dwightlooi

180hp from a 2.0 is nice enough... especially when it is done on 87 Octane. Besides, making 180hp in a 4-pot 2.0L does not involve a lot of extreme stuff. Just copy the combustion chamber, valve sizing and intake ports of the LF1 3.0 V6 (270hp) and you should be right there with 90hp/liter. If anything a four will get slightly better numbers since it does not have to make compromises to fit the intake runners in the narrow V of a 60 deg V6. Also, exhaust tuning is easier on an I4 with all the exhaust ports lined up on one side, vs in a V6 where it is split on two sides and usually with a lousy 3-into-1 collector casting. Historically, given the same technological content and features I4s have always beaten V6es on specific output by a little bit.

BAS is also 36v and about 5hp. But, the BAS -- by definition -- is attached to the accessory pulley with a fat belt. BAS is also NiMH based. NiMH has a 1.2v nominal cell voltage. 30 cells (or a multiple of 30 cells) make up a 36v pack. I was proposing getting rid of the accessory belt altogether, using a flywheel that doubles as the generator motor and all electric accessories. For the battery, I am suggest Lithium-Iron-Phosphate* for its superior charge-discharge cycle advantageous. LiFePO4 is also 3.3 volts nominal, requiring only 11 cells to be 36.3v, simplify battery complexity and costs. * Lithium-Ion batteries actually come in many flavors. Lithium Cobalt Oxide being the most common and most developed. Iron Phosphate has a energy density (~0.50kW.H/kg) in the mid-range of the seven or eight Lithium Ion battery chemistries -- about 54% that of the cutting edge Li-Ion (0.92kWH/kg) batteries. However, it's charge-discharge cycle endurance is about twice as good as the average Li-Ion battery and it is still heck of a lot better than Lead Acid (~0.04kWH/kg).

(1) Not really, HCCI is probably bracketed by engine speed, load and the cam lobe profile. A cam lobe profile which creates the right conditions for HCCI operation at a certain engine speed and load conditions would probably limit the engine to a certain rpm band centered around that condition. Basically, what you want is a particular combination of fuel-air ratio and effective compression so as to achieve engine "knock" at or very near top dead center. The combination of fuel-air ratio, pressure and temperature causes spontaneous ignition, but only if the charge stays at or beyond that threshold for a sufficient period of time. If the engine rpm is too fast, the piston may outrun the knock event and get past TDC before it happens; once temperature and pressure starts to fall, spontaneous ignition may never get to happen. If the engine rpm is too low, the knock event may happen way before TDC and you get highly unhealthy and noisy detonation. (2) The problem with Hybrids is that the cost-benefit ratio simply does not make economic sense. If you go beyond 3~5hp, or if you want to use the integrated generator/motor for actual engine assist, you end up needing a high voltage, high capacity battery which is bulky, heavy and expensive. The power control module then also needs to be the size of a suitcase and the motor tends to get heavy and expensive. The idea is to avoid all that and make the mildest hybrid possible, but make it STANDARD. Let's put things into perspective:- Toyota Prius -- 80 hp Parallel Motor -- 201.6 volts, NiMH battery (~100 lbs w/o encasement) Honda Civic Hybrid -- 20hp IMA -- 158 volt, NiMH, 68 lbs battery (68 lbs w/o encasement) Proposed System -- ~5hp Flywheel Generator/Motor -- 36.3v, LiFePO4 battery (~25 lbs w/o encasement)* * 25 lbs is no more than the weight of the larger size Lead-Acid batteries. The target system weight would be 60 lbs or roughly 1/3 that of the current Civic Hybrid's system weight. The system will provide engine stop at idle and attempts to recharge with regenerative charging during braking as much as possible. It will provide sufficient power for an ensemble of all electric HVAC, cooling fan and steering assist. It will not attempt to provide acceleration assist because the gains against the back drop of a 180~200hp engine is minimal, thus it is better to shoot for reduced battery size and an extended battery life.

