DIY intake mod
 

After reading a few threads a while back about using intake piping to feed "fresher" cold air to the intake, I thought I'd give it a try for myself. The financial outlay was pretty low - $30 for a 1m x 80mm intake tube and about $3 for the ties.

My original plan was to leave the VFAD in-tact and use the intake tube to direct some air from behind my Hymee grill to the intake openings. Once I had the bumper off though, this looked a little harder than first anticipated, so I went with a different approach and pulled the whole VFAD out instead. Now I have the two intake tubes feeding directly into the airbox. The tubes feed air directly from behind the main grill. I drilled out three extra diamonds from the filled in part of the grill for un-impeded flow.

How does it go? Definately no worse than before. The car feels like it has a touch more torque and throtle response at low rpm's, but that could just be me ( or it could be true). I've measured before and after intake temps and pressures using my Hymee scan tool. Before, with 31deg ambient temp, the intake temp never got below 41deg. After, 25deg ambient temp, the intake temp was around 30deg. Makes sense, since air is no longer being sucked from an air pocket buried in the bumper surrounded by the hot metal from the chassis. Intake pressures were unchanged before and after - 100kPa each time (Hymee please explain what that means).

I'm fully aware that this is not a "ram air" intake. The purpose is purely to suck unimpeded air from outside rather than from the VFAD's random location buried under the bumper. Since I'm no worse off than before, I plan on leaving it in until I go FI in the new year. If nothing else, it was a fun mod to do.

Flame away.... :D

Nice. I'll try a variation of this when finals is over! Thanks!

Wildcard

How is your idling handling your mod Same/ rougher/smoother .?

Petrol comsumption better /same ?

In your last paragraph " Since I'm no worse off then before ,i plan on leaving it on until i go........ FI ...............in the NEW YEAR " :cool:

As we know that you were the 1st test pilot for the HYMEE exhaust , :) does this mean that Hymee will be ready to test his FI early in the Newyear . :D

I know that you are sworn to secrecy ;) and Hymee plays his cards close to his chest , BUT YOUR STATEMENT SOUNDS PROMISING TO ME ;)

cheers
michael

Wildcard, the air presure reading is from a barometer which is separate from the intake - 100kpa is 1000 hectopascals (but I'm sure you knew that). It should be unaffected by intake modifications.

I'm thinking of doing something similar but retaining the VFAD... thanks for posting the info. I'm wondering if the intake air sensor is not that accurate - mine seems to be consistently around 6 degrees above ambient.

Cool mod.......should benefit my HKS intake as well.

Nice colour tubing - would match my car colour nicely.

To answer a few questions:

The engine idles the same as before. Since it's only been 2 days, I can't comment on fuel consumption, but I wouldn't expect any change. In fact, unless I told you what I had done, you would assume from driving the car that it is still stock. The mild delay in acceleration as the VFAD secondary duct opens seems to be gone now however.

There may be small gains from feeding the engine slightly cooler/more direct air. As we all know though, the stock setup is pretty good, so even if I've gained 2 kW, I'd be kidding myself if I realistically expected to be able to feel much of a difference. I haven't been up to highway speeds yet though, and I know other guys who have done similar mods report that the gains get better the faster you are going, as a bit of a "ram air" effect kicks in.

Sco, intake temps are now 6deg above ambient. Before they were 10deg above ambient, although it was a hotter day. I'll continue to monitor this for a couple of weeks.

Oh yes, I almost forgot. With the VFAD removed, my car is now about 250g lighter!

I suppose that's better than getting a carbon fibre engine cover. :D

Wildcard this guy is taking the term" ram- air "to the next level :cool:LOL

I just returned yesterday from a 600km trip up the coast and I am now confident that the combination of the intake mod, plus removing the baffles inside the airbox has given my '8 a little bit more poke. It's not FI, but its there. The engine note also seems raspier. I'm glad I did it and I wont be taking it out until something better comes along.

