V-tec vz. VVT- I (and any other form)

[TRD Xiao89]

before you tell me to read the v-tec thread i already did, but didnt get the info i wanted. Please no flaming and no stupid answers like "v-tec owns all". I want informative comparisons. thanks ^___^

so the questoin is what is the better of the 2 variable timinng systems.

[Moppie]

VTEC, and iVTEC.

Honda has been doing it for 15 years on road cars, and nearly 20 years on production engines (they started with bike engines).
And for the last 10 years everysingle mainstream model has had VTEC, and for the last 4 years, every single passanger model has had it.

Toyota have only had VVTi-l in a mainstream production car for only 4 years, and in limited production Japanese market only cars for about 3-4 years before that.

Give Toyota another 3-4 years and they should have VVTi-L at a similar level to Honda's iVTEC.

[TRD Xiao89]

but thats just the point. toyota has had plenty of years to study the v-tec. dont you think that its variable timing would be better? if not explain plz. haha i dont just wana know that v-tec is better, but why. thanks!

[Moppie]

Prehaps you need to read the thread above again.

Then get your terminology right, its VTEC not v-tec.

There is also a differnce between just variable valve timeing, and variable valve time and adjustable lift.
Toyota have been doing Variable valve timeing since the early 90s (about 92 I think) and are very, very good at it. However its not common technology, and every mainstream manufactor now use it, often accross thier entire model range.

Adding variable lift into the system is much much harder, as you now also have to design a cylinder head, fuel system and ignition system capable of providing air, fuel and spark accross a very broud power band with very differnt conditions and requirments at high and low rpm.

Designing the mechanical parts is easy, the know how has been around for as long as the camshaft. Its making them work as a complete system in an engine that is hard, and its something that Honda with their experiance in F1 and 20 years of building production engines with VTEC are very good at.


Now understand that there is a differnce between being able to study something and having the time and resources to develop it.
Im sure Toyota went out and bought a new SiR CRX or Civic when it first went on sale in Japan, and then stripped the engine down to see how it worked. But they would still have to figure out how the ECU was designed, and work out how to replicate the technology in a way that was compatable with thier own engines, and then they would have to design a cylinder head and block combination that suit the requirments of a variable lift cam.
This would take time and money, and the people in R&D would have to justify that time and money to the people in charge of Toyota. And they would have to weigh up the demands of developing a system like Hondas VTEC with all the other R&D requirements of a world leading manufactor.


And of course if you want final proof of what is better take a new RSX Type S or Integra Type R and put it up against a new Celica and tell me which is not only faster, but which enigne has the smoother power curve, produces more hp and torque with less emissions and dosn't have a noticable change over point that the engine drops in and out of between gears.
Even the previous generation Integra GSR/VTi-R has a better engine than the one in the new Celica, and its little changed from the first mass production VTEC engine, the B16a from 1989.

[Reed]

i have had a 2000 corolla with vvt-i and now i own an mr-2 spyder with the 1zz that has vvtL-i and i have noticed absolutely no changeover point whatsoever in either (and thats under VERY spirited driving). i have never driven a honda so i cant speak on the vtec.

also it is important to look at what the engines purpose will be. the 1zz in my car gets 32-35 mpg and is rated at 138 hp. i think (am not sure) that the the honda gets worse gas mileage because it's vtec is designed for higher hp.

we all know that toyota is going the less awesome route of good mpg vs hp

[Moppie]

The engine in the MRS and the Corolla are the same engine, they only adjust the cam timeing, not the valve lift and duration.
They are both VVTi engines.
So far the Celica, TS Corolla and Japanese spec previous generation MR2 and Altezza RS200 are the only cars to get VVTi-L engines, with varaible lift and duration.

In an enigne with variable cam timing you should not notice any change over point as the cam timing is continuosly adjusted as the engine changes rpm.
Note: some older engines with variable cam timeing simply used to stages, and so minor change in exhaust and intake pitch could often be heard at changed over. e.g the 20valve version of the Toyota 4age.

[Kven]

i think toyota is doing a good job. doesnt the 1zzfe(i think thats the right code) celica engine make about 170-180hp from 1.8l using VVTi-L(or was it just VVL)? toyota has had variable cam timing for few years, but started variable lift a few years ago, but honda has had variable lift for awhile; and just started doing variable timing(i).

[Kven]

Originally Posted by Reed

i have had a 2000 corolla with vvt-i and now i own an mr-2 spyder with the 1zz that has vvtL-i and i have noticed absolutely no changeover point whatsoever in either (and thats under VERY spirited driving). i have never driven a honda so i cant speak on the vtec.

also it is important to look at what the engines purpose will be. the 1zz in my car gets 32-35 mpg and is rated at 138 hp. i think (am not sure) that the the honda gets worse gas mileage because it's vtec is designed for higher hp.

we all know that toyota is going the less awesome route of good mpg vs hp

how big is the motor? and what valvetrain configuration does it have? the honda's best econo/horsepower engine was the obd2 jdm d15b; SOHC and 3-Stage VTEC; ~50mpg(highway im guessing) and 130hp.

if you dont notice the change over point then they did a good job selecting a crossover point that will create a smooth power increase or the high-rpm cams suck.