dwightlooi

I have said this many times before, but what's really needed is additional ratio spread and not necessarily more than 7 gears. By about 7-speeds there is more than enough gears to keep the rpm at or around the torque peak after a shift even if you increase the ratio spread by about ~20%. The idea is to increase the spread so the 1st is lower (for better acceleration) and the top gear is taller (for better economy). This is even in the case of smaller displacement engines, especially given the trend towards forced induction which flattens the torque curve. In other words, what's more beneficial -- to performance and/or economy -- is an "extra wide ratio" transmission that has a 7~7.5 ratio spread (vs ~6.0 for 6-speed boxes. This does not necessarily have to be a 9 or 10 speed box, for most applications it doesn't even need to be 8 speeds. The Aisin TL80 (used in the new CTS as well as various Lexus products) is disappointing in this regard with a ratio spread of a mere 6.71 even though it has 8 gears. On the other hand the Mercedes 7G-tronic used in the S-Class is exemplary with a spread of 8.86 with just 7-speeds.

Americans like bigger cars. And, while they are not totally oblivious to fuel economy, that was never and is still not their top priority when shopping for a vehicle. One or two mpg doesn't register as a big reason to choose one model over another. Quite honestly, they are much more likely swayed by a nice alloy wheel design or rear seat headroom than a couple of MPGs. This is especially so with mid-size cars posting more than decent 34~35 mpg highway numbers. There is very little reason to spring for that 38 or 40 mpg sub-compact to save $40 on the annual gas tab -- quite honestly it is immaterial to most people. Sure there are those who drink the global warming coolaid or think it's cool to be seen as "green". But those buy Priuses and Model Ses, they don't shop for Sonics or Versas. Those who are REALLY on a tight budget -- one tight enough that $40 matters -- buy $3000 10 year old vehicles. That $15K they saved is much more than enough to make up for the gas savings or increased maintenance. 90% of the aerodynamic drag of any subsonic object is in the ass -- it comes from the low pressure and turbulent volume of air behind it sucking at its stern. The more distance you have to gradually "collapse" the displaced air stream the better your aerodynamic co-efficient is going to be. Also, let me let you in on a little secret... Sub-compacts tend to not deliver as much additional fuel economy as their downsizing and weight reductions seem to suggest. The reason is simple... all else being similar, long cars are more aerodynamically efficient than short cars.

They are certainly capable of designing handsome cars or admirable content and quality... now JUST STOP COPYING THE MERCEDES_BENZ GRILLE!!!

I like it! But those EJ20 / EJ25 engine needs some serious updating though. For one, DI is a must in this day and age. Secondly, the exhaust routing for turbocharger is about the worst I have seen... the piping is long and contorted between the exhaust ports and the rear mounted turbo... that silly cat converter ahead of the turbine really hurts efficiency... and, the entire exhaust ensemble and heat shielding under the engine removes one of the prime advantages of the boxer -- that the center of gravity of the engine can be very close to the ground. This is one engine where they can really use a reverse flow design where the turbo is above and between the cylinder banks. The manifold should be cast as a single unit as the turbine housing. The compressed charge can then exit the FRONT of the engine and loop down to the bottom where the intake manifold(s) is either through an air-to-water or air-to-air heat exchanger. Given that the boxer is confined to big bores and short strokes by the need to be narrow enough to fit between the front wheel wheels, instead of trying to run generous boosts, they should play to the advantageous of that configuration -- push up compression, reduce boost and make use of the high revving character of an over square engine. With compression at about 10.8:1 and boosts at a very modest 11.8 psi, you end up with about 220 lb-ft @ 3600~7600 rpm and 318 bhp @ 7600 rpm. An EJ style short stroke boxer has no problems revving to 8000 rpm. This will be the most "un-turbo" like turbocharged engine. The power delivery is very much like a high revving 3.0 liter class engine like the BMW S54 (E46 M3). Fast revving, extremely low lag, great economy at cruise (due to high compression). In fact, it'll be a perfect engine to be shared with an uprated FT86.

Well, neither C&D nor Edmunds have any authority on the subject. Their speculation is as good as yours or mine. As far as Europe goes, a CTS Wagon is not as important as a CTS Diesel or an ATS Hatchback.

