Talk:Turbocharger/Archive 2

Chrysler/Dodge VNT material
76.17.61.168, your continued insertion of unsourced, POV original research is not appropriate. My vehicle ownership history is just as irrelevant to this article as yours. It also doesn't make any difference how cool you or I may think the Turbo-IV cars are. Remember, the standard for information in Wikipedia articles is not "truth", but verifiability, and assertions — especially those that can reasonably be challenged — must be supported with citations from reliable sources. It doesn't matter what you or I or anyone else knows or thinks he knows, it matters what we can prove per Wikipedia's requirements. Please try not to take it personally when text you've added to an article is modified as part of an effort to improve the article according to Wikipedia's standards. Please also take a few moments to click the links embedded in this comment to learn more about how to make your contributions more likely to remain part of the article as it evolves and improves with the effort of all who choose to participate. Remember, Wikipedia is a coöperative effort, not a competitive one. If you carry on inserting unencyclopædic text and not engaging on article talk pages, you run the risk of being blocked. Thanks for choosing instead to coöperate. --Scheinwerfermann (talk) 18:16, 30 January 2008 (UTC)

High revving?
Isn't one of the points of turbochargers that while you can't run the cylinders at high pressure due to pre-ignition, you can *force* the air into the cylinder through the inlet valves, and so rev more quickly, and hence develop more power than the simple boost pressure ratio would suggest? Or at least it seems to me a lot of turbocharged engines rev rather higher than normal aspirated ones, there must be a reason for that. If so, this is missing from the article. If not, not to worry :-)- (User) WolfKeeper (Talk) 02:02, 6 February 2008 (UTC)


 * I don't think that the higher revving is due to the turbocharger. I think that because turbos have an incremental increase in power as revs go up, that manufacturers use heavier duty springs, etc., to allow for higher revving on their turbo engines; also of course these are their premium engines so they'll spend more money on them compared to base engines. Davert (talk) 19:03, 10 February 2008 (UTC)


 * No, I'm pretty sure that the extra pressure of the turbocharger permits the engine to force the air through the inlet valving far faster than it would normally go which is especially critical at high revs; but the actual pressure in the cylinder is limited by the octane of the fuel; but if you rev higher, then the engine produces more power anyway, since there is more total flow of fuel and air through the engine.- (User) WolfKeeper (Talk) 19:54, 10 February 2008 (UTC)

Not really relevant since most cars have rev limiters. If you rev an engine high its reliability will decrease. So car manufacturers want more power at the same revs, not just higher revs that will make them have to toughen up a ton of components. 86.44.202.31 (talk) 22:26, 16 September 2008 (UTC)

Power output
In the working principle section it says a turbocharger can increase power output 15-40% if the engine is allowed to run lean. Is this a high number? To achieve a 15-40% increase in power output does that means that 15-40% more energy is being release associated with the lean air/fuel condition? Noah Seidman (talk) 03:45, 26 April 2008 (UTC)


 * The engine running lean is relative to the air fuel ratio, the turbo just crams more air/fuel into the cylinder, so in a case without a turbo, you would have 1 unit of air/fuel mix, in a turbo motor with the same capacity running 1 bar boost, you would technically have 2 units of air/fuel mix in the cylinder (ideally speaking, boost isn't normally measured correctly for this to be strictly true). So whether its lean or rich doesn't matter too much, its the simple fact that turbos (and superchargers) cram more air/fuel into the cylinder so theres more stuff to make power from.The reason i've heard that they like to run turbo motors lean is because lean motors make more heat, and turbos like heat, they work better and spin faster, probably because the hot air takes up more space.Sd4f (talk) 03:19, 16 November 2008 (UTC)

Recent changes
Are these changes correct? Shalom (Hello • Peace) 21:51, 27 May 2008 (UTC)

Too long!
This article has just gotten way out of hand. At 57 kilobytes, it's way past the recommended article size. A lot of the information is useless trivia, too. We really don't need to read "this engine was turbocharged, and so was that one, and so was that one." It's gotten so big that I don't think anyone would want to read the whole thing, not even a gearhead like me. So, unless anyone can come up with a good reason why I shouldn't, I'm going to start cutting the fat out of this article. Shreditor (talk) 02:20, 24 June 2008 (UTC)


