dwightlooi

What is the single mechanical attribute that those three bolded cars have in common that the ZR-1 lacks that would have a bigger affect on 0-60 and handling than the number of camshafts ever could? The ZR-1 vastly out powers all but the Veyron. It weighs 500lbs less than the GT-R and 150lbs less than the Porsche 911 Turbo... yet you want to blame the slightly higher 0-60 time on the number of camshafts it has? You need to pick up some intellectual honesty here sir. There is one thing and one thing only that is holding the current Corvette back from completely wiping the 'Ring with the Nissan and Porsche. It's not the lack of DOHC. The GT-R's prowess has nothing to do with its twin-turbo, DOHC V6 engine. It has everything to do with the traction advantage of its AWD system and the handling advantage of having THREE active differentials metering torque to each of the four wheels. In fact, the GT-R will probably be an even faster and better handling car if it had the LS7 Pushrod V8 instead of the 3.8 Twin-turbo V6, while retaining the same AWD hardware. Why? Because both engines make about the same amount of power -- 505hp / 470 lb-ft (LS7) vs 480~520 hp / 434~451 lb-ft (VR38DETT). The 7.0 liter LS7 pushrod V8 is the smaller, lighter, engine of the two -- 454 lbs (LS7) vs 608 lbs (VR38DETT), a 154 lbs difference.

Actually, I don't see anyone complaining about the CTS-V engines. Not the American journalists, not even the European ones.

In general it is true that DOHC engines -- on the average -- have better emissions than Pushrod engines. However, this has nothing to do with the valve train layout. Rather, it is the result of a technologies that are commonn in DOHC designs, but not traditionally incoporated into Pushrod designs. The first being that DOHC engines frequently have independent cam phasers, whereas Pushrod designs either do not have cam phasers or have synchronous phasing for the intake and exhaust valves. Independent phasing allows EGR to be continuously and effectively managed to control Hydro-Carbon and NOx levels in the exhaust. However, this is a cost decision rather than one which is limited by the valvetrain layout. A pushrod design can have independent timing control -- the Viper 8.4 V10 does that with concentric cams. Other technologies like Direct Injection and wide range oxygen sensing are also more not traditionally found on pushrod designs. These too help with emissions. The important thing to understand is that none of these features cannot be implemented in a Pushrod design. In fact, it looks like the Gen V small block will have them all.

In terms of strength to weight ratio... the next step up will be Titanium-Aluminide followed by Beryllium. Beryllium is really cool. That's for the body... For the high temperature parts like the turbine housing on a turbo, exhaust valves or the exhaust manifold or down pipe, Yttrium will be really good.

I think that if GM really wants a DOHC V8, the best avenue will we a 60 deg V8 created from addding two cylinders and a balance shaft to the 3.6 liter LFX DI V6 engine. Such an engine has numerous benefits over a new 90 deg DOHC V8 design. It will be considerably narrower, allowing it to fit into engine bays designed for the V6 or the Pushrod V8s (which may not accommodate a wide DOHC 90 deg V8. It can also be manufactured on the same production lines sharing most of the tooling with the high volume V6 engines. The 4.8 liter displacement is just about right and the projected output of 430 hp / 370 lb-ft on Regular 87 Octane is also plenty decent.