(1) HCCI will be limited to relatively narrow set of operating conditions. Right now, the 2.2 HCCI experimental engine can do it at idle through 60mph at part throttle. The engine employs a cam switching system (ala VTEC), Dual variable cam phasing, Direct Injection and a centrally located injector. It gets a 15% better fuel economy improvement over a spark ignition 2.2 liter, at a lower cost and weight penalty compared to a hybrid. Personally, I don't think HCCI functionality at idle is important, neither is HCCI functionality at low speed acceleration situations. The reason being the best fuel economy at idle can achieved relatively easily by shutting off the engine. With a simple flywheel integrated generator/motor (say a modest 5hp unit) that is exactly what we can do. When you are putting around in city traffic from 0~35mph you'll often use more throttle than would be feasible for HCCI anyway, so even if it can work at those speeds it most frequently won't. Therefore, I suggested that HCCI be focused on highway cruising efficiency and an engine shutoff feature be used to improve city numbers. (2) I was suggesting commonality between the V6 and the I4 families. This cannot be implemented on the really small 4-potters. The Family Zero is OK for now anyway. Add Direct Injection and an Aluminum Block and you have your next generation. Yes, it'll definitely be a new block.

Well, two things work against the business case for "advanced" Pushrod V6es... The investment in DOHC V6es have already been made (not just in R&D, but also in production and logistics). Abandoning the architecture and starting over will be very expensive in terms of startup costs. Unlike V8s which serve the top tier luxury and performance segments, specific output matters significantly more with mainstream sixes in the 3.0~3.6 liter class. The reason being that many countries still tax cars based on displacement. Even if your 4.0 liter V6 is smaller, lighter, more powerful and more fuel efficient than a competing 3.2 liter product, many countries will still tax it more (sometimes significantly more). While high end luxury and performance buyers are quite tolerant of a few grand in extra taxes, mainstream buyers are not. Instead of Pushrod V6es, I'll rather see GM invest in completely redoing for a ground up family of Direct Injection Ecotec Fours. There are two things which I believe will put GM on top of the 4-cylinder game and these need a complete revamp of the 4-cylinder architecture. Implement a new 4-pot architecture which shares the bore size, piston, connecting rods, lifters, cam followers, valves, guides and springs with the 3.0 and 3.6 liter V6es. This means 89.0 x 80.3 mm and 94 x 85.6 mm for the 2.0 liter and 2.4 liter fours respectively. The slight oversquare design improves engine refinement and raises specific output by reducing piston speeds and increasing valve area to displacement ratios. More importantly, it lowers production costs and make it easier to share future technologies between the V6 and I4 families. Implement HCCI and a beltless accessory drive. HCCI gives a significant improvement in fuel economy and offers GM the claim to being "first" on what I believe is the next significant trend in the evolution of the internal combustion engine. I wouldn't even try to make HCCI operate over a wide range of conditions -- it only has to operate at 55~75 mph at 33% throttle or less. This will be adequate to earn a fantastic EPA highway economy rating, and that is sufficient (for now). The second thing will be to get rid of the accessory belt -- this is the last huddle towards the "No scheduled maintenance for 300,000 miles" engine. The waterpump can be driven by the cam chain, the alternator can be an integrated flywheel generator/motor, power steering can be (and is already) electric and the A/C Compressor can be electric. The flywheel generator/motor also makes it easy to make automatic traffic light engine shutoff a standard feature earning a couple of EPA City economy points. With no improvement over their V6 siblings, the new Gen III Ecotecs should make:- Ecotec 2.0 (Gen III) -- 180 bhp @ 7000 rpm, 149 lb-ft @ 5200 rpm, 7200 rpm Redline, 87 Oct Ecotec 2.4 (Gen III) -- 202 bhp @ 6400 rpm, 182 lb-ft @ 4000 rpm, 6500 rpm Redline, 87 Oct Ecotec 2.0T (Gen III) -- 300 bhp @ 6000 rpm, 270 lb-ft @ 2800~5800 rpm, 6500 rpm Redline, 91 Oct

