[spish]

hey there,

i've read that you can get a slight increase in lower end power by opening the VRIS actuators and leaving them as such? i don't remember where i saw this, but some dude had zip-tied his VRIS actuators wide open and said this yielded some lower end punch...

any thoughts on this? benefits? drawbacks? MIKE?

-d

 

[superflymx6]

i have read the oppisite to what you stated. the VRIS deals with the torque curve. they open up when the computer says too. i beleive the computer in the car should be able to handle this. some people say different but i read that.

i read were a guy wired a switch to the VRIS #1 AND #2 to see if he could make more power by controling them himself but from what i rememer he thought it was to much trouble to do that and drive and think about when to switch on and off. but i will go find the post on PT and read it again to make sure of the details.

 

[Mike 94PGT]

Leave the VRIS system alone unless you've got forced induction and have boost controlled switching or have a sheet-metal intake. The system was designed by Mazda engineers to make use of natural resonances that occur in the intake manifold all through the RPM band to maximize torque output of the little 2.5, which needs all the help it can get.

By monkeying with the VRIS, you interfere with these resonance effects and may lose torque. These guys who report their car was faster or gained somehow by doing this "mod" will probably almost universally find that their system was somehow defective (defective actuators, bad vacuum reservoirs or check-valve, bad or mis-connected VRIS vacuum hoses, defective solenoids etc) and all they are doing is getting back, in the RPM band where their tying suits, the power they should already have, nothing extra.

If they tie both sets open, then all they do is set it up so that they lose below 4250 and above 6250 but within that range, the engine runs well since that's what the PCM would normally have the valves set to then anyway. If they feel a sudden surge at 4250, it's because having #2 open from 3250 to 4250 isn't optimal and the engine is underachieving there. Then, at 4250, the thing hits its stride and goes like hell. They feel this surge and think it's more power. It's not.

 

[Guest]

I've read something like that, but it had to do with a turbo charged engine.

 

[Guest]

Damn, Mike beat me

 

[spish]

excellent!

thanks for the response(s). this is just the kind of info that people need to make informed decisions about what they do to their vehicles. i will indeed leave the VRIS alone.

that being said, is there any way to test the VRIS system to ensure the butterflies are opening at the right RPM?

thanks!

 

[Mike 94PGT]

One simple way is to use sound. Pull of the OEM airbox (if still on) so the VAF is open. Drive car in 2nd gear at about 2000RPM and stand on it. Let the revs climb. At 3250 you'll hear a subtle change of engine note and at 4250 a very pronounced change. At 6250, one more change will be heard. These are subtle, but with a trained ear, you can hear it. With a Hotshot intake, it's already very obvious when the points occur.

Of course, you're likely more curious about whether the valve are actually opening. At idle, the #1 valve should be pulled open. Have someone floor the throttle and rev it to 4500 or more momentarily. You should see the #2 valve toggle open. If it does this, both are fine.