dwightlooi

The point was... it wasn't insignificant. 62 lbs is comparable, for instance, to the entire sound insulation package used in many compact cars.

The Weight is 211 kg. This is somewhat disappointing. For comparison the LS3 is a mere 183 kg, while the LS7 is 206 kg. Yes, DI, VVT and AFM add weight. But 28 kg = 62 lbs is a lot of weight.

BTW, just reading off GM's Powerpoint Slide, the output rpms appear to be 450 bhp @ 6000 rpm 450 lb-ft @ 4200 rpm -- with at least 400 lb-ft (88.9%) available from 2000 to 6200 rpm

No, but the 5.3 might be.

Regardless of whether the ATS-V gets this engine, the CTS-V won't. The CTS-V is already at 556hp with the current LSA engine. It's replacement will need to be either a turbocharged or supercharged version of the LT1 to be at or above the current performance level.

Now that it's out in the sun, here's summary of what made it and what didn't... What Made it Direct Injection Synchronous Variable Valve Timing Cylinder Deactivation What didn't make it Cam-in-cam independent Variable Valve Timing Dual In-bloc Cam Hemispherical Combustion Chamber w/ 3-valves Raised Camshaft location (lighter valvetrain mass / higher rpm capability) -- AFM lifters can't cope anyway so it's moot Variable Ratio Rocker assembly Variable Volume Intake manifold Variable Length Intake Runner Assembly Non-Acoustic Knock Sensing (Ionic Knock detection via sparking plugs) In retrospect I can say the following:- Power came in 20 hp less than my previous expectations (450 vs 470)* Torque cam in 12 lb-ft higher than my previous expectations (450 vs 438**) Compression came in 0.7 points lower than my expectations (11.5 vs 12.2) Cam-in-Cam didn't make it (I expected it to) We can finally put the 5.5 liter mythology to bed I guess. * This may indicate a relatively low red line (perhaps 6000~6100 rpm) perhaps imposed by the the cylinder deactivation system. ** 438 lb-ft was based on the limit of the 6L80 transmission. Regardless, this engine is in the ballpark of expectations and will serve the C7 very well. It will also serve Cadillac very well should they elect to adopt it for the ATS-V. It is, afterall, a lighter, smaller, more powerful and more torque engine than the Ford DOHC 5.0. It is also lighter, simpler and less expensive than Bi-turbo V6es of a similar output.

I have wondered why GM does not use the Buick Quiet steel technology on top of their normal sound deadening material to get an ultra quiet ride. Actually they do. And it's actually quiet effective even in the Malibu.

Perhaps Clatter is not the right word... the engine sounds at lower RPMs have a diesel like "gggrrroooccc" to it. GM's port injected V6es don't have that -- Pushrod or DOHC. The 3.5 and the 3.9 for instance are quieter engines albiet somewhat less rev willing. If you wind down the windows you hear a tock-tock-tock-tock drone from the injectors too. But this is not a responsiveness issue, this is a refinement issue. At this rate, they are better off with 40 hp less and using Port Injection. Drove a Saturn Aura 3.6 once... didn't have these stupid low rpm acoustics. Wind it out to 5000+ rpm and it doesn't sound bad really... it's kinda a baaawwaaahhhhhh with a baritone exhaust note. Not exactly a VTEC like rasp or a turbine like whirl, but not objectionable.

Unfortunately, I came off feeling that it was pretty bad. This engine is not going to cut it as far as impressing luxury buyers of the CTS and ATS. At least not in the refinement department when they cross shop a Lexus, BMW, or Acura.

