dwightlooi

Actually, EGR doesn't increase or reduce compression at all. What it does is allow you to inject less gasoline and still not be have an overly lean mixture -- which may not ignite and if it does burns very hot and create NOX emissions. It does so by putting exhaust gases back in the cylinder and hence reduce the percentage of the oxygen in the cylinders (less of the gaseous mass is actually fresh air with oxygen in it). Traditionally EGR is controlled by using a metal hose and an EGR valve to pipe some exhaust gases back into the intake manifold. However, most current implementations simply utilize variable cam phasing to increase or decrease overlap to achieve the same end. With a late closing exhaust valve you create EGR during the earlier part of the intake stroke at lower engine speeds. By advancing the exhaust cam you allow the power stroke to end a little earlier and eliminate most of the overlap. This is preferable at medium speeds. At high rpms you may once again want to have some overlap because intake velocity trap charging can produce a slight "boost" pressure right when the intake valves open and help chase the stagnant exhaust gases out the cylinder during the overlap period. However, traditional cam phasing is still limited by the fixed duration of the intake and exhaust periods. You cannot have as much or as little overlap as you want without getting really sub-optimal with the duration of the cams. With Cam switching allows this. The way you affect effective compression in the engine is by closing the intake valves late -- very late. By allowing the valves to stay open as the piston comes up in the compression stroke, you kick some of the air back out of the cylinder. Compression doesn't start until the valves close. Hence you have effective reduced the compression of the gaseous charge.

Two things... (1) Most of the current breed of DI Diesels run at 16~18:1 static compression, but that is not because it is preferable or that somehow compression ignition at these compression ratios was not possible before. It is because they are all turbocharged! (2) 13:1 is not all that high. In fact, 13:1 is low enough that it can be reliably spark ignited on premium 91 octane without risk of detonation. Homogeneous charge or not, the problem with compression ignition with gasoline is that the theshold between compression induced conflagration (which is what you want) and detonation (which is true knocking) is very narrow. Gasoline also burns faster and detonate "harder" when it detonates. Diesel for instance won't even burn if you light the fluid with a cigarette lighter.

Well, the benefits are many and charge cooling is only a small part of it. If you think about it, DI or not, roughly the same amount of fuel is injected to be burned with a given amount of intake air charge. Whether the fuel is injected at the intake ports or directly into the cylinders its vaporization removes heat from the intake charge. The only advantage DI has is that 150 bar injection allows for slightly more even and more complete atomization of fuel than 3~5 bar injection. Nonetheless, the specific latent heat of vaporization is the same since the fuel is the same so it is not going to be a huge difference. DI allows for a few things which port injection does not. The first is that the window of opportunity to inject fuel is from the beginning of the intake stroke to the end of the compression stroke. For port injection, the window of opportunity lasts only till the end of the intake stroke. In fact DI engines typically favor late injection (during the compression stroke). This has a big advantage in resisting knocking because unlike port injected engines where the cylinders are filled with combustible fuel-air mixtures from the beginning of the intake stroke through the end of the compression stroke, the DI engine only has fuel in cylinders in the last 25~50% of that period. No fuel means nothing to detonate with during that period. If you are planning on burning ultra lean mixtures you can also direct the injection very late into the compression stroke just before the spark event in s narrow jet to create a local enrichment around the spark plug so the mixture near the tip will ignite while the rest of the cylinder is almost devoid of fuel. This is called stratified injection and is used in many DI engines for economy gains. The GM engines however does not do it mainly because lean burning makes you fail emission rules unless you scrub the oxides of nitrogen from the exhaust. Doing so requires special catalysts that cost a lot and which is absolutely in compatible with sulfur in the fuel (which US gasoline has a $h! load of). Thirdly, DI allows for an injection shot which is not obstructed by the intake valves and the bridge between the two intake valves (in multivalve engines). This "straight shot" allows the designers to use strategies like jetting onto a dished surface cast into the piston tops so the fuel cloud mushrooms back up and promote better mixing. Lastly, of course, more finely atomized fuel in and of itself burns more evenly. You are right that it isn't new. In WWII many German engines were direct injected using a Bosch Mechanical direct injection system. The Daimler-Benz DB601/603/605 aircraft SOHC 4-valve inverted V12s were direct injected. The Junkers-Jumo 211 and 213 aircraft SOHC 3-valve Inverted V12s were direct injected with twin sparking plugs. Even the Maybach HL230 V12s used in the Pzkfw V (Panther) and PzKfw VII (King Tiger) were direct injected.

