dwightlooi

Well... two turbos definitely cost more and brings with them a host of additional plumbing. The question is what advantageous do they bring? First let's get the myths out of the way:- Twin Turbos are not more efficient than a single larger turbo -- in fact, they are LESS EFFICIENT as larger turbines and compressors aerodynamically superior Twin turbos (in parallel) are not more responsive than a single large turbo -- V6es use two for the convenience of not having to route exhaust to one There are two advantageous to using two turbos in a 4-cylinder. Both applies ONLY to SEQUENTIAL setups... (1) Sequential, asymmetric, turbines offer improved low end response. Basically, you have a smaller turbo which spins up sooner and faster provide boost at the lowest rung of the engine rpm range. This turbo's exhaust and waste gated bypass flow feed a second larger turbo which is able to cope with the engine's higher rpm breathing. The most advanced single turbos of today can manage a torque plateau of about ~3500 rpm at a boost level of about 1 bar (14.7 psi). This gets narrower if you run higher boost. With twin sequential turbines you can extend this by about 500 rpm. In otherwords, with a single turbo you may be able to have an engine which makes maximum torque at 2000~5500 rpm. With a sequential setup you can extend this down to 1500~5500 rpm or up to 2000~6000 rpm. (2) Sequential compressors allow higher pressure ratios to be reached. A single stage compressor becomes very inefficient above a pressure ratio of about 2.5:1. That is, they start making more heat than compress air when asked to deliver more than about 22 psi of boost (about 37 psi of absolute pressure on an atmospheric input of 14.7 psi). By the time you reach a pressure ratio about 2.75~3.0:1 (26~29 psi of boost) more boost actually makes less power just a lot of hot air. This is why jet engines have many axial compressor stages and helicopter turbines usually have more than one centrifugal stage. With two sequential compressors you can efficiently reach 30~40 psi of boost. More if you insert an intercooler between the two stages! Realistically though, this advantage is quite irrelevant to road cars running on pump gas given that the static compression will have to be so low (~3:1) that the engine wouldn't run right if at all off boost And, if it did, would be quite lousy on thermal efficiency and fuel economy. So... really it comes down to the ability to create one of those engines capable of 1200 rpm torque peaks or one with a modest torque peak of say 3000 rpm but a plateau stretching to 7000 rpm hence making pretty impressive power. The question is whether that added 500 rpm extension of the torque plateau is worth all the addition complexity and cost. Remember, the sequential setup is NOT more efficient or more responsive than a single setup when the latter is within its already pretty wide optimal operating range. Also, the same broadening of the torque plateau and/or increase in power output can also be achieved by running about 0.2 bar (3 psi) less boost, using a slightly larger displacement and running slightly higher static compression. In fact, the latter probably yields slightly better mpg numbers due to improved off boost thermal efficiency from the higher static compression.

Probably 5~6% better than a 4-cylinder of a similar output. That is about 1.5~1.8 mpg in a 30 mpg car.

Actually, I really hope they will make not just a small 3-cylinder, but a larger three cylinder. Something along the lines of a 1.8 liter three, with the same cylinder dimensions as the 2.4 or 2.5 liter fours. Such an engine will make about 140~150 hp / 135~140 lb-ft in NA trim, and about 200 hp / 235 lb-ft with very reasonable boost levels. These will serve well in the compact and mid-size classes -- at least the base and ECO trims.

A 3-cylinder does not necessarily have to be less refined than a 4-cylinder. The biggest difference from an NVH standpoint is that the 3-cylinder is not 1st order balanced like the 4-cylinder and it has 3/4th as many power pulses at any given rpm. What this means is that a 3-cylinder engine -- if fitted with a balance shaft -- is roughly as smooth from a vibrational standpoint as an equivalent 4-cylinder without balance shafts. However, it will not equal a 4-cylinder with balance shafts to cancel its 2nd order vibrations. The 1.4 liter Turbo is NOT balance shafted. Hence, a 3-potter with a balancer will roughly match its vibrational levels. The good news here is that a 3-cylinder only needs one balance shaft rotating at the same speed as the crank shaft -- unlike a 4-cylinder which needs two contra-rotating shafts at twice the crank speed. From a power pulse standpoint, I don't think the difference is significant although there isn't anything you can do about it. At 3000 rpm, a 3-cylinder engine will have impulses spaced as far apart as a 4-cylinder at 2250 rpm. But really, I haven't heard anyone complain about their car being "less" smooth at 2250 rpm vs 3000, 3000 vs 4000 or 1200 vs 1600. One thing I will do with these engines is lower the redline. This is because both unbalance-shafted fours and balance shafted threes tend to be most unrefined at higher rpms, and -- more importantly -- the sizing of the turbochargers to produce fast response at low rpms means that revving these things past 5500 rpm or so is useless from a performance standpoint. Forcing the engine to shift at 5000~5500 rpm actually makes it more refined AND faster!