OK, got to drive a LFX equipped Camaro for the first time. And, I am sad to report that there had been no significant improvement in the refinement of the engine (compared to the 312hp LLT). The engine is still plagued by the most unpleasant acoustics I can bear. At idle it makes a muted, diesel like clatter. At low rpms between 1000~3000 the engine makes a groany gggaaarrrr. It all gets somewhat drowned out by about 4000~5000 rpm as the rest of the engine noises catches up. To a certain degree, cruising noise on the freeway isn’t bad because the wind noise, tire noise and everything else help mask the utterly uninspiring engine note. But on local streets pulling modestly from a light the GM 3.6 DOHC DI V6 was and continues to be perhaps the most unrefined sounded engine I have experienced. While I applaude the performance of the powerplant on paper, this is possibly the greatest step backwards in refinement GM has taken in years. Forget about class leading refinement from the BMW straight sixes, the Lexus V6es or, heck, the Acura V6es. If you compare it to the 3.9 pushrod, 3.5 pushrod, 3.6 DOHC (non-DI) or the grand old 3.8 it is clearly and unmistakably much worse in the low frequency clatter department. Feels and sounds like a quick revving tractor engine if that’s possible. I believe that this is the biggest refinement issue GM needs to solve if it wants to play in the luxury league with Cadillac and Buick. This engine character will turn off more mainstream buyers than 90hp/liter will attract drinkers of technobabble. I believe the problem is inherent to solenoid direct injectors. And, the isolation that GM put in the LFX simply isn’t cutting it. In fact, it sounded no better than the LLT – at least not to me. No, I didn’t drive both back to back and memory can be a little deceptive on sounds when the events are months apart. But, it was clearly and convincingly better when they need it to be. The solutions are there, however GM’s willingness to embrace them may or may not be there. Toyota/Lexus went to a dual injection system specifically for this reason – port injection for idle and low rpms with direct injection kicking only under high load and engine speeds. VW-Audi went with Piezo direct injectors in lieu of solenoid injectors.

Regarding the C7... It is safe to say that the C7 will have a more fuel efficient engine. Whether that will be a smaller displacement engine remains to be seen because a reduction in displacement does not necessarily equal an improvement in fuel economy. In fact, a reduction in displacement is a comparatively ineffective measure to reduce fuel consumption compared to an increase in the intake duration for instance, cylinder deactivation or simply the adoption of a taller axle ratio. Regardless of what the displacement ends up being, it is safe to say the that there is absolutely no reason to believe that it will more likely be 5.5 liters vs some other (larger or smaller) displacement. The 5.5 liters mythology regarding the C7 arose from the fact that GM raced a 5.5 liter DI V8 in the C6-R with architectural roots in the Gen V engine. That displacement however has no relevance to production engines and is entirely dictated by class rules, in the same manner that Formula 1 rules requiring the cars to have 2.4 liter V8 engines have no bearing on the displacement of Ferrari production car V8s. DI was in fact subsequently deleted from the 5.5 liter C6-R engine, again compelled by changes in class rules. This also has no bearing on the incorporation of DI in the production Gen V engines.

For small trucks, they really should do a large displacement four based on the Gen V V8. There are five reasons for this:- A 3.1 Liter class Pushrod or SOHC 8-valve four with direct injection will be about 210 hp @ 5600 rpm / 210 lb-ft @ 2600 rpm which is about right for a small truck. The power and torque characteristics -- higher torque, lower peaks -- will be more suitable for a truck than the 2.5 liter DOHC-4 Fuel economy will be similar to the 2.5 liter DOHC-16v engine with lower internal friction offsetting lower pumping losses It can be built on the same tooling and assembly line as the V8 It is actually cheaper than the DOHC engine. In fact a direct injected Pushrod 4.6 liter 90 deg V6 may not be a bad idea either in the 315hp @ 5600 rpm / 315 lb-ft @ 2600 rpm bracket. Again, high output is not the goal here, although at the same output as a Northstar V8 it's not bad really. They goal is good towing characteristics with class competitive performance without the complication and costs of forced induction. Again, all the pistons, rods, wrist pins, injectors, valves, rockers, etc.

