dwightlooi

You should be able to do whatever you want. It won't be fair or logical for the new deadline to apply only to people who were late on the original schedule. Personally, I am done... too busy with other stuff right now to do proportionality refinement chores.

I sympathize with your passion... but you may want to tone down the language a little bit... it may get you into trouble with the mods.

The gas turbine is a much less complex animal than a piston engine. There are no valves, no timing chains, no crankshaft, no connecting rods, no pistons, no springs, no water pumps, no ignition coils, no spark plugs, no throttle bodies, no balance shafts, none of that. What you have is a housing in which one or two concentrically rotating parts turn -- depending on whether you have a one or two shaft design. Really, it is very much like a turbocharger with a combustor between the compressor output and the turbine inlet. A typical turbocharger is the size of a stack of CDs. A gas turbine that size is good for about 20~30 hp. So a good question is how much does a really advanced turbocharger cost to manufacture? Of course, some advancements will be needed to made to reach 35% thermal efficiency. But your typical gasoline engine is about 25~28% efficient so even that is competitive because of the size and weight reductions. Let's do some real world examples... This is a 60,000 lbs thrust General Electric CF6 turbofan engine. They make a marine gas turbine out of its core (without the big fat fan and roughly the diameter of the tail cone) called the LM2500. You'll find it in the majority of US warships and even some cruise ships (Celebrity's Infinity class comes to mind). This gas turbine currently makes 40,000 hp. Of course we do not need 40,000 hp in our cars. This is a J402 mini turbojet engine. You'll find it in the Harpoon missile. It has been around for 30 years. It makes about 660 lbs of thrust using one shafts and with one turbine stage. The low pressure compressor is axial, whereas the high pressure one is centrifugal. If you use it to drive a generator, that is about 440hp worth of horsepower. This engine is 13" wide at its fattest point so that kind of gives you an idea how small it is. We also do not need 440hp for a series hybrid's generator drive... 40hp would have be enough to support a 160hp motor by charging a battery capable of handling the motor's current draw. Remember, how often do you use 100% of the horsepower in your car even when you are driving aggressively? I mean what percentage of the time do you spend at 6000 rpm with the pedal to the floor? Less than 10% of the time I hope! Probably less than 1% in normal driving. The turbine always runs at full capacity or not at all. This is a single shaft, recuperated microturbine. A recuperated turbine passes the compressed air output from the compressor through a heat exchanger fed with the exhaust flow to capture most of the heat from the exhaust. This increases efficiency significantly and reduces exhaust temperatures. A 40~60hp unit is probably the size of a waste paper basket with the core itself the size of a stack of CDs. No radiator or coolant loop is needed to support it. You need to bolt a generator/starter to it to get electricity out of it and to spin it up to working speeds, but the same applies to a piston engine. BTW, this is an off-the-shelf FB1-4001 permament magnet motor rated for 100hp @ 144 volts. It is 9.1" in diameter and 15.6" long. You can buy one for ~$900. I am sure it won't cost $900 for GM to get one. This is an FB1-4001 which an Aussie dude installed in his small pickup truck.

