dwightlooi

An interesting way to look at this will be... "Will the Mustang GT 5.0 be a better can if its engine was swapped out for the Camaro's 6.2 Pushrod V8?" It think it will. It'll pick up more power and torque. It'll even lose a few pounds in the nose. Fuel economy will be essentially unchanged -- it's already pretty close now 16/24 vs 17/25 (manual vs manual) and its probably all from the weight difference of 300 lbs.

How so? BTW, I read the article. And one thing they didn't talk about is the higher friction in the DOHC valvetrain because of its complexity and the number of bearing surfaces. Camlobes Cam-Bearings Valve-stems Rocker-interfaces Sprockets Pushrod 16 5 16 16 1 DOHC 32 20 32 32 4 More frictional elements, more friction, less fuel economy. But you get specific output in return. The problem is that is the additional 17% in specific output (82bhp/L vs 70bhp/L) worth the weight, bulk and higher friction of the DOHC powerplant? The Mustang's advantage wasn't in the engine really, it was that it was a significantly lighter car (live axle or not).

For years, cars have relied on (nominally) 12V Lead Acid batteries. However, is it time to leave that behind? Hybrids in general do not make economic sense to most drivers, not the Priuses of the world and certainly not the Volt. They don't make economic sense because the investment in the Hybrid power train will never be recovered for 7~13 years through fuel savings at $3 a gallon even on a Prius like vehicle. This is longer than the average ownership period for a new car buyer. This leaves the notion of owning a Hybrid something that ought to appeal only to solo car pool lane users, green image seekers, Global Warming Coolaid drinkers and people who cannot do elementary school math. However, the advancement of battery technology leaves us wondering whether it's time to ditch the 12V electrical system. Not necessarily for reasons of fuel economy, but because 12V impedes the functionality of the vehicle and going to (let's say) 37 volts can do the following:- Allow the replacement of belt driven accessories with electrically driven ones (A/C, steering assist, water pumps, etc) Allow the implementation of flywheel integrated motor/generators that can start the engine (without the gearing used with 12V starters). I have been advocating for the elimination of the accessory belt and belt driven accessories for some time. And, a 37 Volt electric system allows us to make that leap. Basically, the idea is that you'll dump the accessory belt, the alternator and the other traditional accessories riding on it. We are already doing electric steering, 37V makes the units more efficient. We can also run the A/C compressor electrically. The water pump can be electrical or simply driven of the camshaft. Most importantly, 37V allows you replace the flywheel of the engine with a 15mm thick motor generator which takes up practically no additional room, run all the accessories electrically and be able to start the engine without needing to kick into a really low gear drive like 12V starters. No belts means no scheduled service replacement for the belt. Getting rid of the starter and its kicker gear drive also eliminates one of the most common reasons engines fail (a failing starter gets stuck in the middle of its kick cycle). Of course, a motor generator / electric accessory setup can stop the engine at stoplights and start it seamlessly when you lift the foot of the brake pedal for idle economy without affecting HVAC function or steering effort at rest. In short, a 12 year, 150,000+ mile maintenance free engine (minus oil changes) that is more economical, more reliable, less noisy and more compact. Also, freeing the accessory from the accessory belt in front of the engine means you have absolute freedom in where you want to place the stuff. The A/C compressor for instance can be in the rear quarter panel or unitized under the dash as part of the HVAC head unit or anywhere you want it instead of where the drive belt is. Is the battery expensive? Well... a Volt Li-Ion battery pack costs about $10,000. That's about 16 kWh worth of charge. A Prius's NiMH pack is about $1500 and holds about 1.3 kWh. The Honda Insight's is about 0.58 kWh and about $800. Since we are not planning on actually moving the vehicle on electric power here, all we really need is about ~0.2 kWh. That's around ~$124 using the Volt's dollar /kWH or about ~$275 using the Insight's. It's not all that expensive. Not especially since we are building in the twice traditional charge capacity so we can avoid draining the battery down too much for longevity reasons. Is the battery big? And, assuming we are piggybacking on the Volt's Lithium Ion technology the battery is actually going to be smaller and lighter than a typical 12V lead-acid battery. At 0.2 kWh we are holding about twice the capacity of the 12V battery, but Li-Ion is about ~200 Wh/Liter and about ~300 Wh/kg vs Lead Acid's 40 Wh/Liter and 25Wh/Kg. Hence, the battery can theoretically be about 2/5th the size and 1/6th the weight! And, if we observe good usage models like not going below a 70% discharge the battery can be good for more than 12 years and 150,000 miles.