As for Hymee's SC, by "in the new year" I meant definately not this year. I don't know exact dates any better than Hymee. He keeps his thread in the performance section up to date when ever he has something to share, so I'm watching and waiting just like everyone else.

We've been talking about forced induction for over a year on this forum, but I don't know of a single forum member who owns a Turbo or SC'd RX-8, so I am sure Hymee and co. have plenty of work still ahead of them.

Good work Wildcard!

Cheers,
Hymee.

if it makes any difference, I removed my VFAD and all the other plastic bits in that area and drove around for two days. The car seemed to lack some lower end power and was a bit more noisy. Overall I didn't like how it functioned so I reinstalled the VFAD last night

I removed the VFAD about a year ago while I was trialing my Rotary Extreme intake. I found the same thing as Jason with the VFAD removed and hence I put it back in.

I think the intake tubes are the key. Without something to direct the flow into the airbox, you are just sucking dead air from a cavity behind the bumper. The VFAD was obviously designed by some smart Mazda people, so VFAD is better than no VFAD in that sense.

By directing air through the intake tubes, I'm doing the same thing as the VFAD, but from a more direct air source. There's no Helmholtz resonant tuning going on, but there is more air by having 2 x 80mm tubes open full-time.

The thing I liked about this mod is that it only cost $30, so I really had nothing to lose by giving it a go.

And the thing I like about it, and the other thing you like about it, is that you did it yourself. :D

I've got to get off my lazy ass and do this mod!

What do I need as "tool" wise...

Taka knows nothing about "tool"s

A socket set and a couple of screwdrivers are about all you'll need. I also used a drill and a stanley knife to cut out a few of the filled in diamonds in the grill. Add some scissors to trim the pull-ties and you should be ready to go.

Are you so ignorant that you don't know about your own kind? j/k :D

looks like a great project to work on for the car... and major cons overall from this wildcard...?

The only con is that the performance gain has been measured by my butt-dyno, which may or may not be accurate. Worst case though, if you find it doesn't work for you, you can go back to stock and all it will have cost you is your time.

For anyone who tries this or a similar mod, remember that the ECU is a learning ECU, which means you may not feel an immediate difference. The ECU supposedly takes about 15 minutes of driving to learn the changes. I noticed the difference most when I drove my car the next morning. You could probably speed up the learning process up by doing an ECU reset, but I didn't bother with that.

I also recommend removing the airbox baffles at the same time. Nojooc had a good thread on this a while ago.

Why wouldn't it be accurate?
Have you been dining at Maccas non-stop lately and added a few pounds? :D

Thanks, here it is.

Compare this....

https://www.rx8club.com/attachment.p...chmentid=43742

To this...

https://www.rx8club.com/attachment.p...chmentid=36413

You have removed the bottom board that holds the two black stock tubes?

apparently he has, Taka... you gotta do that, else you will need to trim the bottom board off to allow those 2 huge tubes to go through....

I have done a similar thing to my 350 as well and as what wildcard's experiences, it does work! I haven't told anyone about this mod yet besides Yun, and I guess this is a good time to share with my fellow 350 group too...

Nice work Wildcard... it looks niice... and if you can get 2 extra PVC short hoses, you can actually make a small mods on those to become bell-mouth shape and make them attachted at the front of those 2 hoses you have got there... they will get more air probably... (perform bell-mouth effect, if the air box is sucking air from those 2 tubes and it seems like it too)....

cheers,

richie

ps. bell-mouths can be made by heating up the pvc tubes and by using a funnel to shape the bell-mouth while the pvc hoses are still hot.... and simply use the clamps to attach the blue hoses with the bell-mouths....

cheers,

richie

i did this with an HKS type intake and everytime i put the car in N @ freeway speed it would die.....i did this mod about a year ago w/ the VFAD attached...

xxdevilzeroxx why did you do that :confused:

anyway this mod seems to have some merrit. I don't think bell-mouths are worth the effort since the pipe isn't smooth.

my bet is that the odula will perform better since it has a smooth pipe. but it cost much more. I'd like to see an intake with smooth pipe and a modified vfad.