The new tail end kinda looks like the final generation Honda Prelude. I like it though. It, along with the new front treatment, is cleaner and less cluttered than the current car's.

Basically, yes. But, super quiet is relative. I didn't find the XTS 3.6 to be "super quiet". I find the engine to be a little coarse and the interior noise under acceleration (especially between 1500 and 4000 rpm) to be less refined than in a IS, ES, GS, E-class or 5-series.

I am not a big fan of gaping grilles that go through the bumper -- a really annoying trend started by Audi in the last two model cycles. I am also not a fan of the vertical front fascia although that's more the result of stupid EU regulations on passenger crash safety. If it's me, I'll have two front clips -- an ugly EU front clip to comply with EU rules and a more rakish NA/International front clip for every where else. Burled walnut is a nice touch -- nice and also very American (it's a traditionally American wood). Tail treatment is a little conservative I think. A little too much plastic (lamp covers) and too generic a trunk deck. Headlights and LED light strips look well executed and proportioned. I hope the car has a distributed aperture system for parking and blind spot warning. It's about time...

Dwight, I am surprised as this is one of your shortest comments and I enjoy reading your technical insight. So other than refinement, what other specific issues would you have with this? I have changed my 94 Suburban from TBI to a FuelInjection which allowed me to convert to CNG so it runs on both and runs very well. Well, it's really very simple. If you replace Port Injection with Direct Injection in an otherwise identical engine. Refinement is notably reduced due to a significant increase in injector noise. DI Advantageous 10% Higher Compression Ratio Potential to implement stratified charge lean burn About 3~6% higher power & torque -- all else being equal 2~4% better fuel economy DI Disadvantageous Significant Noise Increase from high pressure injector closures Slight cost increase from 300~1200 psi fuel system hardware Carbon build up on the intake valves and intake tracts are not cleaned up fuel additives Placement on injectors sometimes compromise optimization of intake runner design For maximum performance, efficiency and refinement, a dual injection (port + direct) is best. This however is expensive and, some will argue, unnecessarily complex.

Is it really that hard for you to comprehend? A larger turbo always have more lag compared to a smaller one at the same exhaust flow. However, a larger turbo does not have more lag (it actually has less) when fed twice the exhaust flow. A twin (parallel) turbo design feeds each turbo with 50% the available exhaust flow. A single turbo design feeds the turbo with 100% of the exhaust A 2.0 I4 engine with one large has worse lag and efficiencies compared to a 2.0 I4 with one small turbo. Therefore, to get the most responsive engine you want to use the smallest turbo that meets your power goals. Using a larger turbo will allow you to hit higher boost levels or flow rates without "falling off the map", but using a larger turbo also negatively impacts response and lag. However, if and when you want to hit higher power levels, you are always better off using one bigger unit than two smaller ones in parallel. The reason most V6 and V8 designs use twin parallel setups is because it is impractical and/or inefficient to run exhaust from both banks to a single turbo. It is also impractical and/or inefficient to run a sequential bi-turbo setup for the same reasons -- because you need to get ALL the exhaust to the first turbo, then dump the output from the first turbo into the second.This is the reason Vee type engines commonly use bi-turbo setups and Inline engine (where the exhaust ports are in one place) use either a single larger turbo or two unequal sized turbos in a sequential dual setup. A reverse flow head design allows you to use a larger single or twin sequential design.

Let me give you an of example... BMW N54 3.0 I6 (2007 thru 2010) used two turbochargers in parallel. It made 306 hp @ 5800 rpm & 295 lb-ft from 1400~5000 rpm. BMW switched to a single larger turbo for the N55 3.0 I6 (2010 thru present). It made 302 hp @ 5800 rpm & 300 lb-ft @ 1200~5000 rpm. Not only did the torque go up slightly, response is improved with maximum torque arriving 200 rpm earlier than before (1200 vs 1400 rpm)

It's not a spin. It's a simple fact. Larger turbos are more efficient and do not have higher lag compared to two smaller ones in parallel. They have higher inertial, but you are also feeding it twice the exhaust flow to overcome the inertial. If the efficiencies are the same it'll be a wash -- no better, no worse. But because they have better efficiencies, more exhaust pressure is converted to angular velocity and more angular velocity is converted to boost instead of heat. The ONLY reason they may be less efficient is that if you have a large turbo on one side of a Vee-type engine, getting the exhaust from the far bank over to it is highly inefficient. A reverse flow engine where the exhaust exits the center gets rid of this condiition

