Engine A really newbie question about the whole VVTi thing...

A really newbie question about the whole VVTi thing...

What the hell is it!?

lol ok that sounds stupid. But really, I've read up some docs on VVTi technology and stuff, but judging from what I've read online, it seems as though VVTi works all the time, not just in high RPMs like VTEC does. I'm being told that VVTL-i is similar to VTEC, but not VVTi. Am I wrong? If I'm right, then really, what IS VVTi?

Thanks for answering this by the way

You are right

i think it might be a good idea to put an explanation of vvti as a sticky in this part of the board. i see this ? getting asked alot.

in the new super street(2005 buyers guide) it tells about it, and VVTL-i, you should go check it out

VVT-i varies valve timing by shifting the duration which the valves open in relation to the pistons position to TDC.

VVTL-i Does the same thing except is also has a High Lift Profile Cam Lobe which Opens the valve more (away from the valve seat). The engine is either on the regular cam or the high lift cam.

VTEC is just the L part of VVTL-i, that is it only has the ability to change valve lift height when it follows the high lift cam lobe.

i-VTEC incorporates VVTL-i with Swirl Induction on the intake charge.

ah....

Yeah....VVT-i can NOT change the actual length of time the valve is open, only at what point it opens. How LONG the valve stays open depends on the cam lobes - and for VVT-i, that is fixed and never changes. It can alter intake valve timing from as low as 0º for cold running and deceleration to as much as 60º and any point in between the two. Just whatever is ideal for power, fuel economy, emissions, etc. It's not really anything like VTEC.

VVTL-i does exactly the same thing and adds a high lift cam profile (higher lift and duration for high rpms).

VTEC is like VVTL-i without the VVT-i. It's just lift. Low profile for conservative driving and a high lift profile for high rpms. It's one of those "either it's on or it's off" sort of deals. VVT-i is continuously operating - the engine would not run at all without it.

Late,
Trav

Do Search Man...it In Here Some Where.

is there an HP difference between VVTL-i and VVT-i?



|-Goku-|

hmmm.....so if all lift is, is cam duration, why dont they make cams that will go in the S that work as lift? or does ecu programing have something to do with that

vvt-i

In ordinary engines the relationship between inlet and exhaust valve opening and closing is non-adjustable because it is dependent upon their direct connection to the camshafts.

Engine designers have known for a long time that they could get better performance out of an engine under certain circumstances by allowing the intake valve to open slightly before the exhaust valve closes. This increases the time for the fuel/air mixture to enter the cylinder during the intake stroke. In this condition the exhaust and intake valves are open at the same time; this is called 'valve overlap'. In conventional engines 'valve overlap' timing is fixed.

Fixed valve overlap allows the engine to perform well within a certain rev range, however there are three main undesirable side effects.

Fuel is wasted – the fuel/air mixture is not always efficiently burned and this causes unburnt fuel to pass through the engine.


Higher levels of undesirable exhaust emissions are produced.


Power output potential is not fully realised.
Variable valve timing allows the relationship between the separate inlet and exhaust camshafts to vary the valve timing overlap. In doing so it overcomes the side effects described above by using a computer to continuously vary the intake valve timing and overlap. The valve timing and overlap are adjusted through a series of simple mechanisms to ensure the optimum conditions apply across all the working rev range. The advantages are lower fuel consumption, lower exhaust emissions and higher power output. Because the system is continuously variable, an 'i' for 'intelligent' has been added to the acronym



Explained simply, the valve timing is both intelligent and continuously variable over a 43 degree range. Under light throttle application and low load conditions, the timing is advanced which minimizes valve overlap - the period of time when both the intake and exhaust valves are open. Tromp the pedal and demand maximum output and the timing is gradually retarded which increases the valve overlap. Advancing or retarding the intake valve timing at the appropriate moment has a number of advantages: lower emissions, better idle quality, higher torque output (particularly in the low and mid-ranges) and increased power at higher engine speeds

v.v.t.l-i

VTL-i builds on the foundation of the VVT-i system but adds an exciting sporty dimension to an engine whilst still maintaining good fuel economy and low emissions.

In addition to varying the timing of the intake valve, VVTL-i controls the amount of intake and exhaust valve lift which optimises engine power output.

The VVTL-i system features on the 1.8 litre 2ZZ-GE engine, which powers the new model Celica.

VVTL-i uses a cam changeover mechanism that increases the amount of intake and exhaust valve lift when the engine is operating at high speeds. The mechanism uses a unique rocker arm assembly with intake and exhaust camshafts that have two different types of cam lobes on them.


The lift of the intake and exhaust valves can be increased, allowing for a greater volume of fuel/mixture to enter the combustion chamber.


Additional engine power at engine speeds above 6000 RPM is produced due to the dramatically improved engine breathing.
For the new model Celica, VVTL-i offers all the advantages of VVT-i with the bonus of a dramatic power increase once the 6000 RPM threshold is reached and then keeps on delivering right up to the 7800 RPM limit.

This ensures a pleasurable driving experience around town with useable low and mid range power but enables exhilarating performance for open highway cruising or blowing out the cobwebs on your favourite stretch of back country roads.

Is it possible to install the "changeover mechanism" from a 2zz into a 1zz?

Big different<br />
vvt-i: 00-02 corolla 125hp, 03+ corolla/Matrix 130hp, 00+ MR-S 138hp, 00+ celica GT 140hp<br />
vvtl-i:05 corolla XRS 170hp, 00+ celica GTS/02 Matrix XRS 180hp<br />
<br />
(Matrix XRS keep changing from year to year, so it's not 180hp in 04 and 05)<br />
<br />
correct me if I'm wrong <img src="http://vvti.net/forums/images/smilies/smile.gif" border="0" alt="" title="Smile" />

Spec-wise you're right, but you're wrong on answering the question. From what i've noticed, many people on several Toyota forums seem to associate VVT-i as being the "economy" version of Toyota variable valve timing systems compared to VVTL-i. But if thats the case, why is it that Toyota was able to output 200HP out of a 3S-GE using VVT-i? Now of course i'm sure if Toyota were to add VVTL-i onto the 3S-GE then it would make some more power. But the point that i'm trying to get across is it's not which variable valve timing system that makes up the power output of the engine, it's also, and mainly, the way how the engine is setup itself. Toyota did not just attain 180HP by adding VVTL-i to the engine. They grabbed the 1ZZ and re-worked the entire engine to the point where theres hardly any similarities between the 1ZZ-FE and the 2ZZ-GE.

not to mention we go back to core toyota differences.. The F and G heads are different from the core. So comparing a 1ZZ-FE to a 2ZZ-GE and saying the only difference was the lift differences, would be like saying pamela anderson is hotter than a 100 year old lady because she has bigger boobs.

I'm sure that if toyota had 2 engines, identical, except one has VVT-i and the other has VVTL-i, the VVTL-i would probably be faster. We can theorize on the subject all day long, but until toyota gives us equals to test or someone is skilled enough to make a VVT-i head into a VVTL-i head(not just finding a way to swap the 2ZZ-GE head onto the 1ZZ-FE block, since once again, we're back to the fuel economy vs. performance heads again).

So, have fun dreaming...