dwightlooi

To put it in one sentence.... AFM's downside is that AFM lifters are heavy and this limits the valve lift you can operate with, which in turn reduced the redline and limit high rpm performance. So... maybe you can have a Naturally Aspirated LT6 engine. Same pistons, same bore size, same block, but stroked to 101.6mm (same as LS7), displace 6.8 liters and operate without AFM. This engine will rev to 7000 rpm (same as LS7) and make 550 hp @ 6300 rpm, 512 lb-ft @ 4800 rpm and it'll deliver about 16 / 27 mpg in a 3300 lbs car like the vette. Not a bad engine for a Z06 or an ATS-V.

Is AFM (cylinder deactivation) worth it? I report, you decide… FACT: AFM is worth 2 mpg in on the freeway, 0 mpg in the city. With AFM enabled in Eco mode, the Corvette Stingray posts 17 (city) / 30 (hwy) mpg in the EPA test cycle. With it disabled in Touring mode, the Stingray posts 17 (city) / 28 (hwy) mpg in EPA test cycles. GM chooses to put the “average of the two” 17/29 mpg on the window sticker. FACT: the LT1 V8 makes 460 hp @ 6000 rpm / 465 lb-ft @ 4600 rpm. This is about 45 hp shy of the 7.0 liter port injected LS7 V8, but only 5 lb-ft shy of it. The 7-liter LS7 peaks at 505 hp @ 6300 rpm with 470 lb-ft @ 4800 rpm. Most of the torque gain in the LT1 is from direct injection and the 11.5:1 compression, the LS7 actually has higher lift cams and is tuned for better breathing up top. What’s the cost of AFM you may ask? Well, it’s simple. With about 465 lb-ft of twist from 11.5:1 compression, if it used a similar lift and duration profile on the camshafts as the LS7, it would be a 500 hp engine. It is 460 hp because is slightly hampered by lower valve lift profiles. And this isn’t because GM didn’t want 500 hp, or that somehow emissions or civility would be bad. It had to use slightly lower lift because AFM added valvetrain mass. The AFM lifters are heavy and with the same valve spring tension you could use less lift before the valves floated. So… basically, with AFM, you are getting 2 mpg and sacrificing 40 hp (give or take). Put another way... if you drop AFM and change the cam grind a little, the LT1 will make 500 hp @ ~6300 rpm and 465 lb-ft @ ~4800 rpm. It'll also give 17 / 28 mpg. Is it worth it? You decide!

Anyway, the way Superchargers are playing out, Roots are winning in the market place... Most force induced solutions are turbocharged. Of those that are supercharged, essentially all are roots based. Audi's 3.0 TFSI (despite the "T" in the nomenclature) is an Eaton TVS R1050 twisted rotor roots blower. Jagaur's 3.0 and 5.0 Supercharged engines in the XF, XJ and F-type are Eaton TVS roots blowers -- TVS R1050 and TVS R1650 respectively. GM's LSA and LS9 6.2 V8s in the CTS-V, Camaro ZL1 and Vette ZR1 are Eaton TVS roots blowers -- TVS R1900 and TVS R2300. Mercedes' 5.5 liter M113 V8s in the mid-2000s AMG cars were Lysholm screws, but those are all out of production. I think the reasons are simple... they are cheap, they are reliable, they are linear. And if you run 7~8 psi of boost they are nearly as good as Lysholm screws. At 9 to 10 psi they start to show slight inefficiencies but not much... and at 12 or above screws shine. But most of these engines are NOT high boost designs. LSA at 9 psi and LS9 at 10.5 are actually the lowest boost users. The DOHC engines actually are a psi or so more. Audi's 3.0 TFSI runs at 11.5 psi