Actually, that is exactly what I meant. If you any engine is making 206 lb-ft of maximum torque but only 168 hp, the power peak will have to be pretty low in rev range. Horsepower (by definition) = torque x rpm / 5252. If you are making 206 hp at 5252 rpm, you maximum horsepower would be 206 hp @ 5252 rpm. Given that the engine makes "only" 168 hp, it means that torque had fallen off significantly before 5252 rpm. With a flat torque curve -- like most turbo engines have -- 206 lb-ft @ 4300 rpm = 168hp at 4300 rpm. At any rpm above that torque MUST fall off faster than rpm rises otherwise the HP figure will exceed 168hp. At 6000 rpm for instance, torque must have fallen to no more than 147 hp. Otherwise hp will exceed 168 hp. Now, when I say the turbo is "undersized" I don't mean that it is being overworked and runs ]at damaging speeds shortening it's life. What I meant was simply that the turbo is incapable sustaining maximum boost all the way to the engine's redline. We generally call this an "undersized" setup, whereas a turbo which is capable of sustaining maximum boost beyond the engine's redline or a higher boost than stock is considered "oversized" This is also the reason why torque on must start falling off from 206 lb-ft no later than 4300 rpm. Because beyond that speed, one of two things (or both) must be happening. Either the turbo is exceeding its maximum rated rpm or it is falling of the compressor's efficiency map, and the ECU must progressive reduce boost above that engine speed so the turbo doesn't become short lived or make more heat than it does pressure which does nothing to get you more power. If this is not the case the engine would continue to make it's maximum torque (which collerates roughly with maximum boost) to a higher rpm and generate a higher hp figure than 168hp. Personally, I favor designs which have slightly lower torque than hp. This allows lower boost, higher compression which translates to both better fuel efficiency and a more responsive, more linear, engine. Examples of these will be the ATS 2.0T's 270hp / 262 lb-ft (LTG) engine or the Nissan GT-R's 520hp / 451 lb-ft (VR38DETT) engine.

I generally don't favor turbocharged setup with much higher torque figures than hp numbers. There is only one conclusion you can draw from such figures, and that is that the turbocharger is undersized and over boosted. Let me explain... 206 lb-ft is 206 hp at 5252rpm. What that means is that the power peak arrives at some engine speed lower that. Assuming a flat torque plateau the power peak is probably around 4300 rpm. You can also get 168 hp if you boost the engine to say a mere 160 lb-ft but carry it to 5500 rpm. Generally speaking the effective mass air flow in both power peak instances are about the same and generally speaking the same turbine/compressor pairing would be used in both. The only reason the engine is not about 220 hp @ 5500 rpm is because the selected turbo is too small and runs out of airflow capacity above about 168 hp. There are two reasons why taking an engine with a very small turbo to relatively high boost at lower rpms then having to back off quite early (in the 4000s) to avoid overspeeding the turbo is not ideal. First of all, a 168hp @ 5500 rpm / 160 lb-ft @ 1500~5500 rpm engine is far more linear and enjoyable to drive. Turbolag getting to 160 lb-ft will be significantly less than getting to 206 lb-ft, also the engine won't feel like it's running short of breath early in the mid-4000s. A 168 hp @ 4300 rpm / 206 lb-ft @ 2300~4300 engine feels like a diesel! The second reason is one of efficiency. A significant factor affecting fuel economy is the compression ratio of the engine. This is because the compression ratio in an Otto cycle is it's expansion ratio and a larger expansion ratio extracts more energy from each ounce of fuel burned. If you take an engine to about 100 lb-ft / liter you can have a 10.5~11.0:1 compression with direct injection with a boost pressure of about 10~11 psi. If you want to take the engine to about 130 lb-ft / liter you need about 18 psi of boost which means your compression (even with DI) needs to go down to about 9.0~9.3:1. That in and of itself is worth about 10% mpg (3~4 mpg) in a small engine in a small car. Small turbo, high torque, low hp is the worst of both worlds. It has the increased lag and reduced economy of an engine with a larger turbo and about 130 hp/liter, while not having the power and performance.