Its about time they move to a 3-cylinder. A 3-cylinder engine is more frictionally efficient and better for turbocharging than a 4-cylinder of the same displacement. This is because 12-valves instead of 16 and less frictional surfaces with 3 cylinders translates to lower parasitic losses and superior engine efficiency. Also, because 3-cylinder engines do not have cylinders at the top and bottom of their strokes at any one time, they do not have the problem of exhaust pulses feeding back into the another cylinder in the valve overlap period -- a problem which requires a twin-scroll turbo and segregated manifold to mitigate. The Cruze for instance will be better served with a 1.3~1.5 liter turbo 3 than its current turbo 4. Fuel economy will improve, power will improve and engine response will be better. What many people do not realize is that going to 3/4th the cylinder count generally yields higher fuel economy benefits than going to 3/4th the displacement!

GM needs to stop making excuses though and start tackling the weight problem. I can guarantee you that the Sonic is not 400 lbs heavier because it is carrying 400 lbs of sound deadening!

The Sonic has three glaring problems:- ONE: It's fuel economy is actually 1 mpg WORSE than the larger Cruze* TWO: It is ALMOST THE SAME PRICE than the CRUZE despite an smaller interior volume THREE: You CANNOT get it with a 1.4T and the 6-speed Automatic * Probably because not substantially lighter, while trailing edge drag of its hatchback layout is worse.

Actually, the C300 is not slow. It does 0-60 in 7.5 secs. That's faster than an SRX and fast enough to be "not objectionable" to most buyers who are enthusiasts.

No, it doesn't have to be fixed. But they are a lot more difficult to control than take timing. You need a single slider valve and its control mechanism per exhaust port. This is compounded when you have exhaust ports on both sides of the engine. With intake timing control, all you have is a single phaser on a single camshaft. In a single cylinder 2-stroke engine, I guess this is irrelevant. But when you have 4 cylinders, 8 ports, 8-sliders and 8 actuators it becomes a handful. For the purpose of managing exhaust impulse, a variable exhaust plenum is easier to implement. What you have is basically a wedge shaped volume, a flap on the input end that swings up and down to vary the size of the effective "slice" of the pie. Changing the volume changes when, and at what magnitude, the feedback pulse arrives back at the exhaust ports. When it arrives, it temporally pushes a portion of the exhaust flow back through the port, negating part of the exhalation.

We don't know if this rumor is even true. But in general, a 7-speed transmission will have a ratio spread of around 6.5~7.0:1 compared to 5.9~6.1:1 for a typical 6-speed or 5.0~5.5~1 for a 5-speed. So, yes, that can mean more overdrive. Or, it can mean a lower 1st. The problem with putting more speeds on a big displacement Corvette in the 430 hp/lb-ft class (probably even higher with the C7) is that the car really does not need a shorter 1st (you'll just melt the tires more) and you really don't need closer ratios (shifting itself always slow you down, what they do is perhaps make you accelerate faster in between shifts). The same can be said of fat torque bi-turbo V6es in the same power class. At the end of the day, MOST 7 or 8-speed transmissions end up starting in 2nd, or skipping one or two gears during "normal" driving, or both. This is why I have been saying that 7 or 8-speeds is a low priority for big V8 powered Vettes or Caddys. They are much more useful for less powerful motors. In a big V8 powered Vette or Caddy, if you want better mileage, just put in a taller final drive. Sometimes, that actually makes the car faster because it makes 1st gear wheel spin is easier to manage -- either manually or with less intervention from traction control.