The short answer is yes. DI in and of itself does not increase power. What it does is that it allows extremely good knock resistance and hence permit about 1~2 points of additional compression to be used. This is where the roughly 7~10% of torque and power increase comes from. Just very roughly you get 3~5% per point of compression increase. In order to achieve compression ignition, HCCI will have to operate at an even higher compression in compression ignition mode. Diesels operate at about 22:1 compression. I am presuming that HCCI will operate at a compression ratio around 15~17:1. DI or not, advanced combustion management or not, this kind of compression is probably not possible without uncontrolled knock at full load and/or at certain RPM ranges. I suspect this is why the engines incorporate variable valve lift (ala VTEC). One of the possibilities is to switch over to a cam profile which close the intake valves way into the compression stroke when compression ignition is not desired or possible. This will let the piston kick some of the air back out of the cylinders. Assuming that 25% of the air is pushed back out of the intake ports by the piston because the intake valves closed late, the effective compression ratio will drop from 15:1 to about 11.25:1. At this point compression ignition won't happen and the spark plug is used.

Put simply, because it doesn't really work as well as it should and it takes two turbos. Let me explain... Sequential turbocharging has been tried before. The JZA80 Supra (1993~1997; 2JZ-GTE engine) and the FD RX-7 (1992-1995; 2nd generation 13B turbo engine) are examples of cars which used two turbos in series. Neither car has the kind of torque curve we are shooting for. There are actually four ways to arrange two turbos although in practice only two of these ways have been used in automotive applications. The first way is putting two turbos in parallel. You get the flow capacity of a larger turbo in two smaller ones with lower inertial. Reducing inertial reduces lag much more than not splitting the exhaust energy from all cylinders between two turbines. This is also a convenient arrangement in a Vee type engine since you don't have to route the exhaust from both banks to one turbo. This is by far the most common way to arrange two turbos. The second is to put all the exhaust through one smaller turbo first, then feeding the exhaust of the first turbo (both the turbine exhaust and the wastegate exhaust to a larger turbo. The output of both are combined in parallel and fed to the intercooler. This is the arrangement we encounter whenever a car is said to be sequentially twin turbocharged. The advantage is that the smaller turbo provides boost with reduced lag at lower engine speeds, while the larger one provides flow capacity to handle airflow demands at higher RPMs. The problem with this arrangement is that the exhaust routing is complicated and the results may not be as perfect as one may think. To begin with the first turbo and its wastegate restricts the airflow to the larger second turbo and also soaks away some of the heat. This degrades the performance of the second turbo. More importantly however is that while the arrangement allows boost to come on early, it really doesn't cure boost lag at mid to high rpms as well as we may expect because you stll need to spin up that larger turbo and it is hampered by the small one upstream to some degree. Also, if not handled well, the kicking in of the second turbo can cause a spike in boost and power midway through the powerband. In the end, the idea fell out of favor because the complexity and cost did not bring as much benefit as originally expected. The third way is to parallel the exhaust feed to the turbos, but sequentialize the output. One turbo brings the boost pressure to say 15 psi while the other ingests 15 psi air and boost it up to 30 psi for instance. This allows both turbos to work within the efficient parts of their compressor map because a single centrifugal impeller is simply unable to reach about 30 psi without being rather inefficient regardless of its size. Jet engines use 7 to 15 compressor stages instead of one big one to reach a pressure ratio of 1:20~50 for this reason. In WWII it is popular to sequentialize centrifugal supercharger outputs in this manner. The Junkers-Jumo 213E engine in the high altitude Focke-Wulf Ta152H-1 interceptor is an example of a sequentially supercharged engine. The fourth way is to combine both the second and third methods and sequentialize both the turbines and the compressors. I don't know think it has ever been done for automobiles although the concept is a staple in turbine engines with twin or triple spools. Coming back to the LNF discussion. Basically, the point is that I wanted to keep it simple and stick to one turbine. Lag aside, this is also the most efficient way to get to 15 psi. If you look at the compressor maps, you can see that we won't gain much efficiency or map width going to 7 psi and sequentializing. Also, while a exhaust sequential arrangement would lead to faster boost onset you pay for it with upstream restrictions on the second turbo. There is also the issue that if we go with two turbos, they will have to be two very small ones. The GT25 is the smallest ball bearing unit available. On top of that, all the smaller units are not as efficient (by about 10%) compared to the GT25 and GT28s. Besides, all the suggestions -- except the turbo choice -- holds true whether you use one or two turbos. T