First of all, lets get one thing straight. If alternative energy sources are economical, they won't need subsidies and laws encouraging, or requiring, their adoption to exist. The fact is that they aren't economical. Burning coal, oil and gas to generate power or to run you automobile remains the most cost effective means of powering our society's energy needs. This is true despite $100/barrel oil and $4 a gallon gasoline. It'll remain largely true until oil gets to about $300~500 a barrel and gas prices top about $12 a gallon. Let's take the state of California for an example. The state passed laws requiring that utilities obtain at least about 1/3 of their power from wind, solar or other renewable sources. The result is that Californians now pay about 14.5 cents per kWh. Compared to states like Indiana or Texas where it is about 8 cents and 7.5 cents respectively. This is expected to go up even more in the next few years as California's Cap and Trade racket kicks in. California responded by implementing a tiered system which -- very much like progressive taxation -- gives lower rates to users who do not use a lot of power while punishing heavy users. While this placates some home users who are willing to conserve, it essentially drives industry from the state faster than the bubonic plague. Make no mistakes about it, "green technology" does not bring jobs, they chase them from our shores. America's economic success in the past century wasn't built on our environmental zeal, it was -- in part -- built on the fact that we have always had cheap and plentiful energy. Unfortunately, this is something we are trying to change in the earnest. That we refuse to explore and extract cheap and available fossil fuel domestically is scandalous and flat out stupid to say the least. At some point, fossil fuel will become sufficiently scarce and expensive enough that alternatives start to make sense. That is inevitable, but that is not today or couple of decades from now. From a purely economic standpoint we should let the market decide when to make that transition – very much like we let economics transition us from coal and whale blubber to oil and gas. We should not try to artificially hurry that process when the economics – the supply and demand – simply do not compute. This leaves only one motivation to promote, subsidize and require alternatives today – the misguided believe that somehow androgynous CO2 output is something we should worry about. I personally do not believe in the Global Warming hypothesis -- the planet is not currently warming and all the warming (and cooling) in the last century is not the slightest bit abnormal in the history of the planet's climate. I also happen to believe that there simply isn’t enough fossil fuel reserve for us permanently or tangibly alter the planet’s climate even if we wanted to. But, this post is not about the climate change hoax; it is about alternative energy so I am not going to spend any more time debating this issue. Instead, I will simply talk about what the future will bring in terms of how we power our civilization. This future, IMHO, is inevitable even if I disagree with the policies, reasons and viability of trying to accelerate its arrival. To put it simply, the future is in nuclear generation, electrical grid distribution and battery storage. Why Nuclear generation? Because it is the only alternative source of energy with sufficient generation density to power out civilization’s power demands. Wind, Solar and the rest while attractive in their various niches wouldn’t generate enough power to provide for more than 20~25% of today’s power demands even when fully exploited. They have no chance of replacing fossil fuel as the dominant energy source. The geo-political supply situation is also quite favorable. The new “Middle East” in the era of Nuclear Powser will be Australia and that is a firm and stable US ally. Why electrical grid distribution? Because it is a efficient, proven and practical way of moving power. It certainly beats hydrogen – a near absolute zero cryogenic liquid or the lowest density gas in the universe. Why do you want to produce hydrogen then move it in 5000 psi gas tanks or cryogenic containers then use a fuel cell to convert it to electric power to drive a motor? It also beats micro reactors in your garage simply because of safety and economies of scale in power production. Why Battery Storage? Because, apart from costs, batteries are fully capable of powering a car with the kind of range and performance we demand. The current price of about $400 per kWh for Li-Ion batteries – about $20,000 for enough electric juice to move a midsize car 125 miles can be expected to half in the next decade and ultimately stabilize at roughly the price of lead acid power cells – roughly $100 per KWh. That means that $10,000 in storage cells can get you 250 miles. This is something we can live with even if it is slightly less convenient than gasoline or diesel. Batteries’ biggest downfall – its need to take hours to recharge compared to gas tank’s convenient 2 minute fill up – is also not unconquerable. Instead of plugging-in your car and waiting for the batteries to charge up, if we standardize the dimensions and specifications of battery packs we can have an infrastructure where by you simply swap packs at a gas station. We can have standardized packs very much like we have D sized batteries in flash lights. You drive up, a robotic sled goes under the car, pluck one or more packs off and replace them with fresh ones. You pay for the cost of electric charge and the depreciation of the packs (about 1/1000th the cost of the batteries when new), they even credit you for remaining charge in the packs you left behind and you are on your way in a minute or two. You never buy new batteries the gas station does when it detects a pack that has run out of its useful life. That is the future I see. I just don’t think we should be in a hurry to bring it about. What we need today is not dubiously green and exorbitantly priced energy. What we need is cheap and plentiful energy. So... yes... I'll say “Drill baby drill”!