Well, that's an entire different topics, but to put things concisely... (1) Superchargers can be very efficient in terms of adiabatic efficiency (thermal) (2) Different types of superchargers have different efficiency and operating characteristics (more on that later) (3) The biggest difference between a turbocharger and a supercharger is that it takes power to drive a supercharger it doesn't take power to drive a turbocharger Screw type superchargers can be up to 80% thermally efficient. Roots types are about 70%. Centrifugals are about 75%. Remember those are peak numbers. For the purpose of determing static compression ratios you are looking more at minimum efficiency within the operating range than peak numbers which is about 15~20% lower (same thing for turbos) Screw and centrifugal type chargers are efficient because they offer some degree of internal compression. That is to say that air exiting the supercharger is at a higher pressure than air entering it. Screws do that by progressively having bigger lobes and smaller hollows as you progress up the screw from intake to exit. Centrifugals are basically a turbocharger's compressor driven by a belt (usually with incremental gearing) so they compress air as well as move it by dynamically throwing the air outwards with the impeller at high speeds. Roots are "external" compression chargers. In otherwords, all it does is move air. It does not compress it at all. Air leaving a roots blower is the same pressure as atmospheric air. But because air is being pushed into a plenum, and the roots blower moves more into it than the engine consumes, air builds up pressure in the intake plenum. Because of the way they work, screws are overall not only the most efficient but most consistently efficient over a wide operating speed and boost range, but they are also the heaviest and most expensive (because of the fancy machining needed on the progressive screws). Centrifugals are the cheapest as they are half a turbo with a belt. They are quite efficient at peak but have two major flaws. Firstly, boost is not linear the faster you spin it to more boost it makes. Hence, engines with centrifugals tend to be very peaky since they run boost that increases with rpms! Secondly, while centrifugals are very efficient at speed they are extremely inefficient at low rpms. This is why essentially no OEMs use centrifugals. Roots offer a good balance between cost and consistent boost output. The thing to remember about roots is that because they are external compression pumps, they are VERY EFFICIENT at low boost when the pressure difference between the output air and the plenum pressure is small, but very inefficient at high boost where the plenum is highly pressurized and atmospheric air is being pushed into it by the blower. In fact, at high boost air actually backflows significantly into the supercharger from the plenum before being pushed back out. One good thing about Roots is that air goes in from the front and comes out the top (or bottom) this allows for tighter packaging that screws! To put things into perspective, an LS9 engine like that in the ZR1 make use up about 65~70hp just to drive the roots blower. This means that you are actually burning enough fuel and putting enough strain on the engine internals to make about 700~710hp but you are only getting 638 out of the engine. The rest is consumed by the supercharger itself. Hence, it is not difficult to understand why supercharged solutions are generally less fuel efficient and most have a bypass valve or a clutch to allow the blower to free wheel or be decoupled completely at cruise and low throttle positions.

