Well, to start, I have a 87 N/A GXL, and I've been debating about which way I'd like to go with the intake setup. I've been looking at manifold and air cleaner setups, and haven't decided which way to go. Obviously, you have the possibilities of porting and different throttle bodies and such. From what I've researched, my best bet is going to be doing a S5 intake setup to extract more power with the VDI system and probably get better gas mileage due to the better intake flow. I remember someone saying that porting the RX-7 intakes is basically worthless to do since they have pretty thin intake runners and are already designed with maximum flow taken into consideration. For the air cleaner, it's still a toss-up since the aftermarket intakes are basically just a filter and some hose clamps. Has anyone custom-made one yet that works better than the stock setup? Opinions wanted!

Did a little more research and found out a few things about air cleaner setups. A lot of people have gone the route of a stock air box with holes drilled in the southwest side of the box to increase airflow and use a K&N drop-in filter. I've also seen people use cone filters with heat shields in the stock air box location. What other setups are out there? Also, are there any gains to be had with porting the throttle body and intake manifolds? Also, are there any aftermarket manifolds or throttle bodies made for our cars?

 

Keep the stock intake system, it's pretty efficient. And sorry but there is no aftermarket manifold or intake system for our cars.

 

Actually there is an aftermarket manifold. They are called ITB's. They are pretty damn expensive and require a standalone to operate. They are also overkill on anything short of a large streetport or bridge. If you do it you are looking at around 2k+.
If you have an s4, the s5 UIM is a major upgrade, yielding about 10-15 extra HP up top. There is a writeup here: http://howto.globalvicinity.com/gv_w...i=63&co=1&vi=1

 

 

ITB's are those barrel-type throttle bodies that you mostly see on BP motors right? Yea, those are way overkill for anything without serious modifications and if they require a standalone, that's even more overkill. I'm sure I'll probably just end up doing the S5 intake swap and not trying to port the TB or manifolds since they aren't good candidates to port being so thin as is. Now that the manifold and TB thing is figured out, how about the airbox ideas?

 

ITB means Idividual throttle bodies, meaning there is a TB per piston (or rotor).

 

Yes, but its still an aftermarket intake as it replaces the entire intake manifold.

As for the air box, either leave it as is and use a K&N drop-in or get a cone filter and build a CAI of some sort. Any holes in the air box will bring in hot engine bay air which defeats the purpose of using the stock intake box.

 

Yea, that's what I was talking about with the ITB's. Obviously they are overkill for my application. The way the holes are drilled into the box they are made so that they do not suck in hot air. The holes are on the southwest side of the box away from the radiator and engine. For a while I thought about putting a cone filter in the cruise control location, but decided to keep my cruise control. Any other ideas?

 

Why drill holes? I dont get it, the plastic assembly already sucks air from outside the engine bay.

 

Search the forums for a thread on making an intake. It was an idea I saw that Mark had done, and actually in theory it would work excellent. I believe that Mark attested to it giving a slight power gain too, even though it's not much. Anyone else here made their own setups?

I've tried doing more searches on this subject, but just came up with others threads saying "search." Does anyone actually have links to threads showing intake types? I've seen people who cut holes in the stock box, people who have put cone filters on their intakes, and people who have cut holes in the body panels to accomidate things. Does anyone actually have an intake that works instead of all this bullshit?

 

There are no proper aftermarket intakes for the FC that include a cold air box. You will have to fabricate one yourself.

Buy any of the intake kits except the HKS (filter sucks) and then make a box around the cone filter. Cut a hole in the inner fender such that the box sucks air from the space between the inner and outer fender.

 

Thanks for the merger Aaron.

I understand I need to make one myself. I'm just looking for options in doing it. The aftermarket intakes made are junk, and no better than the stock air box. That is a good idea what you said Aaron. If you built a box to block the hot air from the engine bay and cut out a hole in the inner fender you'd have cooler air coming into where the air box sits. I'm guessing you're talking about using a 3" aluminum pipe with a cone filter on the end of it? Or are you talking about using one of those pod filters?

 

Most people, including myself, just use ABS plumbing pipe. It's cheap, easy to use and doesn't heat soak like metal does. There's a reason why OEM intakes are made out of "crappy plastic".

 

Air density is comprised of two primary components; temperature and pressure. The one problem with the stock intake is that it becomes a bit restrictive at higher airflow levels. The holes increase the airflow cross-sectional area, which reduces this pressure problem. Since the restriction is based on airflow, stock NA engines will see very little if any gain from this modification, while high-boost TII engines would benefit much more.

Throttle body - Not significant on a street-driven NA, and could actually reduce performance.
Intake manifold - Yes, cutting apart the plenum, removing the interior baffles, and welding it back together is a common race modification. I'm not sure how much power increase it will gain on a street car, but many people consider it worth the trouble for serious NA engine competitions that do not allow manifold replacement.