If you listen to Al Gore, we have a Global Warming problem. If you listen to the environmental activist lobby its because of companies like GM and people who buy SUVs. Now, GM is being pressured to reconsider its RWD plans because the yelpers and yanters have made Bush propose some rather ambitious CAFE goals -- of course being a Republican President and public enemy #1 to the Liberal media he'll get zero credits for it. Well, there are two issues here. One being Global Warming, the other being RWD and fuel economy. I'll cover them here and if you don't agree with my assessments please feel free to argue about it in this thread. (1) Global Warming First let me say that the Earth has been warming up a little since late 1970s. If by Global Warming you are referring to that, then thats fine. However, there is NO SCIENTIFIC EVIDENCE whatsoever, or even convincing lay person reasonings, to suggest that this is abnormal. The Earth goes through countless warming and cooling cycles -- some long, some short, some to a greater extent than others. There is no evidence to suggest that this period of warming is unusual or that we'll not see a reversal in the future to a cooling trend regardless of what man does or does not do. In fact, there are MANY periods in this planet's history that temperatures were much warmer than it is today and all of them have occurred prior to industrialization and/or urbanization. We do not need to go back to dinosaur times to find that. Based on glaciation extents, the temperature for AD1000~1400 was about 5~8 degrees (F) warmer than present day. About 1400~1800 the world rapidly cooled to about 1 degrees cooler than present day. There had also been a short period of cooling between 1940 and 1977 where global temperatures dropped overall despite rather brisk postwar industrialization and androgenic (human caused) CO2 emissions increase. This is also rather convenient for the Global Warming purveyors because one can often say "oh, Al Gore was growing up, winters were colder and summers were milder". Thats true! But thats not how it was during the great depression or when the Wright brothers flew, it was how it was in the 40s through the 70s. In fact, if you wind the clock back to the baby boom days, there were activists and tabloids prophetising the coming of the next "Ice Age"! If we look at CO2 itself. There had been times when CO2 levels are 5 to 10 times current levels due to volcanic activities and other causes (eg. the Cretaceous) where the temperature is warmer than it is currently. There have also been periods where CO2 levels are higher, but temperature are cooler -- this is possible because the overwhelming majority of the green house effect is due to water vapor (50~70%) not CO2. Besides, androgenic CO2 is a small fraction of total CO2 production. What I am trying to say is that the argument that we are in a period of ABNORMAL WARMING -- or that Androgenic CO2 production has anything tangible to do with it -- is at best an unproven theory or an article of faith. At worst, it is a convenient act of fraud and false propaganda used by environmental activists to advance their other causes. These causes range from genuine environmental concerns, to a desire to punish the affluent industrialized world and thereby aid the socialistic goals of material equalization, to the need to find big corporate scape goats for the plights of their favorite animals, to a desire for self atonement for the conveniences of modern life, to simply misconceptions about the problems of our times, to who knows what else. (2) RWD and CO2 production. The reason GM gave for suspending RWD expansion is that they do not know how to make RWD vehicles 30% more fuel efficient by 2017. Firstly, let's make it clear that turning the rear wheels as opposed to the front wheels are not any more or less efficient. However, turning the rear wheels via a drive shaft and a differential axle from a front mounted engine incurs roughly a 5% additional drive train loss compared to a front-engined, FWD vehicle. The typical drive train loss of a FF (front-engine, front drive) vehicle is about 8~10%. The typical drive train loss for a FR (Front-engine, Rear-drive) vehicle is about 12~15%. Full-time AWD is typically 18~20%. Secondly, the additional RWD drive train components -- namely the drive shaft, separate differential axle -- and the structural differences between a FWD and a RWD vehicle adds about 150 lbs to the weight of a vehicle in the 3000 lbs class. Thats about it really for economy differences between a FF and an FR car -- 150 lbs more weight and wasting 5% of the horsepower and torque produced to additional mechanical losses. How much is that? Very roughly, its about 1 mpg in a 30 mpg car or about 3%. It sure doesn't help in getting to the 30% fuel economy improvement goals, but it is at best 1/10th of the problem. So GM's problem really isn't RWD, but the big, powerful "muscle cars" that are supposed to receive RWD platforms. Drop these and you also lose much of the potential candidates for the Zeta and Sigma platforms. But IHMO, all of it is moot. They are not going to get to a 30% CAFE improvement regardless of whether they build RWD Impalas or FWD Impalas. The biggest determining factor of fuel economy is not engine size, power or drive train layout. The biggest determining factor is weight! A 3200 lbs Corvette is about 80% as efficient as a 3200 lbs Honda Accord V6 when driven at a similar speed or acceleration profile despite having twice the engine size and 160 more horsepower. So unless they decide to start making Carbon Fiber monocoques for family sedans or start transitioning wholesale to radical hybrids they are not going to get to the 30% target. So perhaps they have halted RWD to made a sudden and radical decision to put every ounce of their R&D dollars into plug in Hybrids or gasoline electric hybrids and radical chassis lightening? If they are going hybrid, I suggest that they drop the piston engine altogether and start pioneering the use of recuperated gas turbines along with electric motor propulsions. If they do that then we may yet get RWD cars because the entire paradigm for car design will have changed. The gas turbine will only need to make about 1/4 the cars electric motor's maximum horsepower. The battery will provide the juice for 5 to 40 miles of driving on its own. A 50hp turbine for a 200hp car will fit in the glove box or occupy the space of a muffler. The permanent magnet electric motor(s) will go where the rear differential will go. The battery can be put in the central tunnel. In essence there will be nothing under the hood and no need for a big engine compartment in the front. there will also be no need for drive shafts, differentials or transmissions. If this is the future, then it is way beyond the RWD/FWD argument!