Actually, it will. One of the reasons traditional intercoolers cannot ever be any where near 100% efficient is that it relies on ambient airflow to either cool the charge directly via a heat exchanger, or it relies on it to cool water which is then used to cool the intake charge via a second heat exchanger. The problem with that is that you can never get to ambient temperature. It's like using a fan on a frying pan on the stove. You can never get the frying pan to room temperature although you will cool it down a bit.As you get closer and closer to room temperatue the amount of heat transfer plummets until it is essentially zero. The only way to cool the air charge back to room temperature or even take it below that is to have a coolant that is below room temperature. Drag racers pack ice slush around their ICs to do that but it only works for a minute or two of running. Theoretically you can also use a refrigerator on your IC. The problem with refrigerator is that they move heat slowly. Notice that it takes an air conditioner 10~15 minutes to cool the cabin or room down in summer. Basically, it doesn't move a lot of heat a minute, but it keeps doing it and gradually cools things down. This doesn't work for air that needs to be cooled in a second before it goes to the cylinders unless you have a AC unit the size of your car. That'll be too heavy and running it will suck up more power than the extra you produce. Ice slush and fridges aside, you also have rally cars -- and street rally car wannabes like the Lancer Evo -- featuring a water mister for the IC. This adds evaporative cooling to the basic air-to-air heat exchange. Doesn't quite take it to room temp, but helps with intercooler efficiency especially after a hard run that heat soaked it. The other thing you can do of course is to not run that much boost! Firstly, turbos tend to be more efficient at about 1.8 Bar (0.8 bar / 11.8 psi of boost) than they are at 2.8 Bar (1.8 bar / 26.5 psi of boost). Consider the compressor map below. This is the map of a Honeywell-Garrett GTX2867R turbo -- possibly the most advanced and most efficient available with a peak efficiency of 79%. Airflow more or less scale linearly with RPMs barring major volumetric efficiency changes. So more or less you want to draw a horizontal line across that map to represent your turbo's thermal efficiency as the engine climbs in revs. Notice that the efficient contours are broader and the numbers are better if you draw that line at 1.8 vs say 2.8... Secondly, even if efficiencies are identical, increasing pressure by 13 psi heats it up half as much as taking it up to 26 psi. Remember, heating is proportional to both pressure rise and efficiency. I have always favored low boost designs for their low lag, greater linearity in relation to the throttle, higher efficiencies and higher static compression (which helps all of the above plus fuel economy). Don't think that low boost equals low power, it just means low torque peaks. You can make very serious power if your turbo can support high airflows. A 13 psi system with about 10.8:1 compression will respond almost like a high compression NA during cruise and gentle driving. But that' make about 1.1 lb-ft per liter. In otherwords a 2.0T running that combo will make about 220 lb-ft. Not, bad and in fact preferable in FWD cars to something in the 260~280 range if only because it is more controllable when the wheels both put pwoer to the ground and steer at the same time. If you mainatin 220 lb-ft to 6000 rpm, that's 251 hp. If you keep it there to 6600 rpm it's 277 hp and if you stretch it to 7200 rpm, it's 302 hp. Not bad at all. Plus the engine will drive like a high reving, 3.0 liter class six making 100 hp/liter.

Sorry, I meant to say that for a 2.77 times increase in pressure, there is about a 30/70 = 42% increase in temperatures. The intercooler is only 70% efficient at removing this heat. Hence, about a 12.6% reduction in compression would make up for the temperature increase in a system that is pretty efficent -- 70% compressor efficiency + 70% intercooler efficiency. Based on such idealistic assumptions going from 11:1 to 9.6:1 compression would suffice. But, I don't believe the CLA45's engine is operating with those efficiencies across the entire range of operating conditions, hence a greater reduction is necessary and 8.6:1 sounds reasonable.