Two things... (1) As long as you don't try to make an engine rev past what the valve spring tension and valvetrain mass combo is suited to handle, there is essentially no refinement difference attributable a pushrod or DOHC valve train. Ultimately, the DOHC powerplant may redline higher, but they should be similarly refined at their respective redlines. (2) Actually they have incorporated VVT and Cylinder Deactivation on the 6.2 small block. That engine is called the L99. It is tuned to produce a broader torque curve and slightly better fuel economy at the expense of peak power. The L99 makes 400hp and 410 lbft of torque; 26 hp and 14 lb-ft less than the LS3. However, its torque peak arrives 500rpm earlier and it gets 1 mpg better fel economy. This is the standard engine in the Automatic Transmission equipped Camaro SS. As far as direct inject is concerned, it has been successfully tested on a modified L92 6.2 liter small block in 2007. Compression was increased from 10.5:1 to 11.5:1 in the test engine. Power increased from 403hp to over 450hp. The engine was put through its paces in an Escalade and proved to be fully functional and mature. Direct Injection is now slated to be introduced with the Gen V small block slated to appear this year or in 2011. A racing version of the new DI small block displacing 5.5 liters will campaign in GT2 class racing this year in the C6-R Corvette. The Gen V small block will feature a new block design with the camshaft raised to a significantly higher position in the valley of the engine. This shortens, lightens and stiffens the pushrods, as well as improving the valve angle by changing the angle of the rods in relation to the heads. In a separate discussion elsewhere, I predicted an output of 432hp for this 5.5 liter engine. In time, I guess we'll see how accurate I was in that prediction.

Cadillac needs a V8 in the 400~450hp class. The engine should be as small, as light and as economical on fuel as possible. It should also have state of the art features like direct injection, variable timing and cylinder deactivation. The question is, why shouldn't it be a big displacement Pushrod V8 with these features instead of a (relatively) smaller displacement DOHC V8? Why shouldn't it be the smaller, lighter engine that gets more miles per gallon, which also happens to fall inline with a uniquely American tradition?

Well, I think they were trying to get better economy numbers than the typical V6 while offering V8 power. A V8, pushrod or otherwise, has lower economy numbers than the 3.6 V6. Perhaps, there is also the idea that 350+hp is "enough" since they obviously aren't going for maximum performance here. Personally, though, I am not big on the two-mode hybrid system. The thing about hybrid drive trains is that you rapidly reach a point of diminishing returns in terms of cost benefit ratios. The value proposition of hybrids are dubious to begin with since it takes an average driver 8~13 years just to break even on the price premium of a hybrid drive train. Instead, I believe that a good strategy would be to adopt a hybridization for handling and performance enhancement. The system will be more than a mild hybrid but doesn't go as far as to carry a heavy battery and enough electric propulsion power to move the car on electric power alone. Instead, the system will focus on using the electric propulsion system to improve handling. I'll do this with a differential motor -- two 20hp motors coupled to the rear differential. Each capable of helping accelerate or brake each rear wheel separately. An electric active differential if you will. A 2kWH battery would be enough to operate such a device. This way, both the tree huggers and enthusiasts and embrace the car.