The LNF is a very good engine. 260hp @ 5300 rpm and 260 lb-ft @ 2500 rpm are very good numbers. BUT, they are not as good as they can be. Here's why... This engine revs to 6300 rpm, but the last 800 rpm or so does nothing but give the driver the flexibility of not shifting if he is in a corner and does not want drive train disruption at that specific time. Other than that, this is one engine that should be short shifted way shy of its redline. The KKK K04 turbo used is again, good but not the best. This is very similar to the unit used in the Audi TT 20v 1.8T (225hp version) and is a little undersized for 260 hp. The response of the engine is good, but not as good as some lower boost turbocharged engines like the 2.0T FSI from VW-Audi group. It is efficient for its output, but again not stellar in this department. How can we make it better? Well, I think that it is possible to improve engine responsiveness, push about 300 hp from the engine, make the engine enjoyable all the way to the 6300 rpm redline and improve economy. Here's how... Change #1: Decrease Boost This may sound like a retrograde step, but it really is not. The reason is three fold. First of all, it allows us to increase the compression ratio of the engine which improves light load response and make the engine feel more "alive". Secondly, when I went through all the compressor maps of most of the turbos from IHI, Mitsubishi, KKK and Honeywell (Garrett), there doesn't appear to be one which has their broadest efficiency bands at 1.25~1.35 bar (18~20 psi) which is what the current LNF is running. I believe that this is the limitation of a single stage centrifugal impeller. There are however quite a good selection with maps that are down right fantastic maps at ~1 bar (14.7 psi). This is important if we want a big flat torque plateau across a wide rpm range. 3~5 psi is not a lot of boost difference and we can hit 260 hp at 14.7 psi on a 2 liter anyway, so bear with me a little. The following are the compressor maps from a Garrett GT2560R and from the KKK K04. Both units have better efficiency working at around 1 bar than at 1.3 bar. The GT2560R is so good in fact that efficiency reaches 78% and never goes below 60%, the K04 reaches 72% and maps as low as 55%. Lastly, for any given compressor and turbine wheel efficiency and inertial, it takes a shorter while to reach 15 psi than it does 18~20. This means an improvement in lag time between off boost lugging and full boost scooting and we all know that's nice. Change #2: Increase compression Now that we have backed off on boost a little we need to make up for it by upping compression a little. How much? How about one full point to 10.2:1 (the LNF is 9.2:1). This is about right. For instance the VW-Audi 2.0T FSI runs about 12.5 psi on 10.5:1 with a K03 turbo. This does three things for us. It makes the engine more responsive off boost. It makes it more economical on the freeway and in gentle driving -- most of which will be done with manifold pressures in some degree of vacuum; -0.4 ~ 0 BAR. It also recovers some of the power and torque lost through the decrease in maximum boost. Change #3: Reduce the pressurized volume The big front mount IC on the LNF is very efficient at dropping charge air temperature. But, it also creates a big volume of air to be pressurized. Think of the turbo as a compressor pump. If you an electric pump to pressurize a basket ball to 15 psi it takes a very short time. Use it to pressurize a sealed room and it takes forever. Basically, big ICs and long hose routings decreases response and increases boost lag. So, ideally we want the pressurized volume to be as small as possible while still meeting our desired charge cooling targets. Now, having decreased the boost a little and working off a more efficient part of the compressor map helps by not heating the air as much and hence reducing our charge air cooling demands. But we can do more. Let's dump the air-to-air intercooler and adopt an air-to-water unit. Water is a much better carrier of heat and the heat exchanger can be as small as a brick and be as good as that big front mount IC. Its size also allows us to mount it on the cylinder head. Basically, the air leaves the turbo, goes through this tiny air-water exchanger placed near the valve cover and go straight to the intake manifold. The pressurized volume is probably about 1/5th that of the current setup (if not smaller). The air-water solution of course still needs a radiator to be mounted somehwere, possibly where the current front mount IC is, but the distance and size of this radiator will not affect pressurized air volume. Change #4: Increase the stroke Normally, I am not a fan of stroker motors for a variety of reasons. But in this case I believe it is warranted. The reason is that a 6300 rpm red line doesn't need a 86mm stroke. We can run a longer stroke and still be well within the piston speed limits. Despite what some people may think, power and torque doesn't limit an engine's redline much. Piston speed does. The reason is that the stressload on the rods and journals increases linearly with torque increases, but exponentially with rpms. Why? Because you are slowing and accelerating piston slugs and the kinetic energy you need to slow from and accelerate to is a function of the square of velocity. Also, increasing stroke length increases displacement, but it DOES NOT increase the combustion chamber size where in matters (near TDC) when ignition events occur. Hence, it does not degrade knock resistance of the engine. Having a slightly undersquare bore x stroke ratio is also ideal for allowing us to extract more energy