The entire notion of turbocharging, big power, boost and compression warrants a discussion. Recently, the following question had been posted on a different site and thread... "The CLA45 AMG runs 8.6:1 Compression and 26 psi of boost. 26 psi of boost is 40.7 psi of absolute pressure. If you are squeezing 8.6 parts of that into 1 won't you have and effective compression of (14.7+26) / 14.7 x 8.6 = 23.8:1? How can any engine run on 23.8:1 of compression without blowing up?" The responses range from the effective compression is not 23.8:1, that somehow you must square root the 40.7 before multiplying it by 8.6, to some other form of alternative fuzzy math to justify the stuff not blowing up. None of these are true or accurate. The truth is that... yes, you in fact have a 23.8:1 compression in terms of cylinder pressures prior to ignition. And, yes, it's perfectly alright!!! Forget any notion you may have that a certain compression will detonate or pre-ignite. It doesn't work like that... if you need proof, just ask yourself this... If you have fuel and air at 3000 psi at 70 deg F do you think they'll somehow burn? Heck no! The ideal gas law (PV=nRT) states that for a given amount of molecues (n) in an enclosed space (V), if Volume(V) goes down, then Pressure (P) goes up and temperatures (T) increases correspondingly because n and R are both constant in this case. At a certain Temperature (T) the mixture of fuel and air goes bang without a spark lighting it because it is hot enough to start burning. Typically, with modern engines on premium gas, you reach the critical temperature (T) when you squeeze air and fuel from about 12~13 parts into one part. That's why you never see street engines with compressions above 12.5:1 or so and even 12:1 is pretty exotic. This is also why Direct Injection engine can run about 1~1.5 points more compression -- because the atomization of fuel in the cylinders cools things down a little! Water injection? Same thing. The important thing about PV=nRT in terms of pre-ignition is that ONLY TEMPERATURE (T) matters. The other numbers and the way they change are only relevant as so far as they affect temperature. Now... the key here is that turbocharged engines with a 23.8:1 effective compression does not do all of that compression in the cylinders only does 8.6:1 in the cylinders, but feeds the cylinders with air that has been compressed by the turbo at a ratio of about 2.77:1. This is crucial to why they don't blow up! First of all, if you start with higher pressure air that is 2.77 times atmospheric pressure and at room temperature. Apply PV=nRT. Now... Pressure (P) starts higher and amount of air molecues in the cylinder (n) starts proportionally higher. R is a constant. V and T can be the same as before without boosted air! Think about it like this... you can have compressed air in your tires at 70 degrees F, and you can also grab the same volume of unpressurized air in your room and have it at 70 degrees F. In otherwords, as long as the air the same temperature, if you can run 12:1 compression on 26 psi of boost (40.7 psi absolute pressure) just as easily as you can run 12:1 compression with 14.7 psi of atmospheric air at sea level! Go to a planet with with same atmospheric composition as Earth and the same climate, but where the air is twice, or three times as dense. Your 12:1 engine will run fine and make a lot of power! The only reason that engine is running a reduced 8.6:1 compression is that air force fed from the turbo is NOT at room temperature when it gets to the cylinders. It is hotter. And, because it is hotter you can compress them less in the cylinders before they reach the critical temperature when they ignite. It is hotter because centrifugal compressions are not 100% efficient. They are at best 70~75% efficient. Which means that, at best only 70~75% is turned into extra density the rest is turned into heat. Now, with an intercooler, you lower that temperature somewhat, but intercoolers are also only about 70% efficient at best. So you still end up with hotter air just not as ridiculously hot as before. In theory, if your turbo compressor is 100% efficient, you won't need an intercooler and you'll be able to run 100 psi of boost with the same compression as in your NA engine (say 12:1). In theory, if your intercooler is 100% efficient, you can also run infinite boost on the same NA compression until your cylinder walls, your turbos overspeed to death or rods give way due to the increased combustion pressures and power! But because the turbo is about 68% thermally efficient and the Intercooler is about 70% efficient, you end up with denser air that is also about 30% or 30% or about 9% hotter. Reducing the compression by 9% will make up for that. As it turns out a little more reduction is needed because the AMG turbo and IC are probably not even 70% efficient. The drop in compression ratio to 8.6:1 is only to compensate for the heating caused by the turbocharging system. It is not to compensate for increased density; you never need to compensate for increased density. The simple answer to the above question is hence simply that, going down to 8.6:1 compression is sufficient to compensate for the heating from the turbos and the failure of the intercooler to remove all of the heat created, such that the total heating before the spark fires is about the same as the naturally aspirated 2.0 engine.

Where's the CTS Coupe? That IMHO is the prettiest Caddy.

Back in the late 80s and early 90s, Hondas were at the pinnacle of their game in design. Honda's look distinctively Honda. And, it's not because of an aggressive grille, tail light or badge. The design language is holistically unique... Honda's had a very low belt-line, lots of green house and a hood that's impossibly low profile. These were markedly different from Toyotas, Nissans, Mazdas or US domestics of the day. The 3rd, 4th, 5th Gen Civics, the 3rd, 4th and 5th gen Preludes exemplified this. Honda also had double wishbones on all four corners right down to the lowly $9,999 Civic DX. And, Honda motors were smaller displacement, free revving machinery that sounded like a turbine if one punctuated by a VTEC "bbbbvvvvrrrrrrttttt" on the switch over cam on those cars that had them. That all went away with the 2001 Civic. Gone were the double wishbones, in were the struts. The motor took on a long stroke profile and a blah blah tone. Belt lines went up, seat cushions moved away from the floor boards and seating positions got vertical like everyone else's. The is perhaps a brief revival or uniqueness in the 2006 model with its extreme windshield rake and super wedge profile with a very short hood. Clean, purposeful if a little diversive. Then with the face lifts, Honda decided to simply add clutter, slats additioal trim bits that weren't cohesive and doesn't seem to work together.

