[HIBBoyScott]

Originally posted by IS300GTE:
what i found wrong with that paragraph is the first statement, "variable valve timing isn't beneficial to performance at all...." then the poster edited some stuff out and put that last part of his statement. the quotes start at the very first post, and don't unquote, until the last word of the post, so i am taking it that the same person said all of the same stuff.

they are right when they say you could use one cam to achieve the same peak hp that a variable valve system does, but they are wrong when they say it doesn't affect performance at all. - that's how i interpreted it, and responded based on that, if i misinterpreted it, my appologies.

No need for apologies of any kind, I'm just tossing in my 2 cents on how I interpreted the post.

I could be the one misinterpreting the post.

 

[sigss]

For every rpm, there is an optimum time and duration of valve opening/closing. VTEC is just one way of doing it but it only has two or three variations. VVTi or VAnos2 (BMW) are infinitely variable. For the ultimate in engine tech, check out Advanced Engine Technology by Heinz Heisler which goes into all the details about the advantages/disadvantages of all types of engine mods (variable timing, induction, turbos, supercharging, etc).

 

[JW]

The first line: "Variable timing/lift isn't beneficial to performance at all..." was actually the subject header and when you clicked to see the message, the statement continued by saying: "....At least, not in the sense of peak power/torque production. What it is is a way to make more radical timing/lift profiles practical. (rest of stuff deleted for sake of expediency)."

Sorry for the confusion...and this statement came from a very knowledgable person, and nothing was edited out. I have the original html if anyone cares to see it.


[This message has been edited by JW (edited November 14, 2000).]

 

[Hyper-X]

Man, this is such an old post... but someone shot me a link to this thread about this so I might as well post something.

From what I understand regarding the previous posts, nobody is really questioning how VVT-i and VTEC works, so far there's been a lot of good explanations of both...

But the real question is which is better, if I'm not mistaken.

To take this thread into a more non-technical direction, here are my experiences in very basic and crude terms.

The VVT-i system is something I wanted to play with a long time ago. When I messed with racing cams on my previous cars, I had to sacrifice some power from the low rpms to gain more at higher rpms. All those who changed out their stock cams to a racey cam would know this. An adjustable cam sprocket became very useful where I could tune and advance/retard to my liking but I often wondered how a fully automatic-adjusting cam gear would work on-the-fly. Back then, there were those cam sprockets that used centrifugal weights on springs, kind of like how a distributor advance mechanism works. This altered the cam "phasing" based on rpms. More advancing gained more power down low and retarding allowed for shifting the power peak upwards towards higher rpms. The VVT-i system is far more advanced but accomplished the same basic task to a much finer degree.

The result would be a much more smooth driveability and better overall street driving experience, which is why you can't "feel" it working. This is an example of linear power delivery.

VTEC on the other hand is a more radical experience having a clear "kick" when you rev it up. It's like having "turbo boost" on a normally aspirated car. I guess you can think of it like having a normal camshaft for street driving/fuel mileage AND having a race camshaft when you need it at the same time. With the help of modern technology, the engine is tuned differently for the experience on the low and high cams, and it would appear that the potential for making a lot of big power on top goes to the VTEC equipped car.

VTEC/VVTL-i having variable lift (pushing the valves open more) allows the car to breathe better and since an engine is basically a huge air pump... the more air that can be introduced/passed through, the more power will result from it. Normal VVT-i doesn't accomplish this effectively as the previously mentioned VTEC/VVTL-i.

So which is better? It depends on what you value more. A smooth power delivery that makes for comfortable street driving, or an experience involving a more radical driving experience with a kick... definitely not for grandma.

 

[crazeazn]

I've got a question.
Let me start off by saying, I'm not a car genius or physics major or blah blah.
You guys say "VVT-i is a hell of a lot more advanced than VTEC"
ok... so... <P>Nissan Maxima
3.0L V6 engine produces 222hp<P>Lexus IS300
3.0L I6 VVT-i engine produces 215hp<P>

granted that VQ makes 222hp u have to also look @ the torque numbers dont you? the is300 has a higher torque number than the nissans.

 

[1SICKLEX]

The I-6 in the GS 300 makes 225hp. Same engine. THat is 3 more hp.

Ball is in your court. :chill:

And from Honda experts, I thought V-TEC kicked in and was some sort of factory turbo. :lol: :chill:

 

[1SICKLEX]

at least the schools where kids can actually read and aren't killing each other.
BTW, my grandfather created the first artificial snow crystal, and he was Japanese

Was that necessary. And we can really apply the artificial snow crystal to???????

 

[Link]

vtec

vtec=super fasssssssssssssssssssssssttt turbo/supercharger/nawzzzzzz

 

[whiteISmine]

Toyota engines are weaker than Honda's, but toyota is more comfortable. IMO Honda Vtec is better in performance, thx to the high RPM. My IS does not allow me to hit the redline, but my wife's Acura lets me hit red whenever I want to (all the way up to 9000rpm) and the car is still super reliable. I love Vtec. I used to hit Vtec range everyday...

There are Vtec and i-Vtec.. Also I heard there are three different stages of Vtec.. the one we generally see on Civics are Stage I Vtec (I might be wrong).

 

[vinceprince]

did someone say 4 cylinder altezza?? :lol: :lol:

its a 2 liter inline 6,, :shame:

 

[vinceprince]

if i can add to this whole subject,, you have 3 big players in the variable valve game, honda vtec, toyota vvti and BMW vanos,,
im pretty sure that hondas system shifts cam trees mecanically and the bmw and toyota uses hydrolic methods, please correct me if im wrong,
basically these technologies make use of two cam trees, one for normal dirving, and another for agressive, leaving the valves open longer to let more air and gas mixture in, \
i heard theyre working a putting a third tree, for even more range