does anyone know what the differences are between the mivec heads and the heads on a 2003 3.5l? i haven't seen one and i am guessing that to start with the mivec heads are a twin cam setup. also how does the the variable timing work on the mivec heads?

Yup, it's DOHC alright. Mivec on the 3.5, 3.0 and 2.0 is based on the cam lobe having two lobes. It hits a certain RPM and switches lobes which has either higher lift, longer duration, different timing or a combination of all three. I'd imagine that the initial lobe will be a conservative grind but designed to reach optimal power at the change over then the second lobe kicks in and away it goes until it reaches peak power.

Wouldn't the mivec heads work on with 2 cams 1 exhaust and 1 intake and then both of them being able to be adjusted with a hydraulic or electronic stepper motor, sort of similar to the falcon heads, or are they linked through a gear set and the timing adjustment affects both of them by the same amount?

The cams physically shift to bring the second set of lobes into play. It would be more beneficial overall power wise than what the Ford does. Sounds like it's like Toyota's VVTi. One set of lobes with varying timing. Increased lift is what the engine wants at high revs. Ford's and Toyota's system can't provide this.

Ford's and Toyota's system can't provide this.

I wuz sure that Toyota had VVTiL (L = Lift) on its performance cars, namely the celica.

celica engine is in the corolla sportivo

wikid little car, hammers with its 140kws !!!

yeah i'm sure some higher model toyota engines have variable lift... i'm sure i've heard of VVTLi.


Tim

switches lobes which has either higher lift, longer duration, different timing or a combination of all three.
I seem to remember a post a while ago with a link to a pdf document explainin MIVEC. It isn't to do with a different lobe but the way the rocker behaves at certain revs. It has a hydraulic & spring arrangement inside the lobe side that under normal speeds behaves normally but as the speeds increase the incompressability and viscosity of the hydraulic fluid retards the springs movment therefore leaving the valves open for longer.

Anyway it is something like that. But what does it mean, read more about how an engine with advanced timing works, there was an article linked to back pressure and why it is good, this explains all of these areas pretty well.

What does it mean for an engine, variable simulatred-grinds and therefore 30-40 kW of power over any normal design. Does it come in 3.5 I am not sure, will it come in 3.5 I hope that the jap engine maker will be asked to supply 3.5L to the Aussie Magna and they will make them MIVEC.

But more complex means less Aussie tradies can fix them.

celica engine is in the corolla sportivo

wikid little car, hammers with its 140kws !!!

Its funny, they have the same 1.8litre engine yet the Celica is faster, the rolla does 0-100 in 8.2 sec (manual) lol

I wuz sure that Toyota had VVTiL (L = Lift) on its performance cars, namely the celica.
I haven't heard of it yet but I was talking about VVTi. Other manufacturers like BMW, (Doube VANOS or whatever it is) and Ferrari have a cam profile that varies accross the length of the lobe. Basically means they can vary the timing and lift while keeping things optimised for the entire rev range.

The cams physically shift to bring the second set of lobes into play. It would be more beneficial overall power wise than what the Ford does. Sounds like it's like Toyota's VVTi. One set of lobes with varying timing. Increased lift is what the engine wants at high revs. Ford's and Toyota's system can't provide this.

valve overlap is very important as well at higher revs, the toyota wastes having DOHC bec it only allows variable timing, its almost a waste of time. the new camry has an ordinary redline and a little more power down low than the old one (helped by an extra 200cc as well). compare that to a real system of increased lift and duration like honda VTEC that screams past 8'000 on the wild grind and u get the difference.

Its funny, they have the same 1.8litre engine yet the Celica is faster, the rolla does 0-100 in 8.2 sec (manual) lol
They, share the same motor, but the Celica is 148kw? from memory? Slightly down tuned in the Corolla.

these engines can also have a Yamaha head, i think thats the 148 kw, it also goes in the best Lotus that weighs about 900kg and does 0-100 in about 5 secs, costs over 100'000$

Celica 140kW
Corolla 141kW....thanks to simpler exhaust plumbing :D