Actually, the Encore is a Gamma, meaning that the 1.8, 2.0T or 2.5NA will fit if they had chosen to use them. The 2.0 Turbo-diesel will fit too. That GM chose the 1.4 for the Gammas is entirely voluntary not something compelled by the platform.

Except CNG has a density (@3000 psi) about 1/4 that of gasoline. So whatever weight is being carried takes up 4 times as much space or offers 1/4 as much range. That is not counting the weight and bulk of the containment system for 3000 psi of pressurized medium -- tanks, fiber wraps, crash protection, etc -- which are considerably more involved than an aluminized or plastic tank of irregular shape holding atmospheric pressure gasoline or diesel.

Small displacement + turbocharging doesn't pan out for better efficiency. It never did and it still hasn't. The reason is simple... by going from a 2.0L I4 to a 1.4L I4 you haven't changed the frictional losses that much because you still have the same number of valves, guides, followers, pistons, rods, etc. The main efficiency gains come from having smaller cylinders working at bigger throttle openings which allows the engine to operate at a higher effective compression -- because larger throttle openings equals lesser vacuum and squishing less vacuum equals higher effective compression. But turbocharging mandates an ~2 point reduction in compression ratio while providing no charge density improvements at cruise. This cancels out much of the efficient gains from displacement loss. The best non-hybrid efficiency is actually achieved with a large displacement Atkinson Cycle engine with least amount of camshafts, valves and cylinders. If you want the most fuel efficient 140hp you'll use a 2.5L 3-cylinder engine with 17.0:1 static compression and a 70% Atkinson cycle cam for a 11.9:1 effective compression @ peak volumetric efficiency. You'll use a single overhead cam or a in-block cam with roller followers/lifters. You'll use 2 valves per cylinders. And, you'll use direct injection. Apart from DI, you'll basically do the exact opposite of what many automakers are doing. In the end, 1.4L Turbo, 2.0L NA and 2.5L Atkinson engines probably have approximately the same output. The 2.5 Atk has the best fuel efficiency whereas the 1.4T has the highest cost and most reliability concerns. The 1.4T is only useful as so far as to take advantage of various countries' displacement tax laws to lower the new car and annual taxes. Whether this is significant depends on the country.

I seriously doubt that this will ever find an application in the C7 or a Caddy. The output gear arrangement is clearly that of a transverse FWD box.

The Model S is sleek, it is fast and it is cool (to the money is no object techno-toy crowd). The market is not big but they have no competition. The Volt is none of the above. It is a dorky plug-in that sin't cool enough for those who can afford it (or more) and it doesn't make economic sense for anyone who isn't into expensive techno-toys and doesn't drink global warming coolaid (90% of car buyers).

It's the PRODUCT guys.

It's like stating the obvious... it really doesn't matter if Ford thinks or thought Lincoln is/was true luxury. Consumers don't and they don't pay luxury dollars for Lincolns.

$39.5K puts it at exactly the same price point as a fully loaded Toyota Avalon. For a car in the 20s, customers would be put in a Malibu. Not a bad pricing strategy if the car is indeed worthy. As far as the Taurus, Ford isn't moving too many of them. The Fusion & Focus is where most of the sales go.

Go with the FB25 2.5L boxer (from the 2012 Forrester/Legacy) and use an Eaton TVS R1050 supercharger -- preferably with air-to-water aftercooling. The combination should be good for about 300hp with a like amount of torque peaking at about 3000 rpm. Boost will be about 17 psi which is a little on the high side, but not any higher than was used in cars like say the C32 AMG. That's enough for a FT86, there will be zero turbo lag and the car will feel as connected as with a large displacement NA engine.

Funny... despite all the punitive taxes and Global Warming coolaid drinking legislation in the EU the Camaro debuts there exclusively as V8 powered beasts.

Fuel economy doesn't rank high on my list of priorities. But 16 / 25 really sucks dirt for a 3.8L V6 pulling a 3600 lbs coupe with DI and 8-speeds. The C55 AMG I had was 16 / 22 and that's a 5.5L V8 pulling about the same weight and with just 5-gears (geared pretty low too with 80 mph being 3000 rpm in 5th).