Let me do a consolidated reply to the dozen or so preceding posts. These represent my opinion and the reasons behind them. I do not claim them to be the only valid opinions. (1) The Corvette is not a, should not, be a GM halo car. If it is to be a halo, it is at best a Chevy halo, and Chevy is not a luxury marque (Cadillac is). The Vette is not, and should not, be a no expense barred, no compromise, halo car. It is a viable, money making, accessible product and it should remain so. To this end -- like it or not -- it should be designed to a price. A $40~45K base price in 2010 dollars. Personally, I feel that such a product does more for Chevy than the Lexus LFA does for Toyota or the GT-R does nor Nissan. (2) The question then becomes how do we get world beating appeal from $40~$45K? And, I think the current formula for the Vette is pretty close to except for the sub-par cabin. Chevy can and should put another $1000~2000 into the cabin. It should not however put $10,000 into the cabin -- sensible improvements, not splurges. Nicer finishes, tactile materials, a premium steering wheel and (for once) a set of supportive seats will do wonders and won't cost that much if you stay away from really expensive hides or extraneous features and amenities. Personally, I think that if they can get it to Buick LaCrosse standards, it should be good enough without engaging in the extraneous polishing of chrome. (3) As far as performance go, 450hp / 3000 lbs is the approximate goal. That is world class. In the interest of heritage, as well as mass and efficiency, the Pushrod V8 can and should soldier on -- but not without the infusion of the latest technology like VVT, AFM and Direct Injection. (4) Personally, I do not see a big advantage from an 8-speed Auto. Not when the current 6L80 (despite its so-so 6.05:1 ratio spread) is already turning the engine at 1600 rpms at 60 mph and putting out more wheel spin than needed in 1st. Instead of the development time and cost of an 8-speed transmission, GM can take a page from the Mercedes' (or should I say ZF's) playbook. Take the existing 6L80 transmission, dump the torque converter and put in a wet clutch. This improves economy by getting rid of the torque converter slippages and provides for shifts almost as fast as a DSG. Planetary automatics basically slams into gear with the converter taking up the shock anyway in in normal practice, so there is no need to use dual clutches.

The journals themselves are centered around the same axis. However, cross plane designs have heavier & bigger counter weights. Cross plane designs carry enough counter weights to balance the crank journal, rod and pistons. Flat plane ones balances the journal and the part of the rod only. The cross plane V8 is the only mainstream engine configuration that does this. Normally engines do not carry this much counter weights because while they can cancel most of the up-down vibrations from the pistons, counter weights also introduce side to side shake. Only in the cross plane V8 does the piston from the opposite bank neatly cancel the side to side moments of the counter weight. This makes cross planes very well balanced, but also rather slow revving. Most of the time, the diameter of the counter weights on the cross plane V8 are slightly larger than the diameter on the journal ends where the rods go. As a consequence, the crank case needs to be a bit bigger and the oil pan a bit taller. The crankshaft itself is also heavier, meaning the engine is heavier, although this is rather inconsequential unless you are trying to shave off the very last 5 pounds.

Well, how one characterize a sound as "nervous" is highly subjective. The difference between a flatplane and crossplane V8 can be summarized as follows:- Cross Plane: + Good Balance, low vibrations (~50% the level of 4-cylinder engine with half the capacity) - Uneven Exhaust Pulses (LRLLRLRR), slower reving (heavy crankshaft), higher center of gravity (large crank case w/big counter weights) Flat Plane: + Even Exhaust Pulses (LRLRLRLR), fast reving (lightweight crankshaft), low center of gravity (slim crank case w/tiny counter weights) - Poor Balance, high vibrations (~140% the level of a 4-cylinder engine with half the capacity)

You are not going to get to 25/30mpg @ 3000 lbs, a 5.0~6.2L V8, a Cd of .25~.32 and something approx. the frontal area of the C6 Vette. The numbers just don't add up with the BFSC of Otto cycle gasoline engines. I am not going to bore you with all the estimating math, but at 3,000 lbs, a Cd of ~0.26, the expected BSFC gains from a DI V8 and a 20% taller overall ratio you are looking at around 22/28. Not bad at all, but you won't get to 25/30. I all likelihood though, GM probably won't go for a 20% taller overall ratio unless they also put in a 7 or 8 speed tranny with a ratio spread wider than the current 6.05:1. So we probably won't even get there. My guess will be 21/27 on the Auto (a bit worse on the manual for the freeway numbers due to the narrower ratio spread of the TR6060). Again, best in the world for a 450-ish hp car, and that is good enough.