Pair it transmissions like these and it gets even more interesting... GM Electramatic 9E30 -- Hybrid Drive Type: Transverse, FWD, Torque converter automatic transmission Input Torque rating: 130 lb-ft Maximum Input speed: 6000 rpm Speeds: 9-speed Ratio Spread: 8.0:1 Flywheel Integrated Motor-Generator-Starter (FMG): 27 hp @ 3000 rpm, 94 lb-ft @ 0 rpm (DC Motor), 6000 rpm Maximum Motor Speed Electric Storage: 0.8 kWh -- 115.2V Lithium-Iron-Phosphate Battery GM Hydramatic 9T30 -- Conventional Drive Type: Transverse, FWD, Torque converter automatic transmission Input Torque rating: 130 lb-ft Maximum Input speed: 7000 rpm Speeds: 9-speed Ratio Spread: 8.0:1 Flywheel Integrated Alternator Starter (FAS): 0.9 kWe Alternator-Starter Electric Storage: 0.08 kWh -- 13.2V Lithium-Iron-Phosphate Battery

You know what will be really interesting? Type: 2.5L Atkinson Cycle Inline-3 w/ single balancer shaft Construction: Aluminum Block and Heads Bore x Stroke: 103.25 x 101 mm Displacement: 2537 cc Compression: 15.5:1 Valve Train: SOHC 2-valves/cyl (6-valves) with cam-in-cam dual VVT and Cylinder Deactivation Fuel Injection: Direct Gasoline Injection Power: 135hp @ 5800 rpm Torque: 126 lb-ft @ 4800 rpm Max Engine Speed: 6000 rpm Fuel Requirement: 87 Octane unleaded It'll be a very nice engine for compact cars like the Cruze, the Sonic or as the generator drive for the Volt or ELR.

It doesn't really work that way... It is perfectly acceptable that a race engine be rebuilt every 3~4 races. It is not acceptable that you rebuilt your mundane engine every 3 to 4 years. It is perfectly acceptable for a race engine to idle at 3000 rpm, any production engine that does that will see the car make a U-turn straight for the service department the moment it is driven of the dealer's lot. It is generally a non-issue for a race engine to make good power between 6000 and 8000 rpm and suck everywhere else, an everyday engine that does that won't be acceptable to the diehard S2000 fan and won't ever pass SMOG. Generally speaking, race engines to not have to be long lived, clean or civil. Fuel economy isn't even a factor. The same thing goes for drive train, brakes, tires and other parts. They just have to deliver maximum performance and not grenade itself for the relatively short duration of a race. By the time you take a race engine, tone it down to the point where it pulls smoothly from 600 rpm, passes emissions, lasts 200,000 miles even when the driver changes the oil every 20,000 miles it is no longer the spectacular performer. In fact, a lot of race grade stuff actually sucks in daily use even when you won't think they would. A good example is forged pistons. Yes, it is stronger, yes it can put up with more abuse and detonation before failing, and yes it is more expensive. But, because it also has a higher thermal expansion it needs to be fitted lose when cold in order to have the right clearances when warmed up. This leaders to a noisy cold engine, high oil burn rates and most importantly greatly increased wear over time. A race car has no problems with that but you do.

