Talk:Variable valve timing

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Untitled[edit]

Moved to 'Variable valve timing' from 'VVT' because we don't write an article at the contraction, but at the full word, and we don't capitalise except on proper nouns, which I don't think variable valve timing as a concept is. See Wikipedia:Naming conventions. —Morven 17:38, Jul 21, 2004 (UTC)

The GM systems mentioned in the history section were separate, one varied timing and one varied lift, both systems were unsuccessful and never produced. I believe GM did however produce a valve system that was used to deactivate pairs of cylinders on a V8 in the early 80s. I can find no reference to any system with the name Smart Valve. I am considering changing the GM part of the history if anyone has any objections please let me know. IJB TA 01:40, 11 August 2006 (UTC)

Nissan VVT[edit]

  • This article is a little off base. VVT or variable valve timing simply changes the timing of the camshaft, using cam phasers. It does NOT change the actual profile of the camshaft. Vtec, on the other hand, utilizes a camshaft that has multiple profiles, and can select which profile to use based on current operating perameters.* —Preceding unsigned comment added by 12.28.232.10 (talk) 16:28, 12 December 2007 (UTC)

Heres an article stating Nissan did design and implement japans first VVT engine. http://autoweb.drive.com.au/cms/newsarticle.html?&start=90&showall=&id=NIS&doc=nis9810153

"Nissan produced Japan’s first variable valve timing system in 1986 and, since then, Nissan Valve Timing Control System (NVCS) has been used in many production vehicle applications."


You can do some research on the 300ZR Z31 if you want, it used the same engine as the NA Z32 though with a different intake manifold.

The Z31 and Z32 were not powered by the same engines, all models of the Z31 were powered by variations of the VG30E SOHC engine, all models of the Z32 were powered by variations of the VG30DE DOHC engine. The VG30DE was not produced until 1990. Also I have located the earliest US patent for the Nissan VVT system (4,960,084), it shows that the earliest date that Nissan applied for a patent in Japan was in September of 1988. The reference you provided is pretty far from definitive proof that Nissan produced a VVT system in 1986. Are there any other references that you can provide? IJB TA 19:30, 13 August 2006 (UTC)


Wrong. In America all Z31s are powered by the VG30E(T) engines. In Austraila and Japan they got the 200Z,200ZR,300ZX,300ZR with VG20E, VG20ETs,VG30E,VG30ETs,RB20DETs, AND VG30DE(300ZR). The VG30DE(TT) engine was originally developed for the Mid-4 in the mid 80s, the naturally aspirated version was first used in the 300ZR in 1986 (87 model year). Heres a bit more info on the DE sereies engines that ALL have VVT.

http://zhome.com/History/MID-4.htm


Also the VH45DE engines used in the Nissan Cederic in Japan (Q45 here) recieved VVT in 1988.

Still nothing on a VVT system. Here's a reference stating that the VG30DE went through extensive development after it was shown in the Mid-4: http://www.zccw.org/History/Z32_part1.htm . The VG30DE with VVT was developed for the Z32 which did not enter into production until 1990 (model year). One obscure reference is simply not enough to disprove what is a very widely accepted fact, so unless you have something a little more concrete I think the article should be reverted to my previous edit. IJB TA 05:20, 14 August 2006 (UTC)

To be quite honest with you, its hard to obtain information on the early VG30DE(TT) engines as they were sold in low #s and only in Japan. Its a pretty widely accepted fact as several sources have mentioned it that Nissan developed the first production VVT system. I know the cederics were using the VG20DET in 87 which also used VVT. Heres the most precise answer I can give you right now: http://www.alljapanesecars.com/specsview.php3?mk=Nissan&md=Cedric&mc=y31&gn=9 ^Lists the cederic having VVT in 1987

http://www.photodump.com/direct/govaard/DavidZproductionqty.jpg ^ and this is when the Z32 began production The Z32 was sold as an 89 model in Japan and was actually on sale in 1988. Either way that was still the first mass produced VVT system in Japan and the world.

Well, most of what has been presented here is not really solid proof. But Nissan had been developing VVT systems as early as the mid 1970s (and maybe even earlier) so it is much more plausible that Nissan did produce the first VVT systems. I have also found it difficult to locate information on Nissan production engine technology so I can't say for sure either way. So I suppose the article will stay as is, unless someone else presents information to say otherwise. IJB TA 07:34, 14 August 2006 (UTC)

Revisions to the History section[edit]

I am considering incorporating some new information into the History section such as the following:

  • Lycoming (not Fiat) would develop the worlds first functional VVT system in 1944 for the R-7755, the largest piston aircraft engine developed in the US. Anyone know if this system was patented?
  • Nissan had developed a VVT system that used "3d" cam lobes which could alter timing, duration and lift. It would later inspire a similar system currently used by Ferrari. US patent numbers 4,182,289 and 4,352,344.

