+ Dodge Viper.