dwightlooi

The current 2.4 has an 88mm bore x 98mm stroke. It also has a 96mm bore center. What this means is that there is basically no room for the engine to be bored out any further. Stroking out the already pretty long stroke will also make the stroke overly long.

It's more than the fact that they won't do it or can't do it. It's also that most drivers won't appreciate a 100hp/liter NA engine very much. In general, the amount of of torque you are going to get out of a liter maxes out at 75~78 lb-ft per liter even with direct injection and lofty compression. There is not a lot you can do about that. It means that you'll have to rev it into the stratosphere to get power to 100 hp/liter. You'll need to be making 140 lb-ft, at 7500 rpm to generate 200hp. To do that, you'll probably have to hit your 150~156 lb-ft peak no earlier than 1500~2000 rpm before that. 200hp @ 7500 rpm + 156 lb-ft @ 6000 rpm... might be nice in a sporty car, but will also be a rather frustrating engine for average family sedan. Not to mention, the current breed of GM 6-speed automatics have a maximum shift speed of 7000 rpm, meaning you need a new family of high rpm compatible transmissions. Making 170hp on 2.0 liters or 200 hp on 2.5 liters allow you to have a more palatable power delivery. Probably something like 170hp @ 6600 rpm + 150 lb-ft @ 5000 rpm & 200hp @ 6400 rpm + 187 lb-ft @ 4800 rpm respectively. It'll also be compatible with the 6L45, 6T40 and 6T70 transmissions.

Well, let's put it in a rough perspective. Going from a 89mm bore to a 94mm bore costs 0.4 points in compression (same cylinder head design, same fuel grade, same basic engine architecture). A 103.25 mm bore will likely cost you another 0.6 points or so. What that means is that a 3.0 4-potter built on the Small Block architecture and using direct injection is likely to be a 10.7:1 (on regular fuel) to 11.2:1 (on premium fuel) engine. This is with the same level of conservatism as the HF V6 family. You can likely push it to 11.5:1 with a more aggressive attitude towards tuning like you might see in an engine destined for the Corvette or a Caddy Sports Sedan -- where Premium is not just recommended but required. You are unlikely to see that in a truck or family sedan engine which has to be more... let's say... idiot proof. That said, a 3.0~3.1 liter 2v per cylinder DI 4-potter may not be a bad engine for entry level trucks. It'll make about 200hp on regular with a similar amount of torque. You can also fortify it with a single turbo to the tune of about 280 hp / 280 lb-ft with an early torque peak (~1600 rpm) while still staying on regular. It'll not be a paragon of refinement, but it'll be cost efficient and more fuel economical than a V6.

The 2.4 is actually quite smooth and unobtrusive. It's rather underpowered for a car like the Regal or the Malibu, but if you don't care about gusty acceleration its actually not bad. I actually find the 2.4L 4-potter to be a smoother engine with better aural refinement than the 3.6 DI V6 in the Camaro.

(1) If you are going to stick with the Pushrod-OHV layout, as you move to an inline configuration all of the advantages disappear. A pushrod valvetrain's advantage is in making a Vee type engine narrower, lighter and in some ways more efficient. It does so by reducing the number of camshafts, by making the heads narrower and lighter, and in doing the aforementioned cut down of parasitic frictional drag from the valve train. When you no longer have two banks of cylinders, all of that goes out the window. (2) From an efficiency standpoint, if you compare two engines of the same displacement but different cylinder count, the one with fewer cylinders tends to be more efficient. Again, because of lower drag from fewer sets of piston, rod and valve assemblies. This however only applies up to a point... as cylinders get bigger, the distance from the spark plug to the edge of the combustion chamber also gets longer. This makes the engine less resistant to knocking. This forces you to lower compression ratio to compensate and that reduces fuel efficient by lowering the thermal efficiency of the combustion process. At some point you break even and start losing more efficiency to compression reduction than you gain in frictional reductions. A 3.0 liter four with 750cc cylinders is pretty close or beyond that point. (3) A 4-potter also has 2nd order vibrations that get progressively worse with piston weight and especially stroke length. You can cancel most of it with a pair of contra-rotating balance shafts. Most of it, but not all of it. A 3.0 liter four with balancers will be a little on the rough side. Probably not horrendous, but definitely not a creamy smooth engine. (4) A 3.0 liter 4-cylinder has actually been tried before on a production car. It was used by none other than Porsche on the 968. The engine made 236 hp in naturally aspirated trim and 305 hp in turbocharged trim.

