03-14-2014, 11:15 AM | #309 | |||
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You can enhance this effect by using two effectively separated low innertia turbochargers instead of just a bigger one in order to reduce the turbo lag even further. Last edited by GoingTooFast; 03-14-2014 at 11:33 AM.. |
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03-14-2014, 02:38 PM | #310 | |||
TIM YOYO
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From a pure character (throttle response/driving feel) perspective, I would say yes, I think the N20 is better. From a performance standpoint, it's a no-brainer. The M133 is a runaway winner. Quote:
To say something is "pure marketing" is to say it has no benefit outside of a bullet point in a marketing brochure. That is categorically false. Just because I would prefer a N/A engine doesn't make all turbocharging decisions equal. Again, you could benefit from a more subtle understanding of how a turbocharger works. An engine makes it power from burning an air-fuel mixture. The more you burn, the more power you make. Because gasoline engines rely on a stoichiometric ratio of around 15:1, you must add air proportionally with fuel. This means that in order to make more power, you must move a greater volume of air. Your options are:
When designing an engine, you can preserve throttle response by using a larger base displacement, and keeping intake pressure levels low. This allows you to use smaller turbos, which spool up much faster. That is why a 3.0L I6 turbo can deliver 300+ HP with better character than a 2.0L I4 turbo can. What BMW has done is try to strike a balance between efficiency and preserving the character of an engine. I'm a BMW buyer because of this attention to balance. Yes, I would prefer a naturally aspirated engine, but in the absence of that option, I'm going to choose the manufacturer who at least prioritizes engine character. Quote:
The twin scroll turbo solves the exact problem I outlined above: in isolation, two cylinders can drive a turbo, but it's not optimal. If you look historically, I4 twin-turbo setups are usually sequential, and involve rather complex plumbing and actuators to route exhaust energy to the right place at the right time. The whole setup is complex, heavy, and prone to failure. In contrast, if you look at the turbo system on the N54, the cylinders were split in the same way that the inlets are split on the N55 and N20. The difference is that with the N54, each turbo operated independently. This setup isn't used with an I4 engine, because the exhaust gas energy from two cylinders isn't substantial enough to drive an impulse turbine efficiently.
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03-14-2014, 05:41 PM | #311 | |
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"The mark of a great car is one whose overall competence exceeds what you should expect from its individual components and the 1M does just that", Chris Harris.
BMW 1M-SOLD-: TECH: Evolve Race+N55mids, Evolve IC, Michelin PSS, ER cp, aFe filter, CDVx, Vorshlag camber plates, BMS OCC EXTERIOR: trunk spoiler, blacklines, black grills, IND goodies INTERIOR: Alcantara steering wheel, steel pedals, custom mats, MPower e-brake. |
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03-14-2014, 06:44 PM | #312 |
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No, I'm not trying to mischaracterizing what you say. Here's what I'm listening from what you say and what is my view:
You are defending the turbocharged inline 6 cyl. engine solution because of its evident throttle response superiority and yet you've dropped the N54 engine for a turbocharged inline-4, the N20, both of which are clearly inferior to the AMG turbocharged inline-4 and even the theoretical throttle response advantage of the N54 wasn't meaningful enough to stop someone that puts so much importance on the throttle response quality such yourself from going with the N20 engine after living with the N54 AND certainly it isn't meaningful enough to justify the extra size, weight, center of gravity height and fuel consumption, except for marketing reasons. Like it or not. Modern BMWs don't turn in due to an heavy front-end. Additionally, saying that the AMG turbocharged inline-4 has poorer throttle response quality than the N20 and believe that someone would opt for the latter on that basis is completely unrealistic, thus there's no point in discussing it. As for the twin-turbocharger solution in an inline-4, it is already used as a sequential 2-stage arrangement, with a small, single-scroll low-inertia turbocharger for low rpm combined with a bigger one for higher rpm, in BMW's high-boost diesel engines and could be easily adapted to the N20, with no or little development cost, to transform it into a better throttle quality response, higher-boosted S20 engine. Of course that the exhaust temperatures are MUCH higher on a petrol engine and that's the main issue to overcome as far as the reliability of such solution is concerned. |