I won't say that. The value of DOHC is substantial if the objective is to achieve the highest output from a given displacement. It does so in two ways... by allowing a larger valve-to-bore area ratio which improves breathing and by reducing the actuated valvetrain mass which permits higher RPMs allowing more power to be had from the same torque output. These are important attributes if you are governed by a certain displacement limit -- either by government tax regulations or by racing class rules. An additional benefit of getting the same power out of a smaller displacement engine -- assuming you have the same cylinder count -- is that the reciprocating mass is lower. This tend to result in better refinement in designs that are not completely balanced (eg. I3, I4, I5, V6 or V8), even if they make little or no difference in balanced layouts (eg. H4, H6, I6, V12). Many common assumptions surrounding DOHC, however, simply aren't true. The most common being that DOHC engines being freer breathing have better fuel economy. This is largely false because DOHC engines actually have higher frictional losses due to their more numerous valve train parts, and volumetric efficiency (freer breathing) at cruise is an oxymoron because the engine is being artificially choked by the throttle body no matter how free breathing it otherwise is! Another common misconception is that DOHC is "higher" tech. This is incorrect both in today's technical reality and from a historical perspective. technically features like an aluminum or magnesium block, variable timing (independent or not), direct injection, cylinder shutoff, coil-per-plug ignition, returnless fuel systems, ionic knock sensing, hypereutectic pistons, you name it, can be implemented on both Pushrod and DOHC designs. Their incorporation or lack thereof makes an engine high tech or low tech, the Pushrod or DOHC layout has nothing to do with it. Historically, Pushrod designs were invented after DOHC designs, period. And of course there is the seemingly logical, but erroneous, assumption that because DOHC engines allow the same output to be attained with less displacement, they lead to smaller and lighter engines, when in fact the reverse is true and a 4 liter class DOHC V8 is typically just as heavy and sometimes heavier than a 6 liter class pushrod engine! DOHC engines are bulky and heavy because of their significantly fatter and taller DOHC heads, along with the packing of four times as many camshafts, sprockets and bearings, as well as twice as many valves and springs.

Well, sparing the peculiarities of a specific motor, such a choice in lieu of a larger displacement Pushrod V8 will mean... More Weight Bigger Size Increased Complexity Higher Costs Inferior Performance No improvement in Fuel Economy All in the name of appearing "high tech" to a subset of misinformed buyers. Even if you baseline DOHC and 4-valves per cylinder, going to a very small V8 with turbocharging is dubious for two reasons... The first being that engines with small displacements and lots of cylinders are inefficient compared to one with fewer cylinders. The reason being that frictional losses are higher when you have 32 valves and 8 cylinders compared to 24 valves and 6 cylinders or 16 valves and 4 cylinders. This means they make less power and burn more fuel. The only reason racing engines are sometimes built that way is because of class regulations. The second being that the main advantages of increased cylinder count with a small displacement is at odds with the basic tenets of turbocharging. The main advantage of a 8-cylinder 3.0 vs a 6-cylinder 3.0 is the ability to have each individual piston be smaller and lighter with each individual stroke being shorter. This allows for higher revs. A 3.0 V8 can reach 10,000~12,000 rpm. Sounds great if you like high reving engines, but when you throw turbos into the mix everything falls apart. Even the most advanced turbochargers of today can maintain a flat torque plateau of no more than 3500~4000 rpm. Hence, a very nice 2.0 turbo engine may reach maximum torque rating of say 250 lb-ft @ 1600~5600 rpm. The power peak usually arrives shortly there after... say 270hp @ 6000 rpm. If your engine revs to 10,000 rpm, you have a problem. For 10,000 rpms to be meaningful you'll probably want to have your powerpeak at 9,500~10,000 rpm. A turbocharger that supports flow rates that maintains your torque peak to 9000 rpm will not reach that peak until 5,000 rpm or so. This means that from idle to 4000 rpm you have no drivability to speak of. The compromise will be something like the McLaren MP4/12... 443 lb-ft @ 3000~7000, 592 hp @ 7000 rpm. If you do something like this it makes 10,000 rpm capability moot, which then makes the 3.0 V8 configuration moot.

Aluminum is stronger than steel per unit mass, meaning the same tensile strength requirement will use fewer pounds of aluminum. As much as 50% less. However, in practice savings are more moderate because aluminum is also weaker than steel per unit volume, meaning that the same give strength requirement will be able to use thinner steel sheets than aluminum sheets. A good illustration will be an Aluminum Bicycle frame compared to a steel one. The Aluminum frame is lighter, but employs fat tubings whereas the steel bike may be heavier but has far skinnier tubings. This is important because in many structural employments you may NOT be able to go thicker or fatter. The "difficult to stamp" characteristics actually has nothing to do with aluminum per say -- 1 mil aluminum sheets are just as easy to stamp as 1 mil steel. The difficulty stems from the fact that for the same strength, the aluminum panel has to be thicker. This becomes a problem for fenders and doors with complex contours simply because it is hard to stamp a thicker material. For aluminum to be most effectively employed, the car must be designed from the ground up to use "bulky hollow" structures. The Audi space frames are like that... big, fat, hollow members with thin walls. It is difficult and not particularly effective to retrofit aluminum into a legacy, steel based, design. This is why all these retrofits almost always get localized to the hood or the trunk lid, and practically never extend to the stressed elements in the body structure. In many cases, it is easier and more effective to retrofit high strength steel into a design than it is aluminum. At least you'll be increasing material strength and DECREASING material thickness. Going thin is easier than going thick in stamped structures.