Honestly, I would have powered the "regular" Cruzes with a normally aspirated version of the 2.0 DI Turbo engine. Should be good for 170~180hp and be a better engine for most drivers. You'll probably end up with similar MPG numbers as he Focus -- 24~25 mpg (city) / 34~36 mpg (Fwy). I don't think most buyers will care that much about + - 1 mpg when considering their purchases. A test drive in a car with a smooth, free breathing 170~180hp 2 liter engine will probably sway more buyers than 1 mpg. They can the do an Eco Model using a 3-cylinder 1.8 liter milled that's basically the 3.6 V6 chopped in half. With a turbo the engine is probably good for the same 170~180 hp as the 2.0 four potter and at least equal the 1.4T four in economy numbers because it has 1/4 fewer frictional elements. This is especially true if it retains the 11.3:1 compression of the 3.6 and use minimal boost (7~8 psi). It'll also be relatively easy on logistics, sharing the rods, pistons, valves, valve cover and heads with the V6. A single balancing shaft should tame it sufficiently to be unobtrusive. The Eco can go full tilt with a dual clutch tranny, aluminum body work and what not. That should be good enough for the launch. In the second or third model year, they can follow up with a 260~300hp 2.0T for the enthusiasts and keep the interest level in the model high. The 2.0T and the Eco should be priced similarly. Basically, if the base car is not good enough the choice is between Performance and Green, drawing on both demographic niches.

Which begs the question... why isn't most of what's being done to the Eco model standard on all Cruzes? Especially stuff that is cost neutral or has a minimal effect on cost... Eg. Less openings in the upper grill? That doesn't cost anything. Thinner gauge steel and narrower flanges? Costs zero, may even save a few bucks. An extended front air dam strip? Cost zero. Underbody tray? Costs a few bucks, but a piece of unpainted plastic or two really doesn't cost that much. Spoiler? OK make that an option. Light weight alloy wheels? OK, I'll drop that but everything else looks like they should be standardized. They really ought to give the Eco Model something significant -- like a clutched automatic (ala M-B AMG), a dual clutch gearbox (don't develop one if they can't afford to, go buy Bord-Warner's off the shelf box like VW-Audi did) or a DI version of the 1.4T with higher compression. Dumbing down the standard ones to make the Eco stand out is... well... rather foolish. Eco or not, the overwhelming majority of Americans don't buy Manuals -- they don't even know how to drive one. And, those who do? They are performance junkies not eco freaks.

GM just announced the official MPG numbers for the Cruze Eco model: http://media.gm.com/content/media/us/en/news/news_detail.brand_gm.html/content/Pages/news/us/en/2010/Nov/1111_cruze_eco This pretty much confirms something I have been saying for years -- reducing displacement has a very small and sometimes intangible effect on fuel economy. Other factors such as weight, aerodynamics, transmission efficiency and friction within the engine has a greater bearing on mpg numbers. If you look at the automatic numbers and compare it to that of the Ford Focus which has a 2.0L engine, you'll notice that it is but 1~2 mpg off. Given that the non-Eco 1.4T Cruze (Automatic) is turning in 24/36 mpg, we can also conclude that practically all of that is from aerodynamics improvements and weight reductions. In other words, going from 2.0 liters to 1.4 liters gained you exactly nothing. This shouldn't be surprising given that displacement reductions itself without reduction in cylinder count, cams or valves does not reduce the internal friction of an engine by much. Yes, a smaller displacement engine pumps less air per revolution but at low loads and cruising speeds the amount of air moved is pretty much constricted by the throttle body anyway. We see the same lack of economy gains when we compare the 3.0 DI V6 and the 3.6 DI V6 too. The 3.0 is no more efficient than the 3.6 in the same vehicle, it is in fact less 1 mpg efficient due to reduced torque ratings forcing larger aggregate throttle openings. I think this should give everyone pause when touting the reduction in engine displacement as a (leading) measure to improve fuel economy. You are better off reducing the cylinder count (without dropping displacement), reducing the number of camshafts, improving the transmission, working on the aerodynamics and/or cutting weight.