from each fuel/air charge, while still maintaining a good valve area for the given displacement. Just about all the reallly good turbocharged engines like the Mitsu 4G63 and the VW-Audi 1.8/2.0Ts are undersquare. The Subarus are not, but that is because its a boxer and they can't make it any wider! This is also partly why the Subaru WRX STis have 8.0:1 compression whereas the Lancer Evos run 8.8:1. For family commonality, let's simply run the stroke length of the 2.3 liter Ecotec motor (90mm). At 86 x 90 mm, this will yield a 2.1 liter displacement. Change #5: Use a GT2560R ball bearing turbo. The K04 is a journal bearing unit, a ball bearing turbo spools faster and is arguably more durable when the oil properties are less than ideal. The GT2560R is very compatible with the airflow requirements of our 300hp target and has a peak compressor efficiency of 78% and peak turbine efficiency of 75%. This is about 6% and 10% better than a K04. Of course the twin scroll manifold design should be maintained. Dual scrolls do not actually direct exhaust onto the turbine better as some people believe (it is actually a little worse due to increased wall drag on the airflow). However, it prevents parasitic exhaust pulses from reaching the cylinder in its intake-exhaust valve overlap period while the cylinder on its exhaust period is exhaling. This reduces the contamination of the engine's breathing cycles making it more efficient and also prevents the loss of pressure that is needed by the turbine from being partially lost to cylinders on the intake phase. Change #6: Use a variation of AFM (aka DoD) to allow part-time Miller Cycle operation Now this is a little complicated so bear with me... An engine that keeps the intake valves open notably into the compression stroke is sometimes called an Atkinson Cycle or Miller Cycle engine (the differences between the two are in aspiration assist methods). Typically, a turbocharged engine benefits from the late closure of the intake valves. This is because with the pressurized intake air, the engine can push air into the cylinders somewhat into the compression stroke even if piston is going up! In fact, this is desirable because the restrictions from the valve area being smaller than the cylinder bore (which is always the case) means that at BDC the cylinder is not completely filled to the same pressure level as the intake manifold. In normally aspirated engines the cylinders are sucking air into themselves through vacuum action hence as the cylinder is going up, there is very little ability to do so. At very high rpms, they are able to do it somewhat from the supercharging effect of the closing valves building up a temporal positive pressure behind them as high speed airflow gets suddenly stopped and air stacks up behind the valves. But that is another topic for another day. The key issue here is that turbocharged engines have very considerable ability to aspirate into the cylinders somewhat into the compression stroke whenever there is boost present regardless of engine speed. The same goes for supercharged engines. However, a turbocharged engine does not always make boost, and if we keep the valves open into the compression stroke it will decrease the engine's output when off boost. It may also negatively affect emissions because we have effectively decreased compression ratio by "kicking" some of the intake charge back out the cylinder (sometimes with fuel already in there) as the piston goes up. Ideally, we'll use a VTEC or VVTL-i style cam switching system to switch between our regular (Otto) cycle operation and Miller cycle operation. But that adds a whole different level of complexity and cost to the cylinder head design. AFM -- Active Fuel Management or Displacement on Demand -- has been used successfully in many GM engines. It has not been employed in 4-potters such as the Ecotec family. But with some additional passages in the heads there is no reason why it can't. What I am proposing is not a fuel economy idea, but one for performance. We will incorporate AFM onto one of the two intake valves for each cylinders. One of the valves follows and Otto Cycle cam, whereas the other follows the Miller Cycle cam. Off boost and at idle, AFM collapses the lifter on the Miller Cycle valve and it never opens. The cylinder is fed by the Otto valve only and closes the intake valves early. The engine also benefits from increased swirling of the intake charge with one intake valve. Once we develop a reasonable amount of boost (say ~5 psi), AFM solidifies the lifters and opens the Miller Cycle valve. The Otto valve opens and closes as it used to, but even after it closes, the second valve remains open feeding the cylinders with compressed air somewhat into the compression stroke. This increases volumetric efficiency and in also creates an asymetrical compression and expansion stroke which is desirable for extraction more energy from each drop of fuel (this is why the Prius uses an Atkinson Cycle engine even though it is NA and reduces the power yield per liter). The concept is simpler than say VTEC style cam switching and the key is that the engine initiates the Miller Cycle mode operation on boost. End result This about it! Conservatively, this should yield a 2.1 liter engine with about 260hp @ 2200~6200 rpm with about 310 hp @ 6300rpm and redlining at the same 6300 rpm. On top of that, we should have made it more responsive, more economical and made it desirable to rev all the way to the red line. Essentially, we have taken the LNF torque flat and broadened it to a higher rpm without compromising the engine speed at which boost first hits.

