dwightlooi
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Everything posted by dwightlooi
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Nope, but they should for a mid-engine sports car. I think ford wasted a good opportunity with the Ecoboost V6 Ford GT. These have a lot of height in the engine bay if you don't mind seeing the engine in the rear window. The Audi R18 Le Mans race car is a hot vee single turbo 3.7L V6. But that is (oddly enough) a DIESEL Le Mans race car, and that doesn't constitute a "production" engine. The C8 is unlikely to use a hot vee single setup since it is a V8 and that is as good as an I4 which is good enough.
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As explained in the original post, a Hot Vee SINGLE TURBO design will provide uninterrupted exhaust flow to the turbine. A twin-scroll turbine housing will be preferred for intake breathing efficiency. Hot Vee Singles are rare because the exhaust collector bridging both sides and a single larger turbo means the turbo sits really high and interferes with the desired hood line. It has been done though... the Duramax 6.6 is an example of a Hot Vee Single Turbo. It makes 445 hp @ 2,800 rpm and 910 lb-ft @ 1,600 rpm (it's a diesel). Note: Notice how tall the entire turbo setup is and why it may be a problem in a sports car or a sedan. However, a Hot Vee Twin Turbo design like Mercedes' M276 DELA30 (3.0L Twin Turbo; C400/C450/C43 AMG) provides no advantage apart from packaging (which is itself debatable). I find Mercedes' coining of the term "Pulse turbocharging" ironically laughable as it describes the interrupted exhaust problem of V6 bi-turbos so succintly. IMHO, conventional flanking turbos can be located just as close to the exhaust ports as a turbos in a Hot Vee, and flanking turbo designs like GM's LGW (3.0L Twin-Turbo; CT6) performs just as well.
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That is what they claim. Ask yourself two things. Firstly, how much of that is due to Multiair itself and how much of that is due to everything else Fiat put in the engine -- say Direct Injection or using tiny displacement engines (like their 1.4L). Secondly, how does cutting off the action of the intake valves partway through the cycle accomplish all those things better than VVL systems that... well... offer long and shorter duration valve actuation with advance and retard of the timing?
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Oh, there is plenty of restriction. Whether you are choking the engine with a throttle plate or by reducing the intake valve openings, you are choking the engine. If that is not the case, you'll have unintended acceleration ,which will be very bad! The only time there is no restriction is in a Diesel Engine. In a Diesel Engine, there is no throttle and the valves always open fully. The engine simply injects more or less fuel to make more or less power. This is half the reason why diesels are so efficient -- you are never choking the diesel engine. But, it runs very lean when you drive gently and running very lean makes a lot of Oxides of Nitrogen which -- unlike Carbon Dioxide -- is actually bad for the air. This is why you have nitrogen storing catalysts on modern diesels. Because these cats get poisoned by sulfur, that is also why low sulfur gasoline is a must for some of these diesels. Or, you can inject piss into the engine -- Mercedes Benz's Bluetec is simply a nicer name for Urea Injection. What Multiair and Valvetronic (not VANOS) do are that they eliminate the vacuumed space between the throttle and the intake ports. This makes throttle response technically superior as there is no plenum to bring up from vacuum to atmospheric pressure. I am not sure it makes the engine more efficient although the engine holistically might be for a host of other reasons.
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And, the reason is simple... When you open the throttle, the naturally aspirated motor has to fill the volume between the throttle body and the intake valves -- aka the plenum -- from vacuum to atmospheric pressure. This is normally very fast. It can actually be faster than the throttle plates can move if you have the throttle plate(s) mounted at the intake port. Remember the the S65 4.0L M3 engine with the individual throttles in the velocity stacks for each cylinder? Or, heck, remember the individual side-draft carburetors on the intake ports of motorcycle engines? The Turbocharged engine has to first do the same thing and fill up the volume to atmospheric pressure, make exhaust energy, spin up the turbines to spin the compressor, start increasing that volume to the working boost pressure. That takes significantly longer. To make matters worse, the volume between compressor and the intake ports is also a lot more voluminous on a turbocharged engine. It usually goes from one side of the engine to the other and includes additional volumes like the intercooler.