Sorry just read my own post again and realized all the typos I made... which really confuses anyone reading it! LOL. A Twin Scroll turbo's benefit is that it keeps exhaust leaving a cylinder near Bottom Dead Center (BDC) from back flowing through the exhaust valve(s) of the cylinder at Top Dead Center (TDC). This severely impacts volumetric and scavenge efficiency by preventing the intake charge from entering the cylinder at the beginning of its intake stroke and pushing out the last remaining exhaust gases. A Twin Scroll Turbo is useful only in engine layouts where you will find a cylinder at Top Dead Center while another is at Bottom Dead Center at the same time. Generally, this means an Inline-4 and an Inline-6.

Actually, I think you bear two misconceptions here:- (1) Two smaller turbos are not more responsive than a single larger unit. In fact, the reverse is true in ALL parallel arrangements. A larger turbo is more responsive than two smaller ones because it has higher turbine efficiency. Sure, the larger unit has a bigger and heavier rotating assembly with a greater inertial. However, a turbo with twice the flow capacity does is not twice the diameter and does not have twice the wheel mass -- it has less than twice, more like 1.5~1.6 times. Also, if you look at turbos from ANY manufacturer, the larger units always have higher turbine and compressor efficiencies. This has a lot to do with aerodynamics of the wheel. As wheels scale in size they become more efficient. Without going into the math, let's just say that it has everything to do with the fact that air molecues are the same size and pressure is pressure even as an object scales. It is easier for a car to go 60 mph than an ant (assuming its shaped just like a car) simply because it is bigger. This is true in aeronautics too. When you scale a wing to 1/4 the size or 1/16th the size for wind tunnel testing you need to adjust the Reynolds number otherwise the result will not be accurate -- not even close. The only time when two turbos are more efficient is when the exhaust routing is horrible -- like when you have the turbo on one side of the engine and have to pipe half the exhaust through a long contorted pipe from the other bank (sometimes even adding a catalyst in between ala Subaru's WRX) -- or when it is a sequential setup. A sequential setup is when ALL the exhaust goes through the smaller turbo first, then as it approaches the limits of its efficient flow capacity, the waste gate opens and dumps all the extras through a larger unit. The only reason a sequential setup is more responsive is that 100% of the exhaust goes through one turbo first until the first waste gate opens. In parallel arrangements typical of V engines where 50% of the exhaust goes to each turbo there is zero responsiveness advantage. This is why you never, ever, see a parallel bi-turbo in an Inline-4 or Inline-6. A parallel Bi-turbo is simply a convenient compromise to easily route exhaust in Vee engines. A reverse flow engine puts all the exhaust in the same place and allows a single turbine to be used with no routing penalties. The larger turbine, being more efficient gets better response compared to two parallel turbines of a smaller size (always). It is perhaps not as good as a sequential twin turbo design. But sequential twins are NOT typically implemented non-reverse flow on V6es or V8es anyway because of the same routing problems with getting all the exhaust to one side then the other. Hence, a reverse flow single turbo is almost always more efficient and a non-reverse flow twin turbo design. (2) A Twin Scroll turbo turbo is not more responsive because it keeps airflow "up and progressive". The twin scroll turbine housing has ONE purpose and one purpose only -- to keep exhaust from a cylinder which is just opening its exhaust ports from pushing exhaust back into another cylinder which is near the beginning of its intake stroke and into the intake mannifold. During this instance, one cylinder near top dead center has both valves open (overlap period) and if the exhaust back pressure from the cylinder just opening its exhaust valves is not segregated, it forces exhaust (which is at a higher pressure than the intake air) into the intake. This is horrible for volumetric and scavenge efficiencies. The solutions are to either uses almost no overlap in the intake and exhaust cams (which is also inefficient but not as bad as if you let exhaust back flow into the intake. The other is to segregate the exhaust flows from two cylinder from the other four in an Inline-4. It is important to note however that this is the essentially an Inline-4 problem! An Inline-3 for instance does not have two pistons at TDC at the same time. Neither does and I-5, V6 or V8. Hence, a Twin Scroll Turbo has ZERO benefits in I3s, I5s, V6es and V8s. Zero, nada, zilch!