Yes, it is because crappy plastic is cheap and easy to work with, as you stated. Significant heat soak via straight wall tubing is a myth that is perpetrated by "performance" aftermarket parts vendors. However, that extra 0.2-0.5% hp certainly doesn't hurt.

ITB's and a standalone EMS are the top choice for performance, and are not overkill. Likewise, many of the lesser performance modifications you see on this forum are more for hobby than actual performance.

http://kgparts.com/index.php?page=jaytech
http://www.tweakit.net/shop/index.php?cPath=326_27_176
http://www.tweakit.net/shop/index.php?cPath=326_27_181
http://www.twminduction.com/Throttle...leBody-FR.html
http://www.injectionperfection.com/
http://www.hogansracingmanifolds.com/
http://www.mazdatrix.com/racing.htm

 

Alright, so actually doing the trick that Ice Mark did with cutting holes in the stock air box would work if you wanna go the cheap route.

I would love the port the stock throttle body and manifolds out if it's going to give performance. Is this possible to do with a S5 intake setup?

When I do figure out an actual intake setup, I guess I'll go with the ABS plastic plumbing pipe then and fabricate one myself. There's no sense in spend the 100+ dollars on an intake that isn't anything better than one I could make for 30. It makes sense that it wouldn't heat soak as bad as metal does. The nice thing is it can easily be cut to accomidate your needs. Also, I do plan on cutting a hole in the inner fender so that the filter can pull air from in between the inner and outer fenders. What are you guys using to make your cold air boxes? Anyone have some pictures of their intake setups? Also, if I go the different filter route, would a pod or cone type filter be better?

When I said overkill, I meant that they're overkill for a daily driver that that isn't going to need the extra performance, especially a N/A. I'm basically looking for cheaper options at this point, and ITB's and a standalone are NOT cheap, and I don't have the time to leave the car down to install that stuff anyways. When I do actually build a RX-7, I will be going that route though.

Those aftermarket intakes you have listed there look promising, but the prices are pretty crazy. Also, I've never heard of any of those websites before besides Mazdatrix. Anyone have experience with these companies?

 

Here is what I am basing mine off of:

https://www.rx7club.com/showthread.p...0&page=5&pp=15

go to the middle of the page. This thread was in the archives under 2nd gen projects.

 

Yea, that looks like a nice setup. That's what I was thinking of doing too, but maybe just cutting out a little bit bigger hole in the inner fender well to let more air in. I'm not sure what materials I want to make mine out of yet besides using PVC pipe for the piece going to the cone filter to reduce heat soak. The box more than likely needs to be made out of metal if you want a proper seal with the hood to prevent hot air from getting inside the box. Would you really need that piece of pipe going down near the brake duct though? I don't understand what that piece is really doing. Now, pod or cone filter...

I'm still wondering if it's possible to really port the S5 TB and intake manifolds though. If it is, I was going to buy some and start doing it while I still have the S4 setup on the car. I guess I could look over those aftermarket intakes again, but they just seem so damn pricey and I've never heard of any of those companies...

 

Is this a daily car?

I dont know if it would be worth porting the s5 manifolds but if you keep your s4 ones porting them will make a big difference if done correctly.
It took me 2 times to get something that worked pretty good i basically gutted everything out of the manifolds,actuators,rod's the whole nine. then i ported it out alot and slowly polished it until it was as smooth as glass.
After that i port matched the UIM to the LIM and reinstalled.
Now you can do this with the actuators and rods and sleeves installed too but the top end wont be as great. This was a drag car not a daily though. And pulled like a straped ape from 3k-7.5k but anything under 2.5k was pretty guttless. by far one of the best things i did to the car though.

I you plan on daily driving this thing i would go with the VDI setup,looks better to me but ive never tried it. but it is dyno proven power!

 

Yes, this is a daily car. I've also got the actuators, sleeves, and rods removed too and I do really love the topend. You do notice the torque loss, but IMO the top end power is worth it. I know the VDI system is supposed to be very nice, and also the S5 intake manifolds and TB flow much better then the S4 setup. Maybe if you ported the S4 setup it might be close to a S5 setup, but then again, if you port the S5 manifolds you'd be even better. Just putting on the S5 intake setup is supposed to be good for 10-15 HP.

 

what exactly did you do to gain the topend power?

 

http://www.mariahmotorsports.com/eng...iah_airbox.htm

?

Also, what is wrong with the hks style filters? Just replace the element when needed, i'd rather do that than wash a piece of paper and put oil on it.

 

Lol, who the hell would pay that much for that?

 

Someone who has no fabrication skills. I'm a software engineer, not a fabricator.

 

The Mariah box is good, but ****, for 300 dollars I'd rather rape my own ***.

When I removed the 5th and 6th port actuators, sleeves, and rods, the car picked up a little more topend power, but lost a little low-end torque.

 

Damn, your cheap! ROFLMAO @ U