Actually, no. The main reason I want a RWD is the superior handling dynamics. In fact, I specifically hope that the Alpha will be made small and light and be designed specifically around 4-cylinder engines such that it will not even accept a V6. For a 3000 lbs car the size of the contemporary Civic with RWD, I believe that the best power plant offerings will be a 150hp 2.0 liter inline-4 with direct injection and VVT and a 260~300hp version of the same engine with a turbocharger. The a 2.0 turbo will make more torque starting from a lower RPM than a 3.6 liter V6, it will also put less weight over the front axle making a 50/50 weight distribution a practical reality. The 2.0 liter swept volume and its associated pumping losses at cruise will also yield better economy numbers overall. In fact, even for larger, heavier cars, I find the V8 configuration unrefined for vibration purposes. I'll much rather see a G8 carry a turbocharged version of the 4.2 liter Vortec 4200 Inline-6 to the tune of about 400~450 hp which is easily achievable at relatively modest boost and stress levels (@10~12 psi boost). At this boost level and with twin turbochargers, response will be pretty much immediate and a maximum torque of about 400~450 lb-ft shoulb be reached by about 1500~2000 rpm. A 4.2 liter I-6 should be able to support up to ~630hp (~150hp/liter) on 91 octane pump gas and with regular factory reliability @ about 20~22 psi of boost pressure (~34.7 to 36.7 psi absolute pressure). As a bonus, turbocharged cars will also not lose power as you climb up a mountain although they may get slightly more laggy respnse wise.

LOL... I know. The butt end on the front quarter view -- especially the tail light representation and boundary lines isn't exactly to proper proportions either. But there was a deadline for 11:59pm friday and I didn't have time to do as many iterations of proportionality refinements as I'll like. Normally, it takes me about 10 to 12 repetitions to get it right. This sketch had about five.

There aren't enough entries... I think we should push the dateline by a week.

OK, I made it... Its not as refined as I'll like and I did not have time to do the interior... but here it is. The 2010 Alpha platform G6 design mission is simple:- (1) Make it RWD. (2) Make the BMW E90 3-series look stodgy and dated. (3) Make it a well proportioned small-midsize sedan compatible with an expected wheelbase of ~110". I know that Pontiac fans "need" extravagance and I need to make up for my total disdain for those Nostrils found on some Pontiac hoods. So I threw in a few gimmicks of sorts. The first is the side intakes inspired by today's latest jet fighter the F-35 Lightning II. Of course the G6 won't go supersonic so the Diverterless Supersonic Intake (DSI) styling with its characteristic "bump" is just a gimmick. Well, they put fins on cars in the 50s . The second is an exhaust outlet that is a huge contoured slot spanning the entire the rear diffuser. (Combined both front and rear views into one picture, didn't really change the content)

I'll tender an entry... but I am kinda busy right now so it probably won't be as extensive an effort as before...