There is a difference between crate engines or race engines and production engines covered by a 5yr/100,000 mile warranty expected to endure the drudgery and neglect of mundane automobiles. Production also has to have a wide and tractable power band whereas motorsport engines only have to perform within a relatively 2000~3000 rpm range and it is the job of the racer to not allow rpms to fall out of the prescribed range. The problem with reving any engine that high is that you end up using a lot of valve lift, duration and overlap to get the engine to breath with good volumetric efficiency high up. Cams like that generally don't idle well at 600 rpm, most do not idle at all that low. VVT mitigates that somewhat by allowing you to dial out the overlap but it still results in a rather soft lower rpm response. Besides, the high valve spring rates needed to prevent valve float at such rpms causes increased wear and reduced fuel economy. With Pushrod engines in the 45~50 cu-in per cylinder bracket, we know that we can get to about 6600 rpm without using exotic materials. Throw in titanium valves and the like and you can push it to about 7000 with no reliability or durability issues. With DOHC 4-valve designs, you can get to about 8200 rpm using the "normal" stuff, about 9000 if you really try. For most production cars though, these are all more than adequate rpm capability.

Yes, a 9~10 speed auto will get you to (or past) a 8:1 ratio spread. My point was that the 9~10 speeds really isn't necessary and may actually hurt performance and/or economy. What's needed is the ratio spread and a 6~7 speed transmission with a wider spread will do just as well if not better.

What's really needed is a wider ratio spread than is currently typical of 6-speed transaxles. We really don't need more speeds. In fact, more speeds can actually hurt performance and economy. Most 6-spds are ~6.0:1; the GM Hydramatic 6T70 is 6.04:1 for example. 7 and 8-speed autos currently achieve ~7.5:1. The ratio spread is the difference between the tallest and lowest gear in the transmission. A wide ratio spread allows for stout acceleration from stand still in first and low rpms on the freeway in top gear. Having more ratios only reduces the amount of rpm drop during an upshift. With 6-speed transmissions we already have what is close to the ideal in rpm drops on upshifts. Let me give you an example... the current GM 6T40 transmission (Cruze Automatic) will see revs drop from the 6300 rpm redline to 4100 rpms in a 1-2 shift at the redline. In more leisurely driving, a shift at let's say 3800 rpm will see revs drop to 2500 rpm. This is quite optimal as is. Because a redline shift drops revs to near the 1.8 NA engine's torque peak of 3800 rpm. The 1.4T with it's wider torque spread doesn't even really need such a close ratio. In higher gears the gap actually gets narrow so there is even less rpm drop (as a percentage). A 5-6 shift at 6300 rpm sees a mere drop to 4700 rpm. Too many speeds actually hurt for three reasons. Firstly, the engine's power is not being fully applied to the wheels during a shift, it is being wasted as heat into the transmission fluid. Hence, energy is wasted during each shift. Secondly, it makes the car slower partly because you are not accelerating during a shift and partly because the car accelerates fastest in any gear at the torque peak hence you want to drop close to that (simply dropping less isn't necessarily better). Finally, a 8-9 speed transmission often employs 3 planetaries instead of 2 -- more gears meshing around = more frictional losses. That going beyond 6 speeds gets you quickly diminishing performance and economy returns is evident in the fact that most 7 or 8 speed boxes "skip shift" routinely. That is they bypass a gear and move two steps up quite often in leisurely driving. The problem with making a 6-speed box with a 7~8:1 ratio spread is that the planetaries get pretty big. So it may actually be easier to make a 9-speed with that kind of spread.

Ok, let me try to explain it a bit better... (1) A SOHC I4 with 2-valves per cylinder has all the frictional benefits over a Pushrod I4 with 2-valves per cylinders. In fact, it has two additional benefits -- the valves can more easily be made opposed as opposed to side-by-side and the absence of pushrods makes the sprung mass lower allowing slightly higher revs although this is probably not useful. (2) The SOHC head is taller than the pushrod head. However, it is not any wider unlike a DOHC head. The additional height is traditionally handled by slanting the I4 to one side in RWD applications or reclining it in FWD applications. This allows the engine to be no taller than a Pushrod I4 while the addition in width is also essentially zero because the exhaust manifold would have projected sideways by approximately the same amount had the engine been upright anyway. To put some numbers into the discussion, if GM ditched the 1.4 litter turbocharged DOHC-16v Inline-4 for a 2.3 liter SOHC-6v line-3 running on an Atkinson intake cam, the Cruze would have have superior MPG numbers while delivering approximately the same output of 140 hp. Specific output should not matter. That 2.3 liter engine would only make 140 hp should not be embarrassing, if one understands that it weighs about the same as the 1.4 turbo (with its forced induction hardware), while delivering better fuel economy and a similar output.

