Wildcard

Smooth pipes would probably have some merit. Remember though that there are already two mesh screens in the airbox to straighten out the airflow before it reaches the MAF.

I think the bell mouth effect could work if there was a clean entry point for air entering the tubes. Where I have my pipes though is right behind the grill, so there would be no aerodynamic benefit to a bell end, I mean a bell mouth in my case, since the air is partially disturbed as it enters the tubes.

The main benefit as I see it from this mod is the reduction in intake temp by porting air directly from the outside world into the airbox, vice sucking it from an air pocket buried in the front bumper. There might also be a little bit of a ram-air effect at high speed, but some would say you have to be going well above the speed limit to experience this kind of effect.

My work vehicle gets a ram-air effect, but only at high speed too. Fortunately not everywhere has speed limits....

Scotty

Has anyone tried to direct outside air into the "air pocket buried in the front bumper" leaving the VFAD and associated hoses in place?
Maybe it a simple matter of triming the bottom board so that the air coming in through the front grill flows up into this area.

takahashi

Scotty,

that will be a very tight twist. You can do it on the side tube but the front tube will be hard to get an extension.

Left At <5500rpm Right At <650rpm


VFAD, from this diagram (from RX-8 book), show that it controls the amount of intake air allowing to go through the air box. It actually limits the amount of air intake. What does it mean I don't know (since I am not clever enough). But I have reached 2 conclusions:

1) People with air filter pod (like the K&N typhoon filter) and does not have the air tight box around it have already defeated the purpose of VFAD, since air can get it from anywhere (not to mention it will be hot air)

2) Any modifications to the tubing, by increasing its size or relocate the opening (hence change the amount of air going in), has change the function of VFAD.

You see the VFAD is a simple device to split the air flow and hence controlling air intake. You have changed it in anyway, and thus you have changed the differences between the amount of air inake of fully open VFAD to fully close VFAD. Yes you might get more colder air into the front and side tube, but can you guarantee the ratio of increase air intake of both tube is the same as stock? You cannot simply say that.

In conclusion, IMHO, changed VFAD and NO VFAD is really the same thing.
So I think I should not be so stress about losing the VFAD, am I right?

Wildcard

The two VFAD "tubes" serve two functions. First, the long intake tube is specifically designed to be that length & width because the stock airbox uses Helmholtz resonant tuning. The length and width control the velocity of the air. Do a search if you are curious. I'll leave it at that....

Second, a Renesis interactive training program I have says that the reason the "front tube" is closed at low rpm to reduce intake noise. This is mass produced car remember, and not everyone wants a car that is too loud. Buy an aftermarket intake and you will hear how loud the intake really is!

Before I did my DIY mod, I was driving around for about 6 months with both tubes in the VFAD open full time. This is easy to do - you just need to work out which vacuum tube to disconnect.

Scotty - my original intent was to leave the VFAD in place and use the tube I bought to direct fresher air to the openings. Once I pulled the bumper off though, it was going to be too hard and would have involved cutting some of the plastic work. Then I thought - why not just remove the VFAD all together?

Scotty

Yes there is a lot of stuff added on to please the masses. I sometimes wonder how much lighter and cheaper (and simplier) cars could be if everyone had an appreciation for the sweet tunes that come from under the bonnet.
Perhaps Mazda should offer a model much along the lines of Porsche GT3/Carrera Cup car - All business! (ain't going to happen :-( )

takahashi

Then it won't be a ~$60K car.

This is what all modification is about... do it as you see fits. Many people do up their cars are nothing like what the manufacturer is done. The company made car for people. And people modified their car to suit them.

Welcome to the Options world (as the Japanese like to say )

takahashi

Wildcard I have done it.

It works as good as you said. Thanks!

https://www.rx8club.com/australia-new-zealand-forum-37/taka%92s-review-odula-ram-intake-duct-58857/

Lock & Load

nice mod Taka whats the damage$$$$.


cheers
michael

takahashi

21000 Yen. So it is about AUD$250 in Japan. Just add shipment and installation cost.

Wildcard

Glad you like it!

Lock & Load

Taka

Wondering why you choose Odula over the racing beat system .??

cheers
michael

takahashi

Racing beat does not have a dick like yours (which does not get up :p).

From the pictures of racing beat, it does have a bigger opening but it does not have an extension. And at least I have not seen a picture of one.

The similar design is RE Amemiya, and I am not prepare to pay 1000 bucks for one. It extension goes forward and have a large mouth. This may collect water in rainy days.

Gomez

I won't collect water unless you drive through a river, Taka. Michael, the RB intake will have a CAI duct like this one available for it later in the year....according to Racing Beat.