The G8 is not a Caprice. It is a Camry sized car -- albeit one driven by the rear wheels. The G6 doesn't need to be another spacious hauler that is as large as the G8. It doesn't have to be the Camry/Accord fighter size wise -- the G8 will do that. It also shouldn't be a "not so high performance version of a G8" which is what it'll be if it stays at its current Epsilon size. Hence, sizing it between the G5 and the current G6 is will make it roughly a 2006+ Civic in size. That is not a small car. If you go back 10 years its how big an Accord is and it is what a mid-size is. The Civic is also 2800~2900 lbs. Hence a target weight for the G6 of 2900 lbs is reasonable even if it may be ambitious for GM which -- with the exception of the Vette -- has pretty lousy weight control discipline. IF the RWD Alpha G6 can be about 2900 lbs with a NA Ecotec and about 3000 lbs with the LNF, it'll be in the right weight category. Even if it, misses the mark by 250 lbs it'll be an Accord or Mazda 6 in weight. That is acceptable. But if it turns up at 3500 lbs it'll be another porky sedan and RWD won't fix it, especially not when a V8 is off the table. IMHO, weight attack is the next thing GM needs to get good at. And if push comes to shove, I'll rather lose size and structural integrity for weight loss. Structural integrity loss may sound like a step backwards, but let's us all ask ourselves this question... Is a 1991~1998 BMW E36 all that bad structurally? Or more importantly, is it unacceptable to YOU from a safety and chassis flex standpoint? Thats a 3000 lbs car. And, no, it is not class leading in space, chassis stiffness or even crash safety. But IMHO, it is GOOD ENOUGH. On the other hand, a 3500lbs car pushed around by either a 260hp LNF turbo or a 250~275hp 3.6 VVT is NOT good enough.

At the cost of SIZE, possibly structural rigidity and perhaps crash worthiness. The current G6 is a BIG car. The interior isn't as roomy as it should be due to poor packaging, but this is a pretty big car. IMHO, the G6 should downsize to the size of a 2001 Civic. Structure should be crash worthy enough to meet regulations but it lightness should be a priority over tank like structures.

Actually, I think what the new G6 should be isn't quite as important as what it SHOULDN'T be. IMHO... (1) It shouldn't be styled with nostril hood intakes which will turn away most buyers and give it a ricey image. (2) It shouldn't try to be a spacious, mid-size which tries to compete with Accords for occupant accommodations. (3) It shouldn't be a 3,500 lbs sedan but rather should shoot for a target weight between the Civic and the Mazda 6 -- ~2900 lbs. (4) It shouldn't be made larger, heavier or more costly to accommodate V6 engines -- stick to a pair of 4-potters making 170 and 260hp. (5) It shouldn't try to copy the 3-series, rather it should carve out its own character -- a ride that is a compromise between an IS and a 3-series may be a good start. (6) It shouldn't package luxury items such as leather, power seats and a moonroof with engine choices. (7) It shouldn't force a manual tranny on buyers who want the top engine or sporty suspension. All versions should have a 6-spd auto option.

The Duramax is not a good example of a multi-valve (meaning greater than 1-intake and 1 exhaust valve per cylinder) pushrod engine. The design is workable only because its a diesel with a flat roofed combustion chamber and no sparking plug. Here is a better one:- This is what GM toyed with for a while when they were thinking about how to improve on the LS1. Problems with this design may include the rather asymmetrical offset rockers with interconnecting rods having poor high rpm stability and projected asymmetrical wear. The significantly increased valve train mass driven by a single lifter also practically double the spring pressure applied on the lifter and hence increases frictional wear on the intake side. In the end, airflow improvements over an optimized 2-valve design may not have been demonstrated. The design was not adopted. Instead the LS2 got LS6 style optimized 2-valve heads with bigger, straighter ports.

In short, no. Magnaride uses a ferros magnetic fluid in the shock absorbers. By passing an electric field through the liquid, the vicousity of the liquid can be adjusted. This changes how easily (or hard) the fluid is to pass through the valving in the shock tubes, hence making the shock absorbers stiffer or less stiff. The system does not actually move anything at all -- it merely changes the properties of the oil if you will. I don't see how this can be applicable in the valve train.

