geoffvalenti Posted June 17, 2004 Share Posted June 17, 2004 Taken from a Newera advert in this weeks autotrader "VVTi models are equipped with variable valve timing, which gives greater urge at higher revs, as the cam lobes are changed to open valves for longer duration, thus improving breathing." I've never found that varying the valve TIMING alters the DURATION one bit, ..................but then, I'm not selling one Link to comment Share on other sites More sharing options...
Barry Posted June 17, 2004 Share Posted June 17, 2004 I would have thought if they were opening further, then they would also be open for longer as the lobe will be incontact with the top of the valve for longer if it moves closer when the VVTi kicks in.? Link to comment Share on other sites More sharing options...
Digsy Posted June 17, 2004 Share Posted June 17, 2004 VVTi engines have a single cam lobe which is swung relative to the cam pulley. The timing alters, but the duration stays the same. VVTLi engines use two physically different cam lobes, which can have different timing and duration, on the same camshaft, and then the variable timing part can swing either lobe relative to the pulley. Therefore both timing and duration can be altered. Note that the timing can be altered infititely between two fixed limits, but the duration / lift is limited to the two different cam profiles and is fixed mechanically. BMW have a production system called "Valvetronic" which can, within reason, give you any cam profile and timing you want. Clearly this guy has either missed out the "L" from VVTLi, or got confused between the two technologies. Link to comment Share on other sites More sharing options...
outatime Posted June 17, 2004 Share Posted June 17, 2004 On the subject of the VVTI Supras, is there any reasoning behind the VVTI system being designed with reduced emissions rather than performance in mind? Link to comment Share on other sites More sharing options...
outatime Posted June 17, 2004 Share Posted June 17, 2004 ... Link to comment Share on other sites More sharing options...
Digsy Posted June 17, 2004 Share Posted June 17, 2004 Originally posted by outatime On the subject of the VVTI Supras, is there any reasoning behind the VVTI system being designed with reduced emissions rather than performance in mind? I think you get a bit of both. The main advantage of variable valve timing is that you effectively have two states of tune for the same engine: one with high midrange torque, and one with high top end power. If you plot these powercurves over each other, they would cross over somewhere just above the middle of the rev range. This is normally where you would switch the timing. Doing it this way makes the switch "transparent" to the driver. i.e. you can't feel it since the torque output at that point in the curve is the same for both timing positions. However, a trick you can play to make the car "feel" more sporty that it realyl is, is to switch at a non-optimal point, so you suddenly get a jump in torque that the driver can get a cheap thrill out of. By not having to have so many inherent disadvantages by trying to make one state of tune do everything, you can do your best to leave the "high power" switch point out of the region that you will be emissions tested in. Link to comment Share on other sites More sharing options...
outatime Posted June 17, 2004 Share Posted June 17, 2004 Thought as much, I was talking to someone about it the other night. They reckoned the VVTi Supras were nothing more than a means of keeping the car on the market for longer in the face of stricter emissions regulations. Link to comment Share on other sites More sharing options...
Ian C Posted June 17, 2004 Share Posted June 17, 2004 That's what I thought. After all, it didn't exactly bestow an 8500rpm rev limit and another 50bhp did it? -Ian Link to comment Share on other sites More sharing options...
geoffvalenti Posted June 17, 2004 Author Share Posted June 17, 2004 Originally posted by Darren Blake Clearly this guy has either missed out the "L" from VVTLi, or got confused between the two technologies. He hasn't missed out the L, its a Supra that he's describing Confused? it sounds like he just doesn't know and is bullsh*tting. I just HATE it when dealers misdescribe their cars or their cars technology. It kind of goes against the speil that they give, that they're in Japan and so know all about the cars and can charge the earth because they allegedly supply the best If they don't understand VVt-i, what else don't they know? Link to comment Share on other sites More sharing options...
Darren Posted June 17, 2004 Share Posted June 17, 2004 Originally posted by Ian C That's what I thought. After all, it didn't exactly bestow an 8500rpm rev limit and another 50bhp did it? -Ian I'm surprised by this comment because at the rolling road session I attended VVTIs were out performing (HP and torque wise) older Supras with the same mods...Just what I saw.... Link to comment Share on other sites More sharing options...
