VVT-i vs. VTEC

well the 00-02 corollas that have vvti have 5 more hp than the 98-99. maybe different fuel mapping i dont know.

ah, vtec and vvti..my friend has a 01 rolla, i got a 00 SI, i definetely can feel the power of V-tec kick in on the civic, but his corolla feels just the same as my rolla..slow and sluggish..=P with the civic, it's kinda like a mini turbo at around 5500 rpms all the way to redline, plus when i accelerate hard, i get a deep tone from idle-5500 rpm, and from then on, it gets all whiny and stuff..but now i got my magnaflow exhaust, it doesn't sound as whiny, but still does..i guess vtec is effecient, like in the lower rpms, it helps you save gas, and once you hit 5500 rpms which is mainly for hard drivers, it'll give you that extra performance..

vvti was created more for better emissions than for power.. look at it this way a pre VVTi 1ZZfe corollas (98-99) produce 120hp and VVTi 1ZZfe corollas (00-02) produce 120hp = +5hp = big freakin whoop!

-VVti only controls Valve Timing, meaning it can advance timing depending on Air Flow so that you are not stuck with constant timing as seen in dizzy engines..

-VVTLi controls valve Lift and timing - which is more comparable to vtec's torqueless wonders - Toyota only has 1 VVTLi motor and it seems very unlikely that toyota would make another..

-Vtec employs a second set of cam lobes on the INTAKE side - basically it has a set of cams for low RPM's for smoother idle and acceleration - and a set of performance cams for high RPM's.. The ECU pretty much regulates at which RPM Vtec activates the second set of cams..

and dont forget about iVtec.. I have no freakin idea how that works as of yet

I-VTEC = VVTL-i

VTEC is more like VVTL-i where 'lift' occurs at a certain RPM in order to increase performance. VVT-i does not have a lift mechanism since it continuously monitors the engine and adjusts the valve timing and cam lifts.

VVT-i vs. VTEC

I heard toyota and honda are rivals since long time, so can u give me more info about VVT-i and its counterpart VTEC so what are their strong and weak points.

they are similar, but this is what i know about vvt-i and v-tec.

on the intake cam there is an actuator which when the ecu decides, changes the timing by adjusting the pressure. so the ecu can determine when to advance timing and when to retard timing for maximum power and efficiency given other factors. variable valve timing (with) intelligence (VVT-i) is a constantly running system.

with honda's V-TEC, (valve electronically controlloed some shit like that)
on the intake cam there is a third lobe i believe for each set of valves. the third lobe has a little pin or something that locks to the rockers of the other two lobes during higher rpms, the profile of the third lobe causes the valves to open sooner and close later, which is why you get that "kick" when the VTEC system engages, because thats when those different profile lobes engage.

if i am wrong about anything, someone please correct me.

welcome

don't forget VVTLi...variable valve timing with lift intelligence.

*Moved to General*

Which gives the better boost in power? I know VVTi runs constantly, but I'm curious how much power it would hypothetically add over the same engine without VVTi. Graphs of a stock civic with VTEC and a stock corolla with VVTi would help. Anyone know of some?

Don't forget you are comparing a 125 HP Corolla (2000-2002) with a 160 HP (Si) Civic. The difference is bound to be there and it is no brainer Corolla would feel a lot slower regardless of how VVT-i handles the performance. VTEC is available on the Civic EX as well and it does not nearly do as good as the VVT-i on the new 130 HP Corollas.

I-Vtec is a lot more complex than the simple VTEC. More like the VVTL-i on the Corolla XRS, Matrix XRS and Celica GT-S since it also optimizes the low RPM torque in addition to the cam lifts. Here is a definition from the Acura site:

i-VTEC

In addition to controlling valve lift and duration, like other VTEC systems, the "intelligent" i-VTEC™ system uses Variable Timing Control (VTC) to adjust "camshaft phasing." By varying oil pressure, VTC can continuously vary intake timing relative to the engine's exhaust timing. The result of i-VTEC is improved response and enhanced performance at low engine speeds and efficiency across a broad power band.