I tend to disagree on that. I think we need to break the causes of "strained" down to two separate factors which really have nothing to do with each other. (1) The first being the onset valve float. This happens at an engine speed beyond which the valve springs can no longer move the valves fast enough to close them at the same rate as the intake cam lobe's trailing edge. What happens then is that the lifters become separated from the cam lobes as the lobes pass under them and then shortly thereafter slaps onto the base circle. This is not only an acoustic issue it also a durability issue as the impacts wears out the valvetrain in relatively short order. In general engines are designed not to have valve float or only extremely minute amounts of it right at with very limits of rev limits. This applies to all engines, OHC or Pushrod. The only difference being that for a given amount of spring tension, it occurs soon on pushrods than on DOHC designs. You can always increase spring tensions and the problem will go away, but this increases startup wear (which accounts for the majority of engine wear) and decreases fuel economy due to increased valve train friction. In otherwords, regardless of valvetrain layout you are not going to see a lot of float related noise. The redline rpm of the engine may be higher or lower due to the limitations imposed by the onset valve float on a particular valvetrain layout, but the amount of float related noise at that rpm is unlikely to be very different. In fact, if the designers are conservative, there won't be any and the redline will simply fall another 200~300 rpms to make sure of that. (2) The second factor for strained is engine vibrations. I4s have 2nd order up-down vibrations. V6es have end to end shake (worse on 90 deg sixes than on 60s). I6es and H engines are naturally balanced. V8s have end to end shake, but less than V6es due to the ability to use heavier counterweights. Vibrations get worse not with rpms per say, but with piston speed. So, it really is more a function of stroke length than displacement. Again, this affects engines univerally irrespective of valvetrain design. IMHO, GM engines of yore were redlined at rather low rpms because the cylinder heads and intakes of the time didn't flow enough air to benefit from higher rpm limits. An L98 makes its maximum 200~240hp at 4000 rpms. Even if you let the engine rev to 6000 rpm, you are not going to get anything out of it. The engines also had rather crude acoustics mainly due to poor tolerances and lack of component stiffness. This is not the case today. At 6000~6400 rpms, the LS3 in the Camaro SS did not rattle or sound more sloppy than a Mercedes M113 5.5 liter in the C55 AMG at the same revolutions. Not that either sounds as silky as a Lexus 4.6 at the redline, but they are both bigger engines with possibly less sound insulation and/or mount damping.

OK... since there seems to be a lot of people calling for a DOHC V8 from the General. Let's set all the cost issues aside and compare what a DOHC V8 and a Pushrod V8 may look like from the general. Please consider the specifications and tell us why you think one is better than the other. Or, if you disagree with my estimates and numbers feel free to challenge them with your reasoning's.

There is two catches in all of this... (1) The heavier actuated mass in an SIBC design limits maximum rpm and the smaller relative valve area limits airflow potential. However, the pushrod design is adequate for handling the rev limits of most production car engines (6600~7000 rpm). And, there airflow advantages of a DOHC design is typically not realized below about 6000 rpm or so. Hence, when you compare a pushrod design a DOHC design redlined at 6000~7000 rpm with power peaks coming in the 5500~6500 rpm range, the advantages of a DOHC valve train is minimal. (2) None of the above matters at cruise, because no matter how well or poorly the engine flows air, the restriction is the throttle body. So no matter how well the engine flows air, the pumping losses governed really by trying to move a given volume of air against the restriction of the throttle body. This in fact is one of the major reasons why diesels are so much more efficient. Diesels don't have a throttle body, the flow the maximum amount of air the engine can suck in at a given rpm all the time. Diesels control power simply by metering fuel -- running very lean at cruise to slightly rich when you floor it.

I was trying to compare apples to apples there. The 5.0 Coyote V8 is 16/24 with the manual transmission. The 6.2 LS3 in the Camaro is also 16/24 with a manual transmission. The Coyote V8 gets a 1 mpg boost with the automatic (which has a wider ratio spread than the manual). The automatic Camaro SS does not use the LS3, but the 6.2 liter L99 engine. The L99 also gets 25mpg on the freeway. However, we were comparing the LS3 and the Coyote previously, so I didn't want to bring the L99 into the discussion.