 * "Too long" isn't an especially good reason to remove material from an article; the article length recommendations grow softer with each passing day as their raisons d'être grow increasingly obsolete. But there is a great deal of material to be removed ASAP from this article. The writing is loose and sloppy, there's a bunch of POV, unsupported (and unsupportable) assertions, personal-essay nonsense, and other such cruft. I've cleaned up the "Automotive applications" section, but am too tired to carry on tonight. Have at it! —Scheinwerfermann (talk) 03:19, 24 June 2008 (UTC)

Turbocharged Engine Efficiency
In my personal experience, as well as my experience with this article and its history, there seems to be a chronic misunderstanding by many people about how a turbocharger will affect the engine's efficiency. I had written several paragraphs clarifying the subject in March but they were deleted in a recent clean-up. As I believe it's important to clarify this subject, I'm re-posting my comments here, with a few edits. If it's really the opinion of other editors that this discussion is "fat," that's fine and please say so here.

"First and foremost, a turbocharger does not necessarily increase the efficiency of an engine. While one can think of a turbocharged engine as having a higher "effective compression ratio" than a naturally aspirated engine, this does not mean that one can compare this "effective" CR to the CR of a naturally aspirated engine, for the purposes of calculating efficiency. Any engine generates power by doing more work during expansion than during compression. While a turbocharger does add more compression and expansion to the engine, the expansion cannot do more work than the compression because the turbine and compressor are mechanically connected! Also, since the turbo spins freely and isn't connected to the crankshaft, in a sense we could disregard the thermodynamics of the turbo and look instead at the engine itself, since that's where the drive power is produced directly. If we knew the pressure on the pistons at all parts of the cycle, we could calculate the indicated power of the engine and ignore the turbo entirely. Of course, the turbo will affect the pressure on the pistons, but how? "The efficiency of an ideal otto cycle is independent of intake charge temperature, pressure, and density. For an ideal engine, we can directly calculate the work done, as a function of heat added during the compression and power strokes. The ratio of work done to heat added depends only on the engine's compression ratio, regardless of turbos or any other type of forced induction. In this sense, the turbo does not affect the efficiency of the engine at all. The turbo *can* affect the work done during the other two strokes, however - intake an exhaust. The boost pressure generated by the turbo actually does work on the pistons during the intake stroke, and this work contributes to the overall power output of the engine. And, since turbos necessarily generate exhaust backpressure, the engine must do work to push out the exhaust, which consumes power. So, the difference in efficiency between a turbo engine and a naturally aspireated engine depends on the relative boost pressure and exhaust backpressure. If boost and backpressure are equal, the ideal engine's thermodynamic efficiency will be exactly the same as a naturally aspirated engine with the same compression ratio. If boost pressure exceeds backpressure, the efficiency will be higher. If backpressure exceeds boost, the efficiency will be lower. An ideal turbo, with isentropic compression and expansion, fitted to an ideal engine, should generate much higher boost than backpressure, so this would tend to increase efficiency. This is related to the much higher temperature (available energy) in the exhaust than the intake, and also the energy which is lost during exhaust blowdown in a NA engine, which the turbo can recover. However, real engines differ from these idealizations. "In practice, the turbine and compressor efficiencies of a turbo are not 100%. Additionally, there is a large heat loss in the exhaust, and there is friction in the turbo assembly as well. Experience shows that modern turbocharged engines are generally split on whether boost is higher than backpressure, or the other way around. Small turbos which spool quickly tend to require higher backpressure, and thus tend to lower engine efficiency, whereas large slower-spooling turbos require less backpressure and can raise the engine's efficiency. However, due to knocking limitations, turbocharged engines tend to run significantly lower compression ratios, so it can be generalized that, under full load, real turbocharged engines tend to have somewhat higher brake-specific fuel consumption (BSFC) than real naturally aspirated engines. At idle or part-load conditions, the situation becomes more complicated, as turbocharged engines tend to have smaller displacement for the same power output, and so have lower pumping losses and friction. Also, the turbo engine will have a lower mass, so if the engine is going into a vehicle where the engine is a significant fraction of the vehicle mass, the *vehicle* efficiency can be higher with a turbo engine, even if the *engine* efficiency is lower (this would especially be true in aircraft). "It is true that enriching the mixture in a turbo engine can allow the engine to make slightly more power, by staving off knock and allowing slightly higher boost or more advanced ignition timing. But, this is far from necessary in a well-designed turbo system, and will most definitely increase BSFC. A turbo engine at the limit of knock running an equivalence ratio of 1.2+ is *not* a good design for a passenger car.

