Bean

iTrader: (1)

And valvematic is even better

gsrthomas

iTrader: (1)

I just remember that when I had my Acura Integra GSR. Toyota later came with their Celica GTS to compete with the GSR.

My friend had a GSR we raced a few times and I beat him every time even though the Celica GTS was "had" 10 more HP than my Acura.

You can really fill the pull on the Acura above 6k RPM. It was a fun little car to drive. I miss it.

ldc

Both vvti and vtec are similar but with vtec you get that noticable "switch-over" point that kicks in to takes things to a new level. The point is about the 5500rpms. Below this point you got a normal car. For fuel efficiency vvti is better. But then they intro'd i-vtec which is far supperior than vtec. That switch-over point is now a matter of timing rather than revs. I would prefer the Lexus to have vtec/i-vtec to be honest.

TRDFantasy

For the most part I agree, but right now we have Dual VVT-i on the market as well as VVT-iE as well as Valvematic on the market in Japan.

VVTL-i is being phased out by Toyota in favour of Valvematic.

Dual VVT-i is almost equal to i-VTEC because i-VTEC cam phasing only works on the intake cams. I-VTEC continously adjusts cam phasing in the intake side only. Dual VVT-i continously adjusts cam phasing on both intake and exhaust cams.

VVTL-i had some issues since it was Toyota's first attempt at a valve lift system.

Most i-VTEC implementations only adjust valve lift and duration on the intake side. On engines like the K20A2, valve lift and duration is adjusted on both intake and exhaust cams.

Then we also have VVT-iE which arguably is better than i-VTEC. VVT-iE is combined with Dual VVT-i so you have continous cam phasing on both intake and exhaust, except the intake side is completely electronically controlled instead of hydraulically. VVT-iE is the first system of it's kind in the world, like VTEC was the first system of it's kind in the 80s. VVT-iE allows for more precise cam phasing as well as greater adjustability and is more reliable than hydraulic cam phasing. VVT-iE is a big step towards fully electric variable valve timing.

Then there is the next generation of VVT systems from Honda and Toyota: Valvematic and A-VTEC.

Valvematic allows for fully continuous electronic valve lift and duration control on the intake side. It's combined with Dual VVT-i. Honda's A-VTEC simiarly offers fully continuous valve lift and duration control on the intake side combined with cam phasing. Honda has not been clear if the cam phasing will be intake-only, or both intake and exhaust. If Honda puts cam phasing on both intake and exhaust for A-VTEC engines then technically it will be equal to Toyota's Valvematic. Of course, Toyota could also add VVT-iE to Valvematic which would make variable valve timing on the intake side as well as variable valve lift on the intake side fully electronic. You'd also still have hydraulic variable valve timing on the exhaust side.

Valvematic is already out and Toyota has mentioned it will be applied to all of its engines by 2010, while A-VTEC won't be out until 2009 at the earliest.

CK6Speed

iTrader: (1)

I think that will depend on what type of cars Honda has and puts A-VTEC on. Similarly how the old VTEC was tuned and implemented differently from say the Accord and Civic compared to the DOHC NSX, Integra and S2000 in which VTEC was on the intake and exhaust. I would say if Honda/Acura actually puts out a performance oriented sports car like the NSX, old Integra/RSX, or S2000 then they will have a dual A-VTEC system. If they use it just for fuel economy like how it is tuned on the Civic then probably not.

TRDFantasy

What do you mean 'dual A-VTEC' system? A-VTEC will have continuous variable valve timing on the intake side only. The 'Advanced' part of A-VTEC is exactly that; the continuous control of valve lift and duration. If you meant 'dual A-VTEC' as in having continuous cam phasing on both intake and exhaust cams, it's possible. Honda could very well implement 'dual VTEC' (continuous cam phasing on both intake and exhaust cams) but the continuous valve lift and duration will be on the intake side only.

It's interesting how Honda, once considered a leader in variable valve timing technology, is going to be quite late to market with its continuous valve lift system. BMW has had their Valvetronic system for years, but it's a cumbersome mechanical system that has a lot of limitations. Nissan last year came out with VVEL as did Toyota with Valvematic. Honda will be quite late in 2009 with their system, assuming there are no delays.

CK6Speed

iTrader: (1)

What I'm trying to say is A-VTEC right now may only control lift and duration on the intake side for the cars it is intended to go in right now. Like with the old VTEC where it controlled lift and duration on the intake for some cars, but on other cars controlled lift and duration for both intake and exhaust valves, I can see Honda doing the same thing in for example a new S2000 or NSX. It is not a limitation of the actual system, just how it is being used. I would bet that any VTEC system uses in a car like the new NSX or new S2000 would hav full control of both intake and exhausts just like it did in the past. I'm pretty sure they wouldn't go backwards on cars like that. The original VTEC already controlled lift and duration for both intake and exhausts so its not like Honda can't do it. That is all I was saying. But, it is a moot point unless Honda actually comes out with performance cars again anyway.

TRDFantasy

Yes, I will agree that *technically* it should be possible for A-VTEC to offer valve lift and duration on both intake and exhaust, as VTEC systems have done in the past. Whether Honda will actually do it is another question. Even less likely is to see continuous cam phasing on both intake and exhaust cams.

Honda over the years has shown to be stubborn and arrogant. Over the past 20 years Honda has squandered their leadership in engine expertise, specifically in variable valve timing expertise. Toyota (and even Nissan) has arguably not just caught up, but surpassed Honda.

For example, Honda has been very stubborn with offering VTEC on the intake cams only and building primarily SOHC engines for the most part. Looking over the VTEC engines Honda has offered over the past 20 years, the vast majority of them have been SOHC engines with VTEC on the intake side only. Using a SOHC design limits how sophisticated and how flexible a variable valve timing system can be.

I don't expect Honda to change much with A-VTEC. They likely won't take a step backwards, but in (now) stubborn Honda tradition they will take a step sideways.