The Camaro may not be particularly sensitive to the dimensions of the engine. But that doesn't make a bigger, heavier, more expensive, less fuel economical, less powerful and less torquey engine preferable! The valve area of a pushrod design is smaller than in a DOHC design. This is why a DOHC design flows more air and has higher specific output. The problem is that, in order to operate the DOHC valvetrain, you end up with two much bigger cylinder heads, four times as many cam shafts and sprockets and twice as many valves. Complexity and costs aside, the DOHC design has much higher internal friction from all these added parts, a lot of extra bulk and a significant amount of extra weight. If you simply increase the displacement by about 20%, you end up with a smaller engine, a lighter engine, an engine with less internal friction and slightly better fuel economy. Bigger displacement, better fuel economy? Sounds counter intuitive? Well, let me try to explain it... It takes two otherwise identical cars the same amount of power to maintain a given speed. To make the same amount of power you need to burn the same amount of fuel. To burn the same amount of fuel, you need to flow the same amount of air. At cruise, flow is being restricted such that just enough power is made for speed to be constant. At cruise, the engine is not being choked by the airflow limits of the intake and valves. At cruise, the engine is being choked by the throttle body. The above holds true regardless of valvetrain design or displacement. This means that none of the airflow advantages of a DOHC design matters. The higher internal friction from the DOHC valvetrain however hurts (by increasing parasitic loss). Hence, a reduction in displacement often do not increase efficiency but can sometimes decrease it. Point to ponder: "When fuel economy is the paramount goal, Honda adopted a 1.3 liter SOHC 8-valve (LDA) Inline-4 for the Civic Hybrid and Insight. This is from the same company who also puts the F20C 125bhp/liter engine in the S2000. Why?" When a DOHC-16v 1.8 liter engine is more efficient than a DOHC-16v 2.4 liter, it is not because it is 1.8 liters per say. It is because the 1.8 liter engine has smaller bore circumferences and/or stroke length which reduces bore friction. Since they are both DOHC-16v designs, the level valvetrain friction may be quite similar. Therefore, the 1.8 liter engine nets an increase in efficiency. However, a SOHC 8v 2.4 liter of a similar output to the 1.8 liter DOHC 16v may have similar or better fuel economy. Similarly, when you compare a 4 liter DOHC V8 and a 6.2 liter Pushrod V8, the amount of reduction in bore friction may be more than offset by the increase in valvetrain drag. This is often excerbated by the lower torque output of the smaller engine necessitating a top gear which keeps the engine at higher rpms. The net result is that the 4.0 liter DOHC V8 in an M3 is less economical on fuel than a 6.2 liter Pushrod V8 in a Camaro SS.

The Mustang is a lighter chassis to begin with. Part of the reason is that Ford decided to for go fully independent suspension for a live axle in the back. The chassis is also less rigid than the Zeta. It all adds up to an ~200 lbs difference in chassis weight. None of this has anything to do with the DOHC 5.0 motor. As a matter of fact, the Mustang would have been even lighter and have more power and torque were it outfitted with a LS3 Pushrod V8. The question I'll like to post to everyone is this: "The 5.0 liter Coyote DOHC V-8 makes 412hp/390lb-ft with the help of four VVT actuators and 32-valves. It gets 16/24mpg in the 2011 Mustang 5.0. The 6.2 liter LS3 Pushrod V8 makes 426hp/420lb-ft with no VVT and just 16-valves. It gets 16/24mpg in the 2010 Camaro SS which is about 200 lbs heavier than the Mustang. The LS3 also weighs less, take up less room and cost less to manufacture. Why is the 5.0 DOHC a better engine?" Anyway... let me summarize the discussion in the past dozen or so posts:- A Pushrod V8 lighter, smaller and less complex than a DOHC V8 of equivalent power. A Pushrod V8 has better fuel economy than a DOHC V8 of equivalent power. A Pushrod V8 is less costly to build than a DOHC V8. A DOHC V8 is advantageous in markets where taxes are levied on displacement. A DOHC V8 is advantageous in those racing series where rules limit maximum displacement. A DOHC V8 is perceived as more refined by some individuals.