The First Corvette had an Inline-6 :AH-HA_wink:

I am conservative... The engine is an oversquare design (88mm x 74 mm) with a significantly larger bore than stroke - the piston speeds it sees at 8500 rpms is roughly the same as that which a 4.2 liter LL8 I6 sees at 6300 rpm. Among other things this tends to lower the compression ratio it can tolerate before pinging becomes an issue. Think of denotation as a race between the spark ignited flame front and the flame front(s) created by hot spots usually in the periphery of the cylinder. Because ignition happens near top dead center bore diameter increments tend to degrade compression tolerance while stroke increases do not -- although both increases displacement. This is because bore increases places the spark plug further away from the furthest reaches of the combustion chamber while stroke increases do not. The reason you go with an oversquare design is that (1)it reduces piston speeds allowing higher redlines, (2)it reduces 2nd order vibrations allowing for greater refinement especially at higher engine speeds and (3)it allows for larger valve areas per unit engine displacement benefiting breathing again at high RPMs. The penalty is that the engine is more prone to detonation and less tolerant of higher compression ratios, is less efficient at extracting energy from each drop of fuel burned, produces less maximum torque and produces less torque at lower engine speeds.

How will you spec a small car engine -- such as one for the Astra or the Cobalt? If it is up to me it'll be as follows:- Displacement: 1800 cc Bore x Stroke: 88 x 74 mm Construction: Aluminum block and heads. Harmonic compensation: Twin Lanchester type balancers driven by timing chain. Compression ratio: 10.8:1 (12.8:1) Aspiration: Normally aspirated with 4 port mounted intake butterflies and trumpeted velocity stacks. Valvetrain: Chain driven DOHC 4-valve per cylinder with continuous intake/exhaust VVT Fuel injection: Direct gasoline injection with 50~150 psi variable pressure rail Maximum engine speed: 7500 rpm (8,500 rpm) Maximum piston speed: 3642 fpm (4127 fpm) Power: 150 hp @ 6800 rpm (200 @ 8300 rpm) Torque: 130 lb-ft @ 3800 rpm (137 @ 5800 rpm) Fuel requirement 87 octane (91 octane)

Neither the 4A nor the 5M gearbox has a transfer case tap off on which to mount a center diff to bring power to the rear wheels. This is no provision in the central hump for a drive shaft or in the rear twist beam axle for a rear differential. To accommodate AWD, will require all new transmission models, a revamped platform and a new independent rear suspension group. I highly doubt that the time, money and effort will be spent to bring AWD to the Delta cars as a mid-life update.

LSDs are both good and bad. There are no true 1-way LSDs whether you go with a viscous, torsen, electronically controlled clutch pack or whatever. At least a portion of the LSD's ability to limit wheel speed differences during acceleration is also applied to the wheels when the car is turning under deceleration or zero speed change. What this means is that a FWD car which understeers on entry and/or mid corner will understeer a little more with an LSD in place. What the LSD does is allows you to apply power earlier and to a greater magnitude on exit without having one wheel idling and the other liquidified. It also of course helps in the same manner in a straight line drag when one wheel momentarily may see a less tractable surface than the other. The problem with FWD is that while there are many techniques to mitigate understeer, most of them are subtractive. That is you reduce understeer by decreasing grip on the rear axle through tuning camber gain/loss during suspension compression or simply over stiffening the roll stiffness (usually with a big anti-roll bar) and hence causing the rear inside wheel to basically lift off (or darn close to it). This improves balance, but it also reduces total grip available to the car. LSD equipped cars tend to require a tad bit more of these kinds of measures than open diff cars to counter the additional understeering it caused. Hence, LSDs may also indirectly cause a reduction in cornering grip when the car is not under accelerative loads.

260hp/260 lb-ft from a 2.0 liter is not stratospheric. It is very decent, no doubt, but not exactly stratospheric. 2.0 liter 4-potter fortified with a turbo can easily make in excess of 300hp on 91 octane. What is remarkable about the LNF is not that it makes 260hp. It is that it makes 260hp with very little turbo lag and with very good engine response. Traditionally (meaning going back 10 years) you have in essence two classes of turbocharged engines. High boost engines with low compression ratios, significant turbo lag and very impressive power output (eg. the Lancer's 4G63 engine or the Skyline's RB26DETT engine). About 140~150hp/liter is a walk in the park, but maximum torque hits at 3500~4800 rpm and there is always a second or two of lag before the boost hits home and you scoot. Then, there is the low boost high compression engines. Made popular by VW-Audi in the late 90s, engines like the 20v 1.8T and 30v 2.7T run the smallest turbos they can find at 0.5~0.8 bar (7.5~11.8 psi) of boost with very high compression ratios of 9.3~9.5:1. These reaches maximum torque (full boost) by 1700~1800 rpm and you probably won't even notice the turbos are there since they are practically lag free. This pedigree continues today with engines like the 3.0 liter I6 in the BMW 335 which reaches maximum torque at 1400 rpm with the aid of a pair of dimunitive turbos. The LNF bridges the gap between these two and offers itself as a high output engine (130hp/liter) with very good response and negligible turbo lag -- thanks in part to DI allowing for 9.2:1 compression with 18 psi of boost, and in part to the low inertial, twin scroll fed turbo. You reach full boost and maximum torque at 2500 rpm, the torque curve is flat through 5250 rpm. You hardly notice any turbo lag and you get very good economy numbers. It is also very refined thanks to twin balancers which are uncommon in 2.0 liter and under 4-potters.

