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How is this the same/difference from the Honda based VTEC?
Im pretty sure it works the same but can you feel the the difference in the 3 with the Variable Valve Timing??
:roll: curious :roll:
 

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It does not work the same. VTEC is, in a way, a very much more advanced version of Mazda's S-VT technology. However, it also results in very spikey power peaks where as Mazda's pulls smoothly to redline.
 

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at a specific rpm, the computer signals an Oil Control Valve to open, this lets oil pressure go through a special gallery in the inlet cam bearing, through the centre of the inlet cam to the VVT pulley. There's a small piston in the VVT pulley, and once it gets enough pressure behind it, it starts to move outwards, causing the outer part of the pulley to turn in relation to the inner part. when the computer signals for the VVT to operate, the OCV opens and thus causes the VVT pulley to advance the inlet cam timing by 30°, reference the crankshaft.
 

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Erv187 said:
at a specific rpm, the computer signals an Oil Control Valve to open, this lets oil pressure go through a special gallery in the inlet cam bearing, through the centre of the inlet cam to the VVT pulley. There's a small piston in the VVT pulley, and once it gets enough pressure behind it, it starts to move outwards, causing the outer part of the pulley to turn in relation to the inner part. when the computer signals for the VVT to operate, the OCV opens and thus causes the VVT pulley to advance the inlet cam timing by 30°, reference the crankshaft.
Excellent! This is exactly how the VVTi in the toyotas work. Wonder if its the same as the S-VT?

Feels like it.
 

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We discuss about this topic before. No, Mazda S-VT and Honda VTEC are different technologies. Both have its own advantage and disadvantage. The best engines would use both techiques (e.g., Honda VTEC-i).

Mazda S-VT is essentially changing the phase of the valve with respect to the crank (how early the valve opens), depending on engine rpm and load. BMV uses the same in their VANOS system. The S-VT of the MZR 2.3L engine operates on the intake valves only. The exhaust valves phase is fixed (whereas BMW double-VANOS controls both). The Mazda system adapt contineously with respect to input parameters by the control unit, i.e., it doesn't have "stage".

The Honda VTEC system changes the lift (and the timing as pass product) of the valves (how far it opens). There are two or three stages because the system must switch different cam profiles in order to change the lift. (Ferrari has developped a continuous cam changing techniques by having a 3D cam profile and slide continuously the camshaft.) Honda VTEC is more expensive than Mazda S-VT.

http://groups.msn.com/BrunoLuong/techtalk.msnw
http://autozine.kyul.net/technical_school/tech_index.htm
 

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Hi Erv187,

If the Mazda 3 (2.3 litre engine) is anything like the Mazda 6 SVT (2.3 litre engine) then you explanation whilst correct initially regarding oil supply control, the rest of your explanation is incorrect.

I have been given the full "PowerPoint" training module explaining the SVT System and will try to attach the "SVT Advance Timing" diagram.

The valve timing is:

INTAKE: Open: 0-25' BTDC Close: 37-62' ABDC
EXHAUST: Open: 42' BBDC Close: 5' ATDC

To explain the very basic's for those with no previous experience please bear with me:

Imagine a 5 inch gear wheel that has 4 evenly spaced "finger width arc cutouts in its centre".

Now imagine the camshaft has 4 paddles at one end that slide neatly into this 5 inch gear wheels arc cutouts. But these paddles aren't a flush fit in the cutouts and can rotate left and right a total of 25 degrees.

Oil pressure is now computer controlled to enter into these cutouts and more the 4 camshaft paddles anywhere within this 25 degrees of radius .... there you have your intake valve variable timing or SVT.

Warren

Your can email me at: [email protected] for the schematic diagram
 

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so if the variable valve timing kicks in at a certain rpm, when does this occur in the 2.3?
 

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I am not sure exactly how this tech works, this is my first (insert acronym here) variable valve etc car.

BUT, either one of two things is happening:

1: my engine is F*ed up bigtime, and strange surges happen on a regular basis. or....

2: I can feel the VVTI/VTEC/VVT kicking in. I have an auto, and I am constantly looking down at the digital gear indicator, to see if the car has downshifted.

It is a strange phenomenon, I have not opened it up yet, as I only have 200 miles on the engine. I will report back once I hit 1200.
 

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From the readings above, it gives me the impression that VVT/SVT technology will contribute to engine power improvement?

But does it contribute to fuel efficiency in the way the technology is used?

IMHO one of the myth abt engine power is that it will leads to better fuel economy because the driver will have a lighter foot on the accelerator. But in reality, the more powerful a car is, the tendancy is for the foot to step on it and hence leads to poor fuel enconomy.
 

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Yes, S-VT does increase the fuel economy.

In the low and medium load condition, the intake is slighly overlap with the exhaust thanks to S-VT system. This will favorite the so called call "exhaust-gas recirculation" (EGR), i.e., the exceeding oxygene or fuel from the the previous combustion is recycle. This will minimise pumping loss and improves fuel economy for less overall CO2 emissions.

Bruno
 

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hmmmm im not too too familiar with how these systems work but... i do understand that the vtec system is completely different then what we have in the mazda3. but since it is computer controlled in our cars to let the oil move to another gallery and such.... so doesnt that mean that if a chip was made for the computer or if a device was made like a vtec controller.. couldnt we just fool the computer into thinking we are at a higher rpm than actuality so the timimg advances much sooner?? does anyone know at what rpm our timing advances?
 

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I am sure when if ever a chip/reflash is released for our car the engagement points of S-VT will be changed in order to shift the powerband.

My understanding of v-tec is that the engine has two sets of camshafts and at a certain crossover point the car switches to the more aggressive cam profile. i v-tec has a variable crossover point, this is used on Honda K-series engines, generally speaking the K20A is the best engine that Honduh makes.
 
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