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You must not be very good at noticing then! Even on the VW-Audi 1.8T (circa 2000) where the turbo is making a paltry 7~8 psi (very low by today's standard) you'll notice it. You'll notice it particularly during part throttle application. You put in 70% throttle and it feels like the throttle takes 2 seconds to roll from 30% to 70%. Even in a laggy engine, full throttle lag is never an issue because you know its there and you know the power coming. The problem with handling a turbocharged car through the corner is that when you apply part throttle mid corner it is as if you are working the throttle via a rubberband. It is non-linear and it is difficult to control. Instead of applying the throttle you need and rolling on more as you straighten out the wheels, you must apply the throttle eventually want a second or two ahead and time the torque rise match your corner exit. In a way, it's like doing differential equations while driving. In any case, if you have a V6 you are not getting a twin scroll.
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You do know that this is physically impossible, right? Turbos will have lag, period. Why? Because they build boost by pumping more air than the engine ingests and building up positive pressure. It takes time to go from vacuum to 15 or 20 or 25 psi just like it takes time to fill up a balloon. It is impossible to do that immediately just like it is impossible to make boost by revving your engine in neutral (where the unloaded engine can rev up faster than the turbos can move air into the manifold). Twin Scroll turbine housings do not eliminate lag they are there to solve an intake problem. You see, in a 4-cylinder engine when the exhaust valves on a cylinder opens towards the end of the power stroke, another cylinder still has its exhaust valve open towards the end of its exhaust stroke. To make matters worse, that cylinder also has its intake valves opening as the end of the exhaust period overlaps with the intake period. This means that the high pressure exhaust gases exiting the cylinder at the end of the power stroke will push into the cylinder ending its exhaust stroke and beginning its intake stroke. This hammers intake aspiration as well as rob the turbo of exhaust pressure that otherwise would be applied towards spinning the turbine! There are two solutions to this problem. The first is to have essentially no intake/exhaust overlap -- most traditional turbocharged engines do this. But, this means the engine won't breathe right above about 5000 rpm and it negates whatever advantage you might gain from a DOHC 4-valve head. The second is to segregate the exhaust flows from cylinders 1 & 4 and that of cylinders 2 & 3 -- that's a twin scroll, twin volute or simply divided turbine housing. You never see twin scroll turbos in bi-turbo V6 engines or inline 3 engines because it is unnecessary and USELESS -- exhaust periods on a 3-cylinder or a V6 bank do not overlap!
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It is an issue they pay a price to deal with. A price in smaller cabins. A price in a heavier engine. A price in a heavier car with unnecessarily long wheelbases. As far as the M256, that is an S-Class only engine for now and not even on US bound S-Classes. Looking at the C-Class engine bay it may take a platform change to fit it in the C-Class. Well, the C8 has a big displacement, Naturally Aspirated, Pushrod V8 for you with 500 hp (give or take)! And, it is probably the cheapest engine on offer. Expect at least 17/30 mpg (already achieved on the LT1 with AFM on) from it which is no worse than anything else making 500 hp either.
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Yes, and a supercharger has (practically) zero lag too. But that is not the point of this thread. The point is that a V6 bi-turbo is architecturally inferior to other turbocharged arrangements. Displacement or not, you'll have the same problems turbocharging a 4.7L V6 as you'll have a 1.8L V6.
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It is if you want to keep the entire engine behind the front axle for balance purposes... You'll either have to have a very long hood and wasted wheelbase length (which does not go towards a roomier cabin), or you'll have to stick the engine past the front axle and have sub-optimal balance. It is significant enough for Nissan to abandon the 2.6 RB26DETT for the 3.8 VR39DETT.
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LOL... I think you'll "like" the Lexus RX350L Hybrid 3rd Row. The top of the seat cushion is about 4 inches from the floor (which is higher than the regular RX350L due to the battery). You seat with your legs up like an "A".- 59 replies
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The I6 is very long and undesirable for that reason. A compromise is the VR6. Remember that? The staggered bore 12 or 15 degree V6? That keeps all the exhaust on one side too. Intake and exhaust port geometry, as well as the slant top pistons are sub-optimal, but not significantly so.