It's not just the rpm at which maximum torque is reached, is how soon the plateau is reach after the driver applies throttle. It always takes longer to go from vacuum to 10 psi than it does to get to 18 psi at any rpm. The combination of higher static compression (9.8:1 vs 9.0:1) and lower boost makes for a more linear, more "NA like", engine. We can easily make this a 312 hp engine with 280 lb-ft (limited by the torque capacity of the 6T70 transmission) by cranking up the boost to about 17.6 psi and swapping in a GT2560 turbo. But, it won't be as linear and as transparent as a low boost engine, and it will lose an mpg or two. Running 280 lb-ft through the front wheels also raises issues with torque steer and handling detriments. Again, because the 2.5T is destined as a family sedan V6 replacement, performance isn't exactly the most important thing here. Overall driving experience, practicality and economy trumps outright performance.

Different mission, different philosophy. The idea here is not to get the most power, but to have the broadest torque plateau, greatest linearity, highest efficiency, lightest weight and smallest engine package. To that end, boost is low, Intercoolers are small, compression is on the high side, the bore spacings are tight and cylinder walls are thin. The engine is destined mostly for FWD vehicles of modest mass. This means that a modest torque output is not necessarily a negative. Basically, you can think of the powerplant as a replacement for the 3.0 liter V6 -- same power, better economy, slightly more torque and greater linearity. For high output turbocharged designs, I'll prefer the 2.0 liter displacement using the same block. The smaller combustion chambers are better for knock resistance. The thicker walls are better for strength. Power wise you can easily top 300bhp which is enough.

No miracles due or expected here... Probably around 22/35 on the NA engine -- which is about 3 mpg (city) / 5 mpg (hwy) better than current DOHC DI-VVT 2.4 in the Regal (which is about the same weight). Most of it due to the Atkinson cycle operation at low loads and steady state cruising. This is also about 1 mpg worse than the Honda Accord in the city, but 2 mpg better on the freeway -- which makes sense given that the Accord is 300 lbs lighter. Expect to lose 1~2mpg on the turbo engine from the reduced compression and "shorty" intake.

No Info yet. But, if it's me, I'll do the following:- Chain Driven16-valves Overhead Concentric Cam (aka SOHC with independent VVT) 2-stage cam switching (Atkinson cycle at idle/low-loads, Otto Cycle at medium-high loads) Idle Stop-Restart Control using precision cam position sensor and stopping at TDC Homogeneous Charge Direct Injection 11.3:1 Compression (NA); 9.8:1 (Turbo) Garrett GT2252 Turbocharger @ 10.3 psi Dual Balance Shafts Ionic Knock detection (using spark plugs instead of acoustic sensors) Naturally Aspirated Version Performance Targets Oil Type: 0W-20 Mobil 1 Advanced Fuel Economy or 5W-20 DEXOS 1 Fuel Grade Target: 87 Octane Unleaded Gasoline Required Output Target: 213 hp @ 6500 rpm Torque Target: 193 lb-ft @ 4500 rpm Rev Limit: 6600 rpm Turbocharged Version Performance Targets Oil Type: 0W-30 Mobil 1 Supersyn or 5W-30 DEXOS 1 Fuel Grade Target: 91 Octane Unleaded Gasoline Recommended Output Target: 270 hp @ 6000 rpm Torque Target: 240 lb-ft @ 1800~5800 rpm Rev Limit: 6600 rpm