Because they are cheap? Right now, GM doesn't have a 5A for transverse applications. Period. It is either that they stick with the 4A or they pony up the costs for the 6T70 6-speed auto. There is also the issue that a big company like GM lacks agility right now the 6A's production is ramping up and there isn't enough 6As to go around even if cost isn't a leading concern. On top of that, were they to switch to the 6A across the board, there will be a bunch of 4As falling off the production line with no homes. Yes, they need to work of this agility problem, but they are not there yet. On the bright side, the 2.0 LNF engine, being a turbocharged power plant has a fantastically flat torque curve with peak torque (260 lb-ft) being constant from 2500 to 5300 rpm. So it really doesn't need a close ratio gear box.

The 2.2 Ecotec Direct is rated at 155hp @ 5600 rpm and 162 lb-ft @ 3800 rpm. Not bad but not particularly awe inspiring. Basically its an engine tuned for blah blah duty, but given DI so it is about 10% better than the run of the mill 2.2L ecotec. I think that a NA Ecotec with DI should be a rev happy engine. Maybe not a 125 hp/liter screamer like the Honda F20, but at least ~200hp @ ~6800 rpm and 162 lb-ft @ ~5200 rpm. This should be very doable in a DI engine without resorting to cam switching systems or a lumpy idle. It really doesn't matter if it is a little soft at 2000rpm. People who drive "softly" won't care if the engine is "soft". People who drive with some gusto usually don't lug around at 1500~2000rpm at 10% throttle anyway. Forget stratified charge lean burning, make it a homogeneous DI engine. US gasoline cannot support lean burn anyway for years to come. Lean burning means a $h! load of oxides of Nitrogen. A $h! load of that means you need to store it in an NOX storage cat. That is an expensive little can which sulfur levels in US Gasoline will destroy in a year or two.

The HHR SS is a big deal. Not that I care for the 50s wagon looks or the vehicle interests me in anyway. (1) It is a big deal because this is the first transverse engine, FWD, application of the 2.0 liter DI-VVT Turbo engine (LNF). (2) It also confirms that GM is not toning down or castrating the LNF to a lower power level for sideways, FWD, applications. Transverse LNFs will still be 260hp. (3) The Chevy Cobalt SS Supercharged has been retired from the lineup. Before the HHR SS came along there are all kinds of doubt as to whether an effort will be made to repackage the LNF for FWD applications and hence whether the Cobalt as a chance of getting the turbo engine. Now, there should be little doubt that the powerplant is available should there be an inclination to bring LNF power to the Deltas. (4) This also means that there now a credible chance that this exceptional powerplant may see service in G5s and G6es. If you ask me, this should be the base engine for the CTS not the 3.6 VVT Port Injection. It should also be the top engine for all FWD GM vehicle lines.

Actually... all the new BMW engines are valvetronic EXCEPT the "M" engines. The "M" engines do not use valvetronic because the infinitely variable valve lift system utilizing an intermediate swipe armature is incapable of supporting the high valve lifts the "M" engines demand and still be able to close sufficiently to support idle requirements. The "M" engines hence use traditional butterflies, albeit eight or ten of them mounted right on the intake ports and fed by trumpeted velocity stacks. The "M" engines also do not use the magnesium-aluminum hybrid blocks. The new V8 and V10 "M" engines use an aluminum block whereas the E46 M3's 333hp 3.2 liter I6 used an IRON block.

The reason you want the throttle butterflies to be as close to the intake ports as possible is to minimize the air volume down stream of the throttle bodies and before the intake valves. This way you enhance throttle response since the time it takes for this volume to change pressurize/depressurize in response to throttle movements become very short. Just about every racing engine uses butterflies mounted on or near the intake ports. The E46 M3 engine and all the current V8 and V10 "M" engines use this arrangement. Theoretically, it doesn't matter where you put the butterflies as long as it is after the filter and before the intake valves. In fact, if you can vary the intake valve lift continuously and with good response times you don't need butterflies. The amount of vaccuum you "see" in the take plumbing upstream of the butterflies will be less than down stream of it, but it'll still be proportional. You can either tap your vaccuum lines downstream of the throttle bodies in the intake port area or you can simply design the vaccuum actuated accessories to work at lower idle vaccuum levels. It shouldn't be a big deal.