I won't give Caddy the "new" stuff and Chevys the "old" stuff. I'll just give Caddy's a different version of the same stuff. For example, Chevys may get a 87 Octane version of the LFX engine with 11.5:1 Compression Ratio rated at 318~323hp. Caddys can get a 12.8:1 version of the same engine requiring 91 Octane and rated at 360hp. From a manufacturing standpoint the 2 engines share 95% of the components, differing only in the pistons, camshafts and ECU firmware. This keeps the supply chain uniform and lowers logistical costs. It also allows GM to make technological progress without half the brands always lagging.

I am not so sure about Buick. Buick probably won't get a RWD or Longitudinal AWD car.

Well, going from 87 to 91 octane allows you to increase compression ratio by about 10%. This was true in 1999 and it is true now. In 1999 -- with port injection -- typical regular fuel engines run roughly 9.5~10:1 compression and engines specifying premium fuel run about 10.5~11:1. An LFX can go from 11.5:1 to somewhere between 12.5 and 13:1 . High compression ratios improve the combustion efficiency of the engine. And that 10% increase is generally worth an increase of between 5~6% in torque across practically the entire power band with no other changes. Hence, 278 lb-ft becomes 295 lb-ft. This is especially important if we want to tune the engine for more high RPM power with a set of camshafts with more valve overlap and base timing advance. Such cam grinds tend to shift the torque curve to the right increasing power output, but they also DECREASE the magnitude of the torque curve practically across the board. Higher compression helps mitigate that torque loss. In short, going from 87 to 91 octane allows 1~1.5 points more compression. This is a key ingredient to increasing power from 323 hp to 360 hp, and do so in a manner that still at least maintain the status quo on torque and drivability from idle up to ~5000 rpm where the new cams would actually be DETRIMENTAL. Another benefit incidental to the use of 91 octane fuel is better engine cleaniness over the VERY long run. Most brands of gasoline have a more generous detergent package with their premium gas than their regular. The downside for specifying premium is actually less pronounced today than in the early 90s when gas was $1.30 a gallon. The reason being that Premium is roughly $0.20 more than Regular regardless of the price of gas in general. Hence $1.50 vs 1.30 represents a greater percentage difference in price than $4.40 vs $4.20.

For anyone who wants to see for themselves how that integrated 3-to-1 exhaust collector on the LFX looks like, here's a cutaway photo...

Let's put it this way... the 3-series is not that light. The E90 is not the E36, not by a long shot. The E90 3-series is about 3425 lbs for a 328, going up to about 3850 lbs for a well equipped 335xi. If the ATS comes in at 3800 lbs for a V8 or Bi-turbo V6 powered ATS-V, that's not ideal but its not the end of the world. I don't think it'll be that bad though... the Zeta is "only" 3900 lbs with the V8 and just by virtue of the shorter wheelbase alone -- even if none of the weight saving efforts paid off -- the Alpha would be no more than about 3800 lbs with a V8. That's not great, but that's not horrible either. Of course we all hope for a 3600 lbs ATS-V with Small block power (maybe 3650~3700 if they went with a twin turbo V6). This will peg a 3500 lbs entry level car with a V6 or Turbo I4 (the V6 and I4 actually weigh about the same). That's fully competitive.

What 16 valve 2.slow? It's an 8 valve 2.slow!

