r0tor

iTrader: (1)

1) Does anyone know what the dimensions are of the VFAD duct? Perhaps someone that ripped this out for their Revi might be able to do a quick measurement???

2) The VFAD is vacuum operated - where does the vacuum tube that operates the solenoid get the vacuum from?


I'm trying to figure out if its viable to extend the VFAD duct to the front of grill as a RB stlye ram air duct. I've always been concerned with the RB unit sucking up dirt during daily driving (especially with the amount of road salt used in the winter making my black car white after driving 2 miles) - so I got thinking that if I used the VFAD duct I could have an intake that gets force fed to a degree only above 5500 rpms.

I'm just wondering if the VFAD is sized big enough and if I do get any form of pressure increase from extending the duct, if that would then cause the solenoid to go closed from a vaccum loss.

StealthTL

iTrader: (1)

1/....don't know.

2/The vacuum line is the one that passes right under the throttle body.
It has a check valve in it, that keeps the flap open at hi speeds. The solenoid is electrical, doesn't care about low vacuum.

S

Spin9k

That's really weird, just yesterday I was formulating this same idea. Looking at the pic it doesn't seem unreasonable...just remove the existing structure, put in a replacement.

Not sure about just rerouting the existing duct...1st maybe dif to have a ram effect when you've got two inlets, and I think the tube accross the front is fabric like to allow air to be sucked through it, as well as from the end. Not 100%, but i believe so, as I've never taken mine out. Anyone know?

r0tor

iTrader: (1)

I've thought about this last night and I don't think it would be a problem unless you get enough ramming effect to get above the pressure at of the primary opening which I would think would be atmospheric or above. Considering normally that the airbox is well below atmospheric, just getting it too the pressure where this becomes a problem would be a benefit. But yea, in a perfect world it would be cool if the VFAD flap could be modded to close the primary path while opening the VFAD part.


From the Mazda training video it says the duct was sized to effectively double the amount of airflow possible. So I am concerned with how big the physical dimensions are... but if it proves not to work its only like $15 of materials invested :p

r0tor

iTrader: (1)

hmm... looking at the pics in this thread it looks like there'n no room to extend the duct without major surgery since it runs pretty much into the bumper

https://www.rx8club.com/showthread.p...Bumper+removed

zoom44

the long tube is what is open normally. the short straigth piece is what opens at 5500

G8rboy

Here's what I did... when building my custom intake box:
https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/custom-green-performance-intake-58939/

... I removed the nylon sock and attached a big 90degree elbow to suck cold air from in front of the radiator. I also have a NACA ram air duct that I've put on (not in the picture, but currently have it off because of fitment issues (I also didn't see any improvement in airflow or temps using it). I find the combination of the green filter and this cold air duct to be very noticeable at higher speeds, and my intake charge stays cooler... basically a poor man's Revi. Here's a closeup of my "handywork" : )
https://www.rx8club.com/attachment.p...chmentid=47289

Very recently I've been playing with disabling the VFAD high-rpm flapper door so that it is open at all RPM levels, not only above 5500... from what I've read there's no noticeable performance difference... just more of an intake sound (which I like). A very strange side effect though (and very possibly unrelated) is that my last 3 tanks of gas after opening up the VFAD flap have seen increases from the mid 15mpg range prior up to 17mpg on the last tank (this is with aggressive city driving with no difference in my driving style). YMMV

Spin9k

Very cool (literally) G8rboy! You have to wonder about the costs associated with a little piping and ductwork that RB and other charge, I think you've made a creditable DYI from the looks of it. Esp I like keeping the stock box just moding it with a filter, and cosmetics, and that rubber duct, aka CAI. Good use of Home Depot's never ending supply of raw materials! :D

G8rboy

Thanks... I started my project before the RB unit was released, but honestly, I really enjoy trying this stuff myself. I probably ended up spending the same amount as a Revi, between trying different K&N filters (one that fit in the box, one with a custom velocity stack without the airbox), the stock one and ultimately the green (measuring all for CFM #'s), and different duct types for intake air temp #'s... but I learned a lot about CAI design, air pressure differentials, ram air "effect", etc. Having a CanScan and a G-tech encourages me do stupid pet projects like this

swoope

iTrader: (5)

1 the vfad duct is 3"x1.5' measured inside. the other fabric tube is 2.5" inside diamater.

2 bottom of intake manifold.

btw the revi duct sucks air from as high up as it can in the nose of the car. the location of the vfad and the intake tube suck.

if you need good photos let me know as my vfad is on a shelf in the garage.

also the ram air duct has been hurricane tested in fla. ok at least really ugly tstorm for 45min of driving.

beers