In trying determine if a car can benefit from more speeds in the transmission, all you have to ask is three questions:- Does the car have enough torque to smoke the tires in 1st gear? Is the cruising rpm in top gear low enough? Between shifts, does the rpm fall too far below the torque peak? If the answer to all the questions are NO. Then the car does not need more speeds in the transmission. In fact, more speeds in such instances will make the car slower with no benefits to fuel economy. For the Corvette, the objective is for enough torque to break the tires lose in 1st, keep top gear rpms at around 1600~1700 rpm at 60 mph and make see to it that when shifted at the redline (6600 rpm) the rpm drops to within 800 rpm of 4,600 rpm. If it is already doing that, then giving it more gears just means more shifts during acceleration (slower), more smoke during launch (slower) or a top gear that cannot be used until you are seriously over the speed limit (pointless).

The power curve will be more peaky than a modern 4-stroke engine with dual VVT. Remember a mid-90s DOHC or SOHC engine before VVT, variable runners and low pressure turbos? Something like that. Let's say you have a torque peak at 4200 rpm, 1000 rpm above and below that is roughly where the meat of your power band is. Not the the engine chokes below 3200 rpm, but it may be a little soft and you may feel it "get on cam" at about 3K. Mainly because the exhaust port timings are fixed and a mechanical amplifies a torque curve it does not linearized it. That's the price you pay for nearly doubling the power density and enjoying frictional drag similar to a 4-stroke engine running at half your rpms. You can mitigate it a somewhat if you implement a variable volume exhaust resonator. But that will add to the complexity and may present a problem in modern automotive context in that the variable resonator needs to be between the exhaust ports and the cat converter slow light off and hurting cold start emissions. If you choose to make it into a Vee configuration the bank angles will be the same for balancing purposes. However, exhaust routing may be a challenge given that you have exhaust coming out both sides as well as the middle of the engine Vee. Your intake air goes into the top of the valve cover... like a big fat spark plug tunnel if you will.

Higher than a 2.0 liter NA 4-atroke engine for sure. But lower than a 4.0 V6 or 2.0 turbo making the same amount of power. If you compare it to either V6 or I4T 4-stroke solutions making the same 300 hp, I'll guess its in the order of about 80~90% of the fuel burn. About 2/3rds coming from the reduced frictional and pumping losses, 1/3 coming from the fact that the 2.0 liter engine is lighter and smaller. For a car like a cruze, a 2.0 liter 2-stroke SPOHV is probably an overkill... that's a 300+ hp powerplant. A 1.0 liter 150hp/165 lb-ft 2-stroke engine will probably be better. Possibly a 3-potter in the displacement class. In that case, probably around 32 (city) / 49 (Hwy) mpg. It's substantial, but this is NOT Cold Fusion!

Versus a 4-engine of a similar displacement. The reasons are two fold. Firstly, the piston skirts need to be long enough to cover the stroke length. This is necessary to segregate the exhaust port from the oil filled sump. 4-stroke engines don't need such a long piston. To a lesser degree, neither does a traditional side intake port 2-stroke engine because that port does not need to be segregated from the crankcase. In fact it is fed by the crankcase with its fuel-oil-air mixture. Secondly, a single large intake valve offers the best intake port area. But it is also heavier than two small ones individually. Higher piston and valve mass means that the engine will not rev as high before bearing wear or valve float becomes a problem. You are looking at a maximum rpm in the 5000s rather than the 6000s or 7000s. Regardless, I think 5000~5500 rpm is NOT bad. It's a very decent limit. Better than most diesels and on the lowest end of long stroke 4-stroker gasoline engines. One has to remember that a 2-stroker at 5,500 rpm is firing just as many times as a 4-stroke at 11,000 rpm. Therein lies the secret to making almost twice the output of a 4-stroke engine of similar displacement and cylinder count. An analogy can be made with the 1.3 liter Wankel Rotary. A Wankel fires 3 times per full rotation of the rotor. This is why a 1.3 liter RX-8 can make 250hp -- it is a lot more than 1.3 liters in air moved per revolution compared to a 4-stroke piston engine! Unlike a Wankel though, the SPOHV engine does not have the finicky apex seals requiring oil injection to lubricate. Also, unlike the rotary it performs compression and combustion in exactly the same place whereas the the Wankel does in in separate parts of the torcoid. Always compressing the charge on a cold part of the engine reduces thermal efficiency of the engine very much like running an engine that never warms up.