The purpose of a DOHC 4/5-valve design is mainly airflow maximization and optimization. In a pushrod OHV design you have a big problem with the pushrods and the intake ports fighting for the same space on the side of the heads. Basically, on the intake side you need a minimum of two pushrods and their tunnels. Typically these are smack in the middle with the intake port snaking to one side. If you have two intake valves there is not enough room to put in the intake tracts to support them. In addition, if you put two small intake ports on each side to feed two intake valves, the airflow collides in the middle and eliminates any swirl that you typically get. In addition, you'll need additional hardware on top of the heads to bridge both valves so the can be operated by one push rod. This is a problem because any hardware that bridges two valves on the intake side also blocks access to the exhaust valve by the other pushrod and its rocker.The only single in block cam, push rod actuated 4-valve per cylinder design is the Duramax 6600. In this engine, if you look at a cylinder from the intake side, the two valve on the left are intake valves and the two on the right are exhaust valves. In otherwords, the valves are tandem in arrangement. A single pushrod tips a rocker arm which pushes down on the middle of a bridge connecting both valves. This is possible because the diesel engine has a totally flat roofed combustion chamber. That is all four valves are parallel to each other. The tandem arrangement does not permit or support the intake port dimensions any where near as large as typical DOHC design, this is bad for airflow, but it is good enough for a diesel which revs in the 3250 rpm redline. In a gasoline engine it would have been completely impractical. Increased airflow = reduced pumping losses. Period. Pumping losses is precisely the power it takes to overcome airflow restrictions. The the cylinder head off and spin the crank pushing the cylinders into open air and you'll have zero pumping losses just frictional losses.

Evidence is not the right word. However, indications are abound. The most obvious, is that in general DOHC-4 valve designs have not just higher power but also higher torque yield than IBC-OHV designs of the same displacement. Remember output yield is really gross - total loss. If the frictional qualities are inferior or even equal, and accessory tap off is roughly the same, then the only reason this can be the case is higher pumping loss. From a more elemental standpoint, 4-valve DOHC designs almost always have larger valve area to piston area ratio. Basically, it is very simple... if you have higher output yield per unit displacement, and you have equal or higher frictional loss, you also necessarily have lower pumping losses. But they do because the wear resistance of the contact surface is very much affected by the material and lubrication. This governs how much spring pressure you can apply before wear becomes unacceptable. Higher valve spring tensions increases frictional wear -- the classic (idealized) equation for frictional force is normal force x friction co-efficient. Let's put it this way.... if we make cam lobes and lifters out of say soft iron, we can apply less pressure between the two than if we use titanium nitride coated high speed steel and it last the required number of cycles. Modern lubricants which leaves a decent film even after the oil drains away also helps. In short, if you have advanced, very wear resistant materials and very good lubricants, you can use higher spring rates and still have the parts last the same amount of time.

I think that a higher bar needs to be set as a general rule for GM or for any company trying to buff up a tarnished reliability/durability image. Exceptions is just that exceptions -- good or bad. Toyota had their goofs as well, but never in the majority if their products and hence they did not tarnish their reputation tangibly. The 3.0 liter 7M-GE inline-6 engine (and the turbocharged 7M-GTE) for instance almost ALL had head gasket issues -- partly due to lousy gasket design and partly due to inconsistent deck expansion due to uneven thermal management of the block -- the 7M-GE/GTE is used in the US market 1986~1992 Toyota Supra. Later in the model cycle, Japanese market cars used the 2.5 liter 1JZ-GE/GTE engines which did not have the issue. the 1993~2002 US model used a 3.0 liter version of the JZ powerplant (2JZ-GE/GTE) which also did not have the problem.

