When does VICS switch over?

[JoshP5]

Just wondering--does anyone know at what engine speed the ecu opens the valve to the short runners on the VICS system? Or does the ecu consider other factors, too, like throttle position, etc?

I notice a little bump in power at about 2700rpm and wonder if that's it.

 

[Robot Romeo]

Thats' probably just the normal tq curve. I think the runners switch on around 5k.

 

[djdanny5000]

yeah at 2700 rpm's your feeling your TQ kicking in I love it but if you keep going up to around 5k you feel another jolt of power and that where our HP comes in and the Vics is open or closed or whatever it does

 

[pasadena_commut]

but if you keep going up to around 5k you feel another jolt of power and that where our HP comes in and the Vics is open or closed or whatever it does

In that case the VICS valves have done their thing about 5 times in the year and a half I've owned my sportAuto P5, and every time it was when passing on a 2 lane highway. That is, stomping on the gas enough to make the transmission downshift into 3rd at highway speeds. In normal driving the motor never goes anywhere near 5k rpm, including on the highway. In 4th gear (remember, auto) 5K rpm is what, 95 mph?

 

[16902]

In that case the VICS valves have done their thing about 5 times in the year and a half I've owned my sportAuto P5, and every time it was when passing on a 2 lane highway. That is, stomping on the gas enough to make the transmission downshift into 3rd at highway speeds. In normal driving the motor never goes anywhere near 5k rpm, including on the highway. In 4th gear (remember, auto) 5K rpm is what, 95 mph?

You're not missing out on anything above 5k. That is when the FS poops out. 3-5k is where it's at.

 

[pasadena_commut]

You're not missing out on anything above 5k. That is when the FS poops out. 3-5k is where it's at.

Why de we have VICS then?

Seems like the valves very rarely change position in normal driving, don't do much when they are open (what you're implying), cost more to build (doubtless), and definitely cost more to maintain (screws through the engine).

Leaving the VICS out Mazda could have simplified and lightened the intake manifold, trimming weight off the car and dollars off the manufacturing costs.
Seems like that might have been a better engineering choice.

 

[16902]

VICS isn't perfect. It tries to strike a balance giving the engine low rpm power and high rpm power. It just doesn't work as well as a manifold designed solely for high rpm power because of it's dual purpose. Still, we need VICS to take advantage of the dual runner design.

Here is some good info: http://flatblack.somethingsomething.org/p5/porting/

from flat_black on the forums

 

[thrasher]

My VICS must be broken... This little engine sucks below 2500rpm. You can put your foot to the floor, it'll crawl up to 2500 and then finally a little power will kick in. It's good after that to about 5000, then everything buzzes. The dash, heat shields, the door somewhere near my head, the glove box...

If only Honda had made the P5. It would look good and drive well.

 

[the tortoise]

Yeah.

Mazda - Design the interior, exterior and chassis.
Honda - Design the drivetrain
Toyota - Screw it together
GM - Give us employee pricing.

 

[magnumP5]

As stated above, the VICS system kicks in above 5000 RPM (it's been debated, and I believe around 5250 RPM?) and it opens a set of butterfly valves to let more air into the engine. However, below that RPM the valves are closed to allow for a higher intake air velocity and give more torque. When the valves are open, large amounts of air is let in to mix with the large amount of fuel being dumped into the system as well - this gives us the 100whp at like 6500 RPM. The system is designed this way so we have some low-end torque (unlike Honda's) while still having decent high-end power. This is why our peak torque occurs around 3500 RPM whereas our peak power comes in around 6500 RPM. Now the VTCS system is a completely different story...

 

[treybrad]

Has anyone that has gone to the trouble to remove the VTCS system like on the link above have anything to say? Make a big difference? Worth the effort? Seems like a job that'd take me just about all day..

trey

 

[JoshP5]

^Search on VTCS--lots of info available. From what I've read there are quite mixed reviews. Common sense suggests it's not great to put obstructions in the intake flow like the VTCS system, but there's a lot going on there from a fluid dynamical point of view, so who knows. I'd like to see some dyno runs with and without the VTCS.

As far as VICS goes, you should think of it as helping out the midrange without hurting the top end too much, although I agree that the system isn't optimized since the fireworks stop at 5500rpm. If you check out the P5's torque curve, it's pretty decent at the low end.