Honestly, I don't see a Pushrod V6 stemming from the Small Block. The reason being:- A 60 degree Pushrod V6 will be a brand new design, not a derivative w/o shared tooling A 90 degree is not a smooth running configuration unless a balance shaft is used. With less cylinders and (possibly) a 60deg angle the packaging advantages of a Pushrod diminishes. The HF V6 already exists and there is no good reason for duplicity in the lineup What I do see (and hope to see) is the continued evolution of the Pushrod Small Block. Probably fortification with VVT, Raised Cam, Cylinder Deactivation and Direct Injection in the Fifth generation due in this year or 2011. This will probably be accompanied by a reduction in displacement to 5.5 liters with little or no reduction in output from the 400~436hp of the current 6.2 (LS3). By 2014~2015, we may see variable valve lift and dual co-axial VVT in the 6th Gen design.

Again, this is a matter of opinion. But, I do not feel that the sharing of the motor(s) between Cadillac and other "less prestigious" GM divisions will have a significant impact on the success of the Cadillac brand. Cadillac can distinguish itself from other GM brands through styling, quality and amenities. It doesn't have to focus on having a unique powertrain. Besides, the same argument for Cadillac possibly receiving a "bashing" for using Chevy motors can be made for Chevy getting an "image boost" for using Cadillac engines. Since Chevy has much greater volume, one can then argue that it works out to GM's overall advantage. Nissan uses the same 3.5 liter VQ35 on both the Nissans and the Altimas. Toyota uses the 2GR-FE 3.5 liter in the ES350, RX350, Camry, Avalon, RAV4, Highlander and (jeez) Sienna. Audi shares the 2.0T FSI with the Volkswagens. None of the sharing has impeded the success of the respective luxury divisions. In anycase, Cadillac doesn't have powertrain exclusivity today to begin with -- the 3.0 and 3.6 liter V6es -- which account for the the majority of the volume -- are Chevy motors also used in the Equinox, Malibu, Camaro, you name it. If, for instance, giving Cadillac a "unique" motor will add $1500 to the cost of the vehicle, I feel that this $1500 is better spent on upgrading the grade of leather used in the upholstery, using laminated glass on all side windows and perhaps making a rear view camera standard.

Well, let me ask you a question... why does having a greater output for a given displacement matter to you? In otherwords, why is specific output important? Does it matter if the engine's displacement is larger, when that engine is lighter, smaller, more powerful, more fuel efficient and cheaper to build? For example, is Ford 5.0 DOHC lighter than a Pushrod 6.2? Doubtful. Does a Ford 5.0 DOHC take up less room in an engine bay? Absolutely not. Does the Ford 5.0 DOHC produce more power? No, it doesn't. Does the Ford 5.0 DOHC cost less to build? No way. Is the Ford 5.0 DOHC more economical on fuel? Again, probably not. So... why is the Ford 5.0 DOHC a better motor?

Well, on what technical or factual basis are you making that argument besides everybody is using it so it must be right? Linking financial performance to engine type is like saying a computer manufacturer is in distress because the CEO wears a red tie instead of white suspenders that the other CEOs wore. Unless you can demonstrate the suspenders affected his performance running the company the connection is quite groundless. As far as the failures of GM. IMHO, it is a failure of design, failure of quality, failure of product focus and a failure of labor. GM tried to be the value leader while doing most of its manufacturing in a high cost country. That in and of itself is a recipe for failure. To that end, it cut back on quality, technology and put out too many uninteresting vehicles -- which compounded the problem. The Pushrod engine has nothing to do with it. I put forth an argument that a Pushrod engine is superior to a DOHC engine in cost, performance, packaging, weight and fuel economy. Perhaps you can educate us as to why that argument is flawed or inaccurate?