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Have you ever wondered by all the Bi-turbo V6 engines are always less impressive than you expect? Specific Output always seem to be worse compared to 4-cylinder counterparts. Maximum Torque seems to always arrive later and the engine always seem a tad lethargic. In short, they always seem to SUCK relative to the 4-cylinder turbo engines the same manufacturer puts out. They really SUCK compared to Inline-6 legends like the Nissan RB26 or the contemporary BMW N55. For example:- GM made a 2.0T (LTG) with 272 hp @ 5,500 rpm with 260 lb-ft at 1,700 rpm. That is 136 hp/liter and 130 lb–ft per liter. This same engine is later tuned to permit more mid-range boost with torque rising to 295 lb-ft @ 3,000 rpm (147.5 lb-ft/liter). This engine operates on 18 to 22 psi of boost and is able to get to full torque at 1,700 rpm or 3,000 rpm. At the same time, GM made the 3.6 Turbo (LF3) with 420 hp @ 5,750 rpm with 430 lb-ft @ 3,500 rpm. That is 116.7 hp/liter and 119.4 lb-ft per liter. This engine operates on a paltry 12 psi of boost but can’t seem to get to full torque until 3,500 rpm. Throwing really fancy and expensive stuff like Titanium Connecting rods and turbine wheels at the engine helps a bit. But, even the uprated 3.6TT (LF4) still took 3,500 rpm to reach 18 psi. A boost level the ubiquitous Malibu engine has no problem hitting at 1,700 rpm. Why? REASON The reason is very simple. And, it is not something you can conquer with expensive turbos or fancy materials. Just look at the diagrams below... In a 4-stroke engine, the exhaust valve opens once every two rotations of the crank for about half a rotation of the crank. In a 3-cylinder engine, or any bank of 3-cylinders, exhaust flow to the turbo is interrupted for significant periods with the exhaust valves closed on ALL cylinders. A V6 Bi-turbo engine is essentially two Inline-3s with each turbo is feeding off one bank of 3-cylinders. In an Inline-4, one exhaust period is always beginning while another is ending. Hence, while exhaust flow diminishes, it never really falls flat completely. In an Inline-6 the periods overlap generously ensuring a continuous exhaust flow to the turbine that does not diminish appreciably throughout the entire cycle of the engine. SOLUTION The solution is to use ONE Turbo for both banks of cylinders in an V6. But that is problematic. You either have to route the exhaust from one side to another -- which is both a packaging nightmare, a source of leaks and a measure which causes it to lose a lot of energy (heat) getting to the turbo. Or, you can use a Hot Vee design with the exhaust exiting in the valley of the Vee. A Hot Vee is problematic in the V6 because most of them are 60 degree engines which has little to no room in the Vee for a turbocharger. In addition, a single large turbo will stick through the hood in a Hot Vee. Hence, a Hot Vee is seldom used. When it is used, it is employed in a 90 degree V6 with two turbos -- which defeats still results in interrupted flow to the turbines. Hence, V6es continues to suck in turbocharged applications -- then, now and (probably) into the future!
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My biggest complaint on the MDX is that the seat cushion DOES NOT go down low enough. I have no desire for a high hip point, to seat higher or to look over other cars (or the steering wheel) more. I do very much prefer to seat closer to the floor board for two reasons -- I like head room and I like feet in front of me not at 90 degrees. Hey, I like couches I don;t like bar stools! This is why I don't buy SUVs (the MDX is Wifey's car) and why I always lower the seat as much as I can when riding in an SUV (or any car for that matter).
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Well, good for you. But, that is like saying none of the math on car values matter if you hit the jackpot on the Powerball Lottery. Well... yeah.... of course not! The GMT900 Escalade has more "gimmicks" like the fake side vent and the Suburbanite interior though. The K2 cars are nicer inside and out. But the K2 is a big missed opportunity for The General in that they could have gone Aluminum like Ford did, but they didn't. Consequently the K2 is not any lighter than the GMT900. The Escalade is also at a price point where it can easily absorb the LT4 V8, but they didn't do that either. This resulted in an Escalade that is neither fast nor miserly on fuel. Being AVERAGE is how you get beat up on when you are the flagship bling car.
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Actually, yes it does! It does no tmatter how long you keep the car. It applies to you the first 3 years you had the car. Yes, you have lower annual depreciation costs from year 4 to year 10. But you will always average out worse than the guy who only foot year 4 to year 10 depreciation. Let's do the math... Buy a $70K car new, keep for 10 years and sell it for $10K. You lose $60K total, burning a average of $6K a year. Buy a $70k car used at $40K, keep it for 7 years and sell it for $10K. You lose $30K at an average rate of $4.3K a year. You are spending 39.5% more money on an annual basis. And, these numbers are about right for an Acura which retains 57% of value over 3 years. It gets worse if you buy a car that depreciates more.