Chris Wilson Posted June 17, 2004 Share Posted June 17, 2004 Originally posted by outatime Thought as much, I was talking to someone about it the other night. They reckoned the VVTi Supras were nothing more than a means of keeping the car on the market for longer in the face of stricter emissions regulations. Thay may well have used VVTi for emissions compliance, but a stock VVTi is also quicker and more responsve, IMO, than a stock earlier model. Link to comment Share on other sites More sharing options...
Darren Posted June 17, 2004 Share Posted June 17, 2004 Originally posted by Chris Wilson Thay may well have used VVTi for emissions compliance, but a stock VVTi is also quicker and more responsve, IMO, than a stock earlier model. :) Link to comment Share on other sites More sharing options...
Tony S Posted June 17, 2004 Share Posted June 17, 2004 Interestingly, Honda, who are the recognised leaders of Variable Valve Timing technology (never had a failure; ever) did not take the approach of a smooth transition on their latest VFR motorcycle, and have now received criticism for the abrupt increase in power as the timing changes, suprising many riders! Also, in top gear, the VVT engine is cycling (no pun) between using advanced valve timing or not, all at legal cruising speeds. probably not so obvious or problem with the weight and momentum of a car, but on a bike, a big issue. I havn't got a VFR by the way (Honda Blackbird + Supra (of course!)) Tony Link to comment Share on other sites More sharing options...
Guest garethbrunt Posted July 1, 2004 Share Posted July 1, 2004 Geoff, I am sorry to hear of your disappointment in our description of the Supra VVTi. It is certainly not our aim to 'convince' people, using deception, into buying a car. We aim to sell good, clean cars only, to people as enthusiastic about cars as ourselves. We aim to provide the most detailed descriptions in the market, so that people such as yourselves can see exactly what you are purchasing. We take 15 or more pictures of the car and describe in detail everything which we know about each vehicle, even offering a copy of the auction sheet for the 'buyer' to view. IMHO these are not the actions of a bulls*itting trader. Newera Imports works hard to build an excellent reputation, we have indirectly supplied alot of Supras into the UK, we were JIC's main supplier until they unfortunatley closed due to personal trouble recently. You have no need to take my word for this, please view attached thread posted today as a typical example of Newera's reputation: http://www.gtr.co.uk/forum/upload/showthread.php?p=207712#post207712 Please also view: http://www.neweraimports.com/stock.htm This shows the quality of supra we aim to provide to Supra enthusiasts. Kind regards. Gareth. Newera Imports. Link to comment Share on other sites More sharing options...
DaveRex Posted July 1, 2004 Share Posted July 1, 2004 er so lnowing didly squat about VVTI is this statement correct ? "VVTi models are equipped with variable valve timing, which gives greater urge at higher revs, as the cam lobes are changed to open valves for longer duration, thus improving breathing." Link to comment Share on other sites More sharing options...
geoffvalenti Posted July 1, 2004 Author Share Posted July 1, 2004 Originally posted by DaveRex er so lnowing didly squat about VVTI is this statement correct ? "VVTi models are equipped with variable valve timing, which gives greater urge at higher revs, as the cam lobes are changed to open valves for longer duration, thus improving breathing." Err............ no its not! VVT-i varies the timing of the intake camshaft, i.e. the moment of valve opening or closing, relative to the crankshaft and exhaust camshaft. Being that the lobes are fixed it cannot alter the duration i.e. the length of time the valve stays open. VVTL-i alters both the timing and (one of two profiles of) duration but is NOT fitted to Supras. Link to comment Share on other sites More sharing options...
