Cam Gears
You have an EVO IX. The IX has MIVEC. You really don't need adjustable cam gears, just a clear understanding of what MIVEC is and how it works.
Learn how to tune your MIVEC, or get to know those who actually do. Having MIVEC and inquiring about adjustable gears seems a bit like asking about a knife when one already has a gun.
Learn how to tune your MIVEC, or get to know those who actually do. Having MIVEC and inquiring about adjustable gears seems a bit like asking about a knife when one already has a gun.
You have an EVO IX. The IX has MIVEC. You really don't need adjustable cam gears, just a clear understanding of what MIVEC is and how it works.
Learn how to tune your MIVEC, or get to know those who actually do. Having MIVEC and inquiring about adjustable gears seems a bit like asking about a knife when one already has a gun.
Learn how to tune your MIVEC, or get to know those who actually do. Having MIVEC and inquiring about adjustable gears seems a bit like asking about a knife when one already has a gun.
but I'd have to question why one wouldn't want an exhaust side cam gear, if for no other reason than the newer motors i.e. 4B11T have a dual MIVEC set up. Do we not need dual MIVEC? What I mean to say is that. Why is it that, before MIVEC happened, people were all about cam gears, and exploiting what power they could, and where in the power band could they best exploit the power they were manipulating? Can we not use that exhaust cam gear to profit the same? These are questions I have only partial answers to, so if some elaboration could be wielded here I'd be delighted.
The single most important valve timing event is the point at which the intake valve closes. This is why the IX has MIVEC on the intake side.
I'm not saying that an adjustable exhaust cam gear isn't potentially useful (especially if the exh cam timing leaves something to be desired), but it isn't as advantageous as an adjustable intake side, especially an intake side that can be adjusted in real time. If one has a IX and is asking about adjustable cam gears, it would appear that he isn't quite aware of what he already has.
As for adjustable cam gears in general, they are most useful to those of us with static valvetrains. MIVEC however, is a step above a set of adjustable gears.
I'm not saying that an adjustable exhaust cam gear isn't potentially useful (especially if the exh cam timing leaves something to be desired), but it isn't as advantageous as an adjustable intake side, especially an intake side that can be adjusted in real time. If one has a IX and is asking about adjustable cam gears, it would appear that he isn't quite aware of what he already has.
As for adjustable cam gears in general, they are most useful to those of us with static valvetrains. MIVEC however, is a step above a set of adjustable gears.
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Joined: Dec 2003
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From: Philly (Bucks Cty.)
So, Ted B, why is this?
Whether we change the timing of the intake or exhaust cam, we affect the timing of one with respect to the other, which is significant in itself because it affects overlap. The reason why we find MIVEC, single VANOS, etc., on the intake cam however is because the timing of the intake valve has a direct impact on VE for any given engine speed, whereas the exhaust timing is less sensitive.
When the intake valve opens and the piston begins its downward motion, it creates a vacuum on the intake port, which draws air into the cylinder. Due to the effect of inertia, the movement of air through the valve continues as the piston rounds BDC and even slightly after it begins its upward movement. So long as air is flowing through the intake valve, VE is increasing. The trick is to close the valve just as the air column stops flowing due to the upward motion of the piston. Since this ideal point changes with rpm, variable intake cam timing is advantageous in that it can be adjusted to be 'ideal' for all rpm.
The ability to change exhaust cam timing is advantageous as well, but because the exhaust gas is under considerable heat and pressure, it doesn't respond to as fine a degree of mechanical manipulation.
This is a very basic explanation. The 'rabbit hole' goes very deep where this is concerned.
When the intake valve opens and the piston begins its downward motion, it creates a vacuum on the intake port, which draws air into the cylinder. Due to the effect of inertia, the movement of air through the valve continues as the piston rounds BDC and even slightly after it begins its upward movement. So long as air is flowing through the intake valve, VE is increasing. The trick is to close the valve just as the air column stops flowing due to the upward motion of the piston. Since this ideal point changes with rpm, variable intake cam timing is advantageous in that it can be adjusted to be 'ideal' for all rpm.
The ability to change exhaust cam timing is advantageous as well, but because the exhaust gas is under considerable heat and pressure, it doesn't respond to as fine a degree of mechanical manipulation.
This is a very basic explanation. The 'rabbit hole' goes very deep where this is concerned.
Whether we change the timing of the intake or exhaust cam, we affect the timing of one with respect to the other, which is significant in itself because it affects overlap. The reason why we find MIVEC, single VANOS, etc., on the intake cam however is because the timing of the intake valve has a direct impact on VE for any given engine speed, whereas the exhaust timing is less sensitive.
When the intake valve opens and the piston begins its downward motion, it creates a vacuum on the intake port, which draws air into the cylinder. Due to the effect of inertia, the movement of air through the valve continues as the piston rounds BDC and even slightly after it begins its upward movement. So long as air is flowing through the intake valve, VE is increasing. The trick is to close the valve just as the air column stops flowing due to the upward motion of the piston. Since this ideal point changes with rpm, variable intake cam timing is advantageous in that it can be adjusted to be 'ideal' for all rpm.
The ability to change exhaust cam timing is advantageous as well, but because the exhaust gas is under considerable heat and pressure, it doesn't respond to as fine a degree of mechanical manipulation.
This is a very basic explanation. The 'rabbit hole' goes very deep where this is concerned.
When the intake valve opens and the piston begins its downward motion, it creates a vacuum on the intake port, which draws air into the cylinder. Due to the effect of inertia, the movement of air through the valve continues as the piston rounds BDC and even slightly after it begins its upward movement. So long as air is flowing through the intake valve, VE is increasing. The trick is to close the valve just as the air column stops flowing due to the upward motion of the piston. Since this ideal point changes with rpm, variable intake cam timing is advantageous in that it can be adjusted to be 'ideal' for all rpm.
The ability to change exhaust cam timing is advantageous as well, but because the exhaust gas is under considerable heat and pressure, it doesn't respond to as fine a degree of mechanical manipulation.
This is a very basic explanation. The 'rabbit hole' goes very deep where this is concerned.
Those hot, combusted gases are looking for a way out, and unlike the intake side, have the benefit of heat and pressure to help them exit.
Like I said, a change of a couple of degrees on the exhaust side isn't nearly as profound as the same on the intake side, noting the fact that the change in the relationship between the two cams is of greater significance than the change between the exhaust valve timing and piston location. And since we can manipluate that change between the two cams by moving the intake cam, and because the intake cam timing is more critical, this is why MIVEC is on the intake side.
With MIVEC, I probably wouldn't touch the exhaust cam timing unless it created an issue with the intake cam timing at some point in the rpm range. And of course, if I had dual MIVEC, I would be able to do some neat tricks with that, but alas, I digress . . .
Like I said, a change of a couple of degrees on the exhaust side isn't nearly as profound as the same on the intake side, noting the fact that the change in the relationship between the two cams is of greater significance than the change between the exhaust valve timing and piston location. And since we can manipluate that change between the two cams by moving the intake cam, and because the intake cam timing is more critical, this is why MIVEC is on the intake side.
With MIVEC, I probably wouldn't touch the exhaust cam timing unless it created an issue with the intake cam timing at some point in the rpm range. And of course, if I had dual MIVEC, I would be able to do some neat tricks with that, but alas, I digress . . .
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