Well, maybe it's because they just don't get it... yet. As far as refinement of an engine is concerned, you can break it into three factors. Balance of the Engine Insulation and engine mounting Valvetrain slop Of these, you are not going to see a difference between a DOHC V8 and a pushrod V8 when it comes to Balance and Insulation. That's has everything to do with bank angle, counter-weights and sound deadening. It has nothing to do with how the valves are operated. With Valve train slop, it is really a matter of not allowing poor tolerances and valve float. It also has very little with whether the engine is a pushrod or overhead cam design. The higher valve train mass in a pushrod engine places a limit on how high of a rpm the engine can get to before the valve train becomes a limiting factor both in terms of durability and/or noise becomes an issue. But while this affects the redline of an engine can acheive without compromising durability, the racket the valvetrain makes at a given level of acceptable float or slop is similar. The only difference is that a given threshold for what's acceptable may arrive at 6000 rpm on a pushrod design, but 8000 rpm on a DOHC one. There are many things when the biggest bandwagon is on the wrong track. People and companies are not immune from the tendency to jump on board with a broad trend even when the underlying facts are highly dubious. Global Warming is one example of what's basically junk science almost becoming a general consenses. The trend towards DOHC Vee type engines, IMHO, is another. The basic Achilles' Heel to the DOHC proposition is that it is a heavier, bulkier, more complicated engine with higher internal friction. It's only advantage is that it provides for better airflow and higher rpm capability. The problem is that a slower turning, bigger displacement engine can be more powerful, lighter, smaller and more fuel efficient. In addition, the airflow potential of a DOHC layout is not realized at the typical 6000~7000 rpm rev limits of a mainstream passenger car engine. In certain racing applications where the rules limit displacement, and in various countries where the rules of the game or the law makes it highly advantageous to have a higher specific output, lower displacment engine. However, these do not apply to the market for V8 powered cars. This is not a displacement restricted competition event. The luxury/performance market for V8s is also not particularly sensitive to higher displacement taxes even when they do exist. The type of buyers who rank this highly will buy the I4 or V6 variant of the car; they'll buy an Audi 2.0T instead of a V8 S4, they'll buy a BMW 525 or 528 and not the 550. The decision to buy a V8 powered car is a deliberate one.

Well, a simple way to gauge that will be to assume the same specific output as the LS3 ~69.8bhp/liter. ~272hp 3.9 liter Pushrod V6. And, that's before VVT, DI or AFM. Not bad really and quite competitive with the 3.5~3.6 liter HF V6es. Remember, the 3.9 pushrod is probably a smaller and lighter powerplant.

To illustrate the competitiveness of the pushrod design, let’s compare three V8 engines. All are fielded in high performance production cars, all being of aluminum construction and none having direct injection. * Chevy Camaro SS ** BMW M3 *** Mercedes-Benz C63 AMG The pushrod engine offers the highest power and torque density, along with the best fuel economy. It is also the simplest, lightest, smallest and cheapest engine. Why wouldn’t you want a pushrod? The most common reply to that is “civility”. Well, have you driven a small block lately? If you have, have you also driven the other two engines? I have done all that and here’s my opinion on the civility issue… The engines have very different characters, but saying that the small block is less civil than the other two is a mischaracterization. The small block is burbly down low and throaty in a throbbing baritone sort of manner when wound out. The BMW V8 quiet and smooth, but also very soft, down low. Get it past 6000 rpm and it wails with a metallic rasp of an engine note. The AMG V8 is (surprising) also rather soft below 4000 rpm, softer in fact than the previous M113 5.5 liter it replaced or the current 5.5 they put in the E550. Wind it out and it responds with vigor and a brash metallic tone from about 4500 rpm to the rev limit of 7200 rpm. Overall, the C63 has the loudest exhaust (I mean this thing is loud enough to wake your neighbors), the M3 has the finest tremble and the Camaro SS is the least edgy and most mellow. I am sure that some of that is how the exhaust and sound insulation in the respective cars are set up, but I didn't get the impression that the pushrod engine is outdated or crude. So, there you go. This is why I advocate that GM should double down on a good thing and stick to the pushrod V8. With direct injection, variable timing and cylinder deactivation, it’ll be more than up to snuff against anything projected for the next decade. If nobody else is doing it, that’s a good thing they get the monopoly on it! And, it seems that they are. Currently, there are no plans for a DOHC replacement for the Northstar. There is however a Gen V small block in the works (rumored to be displacing 5.5 liters and sporting direct injection). So, I'll like to offer my congratulations to the General for not losing good judgment despite government ownership.