If anyone has anything that they would like to add please present it. Thanx, IJB TA 02:06, 26 October 2006 (UTC)

14:44, 5 May 2016 (UTC)14:44, 5 May 2016 (UTC)14:44, 5 May 2016 (UTC)14:44, 5 May 2016 (UTC)14:44, 5 May 2016 (UTC)FifthAgeOfMan (talk) I believe there is an error 14:44, 5 May 2016 (UTC)14:44, 5 May 2016 (UTC)14:44, 5 May 2016 (UTC)14:44, 5 May 2016 (UTC)14:44, 5 May 2016 (UTC)FifthAgeOfMan (talk) Don't know if this is how it's done, however I noted in the article's History section there is no mention that Alfa Romeo had implemented VVT in their Spider Veloce in 1983 and switched to electronic VVT by 1985. Nissan is given credit as first, however, they didn't apply for patent until 1986, three years after Alfa had a system in Production automobiles. There are numerous sources for verification including Alfa's own service advisory updates from 5 May 1990, referring to the means of adjusting the 1983 version, and U.S. Patents, for example [1] There is a great deal more information to be found through the patent office publications alone, however, my job is not to do the correction, for which I do not feel qualified, but to point out what I believe to be "the error." Again, I am unfamiliar with the methods, therefore I hope that this is an acceptable means of calling attention to what may need to be corrected. Thank you for your consideration.

Honda exaggerations[edit]

The exaggerations in the Honda section have to stop. VTEC V-6 is not comparable to a "racing cam." This is a ridiculous assertion along with several other ridiculous assertions removed from the Honda sections. -TP

There are no exaggerations. I changed race cam to high lift, long duration, which is essentially a race cam. VTEC cams in V6 engines have an intake cam profile which is aggressive, maybe not comparable to race cams but fairly aggressive for a mass production vehicle. The high rpm cams in high output DOHC VTEC engines do have profiles comparable to that of a race cam, the ability to use these types of profiles is why the VTEC system was developed in the first place. VTEC engines do not produce less power at low rpm when compared to non-VTEC engines, again, this is the main reason the VTEC system was developed, to allow for an aggressive, high rpm cam to be used without sacrificing low rpm output. DOHC i-VTEC engines do not have an "added lift device", the VTEC system already varies lift. Advanced VTEC will have a device which will allow the system to vary lift continuously like the BMW Valvetronic system. DOHC i-VTEC engines do have continuously variable timing for the intake cam. Fully operate does not apply, that would be like saying a door latch does not fully operate until the door is closed. Please research your edits properly before making them, there is a huge amount of information about these systems on the web. I should not have to teach anyone who edits this article about this subject. IJB TA 05:25, 31 October 2006 (UTC)

Separate notation on 10/29/2008: Someone might want to add to Honda's list of VTEC designs, their A-VTEC, which recently debuted with the 2009 Acura TL. This iteration of VTEC has been deployed to bring independent intake & exhaust timing to their J35 & J37, SOHC, V6 motors...functionality similar to VTEC applications to DOHC configurations. Improved low end torque has been cited. Claims are that this is a more elegant design that BMW's Valvtronic. There's a white paper available & a measure of technical discussion re Honda's new A-VTEC off TEMPLE OF VTEC.COM (see Jeff Palmer's article).

I will add something about Advanced VTEC to the list. I did read the TOV article but there is still only speculation as to how the Advanced VTEC system affects the exhaust valves, if it does at all. If someone finds more detailed information they can change it. IJB TA (talk) 15:54, 30 June 2009 (UTC)

Well, I don't think Advanced VTEC is actually in production, but I can't find any information about the VTEC system in use in the 2009 Acura TL. It is a unique system but does not have a specific name. I'll keep looking. IJB TA (talk) 20:42, 1 July 2009 (UTC)

Variable Valve Actuation[edit]

Why is this page separate from Variable valve actuation? If they are different, there is nothing on either page to explain the differences; If they are the same thing (or closely related), they should be merged. 82.26.227.219 (talk) 09:55, 9 May 2011 (UTC)

New Section On Mechanical Types[edit]

I have added this section as I thought the existing article, although very good, was lacking detail on mechanical only types. In addition to this reason I know that Wiki articles are very often the place both amateur inventors and auto industry researchers alike first turn to when starting a new project. I hope what I have written here will give them some guidance. I know of some researchers who have thought that they had "invented" just about all these types one after another - not knowing that they all ready existed. I have never actually seen anything like the section I have just written on any freely available to the public material - only internal company reports and patent search reports etc. I still have some work to do in finding USPTO numbers as examples, and adding links and references etc. Clivedog (talk) 10:25, 12 January 2012 (UTC)

Wikipedia does not publish original research or anything that is not publicly available. One of Wikipedia's 5 Pillars is Verifiability. This means it must be possible for others, with reasonable effort, to find the same sources you used and verify what you said. Please carefully read the pages I linked to, and revise your contribution using only verifiable sources, and then please cite your sources to make it possible to check them. --Dennis Bratland (talk) 16:39, 12 January 2012 (UTC)

This may explain why nothing has been written previously on mechanical types. Basically very little of what I wrote has been published - so I think there is very little point in trying to get this information into the main article. However, as I explained above, I think what I wrote is very useful for amateur inventors and auto industry professionals alike. I will move the "New Section" to the "talk" page and add a link to it on the main article page - I will presume that this is allowable unbder Wiki rules?Clivedog (talk) 02:26, 13 January 2012 (UTC)

Deleted again. Please read WP:NOTWEBHOST. Wikipedia is not your free web host. You could create a blog and publish your research there. Or you could apporach a magazine, journal, or other reputable publication and ask them to publish your work. If that happened, then you could add it to Wikipedia and cite it. It would have to be pass a bona fide editor, though, and not be self-published. See WP:SPS.