-FYRE4CE


 * I agree with your assessment 100 percent. Unfortunately, a lot of this article lacks references. Much of the information came straight out of the heads of people who don't fully understand important engine fundamentals. Even for the stuff that has sources, there is no evidence that the source is correct. Several major textbooks I've read on the subject have embarrassing errors due to misunderstanding or misapplying the laws of physics. Unfortunately, many times Wikipedia ends up being a democracy of sorts where the most common view of a subject wins, regardless of whether it is verified to be true. Shreditor (talk) 08:38, 31 July 2008 (UTC)

To FYRE4CE, your argument was a very long winded way of saying sometimes a turbo increase efficiency and sometimes it doesn't. And your excessive use of the Otto cycle just confused the matter. Clearly it's not meant to represent a situation with a turbo. It doesn't think exhaust gases exist for god's sake! It also takes a hell of a lot more than the compression ratio to describe the efficiency of a real engine with or without a turbo. The fact is that turbochargers CAN increase the efficiency of an engine, and any failure to do so by a design engineer means he wasn't after efficiency (or was inept). It CANNOT be generalsed that turbo engines run significantly lower compression ratios, as most turbocharges cars today are diesel where that's not as much of a factor. And a turbo engine at the limit of knock running an equivalence ratio of 1.2+ is a very bloody good design for a passenger car if you ask me. Please lay off the excessive, misleading, and boring thermodynamics and go out and drive the crap out of an old supra or something86.44.202.31 (talk) 00:12, 17 September 2008 (UTC).

We engineers use models (eg. Otto cycle) to gain understanding of physical systems. We understand that models do not completely describe the system, but that does not mean they aren't useful. Einstein published his paper on special relativity over 100 years ago, effectively proving that Newtonian mechanics are wrong. But every vehicle you have ever touched has been designed based on Newtonian principles - why? Because they are a good enough approximation for most purposes. The Otto cycle is useful for some things, like understanding how compression ratio affects efficiency. Obviously it's not the be-all of engine design, but I think everyone reading this understands that.

Clearly you don't subscribe to this point of view - that's fine. But people exist who do care about this stuff. Many of them are designing engines. You are not, and for good reason. Good engineers care about the "why" just as much as the "what." The reason I wrote what I did in the first place is that I have heard many people, including some people who should know better, assert that turbos add compression and therefore add efficiency. This is not the case, for the reasons I described in detail. You're right that turbos don't generally lower compression ratios in diesels, but you overlooked the fact that I was talking about the Otto cycle, not the Diesel cycle.

As for liking your engines running super-rich, that's fine for racing engines and aircraft engines in wartime emergency mode, but it sucks for passenger cars. You get a small increase in power at the expense of wrecking your BSFC and your emissions. Just increase your displacement a bit and you'll get that same power gain without the mess. I defy you to find a production car engine that's programmed to run 1.2+ equivalency ratio under load.

-"FYRE4CE" —Preceding unsigned comment added by 192.35.35.34 (talk) 19:51, 30 September 2008 (UTC)

Diesels
"Today, nearly all automotive diesels are turbocharged."

Can we have a reference for this please? This is certainly not the case in Europe. Routlej1 (talk) 14:51, 14 August 2008 (UTC)


 * I don't know who wrote that, but I don't think it's true. In the USA, all you have to do is drive down the freeway with your window down to hear that the majority of diesel truck engines are turbocharged. However, a truck diesel engine is quite a bit different from a car diesel engine. I'm not sure the extra costs incurred with turbocharging are worth it for a passenger car application. A source would be nice, but I don't think you're going to find one, so this statement should probably be removed. Shreditor (talk) 22:45, 14 August 2008 (UTC)

It is most definitely true. Have you never heard of a VW TDI?? Where I come (europe) from there's almost no such thing as a diesel without a turbo anymore. 86.44.202.31 (talk) 00:14, 17 September 2008 (UTC)

Remote turbochargers
Squires holds most of the patents associated with this configuration. If you come across an article about remote mounted turbos that does not mention squires, or mentions another manufacturer, please add it to the references. RXrenesis8 (talk) 16:48, 16 December 2008 (UTC)