Should the Corvette abandon the V8 for an I6? Or, maybe, its Camaro little brother should? Although the Corvette is most identified with a V8 -- more specifically various iterations of the small block V8 -- it started life with an I6. Now that first Corvette wasn't very good, but fundamentally an Inline-6 is a smoother and more refined engine configuration than a V8. The I6 and H engines are the only ones with zero 1st and 2nd order vibrations. It also allows contemporary technology such as VVT phasers to be incorporated with half as many actuators as a V-layout because it has half as many camshafts. The I6 is also fundamentally stronger than a V8 because it has seven main bearings and does not use shared crankpins like V6 and V8 engines do. In many ways, 50/50 weight distribution and inline-6 refinement was what defined the BMW 3-series as the "Ultimate Driving Machine". The BMW M3 abandoned the I6 for a V8, maybe GM should pick up this configuration. Maybe an engine configured as follows (derived from the Vortec 4200) should power the new Corvette, Impala and/or Camaro instead of the small block V8? 2010 3.9L "Blue Flame Six" I6 Turbo DI-VVT ( LIZ) Type: 3.9L I6 (LIZ) Fuel Injection: Direct gasoline injection Construction: Lost foam cast aluminum block and heads, forged steel crank and rods. Aspiration: Twin turbocharged and aftercooled; 1 x Honeywell-Garrett GT2554, 1 x Honeywell-Garrett GT2560 ball bearing turbochargers. Aftercooler: Front mounted aftercooler Compression ratio: 10.3:1 (13.2 psi maximum boost) Valve configuration: chain driven dual overhead camshafts (4 valves per cylinder) Valve lifters: roller finger followers with stationary hydraulic lash adjusters Firing order: 1 - 5 - 3 - 6 - 2 - 4 Bore x stroke: 95.5 x 91 mm Fuel system: direct fuel injection Fuel type: Premium unleaded (91 Octane) Fuel shut off: 7000 rpm Horsepower: 508 hp ( 379 kW ) @ 6300-6800 rpm ( SAE CERTIFIED POWER ) Torque: lb-ft. 432 lb-ft ( 585 Nm ) @ 2100-6100 rpm ( SAE CERTIFIED POWER ) 2010 3.9L "Red Flame Six" I6 DI-VVT ( LIV) Type: 3.9L I6 (LIV) Fuel Injection: Direct gasoline injection Construction: Lost foam cast aluminum block and heads, forged steel crank and rods. Aspiration: Normally aspirated, w/six intake port mounted throttle butterflies. Compression ratio: 11.8:1 Valve configuration: chain driven dual overhead camshafts (4 valves per cylinder) Valve lifters: roller finger followers with stationary hydraulic lash adjusters Firing order: 1 - 5 - 3 - 6 - 2 - 4 Bore x stroke: 95.5 x 91 mm Fuel system: direct fuel injection Fuel type: Regular unleaded (87 Octane) Fuel shut off: 7000 rpm Horsepower: 362 hp ( 270 kW ) @ 6800 rpm ( SAE CERTIFIED POWER ) Torque: lb-ft. 293 lb-ft ( 396 Nm ) @ 4800 rpm ( SAE CERTIFIED POWER )

Well, the 3.6 VVT ranges in output from 240 to 275 hp in port injected form and 304 in DI form. The 2.0 LNF I4 is 260hp in its 1st iteration. You can get between 200 or 300 hp out of the LNF easily depending on how much turbo lag you want to put up with. I'll say that the output of the two engine families are essentially equal. The big difference is that the LNF is:- (1) More economical when driven gently because of its smaller displacement, 2/3 as many cylinders and half as many cylinder heads. (2) Has superior torque characteristics - 260 lb-ft from 2500 rpm vs a torque peak in the 4000~5200 range for the 3.6. (3) Its lighter and slimmer than a 3.6 liter. (4) Is smoother and more refined sounding than the 3.6 (surprisingly enough).

I am all for greater use of the LNF (2.0L DI Turbo). In fact I think GM should simply eliminate the 3.6 liter engine in smaller car applications and simply use the LNF. It is more refined sounding, it is more economical, it is lighter, it is more "tunable" as far as enthusiasts are concerned, it has a fatter torque band and it is easier to work on and fix. It sounds wonderful too, especially at 1500~2500 rpm in a parking lot where it makes a very neat whistling sound as the turbo spools gently on low load. 260hp / 260 lb-ft is basically equal or to the 3.6 VVT. The 2.0 liter I4 is better in just about every measure compared to the 3.6 VVT except for the fact that some buyers are simply stuck on the V6 badging that a 6-cylinder engine will allow for.

It sounds a little gritty. Sort of like tire noise over concrete freeways. The sound is a mixture of low and mid frequencies. And, as I said, there is just a lot of these low and mid frequency "groans" and basically no high frequency, turbine like, whirls, or metallic rasps like some other engines. It isn't horrible, just uninspiring. Maybe... its just that you got used to it and didn't notice as much.