What's probably going to happen is this:- Standard Corvette gets a new DI Pushrod V8 and 440~460 hp. Z06 moves to 550~600 hp with a supercharged version of the engine. ZR-1 goes on a hiatus until GM wants to do something really crazy towards the end of the C7's life cycle.

Well, no. Not really. A flat plane crank sounds like two inline-4s. It is not a well balanced design and vibrates at about 1.4 times the magitude of a 4-potter of half its displacement. This is partly why Ferrari V8s (which are almost always flatplane) are also typically quite small in displacement and have short strokes. A 4.3 liter V8 will vibrate 1.4 times worse than a 2.15 liter Inline four, whereas 6.0 flat plane V8 will shake as 1.4 times worse than a 3.0 Inline 4. The orientation of the crank has nothing to do with whines; whines usually comes from the accessory drive or, in some cars, the belt drive for camshaft(s) or supercharger. A flat crank however will not have the slightly off-beat V8 sound typically associated with muscle cars -- that comes from the fact that cross plane V8s do not fire cylinders alternatively from each bank. Instead, the fire a bank twice every other set -- LRLLRLRR. This causes the exhaust imbalance which unless you have a cross over pipe or H-pipe linking the exhaust streams from both sides you'll end up with that off-beat "di-da-duh-duh-di-da-duh-duh" exhaust note. Racing V8s are often flat plane because their balanced exhaust pulses are better for maximizing output without complex, bulky and heavy exhaust plumbing. Most contemporary European, Japanese or American "production car" V8s are cross plane. The notable exceptions that are flat plane being all the Ferrari V8s and, believe it or not, the 4.0 liter W8 engine in the Volkswagen Passat and Phaeton.

As I said, the physical conditions and nothing else determine combustion efficiency. Engineering details help create those conditions, but it is the conditions themselves that govern the burning. But, yes, combustion chamber design matters a lot. The squish decks help with mixing and compaction. Shapes that avoid localized hot spots resist detonation. A centrally located spark minimizes the flame frront distance from spark to edge of chamber. In the end these mostly allow higher compression ratios and/or are conducive to a homogeneous charge.

Well, I was listing the list of conditions that for the most parts determine combustion efficiency (completeness of burning). This only depends on how close the air and fuel molecues are together (cylinder pressure/effective compression), how evenly they are mingling (homogeneity), in what proportions (mixture) and how much time there is to actually do the burning (time). Ideally you'll want extremely high compression, perfect mixing, ideal fuel-oxidizer ratio and an infinite amount of time. How you get there is a different matter. DI improves combustion efficiency primarily basically because it allows increases compression. Because fuel is injected directly into the cylinder it can be injected even after the intake valves have closed. Late injection prevents knocking and detonation throughout much of the intake and compression cycle because air cannot detonate in the absence of fuel, period. The atomizing of fuel also reduces temperatures but this is minor compared to not having fuel in the cylinder when you don;t want it there. With DI the fuel is injected directly into the cylinder instead of behind the intake valves (or in the case of ancient throttle body injection or carburetion further upstream. This permits more accurate metering of fuel and the high pressure of injection creates a more evenly atomized fuel mist. Again, these effects are minor. The end result is that DI engines can typically operate with 1 to 1.5 points higher compression than an otherwise equivalent port injected engine. GM's DI engines run 11.3 ~ 11.7:1 compression on regular 87 octane. With port injection they would be in the 9.8:1 ~ 10.3:1 bracket. This increase in compression is worth about 6~8% in power and torque by itself.

There is nothing wrong with having the same wheel. It is just that GM had a horribly low rent wheel -- really. The GM 3-spoke wheel in the Malibu and the Vette has to be the lowest quality looking and feeling wheel in the entire auto industry. The new 4-spoke ones in the Cruze, Travese and what not is much better but I still wouldn't call it premium. GM needs a better steering wheel. If it is nice enough I don't care if they use it in the Vette, the Aveo and whatever is in between. The steering wheel the the one thing you look at and feel front and center every day. If there is a place that they want to "polish the chrome" this is where to spend the money. $20 will do wonders to the emblem -- it'll buy a really nice Chevy emblem done in 3D, wrought of metal, with two tone anodizing and three different textures -- brushed, satin bead blasted and polished. Another $20 will coat the plastics with the right sheen or a soft rubber material. Another $50 will wrap the wheel in really nice padded leather.