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03-14-2014, 09:52 PM | #315 |
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03-14-2014, 10:02 PM | #316 | |
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HAHAHA, love it! It's not bad to drive by any standards. It's just mediocre really. |
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03-14-2014, 10:26 PM | #317 | |
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03-15-2014, 12:28 AM | #318 | ||||
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Our X3 is a grocery getter. It's a point-A to point-B car. It only needs a competent power plant. The N20 is a great engine, and as I outlined in great detail before, it does not suffer from the same throttle response issues as the M133, because it uses a sane level of boost for a daily-driver. Our X3 isn't material to this debate though, because it is neither an M235i or a CLA 45 AMG. It's design purpose, and my reasons for purchasing it couldn't be more different than the reasons I apply when deciding between two sports oriented cars. Now you're just pulling stuff out of thin air. It is a fair criticism that modern BMW's have grown heavy and have lost some of their agility when compared with chassis like the E36, but there is no competitor who does not suffer the same failures as models grow in size, safety, and features. You're grasping at straws here. Quote:
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A diesel engine has no throttle plate. RPM is governed by the amount of fuel injected in to the cylinder. This is possible because you needn't maintain the strict 15:1 (or very close) air-fuel ration in a diesel. The full volume of air can flow through a diesel engine at all times, which is why their exhaust gas volumes are higher. Because of this, you cannot simply swap a turbo diesel setup to a gasoline powered engine and expect things to go swimmingly. The turbine and compressor maps will very likely be mismatched to the gasoline engine. I could be wrong. I mean, we're all guessing here, right? Maybe BMW goes all retro on us and drops a sequential setup on the rumored S20 engine, but I think that's unlikely, if only for cost reasons. The benefits just aren't great enough when compared with something like a twin scroll setup.
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03-15-2014, 12:41 AM | #319 |
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I want to get out in the open that I don't think you should by an M235i. I'm not trying to convince you that the M235i is the car you should buy. What I'm trying to explain to you is that you and I may want different cars, and that's OK. You have your reasons and preferences, and I have mine. The problem is that when other people state their reasons, you call them marketing gimmicks or try to refute their subjective reasoning in some objective manner.
The CLA 45 AMG is a great car. I'm glad it exists, because it inspires competition. For my money, Mercedes Benz has prioritized some of the wrong things. That's based on my preferences though. You clearly have different priorities, and it sounds like the CLA is a great fit. You should totally buy one. I'd be thrilled for you; I really would.
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03-15-2014, 03:48 PM | #320 | |
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Look, it's too much talk and very little relevant information about a very simple matter. I'm not guessing, I'm presenting a possible solution for throttle response quality hyper concerned people like yourself, and you are indeed wrong except when you've mentioned that the main issue about a twin-turbocharged solution for a mass-market car is its cost viability, that's the reason why they came up with the twin-scroll solution, one is cheaper than two. You see, long before being used on diesel car's engines the twin-turbocharged solution was used on no cost-object super sport cars such as the Mazda RX-7, the Toyota Supra and the Porsche 959 which were a way ahead of their time. In fact, "the use of sequential twin turbochargers (two small KKK turbochargers) rather than the more usual identical turbochargers for each of the two cylinder banks allowed a smoother and seamless delivery of power across the engine RPM band, in contrast to the abrupt “on-off” power characteristic that distinguished the 959 engine from Porsche’s other turbocharged engines (930 and also 964 turbo) of the era. Sequential turbo charging was controlled as follows: below 4,000 rpm, as exhaust gas was not enough for driving both turbines efficiently; all the exhaust gas was fed to a single (small) turbo. This made the turbo operating earlier and therewith allowed the engine to build up boost earlier compared to using a conventional turbocharger setup. Between 4,000 and 4,200 rpm, the second turbo started “pre-spinning” (preparing for engaging soon at higher revs). Above 4,200 