(1) The ONLY Desmodromic valvetrain still in production is used by Ducati Motocycle engines. The concept is relatively simple -- each valve requires two cam lobes and two followers, one to open the valve and one to close it. The purpose of the design is the elimination of valve springs and hence valve float at higher RPMs. Back when it was originally invented, metallurgy and lubricant quality limited the amount of pressure a valve spring can apply on the contact surfaces before wear becomes unacceptable. Metallurgy back then also had problems with producing valve springs that are strong, light, compact and which does not lose its memory over the expected lifetime of the engine. Desmodromic valvetrains eliminated all of these problems. However, Desmodromic valve trains are noisier -- because it'll require zero tolerance for there to be no zero slop at all points between the opening and closing fingers and the valve, and zero tolerance does not exist. Also, when the system gets out of adjustment, it can tension the valve against the valve seat or fail to close it completely, both of which can have very serious consequences. Its demise however was that today -- or since the 80s for that matter -- metallic valve springs, contact surface material, valvetrain lightening and lubricants have already conquered valve float issues beyond any sane RPM. And for insane RPMs (say 20,000 rpms in an F1 car) pneumatic valve closure is the superior solution compared to Desmodromic. Hence, it became irrelevant. Ducati uses it because it is a brand identity thing. (2) Parasitic frictional drag is higher in OHC designs than in IBC designs. It is also higher the more moving parts you have in a valve train -- more valves, more lobes, more followers, etc. However, the total parasitic loss of an engine is not dependent on frictional drag alone. It is a combination of frictional drag and pumping losses. In fact, more of it is due to pumping losses than frictional losses. An engine is like a syringe. The total surface area of the pistons is a lot larger than the surface area or the intake valves or the cross section of the intake plumbing. In general DOHC engines have less pumping losses but higher frictional losses, but because frictional losses is a smaller fraction of the total parasitic loss they are generally slightly more efficient.

The G8 design is clean and neat enough for the most parts. I'll simply:- (1) Eliminate the phony, ricey and ugly hood intakes. (2) Add a pair of functional brake cooling duct intakes. (3) Eliminate the uncomplimentary spoiler. (4) Remove the side marker/blinkers from the bumper. (5) Add mirror mounted marker/blinkers. (6) Add a full underbody tray feeding into a functional rear diffuser (Not shown)

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I don't see it is a new design; the block is are basically the same except for the addition of oil galleys to support DoD (which is NOT even used on the current LS2 applications; but rather the LS4 and L92) and the relocation of the Knock sensors. As far as what "generation" it should be, GM can call it whatever they want! What is important to note was that there was a huge difference -- in engine design and materials used between the so called Gen II (circa LT1, L98, etc) and Gen III engines. And there was also a lot of difference between the down draft carburetted small blocks of yore (Gen I) and the TPI small blocks in the C4 Corvettes for instance. There is practically no difference other than the above stated ones between the Gen III and Gen IV.

The whole "Generation IV" moniker gives the false impression that the LS2 is a new design. It is not. To put it simply, the LS2 is basically an improved LS1 block casting (with provisions for cylinder deactivation) carrying what is essentially the LS6 cylinder head. The cylinder bores are enlarged slightly from 99mm to 101.6 mm by thinning the siamesed walls. The LS6 was a high performance modification of the LS1 whose biggest difference (other than strengthened internals) is the new cylinder head design. Here are the main differences between the LS1 and LS2:- (1) LS2 uses a mass production version of the LS6 cylinder head. (2) Bore is increased to 101.6mm and displacement to 6.0 liters. (3) Provisions and oil galleries for Displacement-on-Demand (aka Active Fuel Management) (4) Knock sensors were relocated from the valley of the engine to the exterior sides of the block. (5) New "wingless" oil pan design adopted and oil capacity is reduced from 6.6 quarts to 5.5 quarts. Everything else is practically of the same design and specifications and most accessories and parts carry over. If you are looking to modify your motor, or put together one from available parts, I suggest that you use the following combination:- (1) LS2 block. (2) L92 (Vortec 6200) cylinder heads -- its basically the LS7 head and its a reliable, cheap, production piece not some custom job! (3) L76 intake from the Commodore -- the L92 intake won't fit LS2 powered cars, but the L76 will drop right in on the L92 head. (4) Camshaft from the L92. You'll need some custom ECU mapping, but thats a $300 thing.