Anyway, transmission aside, I was kinda disappointed that they used a traditional bi-turbo setup. A reverse flow single turbo design would be better. A reverse flow design will place the exhaust on the inside of the Vee. This allows you to use a single turbo instead of two smaller ones. This is both more economical and superior in terms of performance -- because larger turbines and compressors also tend to have higher efficiencies. Hence, a single large turbo is always more thermally efficient and more responsive than two smaller ones of equivalent technological content. Given that GM is using an air-water intercooler this can also be place in the Vee allowing for a very compact package. Emissions is also superior. The reason V6es traditionally use two turbos is that they are typically adapted from designs that do not easily allow for the intake and exhaust ports to be reversed. Two turbos are hence a necessity because the exhaust ports of the left and right banks are so far apart. If you rout the exhaust from one back to the other there will be a tremendous loss in efficiency. BMW's V8 bi-turbos for instance is a reverse flowed version of the NA 4.4 V8. They also went from two turbos to a single one in the I6es -- albeit more for emissions that anything else.

GM did patent this logo back in 2007-2008, so they were seriously working on something until the sky came crashing down. When they re-started and how close to production they are at this point is anyone's guess.

Well, all things being constant, DI is the biggest downgrade in vehicle refinement in the last few decades. Not that it doesn't have tremendous advantageous going for it. Refinement however is not one of them.

The reason was that GM suspended its 8-speed transmission development during the bankruptcy. GM, today, does not have an 8-speed transmission. I suspect that the CTS's 8-speed is an Aisin sourced transmission (the ratios are exactly the same which is highly unlikely for an indigenous transmission). But, here's my basic take on transmissions... Small, less powerful, engines especially need 7 or 8 speeds to meet fuel efficiency and performance targets. Big engines do not need as many gears, but can use a wider spread. Beyond 7 speeds the benefits are really minimal -- spread is more important. A 7.00 spread on a 6-speed would benefit an ATS-V or Corvette, more than a 6.71 spread 8-speed from a performance and/or MPG standpoint.

You can always use a taller ratio to reduce the engine RPM at cruise for better fuel economy. The problem with that, of course, is that you can only push it so far. Make the ratio too tall and the car becomes really slow accelerating from a standstill. If you have a 505 hp engine with 470 lb-ft of twist -- like the Z06 -- you can use a tall enough ratio that 62 mph arrives in 1st gear and the car turns over at 1400 rpm at 65 mph in 6th. This is in part why that 7.0 liter engined Z06 turns in 25 MPG on the freeway. Try that on a Honda Civic and you'll probably get off the line at a stop light with the acceleration of a caterpillar. Most 7 and 8-speed transmissions do in fact skip gears. However, they generally do that in during gentle acceleration. Many in fact even start in 2nd gear unless you put them in "sport" mode or the equivalent. At full throttle, they generally don't skip. For engines powerfull enough and having a wide enough torque band, a taller final drive (axle ratio) is typically used so the 1st is taller and fewer shifts are needed to reach a given speed (eg. 62 mph). This allows the 8th gear to be taller and provide better fuel economy. You generally do not use a shorter axle ratio then skip through gears so you have fewer shifts during full acceleration -- that defeats the entire purpose of the 8-speed transmission. From a technical standpoint, it is the small engines and lower end cars -- like the Cruze -- that benefits most from 7 or 8 speeds. A corvette really does not, nor does an ATS-V powered by a powerful engine. The problem of course is that cheap cars are less likely to receive expensive transmissions even if they need them the most, whereas expensive (and powerful) cars get them while the benefits are marginal. Regardless, if the ATS-V gets the 8-speed Aisin box, look for 65 mph cruising at something like 1200~1300 rpm!

Short answer is, yes! ZF8-45 is the same transmission as the Chrsyler-Fiat 845RE. There are some differences such as the choice of clutch pack friction material and the oil pan under the tranny. But even the ZF8-45 varies from application to application in this regard. It's the same exact design and architecture. Chryslet-Fiat license builds the 845RE in their Kokomo, IN, tranny plant. But Chrysler is also takes delivery of 845RE from ZF's Greenville, SC facility -- or at least has signed a letter of intent to do so.