Well, there are and have been, overhead valve diesels. But traditionally, these have port fuel injection or carburetion so there was still the problem of fuel following the intake charge into the exhaust due to cross aspiration. Also, aspiration is not as complete and volumetric efficiency is not as high when you rely on two or four into valves in the cylinder heads. This is simply because of the fact that if you have to split the head area between intake and exhaust valves, they cannot be as large as if the head only as to accommodate intake valve(s). Also, when airflow is not from one end of the cylinder to the other some degree of dead spotting on the base of the cylinder is unavoidable. With the SPOHV design, the intake and exhaust areas are much greater, plus the airflow is from the very top of the cylinder to the very bottom eliminating any stagnant areas. The charge pump will be about twice the size of a supercharger on a 4-stroke, 2.0 liter engine with a similar specific output. This is because it has to effect both the basic aspiration (net pressure at 1 atmosphere) and whatever boost you pile on after the exhaust ports close. So picture something the size of a Vortec or Paxton blower used on a V8 used on a 2.0 liter 4-cylinder and you get the approximate idea. It's still not that big though. And part of the reason I am biased towards the centrifugal blower is because it is the smallest and most efficient (when at or near its optimal operating speed). You can use a mechanical blower or positive displacement pump for base aspiration and a turbo for making boost above and beyond that. The Fairbanks-Morse Opposed Piston Direct Injected 2-stroke Diesels does just that. They use the blowers for starting but turbos for running. But these are usually marine diesels or stationary power generator engines, so they tend to run at a constant speed and load, and do not have to contend with the traffic light! You cannot use a turbo exclusively because then the engine won't run to begin with. You don't need it to be variable output, all you need is for it to move roughly just enough air as the engine would ingest without over pressurizing the charge. However, if you want to do this the mechanical air pump MUST be a positive displacement device -- a Roots, Lyshom, G-ladder or Piston Pump. It should not be a centrifugal blower because the boost from a parallel turbocharger can "backflow" through a centrifugal impeller. That is not to say you cannot have a variable output compressor. It is not functionally necessary, but you can. There are several ways to do this. Use a multi-speed transmission between the crank and the blower, use a CVT pulley pair or -- like the WWII German fighter engines -- use a hydraulic coupling to drive the supercharger which you can partially bleed to reduce the drive rate. But all of these increase complexity and add parasitic losses.