OK... I went and drove a Saturn Aura 3.6 over the weekend. Here are the conclusions. The 3.6 liter (LY7) is OK at lower engine speeds (<3000~4000 rpms). But it get's rather coarse at 5000~6500. Yes, I have pretty high standards as to what "coarse" is, but let's just say that it is coarser than the VQ35 (Nissan/Infiniti) which isn't exactly known for upper end refinement and significantly coarser than the Honda C30/C32 engines (Accord-V6/Acura-3.2TL). It is similar in smoothness to the Mazda/Ford 3.0 liter (Duratec30/MZI) in the upper end, but more refined under 4000 rpm. The engine note is an uninspiring blah-blah with a granular rush toward the redline - a combination of an argicultural groan with a rather plastic sounding moan when pushed. Too much low frequency sounds filtering through, no metallic rasp or whirls. I'll say that is below average for a 60 degree V6 of a rather modest 85.6mm stroke. On a 1 to 10 scale for refinement -- if the BMW M52 Inline-6 (E36 2.5 liter) is a 9.5, the Mazda K-series 2.5 liter V-6 is an 8, the Honda C30 is a 7, my Audi 2.7T (2001 S4) is a 6.5 and the Nissan/Infiniti VQ35 (Altima/G35/Murano/350Z/you name it) is a 5 -- I'll rate the LY6 at a 4. The 6T70 automatic was however very well implemented. Shifts very well and very smoothly. The lock-up clutch stays locked more than I am used to which is actually very encouraging. Shift speed is about as good as the Aisin TF60SC (VW-Audi 6A - traverse) which is very decent, but the box is actually smoother in lower gear transitions. Fantastic. This is definitely a solid 9 in my book. I think GM needs to do three things -- (1) Put as balance shaft-in -- yes, you can even on a 60 degree engine although it is not normally done. The shaft will turn at crank speed and quell 1st order end-to-end rocking forces of the 60 degree layout. (2) Increase the stiffness of the block with additional Iso-grids or webbings in the castings with the explicit purpose increasing the resonance frequency of the block. Higher frequencies sound metallic -- lower frequencies sound agricultural and/or plasticky. (3) Re-tune Quiet Tuning measures to reduce low frequency sound passage and increase higher frequency sound passage. Why do all of these? Well, why bother to make a DOHC VVT V6 only to have it sound little better than the 12v push rodder? This engine may cut it as a Saturn or Pontiac mill, but if it is to power Caddys (albiet with a bump in output due to DI) it'll need to shape up. Otherwise, they should take the easy route and de-stroke the 4.2 liter Vortec 4200 Inline-6 (LL8) from 102mm to 88mm to produce a 3.6 liter mill which is naturally vibration free and which already has a very nice metallic whirl to it even in 4.2 liter form.

One of the biggest problems with the Cobalt is that it is an economy car which is not that economical compared to its competition -- that and the ergonomically silly high hip point of the seats which rubs my head on the headliner even at the lowest height adjustment unless I recline the seat backs considerably (I am a very average 5' 9" guy). Other than that, quietening is good, interior quality is good enough although not exactly VW standard and styling is OK. GM said that it wants to not only meet but exceed the offerings of its competition. To do that (in an economy car) the 2.2 liter and 2.4 liter Ecotecs won't do. The 1.8 liter Ecotec in the Astra is more inline with this segment, but a 1.4 or 1.6 liter with the right technological content will help. The USA is a high-cost country. No deal with the UWA is going to change that. GM needs to learn to compete on quality, performance, reliability, technological superiority and (in time) brand perception. Trying to beat the Koreans or the Chinese on price will be futile. I will like to see a technologically advanced 1.6 liter in the Cobalt and the Astra. By that I mean something with Direct Injection, 4-valves per cylinder, at least single (preferrably double) VVT, a harmonic balancer (rare on <2.0 liter I4s), chain drive for the camshafts, roller followers, valve deactivation (shuts off one of the two intake valves to increase swirl and induction velocity and dual stage intake plenum. This should make ~140hp @ 6600 rpm and ~120 lb-ft @ 4600 on regular 87 octane. In order to maximize the economy and performance of a relatively low torque engine, it should be mated to a 6-speed automatic gearbox (or at least a 5A which is the class standard today).

Making the G6 RWD will make it sell better to enthusiasts. Those who are not can be sold Malibus or Buicks. Overall, GM will capture more sales because it will capture more performance minded drivers with Pontiac and has an equal or better ability to capture bargain shoppers or comfort seekers with other brands that will continue to offer FWDs. It really doesn't matter if Pontiac itself gets more sales as long as GM as a whole is advancing on every market segment. It has been shown that trying to make a car that is a little of everything to please everyone a little, then giving it 10 different brands does exactly - NOTHING.

Refinement (noise/vibration) is midpack. Fuel economy is below average. You will be lucky to average 26~27MPG in a cobalt, a Civic genuinely pulls 32~33 in real world combined cycle driving. All in all the Ecotec is not embarrassing but it is nothing to be proud of either. The ONLY exception is the 2.0 liter LNF which is very interesting although still a little behind the curve in terms of noise/vibrations. I belief that GM needs to stop the bean counting and put direct injection, dual VVT and the lanchester balancers on every ecotec. The 1.8 in the upcoming Astra can use DI and Dual VVT for instance.