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Location:
Melbourne
Registered:
November 2004
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VVTi? need info
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Fri, 19 November 2004 00:49
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Im not a tech head, but what is VVTi? (i know what it stands for)
but what are the benefits/advantages/disavantages of this technology. Any info like history, which other car manufacturers has it, etc
Also is there a huge difference between VTEC and VVTi (VVTi better?)
Also i will appreciate if there are any weblinks provided.
Sorry, im still a newbie with these topics.
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Location:
Cabramatta, NSW
Registered:
May 2002
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Location:
Campbelltown
Registered:
November 2003
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Re: VVTi? need info
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Fri, 19 November 2004 02:07
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VTEC is the best no questions asked, just gotta look at the s2000. VVTi Variable vavle timing not sure about i prob injection
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Location:
sydney,nsw.oz.
Registered:
July 2002
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Re: VVTi? need info
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Fri, 19 November 2004 02:15
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VVTi is Toyota's name for "Variable Valve Timing with Intelligence"
Only has Varaible Timing on the Intake Cam. Gives the motor more power/torque at certain RPMs.
Toyota also has VVTLi which is "Variable Valve Timing and Lift with Intelligence" which has variable lift and timing.
Honda's VTEC is similar in that they have a poverty version of VTEC as in the Civic and the High Power VTEC like in S2000,NSX and Integra Type R.
In fact even Holden has some sort of Variable Valve timing with their new V6.
But do what Nark said
This is a great link.
http://www.google.com/
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Location:
macca fields
Registered:
October 2004
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Re: VVTi? need info
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Fri, 19 November 2004 08:46
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vvti is only cam timing on inlet, where as vvtLi has cam timing and lift, lift being a "high lift" cam, feels like its a totally different car after about 6300rpm but you dont really feel the normal vvti "kick in" as the intellegent adjusts itself throttle postion, engine temp, and load
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Location:
Brisbane / Gold Coast
Registered:
May 2002
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Location:
Sydney
Registered:
September 2004
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Re: VVTi? need info
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Sat, 20 November 2004 08:01
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Honda actually came up with VVT(i) not Toyota. You'll see CR-V's etc. with VVTi on the side as well.
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Location:
Melbourne
Registered:
March 2004
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Re: VVTi? need info
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Sat, 20 November 2004 12:57
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I thought that VTEC had an extra set of intake/ exhaust ports that open up when VTEC kicks in, as opposed to VVTi which has the regular number of ports but variable timing. I remember reading about honda motors that had both VTEC and VVT... or maybe I was trippin out? 
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Location:
Cabramatta, NSW
Registered:
May 2002
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Re: VVTi? need info
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Sat, 20 November 2004 22:39
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| thu187 wrote on Sat, 20 November 2004 19:01 |
Honda actually came up with VVT(i) not Toyota. You'll see CR-V's etc. with VVTi on the side as well.
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You sure they don't say iVTEC?
iVTEC is the second gen VTEC AFAIK.
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Location:
Melbourne
Registered:
November 2003
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Re: VVTi? need info
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Sun, 21 November 2004 02:39
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VVT and VVTi both work in the same way. They adjust your cam timing dynamically, just as if you where using adjustable came gears. Obviously, the VVT and VVTi adjust the timing on the fly while the engine is running and not while the engine is off. It does not, however, adjust the cam profile. The different between VVT and VVTi is that VVT has two different cam timings to chose from that switch over at a pre determined RPM. VVTi has a few more, and intelligently switches them based on all sorts of factors.
VTEC works by having not two cam lobes per cylinder, but three. Two of these lobes (the low RPM ones) sit on a rocker that operates the valve. The third lobe sits on a free floating rocker in between the other two lobes. At a certain RPM, a small pin slides from the high RPM rockers to the low RPM rocker while the valve is closed, locking them together as one. The high RPM lobe then lifts the whole rocker (as it's one piece now) off the two low RPM lobes to open the valves for longer and with higher lift. This gives you all the advantages of a large cam profile engine, without the lack of low end performance.
Linkage:
http://www.billzilla.org/vvtvtec.htm
smashed_wombat, what you are talking about is more akin to Toyota's TVIS. At low RPM, a butterfly closes off one of the two ports to increase torque. Above about 4000rpm (is that right guys?) the butterfly opens to improve flow and let the engine rev out. Honda's new economy VTEC works in a similar way. However rather than having a butterfly it uses it's cam profile adjusting technology to stop one of the valves from lifting much at all at low RPM in a similar fashion to what I described above. Both of these only operate on the intake port, not the exhaust port.
There is also a new version of sports VTEC that has 3 stages or something silly like that. While I know it's similar to the other VTEC operation I'm not sure exactly how it works. I think it's kinda a highbred between the old sports VTEC, and the new economy VTEC.
Thank you, that is all. Sorry for the long post.
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Location:
Melbourne
Registered:
March 2004
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Re: VVTi? need info
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Sun, 21 November 2004 02:56
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yeah, i meant to say lobes, not ports.  I had a VTEC B16 head in the garage a while ago (was gonna do a B20 hybrid), should've taken pictures to compare it to the TVIS one down there atm!
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Location:
Melbourne
Registered:
November 2004
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Re: VVTi? need info
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Tue, 23 November 2004 05:37
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Thanks guys for all the info and links provided! much appreciated!
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