Speaking of smoothness... High tech doesn't mean smooth and refined. I know a lot of people don't want to hear this, but the 3.5 Pushrod V6 in the last generation Malibu and the G6 was smoother and more refined than the 3.6 liter DOHC DI-VVT engine in the Camaro. Don't believe me? Go drive both. It's significant in enough that you don't even have to do it back to back to register the difference. Now the Lacrosse and the CTS have plenty of insulation to mute the engine, but in the Camaro it has a grainy, coarse, groan that's very annoying from 4500 rpm on up. Rougher than the 2.4 liter four IMHO. Even at 3000~4500 its worse than the Pushrod V6. Maybe its the higher compression leading to higher combustion noise. Maybe its the plastic valve covers and intake manifold. Maybe its something else, but the engine is irrefutably coarse. One thing GM ought to consider is a balance shaft. Even though 60 deg V6es generally don't have them because they are reasonably well balanced as is, they CAN benefit from one. A 60 deg six is NOT perfectly balanced like an I6 or a H6, its just better than a 90 deg six in this regard. In fact, if anyone remembers, the Twin Dual Cam 3.4 V6 (LQ1) from the early 90s is a 60 deg V6 with a balance shaft. The engine was built on the pushrod 60 deg block, but had belt driven DOHC heads added. It had a balance shaft where the in-block cam normally was. The motor was not without its failings in terms of reliability and especially serviceability -- the amount of dis-assembly needed to just get to the spark plugs borders on the ridiculous -- but it was one of the smoothest V6es ever.

Actually, it's most of it has to do with the fact that motorcycle engines that rev to 12,000 rpm also have pretty small cylinders, somewhat tiny pistons and, most importantly, pretty short strokes. Engine vibrations from the reciprocating mass is a function of the mass of the reciprocating mass (piston and rods) and the square of velocity (piston speed). You are building and reversing the kinetic energy of each pistons two times per revolution. Kinetic energy is 0.5MV^2. So, lighter mass helps somewhat. But, having shorter strokes help tremendously.

(1) I honestly don't think they even consider turbocharging the Pushrod V8. It kind of defeats the mission of the engine which is to make a lot of power in a simple, cost effective, light weight, compact and fuel efficient package. There is plenty of torque in the big displacement eight -- around 430~440 lb-ft with about 80% available from 1500 rpm or so -- and there really isn't a lot of need to fltten the curve of that one. (2) If you compare the aforementioned turbocharged 3.2 V6 to a Pushrod V8, I'll give the weight advantage to the V8, but not by much. The 3.6 V6 (LLT) is 172 kg. The 6.2 V8 (LS3) is 183 kg. A 3.2 with smaller bores will be slightly heavier as it is. And, the Turbos, intercooler and plumbing will be more than 11 kg (~24 lbs). If I have to guess, I'll peg he 3.2 V6 Bi-turbo at about 200 kg.

Well... there are three issues here:- (1) Driving Experience: If we increase the peak torque to 430 lb-ft -- which we can easily do -- a few things happen. The first is that the power peak won't be 6300 rpm. Rather, it'll probably arrive sooner at about 5300 rpm. This is actually a good thing. The second thing is that the torque plateau of 430 lb-ft probably won't be reached at 2200 rpm, but rather around 2800 rpm or so and will end at about 5200 rpm. So you end up with more torque, but a narrower plateau 2400 rpm wide instead of one that is 4000 rpm. This is both good and bad. It is good because you are making more torque and the car will be faster. It is bad because it takes more boost to get more torque and boost takes more time to build to the higher level. This means that there is more of a "rubberband" effect when the driver floors the gas making the engine feel less linear and making the caar more difficult to control mid-corner when throttle is applied. With a lower boost design we are getting greater linearity and a driving characteristic more akinned to a large displacement NA engine, at the expense of some straight line acceleration performance. With a higher boost, higher torque design the engine will feel like a more traditional turbocharged engine, but the car will be slightly faster. (2) Fuel Economy: If gasoline has unlimited octane rating and combustion chambers are knock proof under any circumstance, the aforementioned would have been all there is to be said. But they don't. To get to the higher torque peak, we have to run higher boost. 430 lb-ft will require about 18~19 psi instead of 13.2 psi. Consequently, we need to lower the static compression to accommodate the increased boost level. Instead of 10.7:1, we'll need to lower it to about 9.2~9.7:1. This in turn hurt fuel economy and power production at cruise and at light throttle when the engine is off boost. (3) Accessory Bulk: This is relatively minor, but since we are discussing the consequences in detail, I thought I should mention it. With higher boost comes the need for bigger intercooler assemblies, adding bulk, weight and reducing responsiveness of the engine because the increased volume in the plumbing between the turbo and the intake valves needs more time to get pressurized. My preference is for a more linear, easier to drive, more fuel economical and more compact power plant. Hence, I prefer the low peak torque, wide plateau setup -- aka the high compression, low boost setup, higher revving. The Nissan GTR's VR38DETT follows a similar philosophy. The BMW 4.4 and M-B 6.0 Bi-turbos are the exact opposite, focusing on delivering as much torque as is practical which enhances performance especially on heavier vehicles. The GM 2.0T (LNF) engines is somewhere in between. 430hp / 360 lb-ft will feel like a 5 Liter DOHC V8. That's not a bad feeling IMHO, especially when the high compression makes it more likely that the 3.2 Bi-Turbo will post a tangible fuel economy advantage over a Pushrod V8.