Why Two Stroke? Because a 2-stroke engine fires twice for every firing of a 4-stroke engine. This means that the 2-stroke engine has potentially up to twice the output of a 4-stroke engine of the same displacement. Because it does twice the work at the same rpm, it also makes does it with half the parasitic friction (all else being equal). Eg. when both types were available on the market, no 125cc 4-stroke motorcycle ever makes as much power and/or weigh as little as a 125cc 2-stroke bike. The problem with 2-Stroke designs... However, the 2-stroke engine has many traditional short comings, some of them utter show stoppers. To begin with 2-stroke engines usually burn a premix of lubricant oil and fuel. This is because they tend to use the crank case as a piston pump to push the intake charge into the combustion chamber when both the intake and exhaust ports are open. This means that instead of having lubrication oil in the crankcase, they must fill it with a fuel, air and oil mixture. This is a serious problem because with enough oil content in the mixture to lubricate the load bearing main bearings, journal bearings and wrist pins, the mixture will burn in a smoky manner and is guaranteed to fail modern emission standards. Despite this, lubrication is still poor compared to 4-stroke engines leading to 2-stroke motors wearing out twice to three times as quickly as 4-cycle engines. To make matters worse, because both the intake and exhaust ports must be open concurrently at some point, 2-stroke cycles must either exhale the exhaust gases incompletely or over aspirate the intake charge such at a portion of the fuel-air mixture escapes into the exhaust. The former leads to reduced power output from not having enough air to burn all the fuel in the mixture. The latter leads to wasted fuel going straight into the exhaust. Both further compromises hydrocarbon emissions and lead to reduced fuel efficiency. As if that is not enough, the use of tuned exhaust systems provide a back pressure pulse to help achieve a balance between the two aforementioned problems also leads to a very narrow rpm range where the engine is optimally powerful, efficient and clean running. Even when everything is perfect, at the ideal rpm and load range, because both ports are on the lower lower of the cylinder scavenging is never as complete as a 4-stroke engine due to dead spots on the upper part of the combustion chamber and some degree of inefficiency cannot be avoided. All it all, inferior fuel economy, lousy emissions, poor longevity and narrow power bands have condemned the traditional 2-stroke engine to garden blowers and RC models. In fact, in many countries 2-stroke engines are outright banned not just on cars, but motorcycles and Jet Skis alike. Direct Injected SPOHV Engine Changes Everything Here I am presenting a concept that changes everything while retaining the advantageous of a 2-stroke design. The engine uses an overhead valve and side exhaust ports. Fueling is by means of direct gasoline injection during the compression stroke. It uses a wet sump lubrication system for the main bearings, journal bearings, wrist pins and part of the cylinder walls. The crankcase is filled with oil like a 4-stroke engine and is not used to pump a fuel-air-oil charge into the combustion chamber. Instead aspiration is enabled by an external centrifugal supercharger. The engine operates on a hybrid 2-stroke / Miller Cycle in that the intake valve stays open during a good portion of upward travel of the piston after the exhaust ports have closed. This results in an air charge that is above atmospheric pressure when the intake valve closes making this a true force induction engine. It also creates an asymmetrical compression and power stroke with the latter being longer than the former for superior combustion efficiency very much like Atkinson and Miller Cycle 4-stroke engines. SPOHV Advantageous:- Emissions: Because the engine does not burn oil and there is no fuel introduced into the engine by the direct injectors until after the exhaust ports have closed there is no possibility of unburnt fuel escaping into the exhaust or significant amounts of oil being combusted. Because of this emissions are squeaky clean. Longevity: Because all the elements in the bottom end is lubricated in the same manner as a 4-Stroke engine, durability of the SPOHV design should be comparable to contemporary 4-stroke engines. Performance: With twice as many firings at any given rpm, the SPOHV engine is potentially twice as powerful as a 4-stroke engine of equal displacement. This is further enhanced by the fact that because the heads only have to house an intake valve and no exhaust valve, whereas the side ports on the cylinder walls are exhaust only, the total area of the intake and exhaust openings are insanely high compared to both traditional 2-stroke engines and DOHC 4-valve 4-stroke designs. This allows the engine to be lighter and smaller than a 4-stroke engine of equivalent output. Potentially half the size. Refinement: While the 2-stroke cycle does nothing to change the harmonics of any particular cylinder arrangement it does double the number of firing pulses at any given rpm. In this sense, a 4-cylinder 2-stroke engine has pulse intervals equivalent to an 8-cylinder engine. Fuel Economy: For any given amount of power made in an engine of a given displacement, the SPOHV engine turns over at half the rpm of a 4-stroke engine. It also has only 1 intake valve and 1 camshaft compared to 4 and 2 respectively for a DOHC 4-valve engine. This equates to significantly lower parasitic frictional losses. With extremely high intake & exhaust cross sections, the engine also has lower aspirational losses. SPOHV Disadvantageous:- Forced Induction is a Must: Because the crank case is not used to push the intake charge into the the cylinders, an external compressor is a requirement. This can be a roots blower, centrifugal compressor, Lysholm Screw, G-ladder or even a piston pump. But some kind of air mover is needed and it cannot be a turbocharger because at idle with no load, the turbos will make no boost. Because the engine does not draw air into the cylinders with a downward stroke of the pistons and the engine won't run at all unless it is fed by a positive displacement air pump Reduced Maximum RPMs: Because the engine has longer, heavier pistons as well as bigger heavier valves, the rpm limit is consequently lower. Dual Exhaust Outlets: For optimal egress of exhaust gases the exhaust ports are on both sides of the engine block. This complicates exhaust routing a little, in the same manner that a V type engine does. Hypothetical 2.0 liter 4-cylinder SPOHV engine statistics:- Type: Direct Injected 2-Stroke, 4-Cylinder Engine Valvetrain: Single Overhead Cam, 1-valve per cylinder Construction: Aluminum Block & Heads Aspiration: Centrifugal Blower Assisted, 2-stroke Miller Cycle Bore x Stroke: 89 x 80.3 mm Displacement: 1998 cc Fuel Type: 87 Octane Unleaded Gasoline Lubrication: Mobil 1 0W-20 Synthetic motor oil; 5 Quarts / 10,000 mile change interval Power Output: 300 bhp @ 5200 rpm Torque Output: 330 lb-ft @ 4200 rpm Maximum Engine Speed: 5500 rpm

