WHY VTEC IS WAY BETTER THAN VVTI

[Qwooootz]

im real interested in the techinical side of things can any1 help me out or lead me to a similar thread.. thankz

[XXpl0Sive]

The Toyota engines seem to run slightly more aggressive cams than the Honda's, and so at lower revs they seem to (anecdotal evidence here ...) be a bit more pleasant to drive and make a little more power. There's also less of a transition when the cam shifting systems operate, but this is obvious due to the Honda system swapping over to a much more 'racy' cam profile.

Pro's - Both systems allow you to have an engine that's quite a lot more powerful and yet still driveable than a 'conventional' engine would otherwise possibly be. The V-TEC is the obvious choice for outright power, and the Honda's certainly seem to rev a heck of a lot more than the Toyota's do. (The S2000 red lines at a stratospheric 9,000rpm - stock!)

Con's - You are pretty much stuck with limited modifications to the engine, eg, air filters, extractors, etc, to get more power. The reason for this is the very system that give the engine all that extra power - The cams & VVT/V-TEC. You can of course use larger cams to get more power, but this defeats the purpose of having the VVT/V-TEC in the first place. You'll most likely lose power at low revs, and not gain a great deal at high revs. (The VVT will gain proportionally more than the V-TEC, however, as the V-TEC head is optimised - well, compromised - for the 'big' cam & 'small' cam and so using a larger cam may not help much at all)

So, if you want an engine with power like a racing engine, then you're better off building a straight race engine right from the start. Or maybe a turbo engine ...

The other concern I have is the longevity of these sorts of engines. I believe that the VVT system would be largely trouble free for the life of the engine provided that you keep the oil clean and change it regularly. Even more so with the V-TEC, as with all it's little bits & pieces in close formation in the head I'd hate to think what would happen if some of those little locking pins didn't engage properly at 6000rpm+. All that being said though, I have it on reliable advice that Honda have never had a warrantee claim for any V-TEC engine in the area of the head and/or valve gear. Quite impressive.

I think that perhaps the best long term solution to getting large amounts of power from a relatively small engine is still by using a turbo, but if you like to hear the engine scream at high revs then one of these two systems is the way to go.

From http://www.billzilla.org/vvtvtec.htm

[SIKCVC]

uuuummmm last time I checked VVTi is Variable Valve Timing, not Varable Cam lobe possitioning.

I'm pretty sure I've read a few times, That VVTi meirly Shifts the Cam shafts into a different timing possition (ie advance the timing) so fuel is injected earlier in the revolution.

I mean the name says it all doesn't it... VVTi stands for Variable Valve Timing (intelgence? Injection? something along those lines) the key word there Timing not duration, not Lift.

But I'm only going on what I've read a few times on MCCR I'll try and find the link to the site that explains all the forms of change in Valve timing etc, I could be mistaking it for Vanos (BMW) or nissans version of VVT. But I will find out.

[XXpl0Sive]

Yeh see if you can find more information and post it up. Find out how Nissans' VVT works with the turbo. VVTi-L is the Lift version (simlar to VTEC) that Toyota devised.

[SIKCVC]

OOOHHHH thats what they have... see i must have been thinking of VVTi which I was sure was only timing adjustment on the fly, so they do have a VTec spin off... Kool.

[XXpl0Sive]

Yep it's in the newer Celica's

[SIKCVC]

heres the Link... [post edited after reading the page again :P]

http://www.billzilla.org/vvtvtec.htm

[SIKCVC]

and after reading i take it its the same link you quoted :P

[pornstar]

Xxplosive, where did u get all those misconceptions from man?

I dont see how having a more agressive cam is going to defeat the purpose of VTEC?

I dont see how having VTEC or not limits power either, if anything it helps make more driveaboility for big hp engines using high revs.

Overall man, what u just posted is so mis-informed man.

[SIKCVC]

those Neo Sr 1.6 VVL engines make the same power as a JDM B16a :P there was one for sale recently.

[crx2gen]

read this, should give you a pretty good idea.

http://autozine.kyul.net/technical_s...dex.htm#Engine

[wynode]

Overall man, what u just posted is so mis-informed man.

I agree.

Not only is VTEC spelt wrong but it overlooks the fact that VTEC/VVTL-i allow you to run a lumpy cam on the street without sacrificing a smooth idle and low RPM pulling power.

As for Nissan, the SR20VE is the only engine (AFAIK) which has variable valve lift and was found in the primeras in Japan. The SR20DETs found in the 180sx etc only have variable timing and I belive thats only on the intake (or was it exhaust) cam.

As for the title, you cannot compare VVT-i with VTEC. The proper comparison is VVTL-i with i-VTEC, where both allow continously variable valve timing.

I posted a link up in regards to the SR20VE someone around here so search for it if you wanna learn more!

Ok now lets discuss VVTL-i vs VTEC/i-VTEC!