VICS question...

[ProtoRice]

Why not deactivate the VICS and remove it's components, making the intake manifold all open all the time? Or why not trick it into opening whenever the TB is at WOT?

The reason I ask this, is back when I used to tune Ford Focii (plural of Focus), the big "trick" for the SPI motor (split-port-injection) was to have the VICS (Ford had a different name for it) to open at WOT, or at a lower RPM, or just be open all the time. You lost a small amount of low-end, way at the bottom, but mid- and high-range power was increased.

Next question would be, how exactly does the VICS on these motors work? I'm assuming it's electrically activated, in which case it would be easy to "trick" into opening at lower RPM, or at WOT.

Any help?

[lscrx]

Why not deactivate the VICS and remove it's components, making the intake manifold all open all the time? Or why not trick it into opening whenever the TB is at WOT?

The reason I ask this, is back when I used to tune Ford Focii (plural of Focus), the big "trick" for the SPI motor (split-port-injection) was to have the VICS (Ford had a different name for it) to open at WOT, or at a lower RPM, or just be open all the time. You lost a small amount of low-end, way at the bottom, but mid- and high-range power was increased.

Next question would be, how exactly does the VICS on these motors work? I'm assuming it's electrically activated, in which case it would be easy to "trick" into opening at lower RPM, or at WOT.

Any help?

It's vacuum operated.

[ProtoRice]

Ah... nevermind... I see dyno...

What about if it were "partially opened" during lower RPM...

I dunno... it just seems wierd that less air = more power.

What about HP? That dyno just shows torque...

[Speedyj]

It is about speed of air in the intake manifold...
I thing that, if You just open it, You will lose torque in low and middle rpm with no significant increase of power.

[ProtoRice]

I know it has to do with intake air velocity... but still, more air SHOULD still get you a little more power...

[Gen1GT]

Yes, you'll get a couple more hp at peak, but lose MASSIVE amounts of power in the low-midrange. Here's my dyno with the VICS open after my exhintake cam and cam gears, before they were tuned properly.

[ProtoRice]

Well, if you were going for peak HP it would be, but for drivability, it's not.

[ThatCarGuy]

If by that you mean a dyno queen, then yes... do it. but it will still be slower.

[ProtoRice]

Right, well, unless you kept your RPM's above 3000 at all times. Seems thats where the severe drop is. So in a RACING motor, it would be good, but in a STREET motor, you'd lose DRIVABILITY.

[lscrx]

Right, well, unless you kept your RPM's above 3000 at all times. Seems thats where the severe drop is. So in a RACING motor, it would be good, but in a STREET motor, you'd lose DRIVABILITY.

That's why Honda racecars don't use VTEC... why have a "drivability-cam" in a racecar?

[hienishere]

good point.. i always thought they did use vtec... eh whatever, anyways.. the man is right.. bigger isn't always better.. i guess, if it's big, but can't be pushed, it's worthless.. right? i mean if it can't be forced into the enginie, then there's no point if having all of that o2 in there... makes sense... =) <3

[Gen1GT]

I wish I had a dyno showing the back to back runs with the VICS open and closed. There's actually a noticable difference in peak power(2-3hp), but as you already know you lose 25hp down low. The reasons for the gains I believe are twofold. First, with the vacuum line detached, the butterfly valves are probably more fully open. I suppose this could be adjusted, but you'd have to make sure that they're fulled closed when at idle. Also, there's a continuity of laminar flow with them open, resulting in a smoother and larger gain in power. These are just educated guesses, because the gain is more than just anectdotal.

Next time I'm on the dyno, I'm going to do back to back runs with the VICS held open and closed.

[John Long]

I know it has to do with intake air velocity... but still, more air SHOULD still get you a little more power...

Read up on scavenging and it will make more sense. Scavenging is a phenomena in the exhaust system that is analogous to the process in the intake system, but I forget what it is called in the intake.

Basically, air has inertia, and the flow in a manifold pulsates. These pulses of air tend to pull (and push) each other, and a certain amount of restriction can actually increase the air flow. When the VICS opens, it only adds a tiny amount to the cross-sectional area from the TB. Its main purpose is not to open a larger path as much as it changes the tuning relative to these pulses.

I took extensive photos of the VICS when I was doing my rebuild. They are floating around somewhere on www.mx-3.com. The additional air path is only a small square opening about 1.5 cm to a side.

[ProtoRice]

^^^ interesting

I've heard about that "scavenging" before, when I was doing a custom header on my Focus, I used a Pacesetter as my base, but someone told me that it was off pulse.

I've never seen the inside of a VICS before...

IDEA: If there was a way to control the VICS electronically, so that at WOT it would be open at all times but at idle and not WOT it would act normal?

[ThatCarGuy]

I bet the mazda engineers put a whole lot of thought into VICS... It works, and well at that. while I'm sure you could put a servo motor where the vaccum linkage attaches, why? the motor doesn't develop the kind of airflow required for the open VICS to be benificial at 1500rpm at full throttle... intake pressure values are closely related to rpms of the motor... If you are so determined to modify the VICS, why don't you try widining the secondary ports and installing larger butterflies? one thing the electric motor could be useful is if you used a stepper motor and used rpm pills (like shift lights) to trigger the secondary butterflies to open differnt amounts as the rpm went up... but that would cost too much money and im sure the benefits would be small... money better spent on cams and tuning.