geoffvalenti Posted July 1, 2004 Author Share Posted July 1, 2004 Originally posted by garethbrunt Geoff, I am sorry to hear of your disappointment in our description of the Supra VVTi. It is certainly not our aim to 'convince' people, using deception, into buying a car. I don't think that you're deliberately trying to deceive, you're just not quite as knowledgeable as you like to make out Originally posted by garethbrunt We aim to sell good, clean cars only, to people as enthusiastic about cars as ourselves. From what I've seen of your cars this is true Originally posted by garethbrunt We aim to provide the most detailed descriptions in the market, so that people such as yourselves can see exactly what you are purchasing. I'll not argue with that, but when some of the information given is incorrect what can the buyers really rely on. A solid belief that descriptions are fact, rather than fantasy, is all that a buyer, who is about to pay up front for a car, and not see it for a few weeks, has to cling on to. Originally posted by garethbrunt We take 15 or more pictures of the car and describe in detail everything which we know about each vehicle, . Unfortunately, in this case, you also managed to describe in detail something about which you didn't know Originally posted by garethbrunt IMHO these are not the actions of a bulls*itting trader.. Sadly, in this instance, IMHO they are exactly that. Gareth, I'm not trying to have a go at Newera, I do think that they are one of the best dealers around, it just annoys me intensely when sellers, especially dealers, spout forth garbage about the vehicle that they are selling. Its so much better to say nothing than a load of misinformation. God knows, there's little enough published about VVT-i Supras as it is, without a load of incorrect info from an alleged knowledgeable source. Unfortunately Newera were in the wrong place at the wrong time when I was reading the ads, it could so easily been any of the others Link to comment Share on other sites More sharing options...
Aerotop Dave Posted July 1, 2004 Share Posted July 1, 2004 IMHO, the reaction is a bit over the top. A better course of action might have been to contact Newera to give them the benefit of your knowledge...? Just a thought. Link to comment Share on other sites More sharing options...
Supragal Posted July 1, 2004 Share Posted July 1, 2004 maybe someone should write this up for the technical section? Link to comment Share on other sites More sharing options...
Digsy Posted July 1, 2004 Share Posted July 1, 2004 Would now be a good time to mention the Rover system that gets variable cam duration from only one cam lobe? I can write up a bit on variable valvetrain, if you like. It's one of those interesting technologies when there are loads of ways to crack the same nut. Link to comment Share on other sites More sharing options...
Steve Cargill Posted July 1, 2004 Share Posted July 1, 2004 Originally posted by Darren Blake Would now be a good time to mention the Rover system that gets variable cam duration from only one cam lobe? I can write up a bit on variable valvetrain, if you like. It's one of those interesting technologies when there are loads of ways to crack the same nut. Not heard of that. Does it use non linear rotation of the cams to do this? Link to comment Share on other sites More sharing options...
Digsy Posted July 1, 2004 Share Posted July 1, 2004 Yeah. Its a really odd system. Basically it allows the camshaft to "dwell" slightly at the maximum opening point (MOP) by slowing the speed of rotation as the cam rotates. The cam drive is still at half engine speed, but the lobes slow down at the MOP point, and then speed up again to "catch up" with the drive. I just got about 2 paragraphs into trying to describe how it works but realised that (a) I don't know all the details and (b) the verbal description of what I do know wasn't making any sense. What I do have is a friendly Manager at work who used to work for Rover and has one of the phaser units on his desk. I'll see if he has any technical articles on it that I can scan in. Link to comment Share on other sites More sharing options...
Guest garethbrunt Posted July 2, 2004 Share Posted July 2, 2004 Ok guys, I feel 200sx boy had a great idea. To cure the Problem perhaps you should have spoke to us directly, that way we would have ammended our website with the minimum fuss. Now that you have brought it to our attention, i shall ensure the website is ammended. Regards, Gareth. Link to comment Share on other sites More sharing options...
Paul -C- Posted July 2, 2004 Share Posted July 2, 2004 Originally posted by garethbrunt To cure the Problem perhaps you should have spoke to us directly, that way we would have ammended our website with the minimum fuss. At least you got some free publicity this way Link to comment Share on other sites More sharing options...
DaveRex Posted July 2, 2004 Share Posted July 2, 2004 I think Newera have a good enough rep on here from what I have read previously Personally I was interested how the VVti works so cheers for the info Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now