Combustion efficiency is affected mainly by:- Compression Ratio* How homogeneous (well mixed) the charge is Fuel-air-ratio Time** * Actually it's more like cylinder pressure. Although static compression has a lot to do with it, supercharging or leaving the intake valves open well into the compression stroke (Atkinson/Miller cycle) can also affect the effective cylinder pressures (effective compression). ** Gasoline in air burns at the same rate regardless of speed at which the engine operates. In fact, the flame front from the spark travels at less than the speed of sound unless the engine is detonating (knocking/pinging). Higher operating speed, less time before the exhaust valves open. Pretty much that's it. The spark only matters if it is not powerful enough to consistently ignite the charge. Once you have a flame front propagating through the cylinder it doesn't really matter how intense the spark is. Similarly, Octane also does not matter at all except in allowing you to operate at higher compression ratios (or run more boost) without knocking. Knocking is when the combination of pressure and heat causes the mixture to spontaneously ignite. This causes a shock front that can be damaging to engines. There is also a difference between spontaneous conflagration and spontaneous detonation, one's nastier than the other, but that's a separate discussion for another time. If controlled and expected this can be harness to improve combustion efficiency -- in diesel engines or HCCI engines for instance. If uncontrolled it can hurt your engine. Octane doesn't make power, compression does. Without increasing compression (or boost), using higher octane fuel is a waste of your money.

I think one point that most people are missing is this... An engine's breathing ability has very little, if anything, to do with fuel economy! Sounds counter intuitive? Not really. Let's look at it this way. Picture yourself moving a plunger inside a syringe. An engine's cylinder is similar. The small hole on top of the syringe causes resistance as you try to pump air in and out with the plunger. If you cut off the top of the syringe such that it is essentially an open ended cylinder, you'll have perfect volumetric efficiency -- perfect breathing with no restrictions -- and the only resistance comes from the friction between the plunger and the walls. Now picture a DOHC 4-valve engine as one with a bigger hole on top and a push rod 2-valve engine as one with a smaller hole. Naturally, as you work the plunger the syringe with a bigger hole has less resistance. In an engine this translate to lower pumping losses, more air being aspirated and more power! However, this is under wide open throttle conditions! Now... picture attaching a rubber tube to both syringes and pinching the tube to constrict flow. That is exactly what the throttle plate does at all driving conditions except when you are flooring it. Therefore, at cruise and under moderate driving conditions, any intake restriction not present in the intake and through the valves is intentionally introduced by the throttle body! If your car doesn't do this, it needs to be recalled for a "stuck accelerator pedal". Therefor intake side restrictions of any engine typically does not introduce additional pumping losses at cruise and does not impact fuel economy. Now, we are talking about intake restictions of course. On the exhasut side there is no throttle plate. However, exhaust under pressure self-aspirate quite easily even through one valve or valves with less opening. And, exhaust restrictions, while ever present typically does not impact power or economy until reasonably high up in the rev range (4000~5000 rpm or so). At cruise and under moderate driving conditions the impact is minimal.

I don't think the Vette will have any wood. So it'll probably be all plastic or plastic with a bit of metal trim here and there. As I said, I didn't want it to have a $10,000 interior treatment. Buick's is good enough. The current Vette's is worse than the Koreans.

To put it simply, I think they should shoot for an interior done to the Buick Lacrosse's standard, minus the much of the amenities and extraneous switch gear. The same thing goes for the seat... it should be comfortable, supportive and upholstered in superior quality materials (be it leather or fabric), but I am OK if it only has a 2-way manually operated reach and recline adjustments.

Personally, I think it'll be the wrong mission for a Vette. A Vette needs to be a top notch performance car to start with, everything else is icing on the cake. As far as the young dreaming of the GTR, well, if the Vette outperforms the GTR (which it currently doesn't) and has a reputation of being well built, in time they'll be dream of a Vette instead. And, guess what, until they can afford one that dream translates into sales of lesser Chevys. If Chevrolet wants a Boxster, SLK or some other cool looking, well handling and modestly performing vehicle. They can build one off an improved Kappa. Call it a Chevrolet "Speed" or something, and give it scissor doors. The Kappa is decent enough, they just need to get rid of the Inca Temple in the trunk.

Honestly, I don't think the Corvette needs a luxurious interior -- it is not strictly speaking a luxury car. It needs to look high quality, but it doesn't have to be fancy. Really, it doesn't have to have electronic climate control, it doesn't need dual zone HVAC, it doesn't need napa leather upholstery. Keep it simple, keep it basic, keep it functional. But make sure there are no hard, shinny plastic, make sure that what looks like metal is metal and what looks like leather is leather and what looks like wood is wood and make sure the switch gear clicks with smooth, well dampened and positive detents.