rpm, the two turbos operated simultaneously to provide full boost". Also, the computer-controlled waste gates now used on the S55 engine of the M3/M4 were, naturally, already used on the 959's engine twenty five years ago. What you find on the BMW's twin-turbocharger inline-4 diesel engines is exactly the same principle, except for the size of the second turbocharger which is bigger than the first one in order to achieve higher boost while the turbo lag is reduced even further. So, if low inertia, exhaust manifold integrated small twin-scroll turbines on the modern turbocharged inline-4s are not enough for you as far as throttle response quality goes the above solution is what I would recommend to BMW for the S20 engine. Why is the inline-4 engine so important then?! Because with turbocharged inline 6 cyl. modern BMWs not only aren't as fuel-efficient as they could be with 4-cyl. engines but also they are too nose heavy which translates into poor turn-in characteristics, and ultimately less agility or sporty character, and less than ideal braking performance. Bottom line, the inline-6 cyl. engines are today a marketing thing for BMW. Last edited by GoingTooFast; 03-15-2014 at 04:59 PM.. |
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03-15-2014, 09:51 PM | #322 |
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I rather trust professional drivers than professional reviewers...
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03-15-2014, 10:43 PM | #323 | ||||||
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That was a nice little write up on sequential turbochargers, but the only argument I've made regarding sequential turbochargers is that I don't believe they'll use them on any upcoming I4 turbo motor in the BMW line up. I also said that I don't think it's a certainty; just that it's very unlikely. Unless I've missed something, you haven't presented any argument against that claim. Quote:
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The M235i isn't that pure of a car though. It's balanced more toward a car that you can live with day-to-day. The CLA 45 AMG is a full-blown AMG car. Wait, I feel like I've said this before. Are you breaking space-time or something? Time is a flat circle. The cake is a lie! How can you keep saying that? I've explained to you in very clear terms the very real benefits of a larger base displacement. You really are an enigma. Most people I argue with on the internet at least make an attempt to refute my arguments, rather than simply repeating themselves over and over.
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03-15-2014, 11:09 PM | #325 | |
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I'll get tired of it eventually, but this is too entertaining.
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03-16-2014, 10:08 AM | #328 | ||
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Therefore, a very high-boost is necessary from the turbocharging system in a diesel engine which means BIG turbochargers, which, in turn, means HIGH turbo lag. To overcome this, BMW went as far as using not two but three turbochargers - two small, low inertia and a bigger one - that work in sequence or simultaneously, depending on the engine rpm, forming a three stage arrangement that you can find in the M35d models such as the M535d. This car costs as much as an M3. And, I can assure you that the right pedal response of the M535d is on pair with my 1M's and that it revs eagerly right to the redline. So, if we recall that the use of sequential twin-turbochargers was first introduced on petrol cars for the very same throttle response quality reasons and it was then adopted by diesel engines for which the issue is in fact critical, it's very easy to understand why such solution makes every possible sense for an high-boost turbocharged inline-4. This is the last time I'll try to explain to you why BMW's bigger, heavier, higher COG and less fuel-efficient turbocharged inline-6s are a marketing thing. I'll leave your far too many personal remarks unanswered, past, present and future, for reasons I'm sure you can understand... I really don't care! Quote:
So, it's a non issue really! And yet the CLA AMG offers the same, if not better with its 4 doors, day-to-day practicality. Last edited by GoingTooFast; 03-16-2014 at 09:24 PM.. |
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03-17-2014, 08:56 AM | #329 | ||||
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Every comparison video I've seen from a competent reviewer has noted the difference in engine character between the M135i and the CLA 45 AMG. The CLA 45 AMG is a car to be respected. No question about it. That doesn't mean everyone has to choose it though. There are plenty of reasons to choose the M235i, and the turbo I6 is key amongst those reasons.
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03-22-2014, 03:37 PM | #330 | ||
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