MIVEC alters the cam profiles, tailoring engine performance in response to driver input.

Under low-rev conditions, MIVEC selects a smaller cam profile, yielding medium lift on the valves to provide stable combustion and lower emissions. When the throttle is opened wide and engine speed reaches the switchover point, MIVEC gives the intake valves a longer duration and higher lift, providing maximum and efficient power and torque over a broader range of engine speeds.

Source http://www.conceptcarz.com/vehicle/z10805/default.aspx

Here is a very simple explanation.  This explanation is somewhat specific to the 08 lancer but still more or less covers all mitsubishi mivec engines.  Also I will be explaining some basic terms because I don't know how much you or others know.

Mivec stands for Mitsubishi innovative valve timing electronice control.

There is a hydrolic lever in your camshaft that is activated when you step on the gas and get the engine up to 4000 rpms or higher.  When the lever is activated it more or less does two things.  All of these components are located under the valve cover.

It lifts the valve up higher than normal and for a longer duration than normal.  The valve allows air flow into the engine.  The more air flow, the more power.  This is why cold air intakes increase powere because they add more air.  You also need more fuel when you add more air.  When the ecu or computer activates the mivec system it allows more air into the engine while telling the fuel injectors to add more fuel.  The result is more power.

The point is that when you the driver want more power, you step on the gas and the car gives you the extra power that you want and that just so happens to start at 4000rpms on our cars.    The reason why this is important is because at low rpms, your car behaves like a gas saving grocery getter, but at higher rpms you get perfomance. This way you have a high performance car that saves gas as well.
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This is not how MIVEC works at all on the 4b11.  Watch this video before spreading false info
http://www.youtube.com/watch?v=Bb4zdcD0G-Y

The only thing that changes with the MIVEC on the 4b11 is cam timing, thats it.  There is no additional lift or duration and it does not "engage" at 4K rpm.  It is constantly changing depending on several variables in the engine.  VTEC is the Valve timing system that engages at a preset RPM.  A physical rocker arm becomes engaged in the head and uses a 3rd camshaft lobe per valve that DOES have higher lift, more duration, and timing.  That is why there is an audible difference on a VTEC engine when VTEC engages.  There is also an increase of power because of the physical difference in camshaft lobes.  MIVEC provides a smooth increase from 100-redline because there is no immediate switch.  So if you think your "MIVEC is kicking in at xxxx rpm", then you should take your car to the dealer or just stop saying stupid crap like that.
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This is not how MIVEC works at all on the 4b11.  Watch this video before spreading false info
http://www.youtube.com/watch?v=Bb4zdcD0G-Y

The only thing that changes with the MIVEC on the 4b11 is cam timing, thats it.  There is no additional lift or duration and it does not "engage" at 4K rpm.  It is constantly changing depending on several variables in the engine.  VTEC is the Valve timing system that engages at a preset RPM.  A physical rocker arm becomes engaged in the head and uses a 3rd camshaft lobe per valve that DOES have higher lift, more duration, and timing.  That is why there is an audible difference on a VTEC engine when VTEC engages.  There is also an increase of power because of the physical difference in camshaft lobes.  MIVEC provides a smooth increase from 100-redline because there is no immediate switch.  So if you think your "MIVEC is kicking in at xxxx rpm", then you should take your car to the dealer or just stop saying stupid crap like that.
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Ok are you 100% sure that you know what you're talking about too?
I had a dyno done on my Lancer and there is a significant increase in power and torque at around 3.85k RPMs. You can also feel the increase when you're driving.
So how do you explain that?
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Ok are you 100% sure that you know what you're talking about too?
I had a dyno done on my Lancer and there is a significant increase in power and torque at around 3.85k RPMs. You can also feel the increase when you're driving.
So how do you explain that?
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Hm. Well I have no idea ... which is why I started this topic. I'm trying to put together what you guys are telling me and use the little physics knowledge that I have to make something out of this. So far you both make a valid enough point.

But have you looked at the spike in the torque that is created around 4000 RPMs? It just seems to me like something extra would be engaged at that moment because it's a rather dramatic increase.

I mean doesn't a turbo or a supercharger do something (well obviously not really the same thing cause those are external components) similar, as in they only work within a certain power range?
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I don't know how much more specific I could have been about my explanation being an overly simplified explanation.  Yes it is continually variable and yes that is the main difference between vtec and mivec.  I know all about vtec cam profiles and how they work as I have pulled apart numerous b series engines and put them back together including a 1.6 vtec head that I put on top of a b20 block.  The point of this post was not to show how much I know about variable valve systems so I did not get into specifics.  The point was to answer rox's question.  Notice he asked how mivec works, not how the new mivec on the 4b11 works specifically.

Yes mivec is functioning from 100rpms to redline however if you look at a dyno graph you will see a spike at 4000rpm on any 08 lancer.  While mivec engagement is gradual, there is a point where it does add more power.  If this wasn't true then there would be no spike in the dyno graph.  You don't even need to look at a dyno, any normal person driving a car can feel the noticable gain in power at around 4000rpms.

Honestly there is no reason to be hostile.  You obviously know what you are talking about but that doesn't help anyone if you go around the forums simply to be argumentative.  I happen to know what I am talking about as well.  I am new to the 4b11 but I have worked with 4g63's for years.  I built my 1g eclipse and tuned it to 410hp at the wheels and if you would like to see just how much I don't know you should come race me and find out.  :57:
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