There has been much talk about a GM Turbo Six. Here’s how I feel it should be built:- V6 DI Twin-Turbo 3.2 liters engine built using as many off-the-shelf components as possible Engine block from 3.0 DI V6 (LF1) Crank and rods from 3.6 DI V6 (LLT) High efficiency turbochargers optimized for flow. Moderate Boost, High Compression Air-to-water intercooler to avoid bulky air hoses, intercoolers and minimize pressurized volume Specifications:- Valvetrain: Chain driven DOHC 4-valves/cyl w/intake & exhaust VVT Fuel Injection: Homogeneous Charge Direct Gasoline Injection Bore x Stroke: 89 x 85.6 mm (LF1 Bore x LLT Stroke) Capacity: 3195 cc Turbo(s): 2 x Garrett GT2052 Intercooler: Air-to-water Compression: 10.7:1 Boost: ~13.2 psi (@ Sea Level ~70 deg C) Power: 430 hp @ 6300 rpm Torque: 360 lb-ft @ 2200~6200 rpm Rev Limit: 6500 rpm Transmission(s): Hydramatic 6L80 6-speed Automatic or Tremec TR6060 6-speed Manual

The I6 is naturally balanced and practically vibration free. However, the industry has moved away from it because it is very long and rather heavy. An I6 will require all the current RWD platforms to be altered to accommodate it. It'll also not fit the transverse bays of cars like the Lacrosse. You can go with high static compression and light pressure turbocharging. But this is significantly more complex and costly than switching out the intake manifold, adding insulation around the block and making half of the lifters collapsible. In addition, turbochargers bring with them a myriad of hoses, intercoolers and bypass tubes. Turbochargers -- especially twin turbo setups typical of V type engines -- are also rather expensive to service 10~15 years down the line. Eg. replacing a pair of turbos on a B5 Audi S4 is a $4500 job. Regardless of how longevity of turbos have improved and how GM markets it, "twin-turbos" will make some buyers hesitate based on reliability and maintenance cost stories related to other so equipped vehicles in the past. With light pressure forced induction, you are investing in all that with practically no return in power output but simply a remodeling of the torque curve. The idea here is to build the V6 GM can build if it is not hamstrung by considerations such as accommodating the 87 octane rating or making the engine cheap enough for deployment in all vehicles right down to the Malibu. 91 Octane ratings are not unusal for luxury marques. In fact, it is typical. Acura, Audi, BMW, Infiniti, Lexus and M-B all drink 91 octane fuel. When you put 87 octane in the engine, it's not going to grenade itself -- no modern engine will, not even a 911 GT3. What'll happen is that you'll lose 10 maybe 20 horses and suffer from reduced fuel economy when the ECU detects the onset of very mild pining inperceptible to the driver and dials back timing and enrich the fuel mix. In extreme cases -- such as pulling a heavy load at low rpms when knocking is at its worst, the over enrichment may get bad enough that prolonged operation may cause spark plug fouling. The ECU will probably flash a warning to the driver in such cases, but not usually. I ran out of fuel once on the freeway and had a gallon of 87 added by AAA into the C55's tank to get to the gas station. The engine ran fine, nothing perceptible in power delivery, no pinging, nothing. I wasn't pushing it of course so I don't know if it made noticeably less power. The M113 5.5 liter SOHC V8 engine has conventional port injection and a pretty high compression ratio (11:1).