Actually, it is easier to build a high reving DOHC 4-valve motor that lasts than a Push rod one. If you want a 7000 rpm motor and you are using push rods, you'll be using very heavy valve springs. You may also be using exotic materials or construction techniques to lighten the lifter, rod, rocker, valve retainer and all of that stuff. Heavy springs actuating a heavy valve train linkage is bad for durability. Skeletonized and aggressively lightened parrts may also narrow your margin to material failure. In DOHC designs the reciprocating components are much lighter and the spring tension is usually much lower for a given maximum rated engine speed. This is good for durability and reliability. 7000 rpm is no big deal; something an economy car designed for low manufacturing costs can easily pull off. With the same kind of effort and wear acceptance as you may experience with an LS7 you can easily push a DOHC design to rev at 10000 rpm and still cover it with manufacturers warranties. In fact, with DOHC designs today piston speed is a bigger concern than the limits of the valve train. The spring actuated DOHC valve train is good for about 18000 rpm is small engines (~0.15 liters per cylinder; ~600cc I4) and about ~13000 rpm medium sized engines (0.5 liters per cylinder; ~2.0 I4 or ~4.0 V8). It is when you want to go higher than these stratospheric numbers that you need to think of something other than metallic coil springs. This is why innovations like Ducati's Desmodromic valve train are really novelties which addresses what is today a non-existent problem. The more limiting factor is piston speed. The Honda F20C engine (2.0 liter S2000s) reaches a piston speed of 1512 m/min (4961 ft/min) at the rev limit -- thats roughly Formula 1 territory.

That's the idler spring for the center follower (which follows the "aggressive" lobe). When the steel pins are not engaged, the center follower does not open any valve, it simply rides its idler spring while the followers on its side open the their respective valves under as dictated by their own mild and gentle lobes. The primary reason rollers are not employed is because the space under the swiping "pads" are where the steel locking pins are housed.

All Honda "VTEC", Toyota VVTL-i and previous generation Mitsubishi MIVEC engines use lobe switching. Even though the actual implementation of the follower mechanism differ -- Honda uses steel pins for locking, whereas Toyota uses a sliding slipper for instance -- the concept is the same.The answer to your question regarding synchronization is that the lobes and the followers that rides on them are NOT synchronized during their lift duration. That is one lobe may open the valve earlier or later than the other, it may open it with a greater or lesser lift, and it may have a completely different opening and closure ramp. However, both lobes have the same base circle. The switching occurs when the valves are closed and both followers are riding their base circle. When the followers are actually being lifted by the lobes the pin and holes do not align and the steel pins do not slide in place even when hydraulic pressure is being applied to them. They'll slide in place when the followers all drop back to the base circle and the locking mechanism align. The next time the valves open they'll follow the high lift profile. If you look at VTEC in detail, it actually has three lobes per pair of valves. The followers on the sides actuate the pair of valves directly. These provide the velvety idle and smooth, low emissions, drivability at low and mid engine speeds. The one in the middle has a completely different timing, lift, duration and ramp profile. This lobe is practically a racing lobe which will not idle even at 2000 rpm and definitely won't pass emissions at low speeds. At about 5200 rpm, a pair of steel pins lock the three followers together and they all follow the center aggressive lobe. In some VTEC engines the system is actually a 3-stage one. This is because the two side lobes are not identical. One practically does not even open the valve! At low engine speeds, one valve opens regularly, the other is barely cracked open. This causes high swirl and provides high intake velocity at low speeds. At a certain RPM, the barely opening valve is locked to the center "racing cam" while the normally opening one continues to follow its lobe. At an even higher RPM, the normally opening one also follows the high lift cam lobe. Hence there are three stages of cam aggressiveness. On top of that the system adjusts cam timing continuously with the traditional CVVT mechanism on the drive sprocket. Honda engines using both CVVT and cam profile switching are given the moniker i-VTEC. Here are some pictures of the real thing... Well, there shouldn't be any float related clatter at idle. In fact, if you listen to a modern pushrod V-6 at idle it is pretty darn quite. However, because the valve train of a push rod engine comprises of twice as many elements that are not rigidly coupled together, there tend to be considerably more slop in the whole setup. The whole float thing is harder to quantify. It is not as if float suddenly happens at a certain speed. It doesn't. For a given spring rate and actuated mass, there is progressively more slop. In general people define float as when the valve actually closes after the cam lobes have past over it extending the cam duration. However, even before that happens the valve lifter will tend to "lift off" the cam minutely between its peak and the base circle, but catching up before arriving at the base circle and hence close on time. The 3.5 LZ4 for instance -- in my experience -- exhibit some notable amount of what appears tto be valve clatter at about 4500~5000 rpm onwards.