Pushrod I4s never made sense -- there is no packaging or efficiency advantage over an SOHC I4. The reasons for DOHC small displacement engines have been more than adequately covered in the thread. As far a the Ultra V8, I do not believe it is necessary or a good investment. At the end of the day luxury buyers are not acronym buyers by and large. If you have the right output, the right refinement and right MPG numbers, it won't matter if you have a pushrod engine or 2-stroke engine with no valves. The direct injected Gen V in a 6.2 liter trim delivering between 450~500 hp will be a more than attractive engine for Caddy's V8 needs if it gets MPG numbers in the 15~17/24~28 range in a 4000 lbs car. If GM wants to build an exclusive, premium engine for Cadillac, the money is better spent on an over-the-top 7.2 liter V12 based doubling the LFX 3.6 V6. Such an engine will deliver about 640hp / 550 lb-ft in normally aspirated trim, rev to 7000 rpm and if turbocharged for special applications yield a 1000hp powerplant. Development cost will be relatively low given that it is not a ground up architecture -- the valves, lash adjusters, pistons, sings, bearings, rods, combustion chamber modelling, injectors, cam phasers and many other parts will come directly from the LFX 3.6's parts bin. Only the block, crank and camshafts will be unique. And, given that the bore size, spacing and bank angle are identical to the 3.6 it can be made on the same assembly line and with the same tooling.

I haven't been been a big supporter of the Volt since its inception. This is not because I am against the technology or plug-in hybrid drivetrains per say, but because I have believed that the Volt is the wrong approach in GM's attempt to make a break through in this segment. The problem with the Volt is that -- being a plug-in -- it requires a very big and very expensive battery. Even so, it is essentially a 40 mile vehicle beyond which it is a rather poor hybrid with fuel economy barely better than a compact car like the Cruze Eco or Honda Civic. In fact, many of these compact cars actually beat the Volt on the freeway -- primarily because they are lighter. The entire Voltec drive train also has practically no alternative applications. I would very much have preferred that GM used that engineering and monetary resource to do two things:- Overall their entire automatic transmission lineup to include the option for a modest Flywheel integrated DC Motor-generator (FIM) in 15~20kWe range (ala Honda's IMA) ahead of the torque converter. Develop an Exhaust Turbine Generator (ETG) in the 5~8 kWe range This will allow for options to hybridize their entire lineup it two levels. The basic hybrid will have the FIM and a 0.4~0.8 KWh battery will add no more than $1500 to the vehicle but will out perform the eAssist system in terms of economy benefits. The premium Hybrid will include the ETG -- essentially half a turbocharger connected to a small generator -- and a 0.8~1.6KWh battery. This allow energy recovery from two sources instead of just regenerative braking and will increase the amount of electric recovery by about 30~40% compared to today's hybrid. This allows for vehicles that actually match or exceed the Priuses without requiring a unique drivetrain applicable only to a particular paring of engine and electric motor size like planetary systems. The ETG equipped systems will add about $3000 to the price tag. The key here is that the two components developed -- the FIM and ETG can be applied to practically all engines and drivetrain layouts in existence, and the use of a simple, lightweight setup allows means that the vehicle does not need to find space for a massive battery (the battery will only be 1/40th to 1/10th the capacity of the Volt's) The basic version of the "Electra" driveline without the ETG is depicted here. If you couple it to a modest normally aspirated four the system will be slightly better than the 45/45 mpg from the Civic Hybrid by virtue of its 20 kWe FIM rating vs the Civic's 15 kWe. With an ETG we can expect numbers in the low to mid 50s because the system will be generating free electricity at all times not just when the car is decelerating. In the above concept however, fuel economy is not 1st priority. This is essentially a car with a similar output level as a Lancer Evolution, but capable of better fuel economy than a Cruze Eco.

In case you are wondering, this is how the torque and power curves look like...