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And, buying a 2~4 year old car as a CPO or used vehicle DIRECTLY props up residual values and DIRECTLY lowers the lease rates. Lease rate = (New Price + dealer profit - Residual value - manufacturer's incentives) * effective contractual interest / months of lease term Ever notice that cars which nobody wants on the used market are also those that are very expensive to lease or are money losers for the manufacturer or both?
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I don't own a CTS V; I own a CTS VSport. Big difference there. 420hp 3.6TT vs 640hp 6.2SC. The Jag was a 5.0SC with 470hp, but it is a heavier car and it's 424 lb-ft isn't exactly a a lot. It doesn;t feel faster and it actually isn't faster.
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Good to hear that the VW-Audi MPG cheating scandal did not affect the resale value of your TDi!
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Demand doesn't really work that way. Demand for new cars is a summation of all buyers' desire and ability to buy or lease it new. But that desire and ability is also affected -- and in no small part -- by the residual demand and hence value as a used vehicle. This DIRECTLY affects lease rates and heavily influences the desirability of brands. Trust me, a BIG part of the reason somebody bought a Camry or RAV4 is how much he believes it'll be worth in 3 to 5 years. At least 30% of the cars Toyota sold they probably sold because people believe (correctly) that Toyotas have one of the highest value retention rates amongst all the manufacturers. So, whether you are buying new or used, you are contributing to the demand for the brand, model and type of vehicle you buy. However, if there is relatively speaking a high resale value but weak new sales for a particular model, manufacturers should conclude that their product is overpriced for the demographics they are targeting with it. Again, not rocket science is it?
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Well, I am glad somebody else is buying new then! I NEVER, EVER, buy a new car and it is not a matter of affordability but one of value. The current car -- a 2014 CTS VSport Premium -- was bought in 2017 with 26K miles on it for $33K. Its new sticker price was $73K. The previous car, a 2011 Jaguar XF 5.0 Supercharged was bought in 2013 as a CPO for $40K, it was a $68K car new. The car before that was arguably the best value. It was a 2005 C55 AMG bought in 2008 at the depth of the recession with 24K miles on it for $26K it stickered for $60K new -- I put 90K miles on it. The other cars in the familty, a 2017 Acura MDX Advanced Pkg SH-AWD was recently acquired for $40K with 22K miles on the clock, beating an as new price of $58K, and the 2015 GMC Terrain SLT was acquired with 17K miles in 2017 for $18K and it stickered for $28K new. The point is that you save a lot of money by avoiding the first 2~3 years of horrendous depreciation. Regardless of your income, value is value. Trust me, rich people do not get or stay rich by throwing money away when they don't have to. Buying used cars and used homes are some of the best things you can do for your finances regardless of how much you make and how much you want to spend on your car. (I am not going to tell you exactly how much we make, but we paid Uncle Sam and the People's Republic of California in excess of $160K in taxes last year).
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Because... #1 Americans weren't really into Kamikaze AWD Superhero Sport Compacts. #2 The WRX STi is no longer particularly high performance in today's context.
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The best and least cluttered Evo is the Evolution IV with the low profile spoiler. Unfortunately, you don't get it in the USA. The Evo IX is the next most desirable version. The Evo VIII is ugly with the elephant trunk grille. The Evo X is not too bad looking, but it gained 300 lbs and has the 4B11 engine shared with Chrysler and Hyundai. The 4B11 is LESS refined and LESS durable than the old 4G63. Less refined because it eliminated the Balance Shafts. Less Durable because it has a die cast, semi-open deck block, whereas the 4G63 is has a super durable closed deck iron block.
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Yes, the Lancer does have a sh!tty interior, but so does the Imprezas including the WRX STi Editions. These are supposed to be Kamikaze AWD Superhero Economy Cars. The 9-Speed is garbage because it BREAKS. It'll suddenly start slam shifting from 1st through 3rd with the torque converter clutch still engaged which feels like getting rear ended. It'll also go into neutral and shutdown while you are driving, and you'll need to pull over, turn off the engine, lock the car, unlock the car, restart the car to reset. It has nothing to do with output of the engine or driving aggressively so V6 or not doesn't matter.