There are a few dubious assertions here... (1) That the suspension geometry becomes sub-optimal because heavier V6 or even V8 engines are fitted is utter rubbish. Suspension geometry has everything to do with maintaining proper camber and toe during cornering and braking/acceleration. Given a particular geometry, the amount of these you experience has everything to do with the amount of actual body roll and squat. It has nothing to do with the weight of the vehicle. If the vehicle is say 10% heavier, you'll simply increase the spring rate and anti-roll bar size by the appropriate amount so the roll an squat at a given driving condition remains the same. Of course it is fixed by tuning, you don't change the control arm length or pick up points to fix these. You only change that if you are trying to lower or raise the ride height or change the centering force, etc. None of that has anything to do with weight! (2) That somehow protecting the car for V6 or V8s will make the car heavier. Well, that may be the case when you actually install those engines, but the chassis weight probably won't change very much. The weight distribution may become less favorable with the heavier engines, but when these engines are not installed then the weight distrubtion ought to be as favorable as before. (3) That a car can somehow benefit from being I4 only in terms of packaging and handling is also for the most parts nonsense. First of all an I4 is for the most parts as long as a V8. A V6 is shorter! Width wise, most cars are governed by the width of the desired passenger cell, not be the engine width. Let me put it this way... the widest suspension tower boxes in the industry are the 1990s Honda ones because of the double wishbone fronts. Even then, if you look at an S2000, there is plenty of room on each side of the F20C Inline-4. The additional width introduced by a 60 deg DOHC V6 or a 90 deg Pushrod V8 is about the same as the room needed for a typical Inline-4's intake runner andd plenum assembly!

nice. i was on the right track with my ideas. lol It's a good engine on paper. I'll reserve the "improved refinement" judgement until I actually drive one. I am kinda disappointed they didn't make a 91 Octane version for Cadillac though. The differences can simply be a set of higher compression pistons and slightly more aggressive camshafts. That'll take it to the 100hp/liter mark. 323 hp is nice and decent. But, 360hp out of 3.6 liters is actually something to brag about and most Caddy buyers probably won't mind the Premium Fuel requirement. A 12.5:1 or 13:1 engine will probably make 350~360hp @ 7000 rpm and about 280~290 lb-ft @ 5500~5800 rpm. It'll be peakier, but it should still have about the same torque output as the LFX below 5000 rpm.

I have actually driven one... Here's the verdict:- Exterior looks -- looks less defined and less solid than the previous generation. Nice chrome grille gives way to black plastic slots. Interior Finish -- Significantly WORSE than the rather posh previous two generations. Looks cheaper without the flush shut vents and rubberized thumb wheels. Lots more hard plastics, dubious chrome trim that's plastic and looks plastic. One piece dash molding looks like Rubbermaid is the subcontractor. Ergonomics -- Generally an improvement over the previous A5 Jetta/Golf. White on black is sharp and well defined over the booey blue lighting. Buttons are easy to reach, but are no longer exquisitely damped in their detent action. Powertrain -- 2.5L I-5 engine revs slowly but is relatively smooth. 5000 rpm redline is a tad low though and the 170hp feels like 130~140. NVH -- Pretty good, better than the kinda roary Civic, but not as good as previous two generations. More road noise and wind noise. Handling -- Nicely Planted but a tad too much under steer up to 7/10ths. Didn't push beyond that because colleague is in the car. Generally, the new Jetta looks and feels like it went downmarket with this revision. But, wait, that is exactly what it did. The new Jetta starts at $16.5K. That's about 2K less than the previous based model despite less favorable exchange rates. Heck, that is less than the Cruze. And... well... it shows! BTW, I haven't driven the BASE modek with the 115hp 2.0L SOHC-8v I4 in the A6 Jetta, but if memories of the A3 (1992 model) which has the same engine serves me correctly, that engine might actually rev a tad higher and be a tad quieter. The good old 115hp iron block 8v is actually quite smooth. Volkswagen tried the posh compact route and now it is trying the me-too at a low price route.

The 528i weighs 3814 lbs, which is heavy, but not LaCrosse weight. The 528i also gets 32 mpg from a six cylinder. GM has 4-bangers that can't get 32 mpg. 535i will top 4,000 lbs, I think they made the 5-series too big, why make it bigger than it was, although now it is closer to the XF and A6 in size. I'm looking forward to when the XF gets on an aluminum chassis and gets the weight way down. Safety regs are killing new cars with weight gain. I'd like to see Cadillac build sedans off an aluminum chassis, but if they have to platform share with Chevy, Chevy can't get priced needed to offset aluminum. Engine size is not really as important as weight and aerodynamics. A 3.6 liter Camaro is 30 mpg on the freeway. That's close to a 528. The biggest difference being the Hydramatic 6-speed auto having a narrower ratio spread than the ZF 8-speed. A taller cruising ratio can easily bridge the gap.