The Cruze is a good looking car. Better looking the squid like Focus, bland Corolla or the overly raked Civic. Not that its perfect, the black plastic trim trying to fake a C-pillar window and the overly generic tail lamps being leading thumbs downs. But, the front and side views are class leading gorgeous and that certainly helps. The interior is neat, tidy and good looking. There are a few too many hard plastic, but at least they are well textured and the competition is not lacking of hard trim pieces either. The one thing I don't like about the new Bu (compared to the Cruze) is that the Bu seems more cluttered in its design. To me, clean and sleek is beautiful. Unnecessary lines are not.

I don't think a Hatch is that important. I like hatches, but hatches don't sell in the USA. The Cruze is an embarassment and a mistake from a powertrain standpoint though. After cutting displacement to 1.4 liters, adding a turbo, putting in an after cooler and connecting all that with bunch of hoses, it is not more powerful and less efficient than the competition's plain and simple 1.8~2.0 liter fours. That much effort deserves the fuel economy crown, and a few changes will get GM there. Phase 1 -- 28/42 mpg w/ 6-spd Auto Increase boost pressure to 15 psi -- still 87 Oct Compatible Remove the obstructive intake port dams -- who cares about trying for an ULEV/SULEV II rating?* Make all the lightening and aerodynamic changes on the ECO model standard -- This is worth 0~1 mpg city / 1~2 mpg hwy With about 160 hp / 170 lb-ft from both changes, drop final axle ratio from 3.53:1 (2012 model) --> 2.87:1 -- this is worth ~1 mpg city / 2~3 mpg Hwy Standardize on a low rolling resistance tire (Eg. Goodyear Assurance FuelMax) -- worth ~1mpg hwy * MPG and Performance is more important the SULEV or ULEV ratings. How many customers actually care about that? 1%? Those 1% will probably buy a Prius, Leaf or a Volt anyway. Phase 2 (with facelift) -- 30/45 mpg Implement Direct Injection, raise compression from 9.5:1 --> 10.5:1 -- worth ~8 hp and 2~3% improvement in fuel economy (1~2 mpg) Implement a 2-stage cam switching valvetrain (same design as HCCI prototype engine) allowing part-time Atkinson/Miller Cycle operation -- worth 2~3 mpg Hwy Implement a variable oil pump -- worth ~0.5 mpg hwy Switch to an Aluminum block -- offsets some of the weight in the nose of the car Phase 3 (all new model) -- 32/48 mpg + 0-60 in 7.8 secs Switch to 1.8 liter DI 3-cylinder engine with cam switching and part-time Atkinson/Miller Cycle** Ball Bearing Turbocharger -- superior response and efficiency Pneumatic Automatic Start-Stop -- in ECO mode High Strength Steel + Aluminum hood -- target weight = 2,750 lbs ** Target output = 175 bhp @ 5200 rpm, 177 lb-ft @ 1200~5200 rpm, Redline 5200 rpm, Max Engine Speed 6000 rpm All these without expensive and heavy Hybrid drive trains.

The idea I am trying to get across is not one particular engine or another. The points are simply two things:- Less variants is better Think different Like a restaurant, a smaller menu. A manageable and not extraneous one is better than one with 100 dishes. For the Malibu, the line up can be such that the car is built in four variants, period. 4-cyl Basic, 4-cyliner with premium package, ECO (Includes premium package) and SS. Also, I believe that if a product is not differentiated -- actually let's up the ante to "not sufficiently differentiated" -- a company like GM operating in a high cost country (USA) has no business building it.

