Talk:Variable valve timing
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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)
[edit] Nissan VVT
- 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 Japans 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)
[edit] Revisions to the History section
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)
[edit] Honda exaggerations
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)