All else being constant, a vehicle's size translates into weight and unwieldiness. But it's size also translate to interior roominess stowage space. How big, or how small do you wish the next Corvette to be?

Actually, there are advantages to a Pushrod V6 over a DOHC V6. These being that, like a pushrod V6, it is smaller and lighter than a DOHC V6 of similar output and it can have better fuel economy through comparatively lower internal friction. The reason DOHC I4s and DOHC V6es are preferred are three fold. The first being the fact that many countries tax vehicles based on displacement. DOHC engines have higher specific output -- that is, they have higher horsepower and torque numbers per unit displacement. It is advantageous for most economy cars and family haulers to be taxed less while offering a given amount of power. The second being that I4s and V6es, unlike I6es and 90 deg V8s are not well balanced unless additional measures are taken to balance them via balancer shaft(s). The problem with balance gets worse with increased reciprocating mass and stroke. This tends to get worse with displacement. Hence, with V6es and I4s civility tends to suffer worse than with V8s if you adopt a big displacement solution (pushrod or not). This is why really big engines tend to be I6es, V8s or V12s -- the first and last having perfect natural balancer and the V8 being very well balanced simply through the use of a cross plane crank and heavy counter weights because the pistons on the other bank balances the counterweights. Lastly, one of the biggest reasons for a pushrod layout is superior compactness in a 90 deg V8 because the heads are very compact and narrow compared to DOHC designs. In an I4 there is no packaging advantage whatsoever. In a 60 deg V6 the advantage is much less significant because a 60 deg engine is already narrow. None of the above are particularly important for light trucks.

LOL... how about the Cadillac "Symphony V8" Cruising along at 1600 rpm at 60mph -- riding on roller rockers and roller lifters, with direct injection metering fuel, dual concentric VVT trimming out the overlap, dual length runners routing air through the long runners and (as a first among contemporary V8s) a single contra-rotating balancer damping out residual end-to-end rock of a 90 deg cross plane engine -- there isn't a lot to hear or feel though.

It is not what GM needs for pickups, or what Hyundai does or does not have. It is that GM ought to consider an engine that is:- Physically more compact and lighter than a DOHC engine of similar output. More Economical than a DOHC engine of similar output. Is unique to GM. Can be applied across a wide array of applications. No, a 6.2 V8 will not get 35 MPG. Neither will DOHC designs including Toyota's 4.6, Hyundai's 4.6, BMW's 4.4 (turbo), Mercedes' 5.5, Ford's 5.0, Audi's 4.2, Nissan's 5.6. A 6.2 Pushrod V8 however can have MPG numbers that is slightly BETTER than the best of these engines, and significantly better than some of them. The only argument against a pushrod engine is that it is somewhat low tech and uncivil. A design using dual VVT, direct injection and cylinder deactivation is not low tech. And, if you successfully benchmark a Bentley 6.75 liter Pushrod V8 you are pretty darn civil.

This was the "Serene" V8

(1) If you have a 60 deg V6, it is a separate engine line. The reason 90 deg V6es exists for the most parts is because it can be built together with the 90 deg V8s. Once the 3.5 and 3.9 retires, an all 90 deg lineup simplifies production and logistics. (2) A 3.1 liter Pushrod-4 will not be smoother than an OHC design, although it won't be any worse than a 2.9~3.1 liter class SOHC or DOHC four. It won't be dramatically more efficient than a 2.9 DOHC either and may in fact be less economical than a SOHC 8v four of the same displacement. It will however be more efficient than a 3.0 liter six and that is it's mission. And, with dual balancers, it is livable in terms of vibrations, especially since it is used exclusively in entry level trucks. If you ever want to experience a 3 liter four you can try out a Colorado with the 2.9 I-4 or... heh... a Porsche 968 (or late production 944) if you can find one!

Thought about that. But, if we are going for maximum commonality and have to share a single bore & stroke, the logic goes that a pushrod V8's architectural advantage is the greatest when displacement is maximized. The same thing goes for V6es and I4s when it comes to fuel economy. Actually, the original "Passenger Car" table has three columns. There was originally a V8 just for Caddy exclusively. This has a traditional cross plane crank, dual VVT, DI, Cylinder De-activation and a BALANCE SHAFT under the high mounted camshaft to damp out residual end to end vibration on cross plane V8s. This is the "Serene V8" and it should make about 430~450 hp. Vette and Camaro SSes were supposed to get a more ranchous V8 making 480 hp NA. This has cylinder de-activation deleted and uses a flat plane crank with no balancer! I decided that it is one too many engine and a compromised "universal 6.2" may be a better idea.