Torque does not matter if, and only if, you can change gearing instantaneously, continually and through an infinite range. That is not reality, at least not with today's transmissions. In any particular gear, the torque multiplication is the same throughout the rev range. Today's best automatics only give you about 6:1 to 7:1 ratio spread to play with. An engine whose torque peak is further removed from the cruising rpm is likely to require more downshifts more often. Reasons for using 91 octane in exchange for higher compression is as follows:- A $0.20 difference in gas price (per gallon) at $3 a gallon is quite well tolerated by owners of luxury vehicles. The increase in compression yields improvement in MPG numbers Higher torque at lower rpms allows the vehicle to accelerate more quickly without having to trigger a downshift. This in turn improves the perceived refinement level by allowing a more relaxed operating speed in typical driving.

Actually, hp is not a factor. The 87 octane DI V6 is alrready making 312hp in the Camaro. Increasing the octane rating allows you to increase the compression ratio. This in turn means you can make more torque. With the hp target being relatively unchanged, you can move the torque peak lower and flatten the curve. This improves the perceived power delivery in daily driving. The higher compression also improves specific fuel consumption.

When the so called HF V6 was created, it was the premium six cylinder in GM's line-up. It went into premium models while the 3.5 and 3.9 Pushrod sixes served the Malibu, G6es and other high volume models. With GM going to the DI V6 across the board in the near future, there no longer a Hi-Lo mix. I believe that it'll be worthwhile to create a new derivative of the DI V6 engine specifically for premium applications as the Standard DI V6 moves into the mainstream. The premium version will focus on delivering greater refinement, performance and runs on 91 Octane. The idea is not to build a sports car engine here, rather it is to give the engineers a free hand to improve the DI V6 without having the compromise of 87 octane compatibility and cost sensitiveness. 3.6 liter Premium Six Changes Aluminum valve covers replace polymer ones for improved acoustics Aluminum continuously variable intake runner assembly for flatter torque curve 12.3:1 compression instead of 11.3:1 for improved torque output Cylinder deactivation on 3-cylinders Anechoic skirt around engine block for noise reduction Anechoic acoustic cover over engine for noise reduction Performance Power Output: 312 hp @ 6600 rpm Torque output: 292 lb-ft @ 3600~5600 rpm Rev limit: 7000 rpm Fuel: 91 Octane Unleaded Est. Fuel Economy (RWD CTS w/6L50): 19 (City) / 28 (Hwy) Price Delta (vs regular 3.6 DI V6): $2000

Nobody is saying that GM shouldn't tackle all of the items. The key here is what is most important amongst all these important things. A Poll with an "All of the above" option would be worthless in shedding light on what members of this board feels is the #1 concern regarding GM products. BTW, since you brought up the Civic, will you care to share what is it about the Civic that you like over the Cruze?

BTW, I voted Vehicular weight. This is not because the others are not as important. In fact, I think that exterior styling and interior quality are perhaps more important in getting sales up. However, I honestly think GM styling in recent years is actually pretty good and they have made huge strides in interior quality. Whether they are on the way to the top of the class may be debatable, I am happy with the progress. On the other hand, the mass of GM vehicles are egregiously porky. There is no excuse for the LaCrosse to be tipping the scales at 4000 lbs when a similarly sized and similarly insulated ES350 is 3600 lbs. There is no excuse for the CTS to be 300 lbs heavier than a 5-series, for the Camaro to be 400 lbs more than the Mustang or the Cruze to be 300 lbs more than the Civic. Permanently carrying an NFL linebacker and his mother around makes it so much harder to beat the competition in acceleration, handling or fuel economy. Get the weight down a bit and all of a sudden everything gets better.