It may not be as bad as you think. Sporty versions of big sedans do not really have to be ultra athletic. They just need to be refined and brawny -- think S63 AMG -- big, heavy, fast, stately, but not exactly an autocross contender. The XTS can use a V8 (the 6.2 LT1 will fit where the 3.6TT fits). I won't call it a V though, just the top rung XTS model -- XTS 6.2.

I urge you to drive a 3.6 HFV6 w/o DI and one with DI. You CAN definitely tell the difference in engine note. The DI has a distinctly less refined sound. I am not talking about the tick tick tick you hear from the outside, rather it's the grainy "gggrrrrrrr" that the DI engine make at 1500~3000 rpm which is absent in the port injected engines. The pump on DI engine is actually not the biggest noise source. It's the injectors themselves slamming shut under over a thousand pounds of pressure. Honestly, I think GM should revive "throttle body injection". Yes, it's somewhat imprecise and doesn't offer perfect fuel distribution from cylinder to cylinder and no it's not every knock resistant for that reason. But, high knock resistance is not always important -- it's only important under moderate to high loads and at lower rpms. If you retain Direct Injection for performance and under load emissions, but add a single throttle body injector, you can dramatically cut down on idle and low speed noise, provide for valve cleaning and do so at a lower cost and complexity compared to direct + port injectors.

I have always said that what's needed isn't more gears per say but a wider ratio spread -- the lowest gear divided by the tallest. The 7-speed and 8-speed boxes tend to have a wider spread, and this is where the overwhelming majority (like 95%) of the fuel economy advantage comes from. However, more speeds doesn't automatically translate to wider spread. For example:- The current GM 6L80 6-spds auto = 6.05 ratio spread (This is about as good as 6-speed conventional automatics get) ZF's 8HP 8-speed auto (used by BMW) = 7.04 ratio spread Aisin's TL80SN (used by Lexus) = 6.71 ratio spread GM's latest 8-speed to be put into the CTS 3.6 Bi-turbo = 6.71 ratio spread (I suspect it's the same Aisin sourced box as Lexus') Mercedes' 7G-tronic 7-speed auto = 8.86 (best in the world at the moment) Hypothetically, if you are to create a 6-speed transmission with a ratio spread of 7.05:1 it'll accelerate just as fast as the 8-speed ZF in 1st and be just as economical on the freeway in top gear. Acceleration performance through the gears is arguable. An 8-speed allows for closer ratios in between gears and keeps the engine in a slightly more optimal powerband. Yet, having 8-speeds and closer ratios means that you shift more often and in the fraction of a second when the shift occurs, engine power is temporarily interrupted. So, it is hard to say which will be faster. In a V8 or bi-turbo V6 engine with meaty and flat power curves, less gears may actually be faster. In a small displacement engine making peak power high up and in a narrow rpm range (like a Honda S2000 engine for instance) more speeds is probably faster.

I doubt that there is a realistic chance of that. The CTS-V may get a supercharged version of the LT1 6.2 liter. But if the ATS-V gets a V8 it'll most likely be the naturally aspirated 6.2 engine from the Corvette. At "at least 450hp and 450 lb-ft" while weighing less than any V6 or DOHC V8 from the competition in the same power class, the engine is right where the ATS-V needs it to be to slot in below the CTS-V -- enough power to battle the M3, RS4 and C63, but not so much that there'll be any confusion between it and the CTS-V. A supercharger coupled to a lower displacement V8 adds additional costs (from the blower to the air-to-water intercooler assembly), very little performance advantage and no fuel economy advantage.

A more luxuriously appointed version of a Lancer Evolution on over-boost is unique. It really takes about 26~27 psi of boost to make a turbocharged powerplant shine over its larger displacement, lower specific output, alternatives. The problem of course is that any such engine will take a while to go from vacuum to full boost making the driving experience sub-optimal. Where that "45" comes from is lost on me though. The engine is clearly not 4.5 liters and does not reflect the output of a Mercedes' 4.5 liter naturally aspirated engine.