Gomez

The long VFAD tube is that length and made of fabric to reduce intake noise....not for tuning purposes. Racing Beat (who have a close relationship with Mazda) recently confirmed that on their website.

treitz

So I am going to remove my VFAD this weekend and was going to gut my stock intake a throw a cone filter as recommended in this thread:https://www.rx8club.com/showthread.p...Ram+Air+Intake

If I do that, will adding this pipes help significantly? The pipes and cone filter cost me $66. If removing the VFAD alone will sound and perform the same with my stock filter I will return the cone and the pipes. But if they will sound better and offer more power I will keep them.

What should I do?

takahashi

What kind of piping you are talking about?

I stand on my believe that the VFAD is for sound reduction only. There is no benefit of having it in terms of how the engine performs. I have recorded a lower intake temperature with a non VFAD direct tubing from the outside.

I never have problem with water to the filter.

Sounds are similar though but there is more but not significant noise from the front. You can prob can just hear it from the outside.

HKS has proven the use of cone filter benefit as long as you enclose it properly. In fact they recorded a higher power output with a system that have a box open ajar inside (if you know what I mean ... close but not air tight).
Linky: https://www.rx8club.com/showthread.p...ght=intake+HKS

treitz

Basically my plan is to combine 3 different threads I have found on here.

First, remove the VFAD to increase the airflow

Second, gut my intake box and drop in a cone filter as shown in this thread...
https://www.rx8club.com/showthread.p...Ram+Air+Intake

Third, add intake piping to direct air straight into the filter. Basically a cheap air duct system as shown in this thread, the thread we are on right now...
https://www.rx8club.com/showthread.p...Ram+Air+Intake

My question is, if I remove the VFAD and drop in the cone filter is it really necessary to add in the duct piping? I would assume the answer is yes because otherwise, without the VFAD you aren't getting any direct airflow into the intake. Just wanted some other input.

Huey52

iTrader: (2)

Wow, some folks were doing some "interesting" mod's back in the dark ages.

I went another route; removed my VFAD and mated a Racing Beat Ram air duct (instead of blue poly clothes dryer pipes to my stock air box with a K&N drop in filter. Also removed the two plastic baffles from the box.

It's not absolutely necessary to add duct piping, as air will certainly find its way to your cone filter, but to make it closer to a true Cold Air Intake (CAI) the duct does serve to more directly channel outside air when moving.

treitz

Right on. Thanks for the input huey. I plan on replacing the pipes with the RB Duct when I can. But I figured since I am going to have the bumper off already I might as well try something!

I Considered the home made CAI option that puts the cone filter in the bumper... but I really don't see how the extra cost involved in that would provide much better results than just installing a cone filter in the stock box?

Jon316G

iTrader: (1)

Instead of removing the VFAD/intake duct, why not just remove vacuum from the VFAD actuator so the valve stays open all the time?
And you don't need to remove the front bumper to do this.
But hey... to each their own.

treitz

Can you give me some instructions on that? And with it open all the time, will the VFAD allow as much air flow as the intake pipes would?

Jon316G

iTrader: (1)

There are a few threads where I discussed this idea in depth.
Here is one of them:
https://www.rx8club.com/series-i-tech-garage-22/help-vfad-trouble-177057/

Just keep in mind this... you are not going to get a performance gain with any other intake, rather that be aftermarket or home-made.
In fact, some people experienced issues such as rough idles and even lost performance with home-made intakes.
You are not going to engineer a better intake than Mazda produced.
All you're doing is increasing the sound.

treitz

Alright... So be honest with me. Would I be better of just removing and capping the vacuum hose and dropping a K&N intake in the stock air box as apposed to all the crap I was going to do?

I WAS looking for performance, a little more sound would be nice too, but if I am not going to get any more power response with the hoses and the cone filter I'd rather not take of the bumper if I don't have to.

Jon316G

iTrader: (1)

You are better off just capping the VFAD and leaving the valve always open if you want to achieve a louder sound.
Like I mentioned... even aftermarket intakes like AEM won't give you noticeable gains in performance.
Now if you want to get technical... if you ever look at a dyno sheet for an RX8 you'll see a few dips in the RPM band.
These are the intake valves opening at certain RPMs.
By removing the VFAD (or capping it, leaving the valve open at all times) you won't have that "dip" at around 5500RPM.
Its not much of a dip, but its something.

Now keep this in mind, by capping the VFAD, vacuum will remain in the line (keeping the valve closed) until you run the car above 5500RPM or disconnect the vacuum line after the solenoid to "bleed" the remaining vacuum.

treitz

Man, I am so new at this, I hardly understand anything you said. Lol.

I see where I can CAP the line (from your illustrations) but disconnecting the vacuum line to "bleed" the remaining vacuum is beyond me at this point.