Turbines have no economies of scale today and are used only in niche applications outside of the aeronautical, marine and power generation industries. However, there is nothing in a turbine that is "expensive" by design or material. The compressor wheels and turbine wheels are no more complicated to make and require no more exotic materials than your typical turbocharger. In fact, they are a lot simpler than even the crudest 4-cylinder engine -- there only two moving parts compared to over 50. If you think the concentric shafts of a two spool design is a technical challenge, you can always use two parallel shafts -- it'll be like two turbos side-by-side, one driven by and feeding on the exhaust from the other. The reason you use two spools is because a single centrifugal compressor is only good for about 3~5:1 compression. You need two to get to the 10:1 ratio of a piston engine or the 20:1 ratio of a typical aviation turbine engine. The efficiency enhancing attachments are also proven and commonplace tech. The intercooler is basically the same construct as you'll find in a turbocharged car. The recuperator is simply a heat exchanger between the exhaust and the compressed air. If you really want to go "crude" something similar to the heat exchanger found in those gas fired wall heaters an old home is basically the same concept. Actually, it is a fallacy to assume that turbine systems have larger filters. They don't. The filters may be very big compared to the size of the turbine engine itself. But the filter is about the same size as you'll find in a piston engine of the same power output. This is because both burn fuel to make power, and both burn fuel at the same fuel-to-air ratio. For Gasoline, this is about 14.7 parts air to 1 part gasoline. Hence, a 100 hp engine must burn a given amount of fuel and ingest a given amount of air per minute. This is roughly the same whether regardless of the engine type. The only difference is that the Turbine is a lot smaller and moves the same amount of air by spinning a lot faster.

Can GM leave the pulsatile engine behind? Regardless of whether someone worships the Global Warming religion or think androgynous climate change is utter rubbish, regardless of whether that person cares a lot about fuel economy or not at all, anyone who has ever driven an electric car or a hybrid in purely electric mode will immediately appreciate the eerie absence of noise and vibration of an electric motor. Afterall, there are no contained explosions, no exhaust pulses and no vibrations from metal slugs going up & down. Put the smoothest V12 next to an electric motor and it suddenly sounds and feels crude. Selling "Green" only goes so far... selling ultimate refinement that just happens to be green goes a lot further. But, the electric motor is not the only thing in the world with no reciprocating parts, no exhaust pulses and no vibrations. A gas turbine does exactly that. A Gas Turbine in industrial generation operates between 15~20 dB quieter than a diesel generator set of similar output. A turbine engine also have ony one or two moving parts and is traditionally a lot simpler to maintain than a reciprocating engine. In addition, it runs on fuel that weighs a heck of a lot less and takes up a lot less space than batteries big enough to power a fully electric vehicle with decent range. Traditionally, gas turbines are not particularly suitable for automotive use. Fuel efficiency is worse than with the piston engine and especially so at lower rpms where the achieved compression is reduced. More importantly, turbines respond slowly to throttle inputs. It may be OK for a Boeing 737 to take 3 seconds reach full power after the pilot slams the throttle wide open. It is not OK by any measure to wait three seconds for power to build when you floor the gas pedal in city traffic and then wait another 3 seconds for power to fade after you lift off the gas. A car with this kind throttle behavior is beyond having bad case of turbolag, it is an accident waiting to happen. However, with electric motors driving the wheels and the engine operating only to generate electricity none of these concerns are valid. In fact, because the turbine's only job is to charge and sustain the batteries in can always operate at it's most efficient speed or not at all. Add to that the fact that we can get efficiency that matches and exceeds the best piston diesels by adding an intercooler and recuperator to the turbine system, and turbines become very attractive. Here's an Idea:- GM Advanced Propulsion Technology for high-end luxury vehicles Power Source: General Electric LV10 Gas turbine generator Spools: Two Compressor Stages: 2 x Centrifugal Compressor Stages Turbine Stages: 1 x Axial, 1 x Centrifugal Turbine Stages Intercooler: Air-to-water intercooler between compressor stages Recuperator: Air-to-air recuperator between compressor output and combustor Output: 100 kWe (134hp) Thermal Efficiency: 34% Propulsion Motors: Front Axle: 1 x 149 hp Permanent Magnet Synchronous Motor w/open differential Rear Axle: 1 x 149 hp Permanent Magent Synchronous Motorsw/open differential Total Motor Output: 298 hp Battery: Plug-in version: 20 kWh Li-Ion Battery Non Plug-in version: 4 kWh Li-Ion Battery