No, but GM can spread ONE 5.5 liter Push Rod V8 with different tunings, with or sans a supercharger across the entire V8 lineup. In fact, that's what I am advocating. BMW is not replacing the Inline Sixes with the N63 or its derivatives either.

How is this the better solution? Let's compare the numbers shall we? In naturally aspirated form... BMW N62 V8 w/Double Vanos (VVT) & Valvetronic (CVVL) Type: DOHC-32v, 90deg V8 Displacement: 4.8 liters Horsepower: 360 @ 6300 rpm Torque: 360 @ 3400 rpm Fuel Economy: 15 (City) / 22 (Hwy) mpg* *3968 lbs BMW 550i w/6-spd Automatic Chevy L99 V8 w/Synchronous VVT & AFM (DoD) Type: Pushrod-16v, 90 deg V8 Displacement: 6.2 liters Horsepower: 400 @ 5900 rpm Torque: 410 @ 4300 rpm Fuel Economy: 16 (City) / 25 (Hwy) mpg* *3908 lbs Camaro SS w/6-spd Automatic In force induction form... BMW N63 V8 w/twin turbos & intercooler Type: DOHC-32v, 90deg V8 Displacement: 4.4 liters Horsepower: 400 @ 5500 rpm Torque: 450 @ 1800 rpm Fuel Economy: 15 (City) / 22 (Hwy) mpg* *4564 lbs BMW 750i w/6-spd Automatic Cadillac LSA V8 w/Eaton VSR Supercharger & aftercooler Type: Pushrod-16v, 90 deg V8 Displacement: 6.2 liters Horsepower: 556 @ 6100 rpm Torque: 551 @ 3800 rpm Fuel Economy: 14 (City) / 19 (Hwy) mpg* *4292 lbs Cadillac CTS-V w/6-spd Automatic

I don't think most of today's Cadillac buyers know about Cadillac's ancient history. If they know anything it's the spotty reliability and quality of Caddys from the 80s and 90s -- that's actually better forgotten. Cadillac doesn't need unique engines. They can simply be the highest priced, best finished, most luxurious GM. And, for the most parts, that's how the brand is seen today. As far as the engine goes, it has to be competitive with BMW, Mercedes Benz, Audi and Lexus. Where is comes from and what it is shared with isn't particularly important. A 5.5 liter making 400hp and delivering better fuel economy numbers than the competition's 4.6~5.0 liter DOHC engines is competitive. With proper quiet tuning it can be quiet enough too. That should be good enough shouldn't it?

From an economics standpoint, the other "affordable" option is to have a DOHC 4.8 liter 60 degree V8 based on adding 2-cylinders to the 3.6 liter DI V6 (LLT). It'll make ~400 hp and ~364 lb-ft. The 60 deg angle hurts smoothness a bit, but the deg degree angle will allow it to fit in the same envelope as a pushrod small block of the 5.5~6.2 liter class. Being DOHC and having higher internal friction means that fuel economy numbers will be down 1 mpg or so. I am not convinced that this is a better engine for caddy or any other brand. Besides, the whole point about sharing engines is to reduce the cost of each individual engine so you can have higher technological content on each one. It may mean the absence or absence of Direct Injection across the board. I personally do not think that there will be a psychological barrier to caddy buyers if the cars use the same engines as top of the line Chevys. Toyota uses the same 3.5 liter in both their Lexus and Toyota models. Nissan shares the VQ35/37 between the Infiniti and Nissan models. It hasn't impeded on the success of the RX, ES, G or FX models.