The key is that Wikipedia does not lead. Wikipedia follows. Secondary sources are the main sources used here; well-established, mainstream facts. Nothing cutting edge. Nothing from the fringes. Or next to nothing.

I'm not saying it's not useful. We can agree that it's useful but useful doesn't meet Wikipedia's criteria. Use your expertise to find and cite published sources. Work that breaks new ground goes elsewhere. --Dennis Bratland (talk) 03:13, 13 January 2012 (UTC)

Dennis - Thank you for your explanation of the situation - which I must admit that I didn't quite understand. However it does seem a slightly odd and paradoxical situation that when something is published by a magazine it then becomes "OK". I know a few editors of motoring-type magazines and, generally speaking, they are so desperate for new and interesting material that they are quite happy to publish pretty much anything within reason - and by Wiki standards this would then make it "kosher"? I will see what I can do about publishing elsewhere - but until then Wiki may have to do without my words of wisdom.Clivedog (talk) 05:07, 13 January 2012 (UTC)

The Wiki system of referencing turned out to be not as quite as indecipherable as it first appeared to be - so I have added some references and resubmitted the addition to the article.Clivedog (talk) 07:01, 17 January 2012 (UTC)

Citations needed regarding steam engines[edit]

Article as I found it [1] read in part Almost all steam engines had some form of variable cut-off. That they are not in wide use is a reflection that they are all lacking in some aspect of variable valve actuation.

On reflection this seems to be not only WP:OR about the history of the steam engine but, more important, WP:POV about the merits of VVT. The author doesn't like VVT! We've had such problems before with automotive articles, notably that one editor doesn't like extractor manifolds. And their opinions may be valid for all I know, it's just that Wikipedia is not the place to express them. Andrewa (talk) 20:53, 27 September 2012 (UTC)

I've added some details and wikilinks and two requests fro citations [2], but frankly I'm skeptical of both claims. Our article on cut-off reads in part Smaller stationary steam engines generally have a fixed cutoff point while, in large ones, the speed and power output is generally governed by altering the cutoff... [3] in view of which I think the claim about almost all such engines having cut-off gear needs at least clarification. And I'm guessing that the observation about the reason for the demise of steam is WP:OR but I could be wrong. It certainly needs a citation and probably rephrasing.

It's an interesting comparison and should be kept. Just needs some cleaning up.

Certainly the "Almost all steam engines etc." statement is something of a generalisation. Maybe it should read "Almost all steam engines used for transport had variable cutoff etc." Being able to vary the cutoff makes the steam engine far more economical of fuel at lower power settings. Full throttle (regulator) and the shortest cutoff gave the highest thermal efficiency. If a means of steam transport of any kind had to carry its own fuel it needed the economy gains of variable cutoff. A coal-burning stationary engine at a coal mine would not have the same need for fuel economy. This is an article about internal combustion VVT and I don't think you really need to qualify statements like the contentious "Almost all steam engines etc." too much. I suspect the author was not referring to Stephenson's valve gear (or any of the many other "link" motions) but the more rare varities of steam valve gear such as having selectable differently-shaped cam lobes on a shaft (ancestor of Honda VTEC-type arrangements) or the even more rare "oscillating cam" varities (ancestor of BMW's Valvetronic-type systems). I don't get the impression that he or she doesn't like VVT in general? Although I like the overall article generally there are quite a few "debateable" statements scattered throughout it. I seem to have written this in the middle of Andrewa's comments - sorry. Clivedog (talk) 07:23, 1 January 2013 (UTC)

Actually the whole article needs cleanup, particularly to sort out the gossip from the information. Andrewa (talk) 20:05, 26 September 2012 (UTC)

Information out of date?[edit]

Isn't the Fiat group "multiair" (and twinair) system at least partly camless? IE the intake valve, iirc, is entirely electromechanically actuated? (With a conventional exhaust valve) 87.112.90.182 (talk) 22:22, 31 August 2015 (UTC)

  1. ^ Patents Find prior artDiscuss this patentView PDFDownload PDF Publication number US4421074 A Publication type Grant Application number US 06/285,614 → Publication date 20 Dec 1983 ← Note → Filing date 21 Jul 1981 ← Note Priority date 31 Jul 1980 Fee status Lapsed Also published as DE3126620A1, DE3126620C2 Inventors Giampaolo Garcea, Ambrogio Banfi, Michele L. Di Stefano → Original Assignee Alfa Romeo S.P.A. ← Note Export Citation BiBTeX, EndNote, RefMan Patent Citations (5), Referenced by (29), Classifications (5), Legal Events (9) External Links: USPTO, USPTO Assignment, Espacenet (sic)