I am not sold on the lacquered metallic grey plastic trim on the console and instrument surrounds. GM seems to have fallen in love with this stuff, but I think it just looks tacky and cheap. Plain old matte, soft touch upholstery would be better. I am also not sold on the broad stretch of black "canyons" above and below the silver trim across the dash. Is it better than the current car? I think so. Very much so. But is it bewitchingly beautiful and appealing? No, I think something cleaner and less cluttered will be better. From a power train standpoint, I wish GM will think outside the box a little bit. This is especially true of the niche models like the ECO. Instead of recycling the "old" 2.4 DI four with its eAssist BAS setup, I would have preferred if they tried something unique and more substantially different. If its me, I'll use a 1843 cc (1.8L) 3-cylinder version of the new 2.5 engine running a late closing intake cam with a turbocharger (Miller Cycle). The engine should provide about 170 hp & 200 lb-ft with substantial fuel economy benefits over a 4-cylinder engine in the 1.8 liter class. With a 15hp BAS this is also "adequate power" such that the car wouldn't be embarrassingly slow. I'll eschew a main stream V6 or turbo 4 altogether, but introduce a seriously performing SS model. I think this makes sense in that the typical soccer mom doesn't care for a V6 or a turbo 4. 4-cylinder Camry performance is more than enough. For the most parts they won't even know what a V6 or turbo is. All that matters is if the car is quiet, comfy, spacious, reliable and reasonably efficient. For the enthusiast, a mild turbo like the 220hp Regal or a 252hp V6 Malibu is not enough either. Instead, the SS can be exclusively an AWD car with a 3.0 Bi-turbo engine making ~360/360 lb-ft hp and hitting 60 mph in 4.6~4.8 secs.

Not quite. The Quad 4 had a 94 mm stroke compared to the 2.5's 101mm. It also runs at a lower redline -- 6800 rpm for the unbalanced engines and 6500 rpm for those with balance shafts. Hence the Quad 4 runs with a maximum piston speed 86~90% that of the new 2.5.

Piston speed = stroke (in feet) x rpm x 2 Basically, if an engine makes 7000 revolutions per minute, each piston is covering a traversed distance of 2 x 7000 the length of its stroke a minute. The common expression of piston speed is either in meters/sec or feet/min. Piston speed is important because it is one of the leading indicators of stress at the wrist pins and journal bearings within an engine. The stress loads are generally a function of the square of piston speed. Hence, when the maximum rpms are raised from 6000 to 8000 rpm, this 33% increase raised stress loads by about 78%. This is why rpms is potentially much more harmful to engine integrity and durability than high torque loads from turbo or supercharging -- because stresses increase linearly with torque loads, but exponentially with rpm increases. Before you get scared stiff however, know that an Ecotec engine only spends a tiny fraction of this duty cycle at or near its 7000 rpm red line or its 4639ft/min max piston speed, whereas a Formula 1 car spends the majority of its life there. If you run that ecotec at 6500~7000 rpm continuously under load for 3~4 hours straight and do that every day, you'll probably grenade it. But you won't.

Actually it was a little more contrived than that. BMW switched to a ZF 6-speed for RWD cars, but the the ZF box did not have the appropriate accommodations for AWD, so the AWD models (eg. 330xi and X3) used a GM Hydramatic 6L45 6-speed automatic to get all 4-wheels turning.

Actually, no they don't. The Mini uses a Getrag 252 (5-speed) and Getrag 285 (6-speed) manuals, as well as the Aisin GA6F21 6-speed automatic. None of which are of BMW origin; BMW does not do transmissions. Who builds the DCT in the M3 and M5? Getrag supplied both the SMG and the DCT used by BMW. The SMG is basically a Getrag D-type 200-series manual transmission with electro-hydraulic actuation of the singular clutch. The DCT is designed from the ground up as an automated manual with a concentric shaft and dual clutches. Getrag was traditionally a manual gearbox maker. Like Borg-warner (which supplies VW-Audi's DSG) they evolved into an automated manual maker. GM uses Getrag boxes too. The Getrag F23 5-speed manual was in the Cobalt/HHR SS. The F28/6 is in the manual trans Turbo Opels (Buicks).

Actually, no they don't. The Mini uses a Getrag 252 (5-speed) and Getrag 285 (6-speed) manuals, as well as the Aisin GA6F21 6-speed automatic. None of which are of BMW origin; BMW does not do transmissions.