I don't think the GMC brand should go away. I think the Chevy Truck and SUV operations should wind down and go away. Chevrolet should simply concentrate on Coupes, Sedans, Convertibles and passenger crossovers like the Traverse. No trucks, no body on frame SUVs for Chevy. Not even a baby SUV like the Equinox for Chevy, that's the GMC Acadia period. All GM trucks should be GMCs -- work trucks are GMCs, spiced up articles get the Denali post-fix. All Chevy Dealerships will be given the option to carry the GMC brand to make up for the loss of Chevrolet's truck and SUV lineup.

The Axle ratio is basically the difference in the diameter between the transmission output gear and the differential's ring gear. You can have your choice of ratios, but only one at time is possible. To make it 2-speed you need to introduce a shaft in between the two. The transmission output carries two gears which permanently engages two free spinning gears on the shaft. A set of dog gears slide up and down the shaft so you can select between the two. This intermediate shaft then drives the differential ring gear at a fixed ratio. Basically, it's a 2-speed manual transmission where one of the shaft is the transmission output, the other is the intemediate shaft and the differential is still the differential. You can do this or you can introduce a planetary set with clutch packs. Either way you need to put something between the transmission output shaft and the differential ring gear if you what more than a single fixed ratio.

It does make me question why its 2011 and we don't have CVDs... Continuously Variable Differentials. Or at least a two speed diff, that could provide added economy or performance. Obviously weight is a factor and 6,8,14 speed transmissions negate some of the benefit. Because that means adding a shaft to the transmission and it takes up a lot of room. If you are going to put up with the added size, weight and complexity you won't put the shaft next to the differential, you'll put it in the transmission itself and turn it into a 8 or 9-speed. In fact this is exactly what they are doing... the 8-speed boxes tend to have a ratio spread of between 7.0 and 7.5, which is better than than 5.9~6.05 we see in 6-speed autos. That one point is roughly equivalent to being able to switch between a 2.9 and 3.5 axle ratio.

Actually if you clicked on the link to the 2012 ordering guide, under STANDARD EQUIPMENT it states the axle ratio under "FXH Axle, 3.53 final drive ratio 1 - Included and only available with (MH8) 6-speed automatic transmission." The 2011 Axle ratio is 3.83. So the new 2012 cars are getting taller gearing.

It's not as impossible as you make it sound. The way it'll work is that ALL GMC dealerships and Chevy dealerships become Chevy-GMC dealerships (many already are anyway). Over the next 2~4 years Chevy begins to phase out all truck and SUV products; when current models get to the end of their life cycles they are simply phased out. All future GM trucks and SUVs starting from the next model cycle are GMCs. Buyers showing up looking for the Silverado or the Suburban gets shown the new Sierra and the new Yukon.

I only care about one reason... Every single automaker who had not more than 2 or 3 brands were successful and profitable. Every single one that added brands and badges with considerable overlap would up as a disaster.

Wrong. We know exactly how they did that... for 2012 they dropped the axle ratio on the 6-speed automatic transmission cars to 3.53:1 (FXH), it was 3.87:1 in the 2011 models. They could probably have topped 40 mpg if they went with the 2.87:1 axle ratio used by the Equinox or Malibu with the same 6T40 transmission, but that would cost more loss in peppiness than they think buyers would put up with. Again, I am not a subscriber to the small displacement = great fuel economy argument. Gear ratios and reducing cylinder / valve count probably works out to be more significant. If going from 2.0 to 1.4 liters (30%) didn't do much, whereas going from 3.87 to 3.53 axle ratio (8.8%) is worth 2 mpg, what does that tell you? Imagine this... the Cruze could have had a 1.8 liter DI-VVT 3-cylinder based on the LFX V6 engine making about 160 hp @ 6800 rpm and 138 lb-ft @ 4800 rpm, all while running on regular 87. This compares favorably to the new Focus's 2.0 liter DI four with 160hp and 146 lb-ft, but with 1 less cylinder, 4 less valves and 0.2 liters less swept volume it will probably beat it fuel economy. Besides a 90hp/liter Three is really unique. It might even make a good engine for the SS version of the Sonic.