Well, back to the point of this thread... The point isn't 2-valve or 4-valve being "better". They have their own characteristics and better is subjective. The point is just that... with a 260~270hp 3.6L engine -- which seems perfectly acceptable to Toyota and Honda -- there is no advantage to using a DOHC 4-valve setup. You'll just end up with inferior fuel economy and with not much else to show for it. Whatever the theoretical potential of a DOHC 4-valve design, such engines are not taking advantage of them. In fact, they are deliberately NOT taking advantage of them.

It's 300,000 in the EU, how many cars you sell and what kind outside of the EU is not within their jurisdiction. There is no legal basis for the EU to fine a company for products sold or not sold in China or the USA. The EU regulations apply only to the EU. In fact, it is based on new vehicles REGISTERED in the EU not sold or made or whatever. Manufacturers making 10,000~300,000 cars are subjected to a less stringent (and fixed) 25% reduction from their 2007 carbon footprint rule. The same fines apply for going over. Manufacturers doing under 10,000 cars are not subject to the new emission rules or crash standards. But they are subject to a different tax applicable to custom vehicles and some countries won't let owners register them. Eg. your Koenigseggs and Caterhams are exempt.

Two reasons... (1) The whole idea is that you want to get rid of the torque lossy converter or complex electrohydraulic clutch assembly. This way, the engine, motor and transmission input shaft spins together all the time with no slippage losses. (2) It forces the ICE to turn over whenever the car is moving. And, not only that but turn over at the same speed as the electric motor. This eliminates the need for separate starter or the need for a separate cranking event to start the engine. The lack of a speed difference eliminates the need to decouple the engine from the motor or the transmission. There is no deliberate starting of the engine, the moment electric motor rpm goes from 0 to 0.00001 the engine starts turning. The only thing that happens at ~800 rpms is that instead of being a pure load, the engine starts to make power. As far as being a load, the effort is akinned to reving an engine with the heads removed (no pumping loss). Yes, it's there, but it is relatively insignificant compared to the load of actually turning wheels that must push 3000 lbs of car around. An analogy will be the power used to run the turn-table in the microwave oven as opposed to that used to generate the food heating microave radiation itself.

Because diesel being a compression ignition engine as opposed to a spark ignition engine and operating at with no throttle body constrictions all the time has better thermal efficiency than CNG. Diesel is more available than CNG and a given volume of diesel or a given weight (inlcuding the tank) of diesel goes further than an equivalent amount of contained mass of CNG.

Not really... The reason cranking an engine is "jerky" is that the effort is not constant. That is the engine is compression four cylinders in succession and each compression stroke takes more effort towards the end than in the beginning. If you have deactivated the engine by closing all the valves, the reciprocating assembly is now a balanced spring system. Any effort compressing one cylinder is balanced by pressure assisting the downward stroke on another. Apart from the frictional drag there is no effort and the frictional drag is constant at any given rpm. You'll reactivate the engine by injecting fuel into the cylinder in its compression stroke. Near TDC the combination of heat and pressure will light the charge. To keep cylinder temperatures in you'll probably close the thermostat and keep the coolant hot. If the engine has been off more a few minutes and it's cold outside you may turn on the glow plugs. To moderate the "jerkiness" when the cylinders first light up you'll not inject the amount of fuel called for by the current throttle position but rather ramp it up for the minimum. The first injection pulse gives only enough power to overcome the drag at 800 rpm so that first ignition is essentially imperceptible. Power ramps up in the next dozen or so injections over a ~1/2 second period of time. It is not unlike idle start with a gasoline engined hybrid like the Prius except you don't have that planetary power spliter and you don't have a spark. If you are thinking about the dieseling effect after an engine is shut off, that essentially cease to exist when the engine is shutoff by shutting all its valves. Modern diesels use a shut off flap to cut air supply and eliminate dieselling which is what happened when you cut off the fuel to a compression ignition engine that doesn't have a throttle body. Shutting all the valves has the same effect, if fact it is more immediate and more effective because there is essentially zero reserve air volume.