Well after searching around and realizing that my friend's 4.6 Mustang will beat my N/A, it needs some more, cheap power. I was looking into working the intake some. I just put a Bonez race pipe on it not too long ago with the thought that if anyone gives me crap for no converters at inspection time, I can swap the cats back in. I love the exhaust but I know how restrictive that manifold is. Does anyone make like a short tube manifold that bolts up to factory exhaust, or is my best bet to cut up my race pipe and mod it to work with a different header. I also looked into the Pineapple port inserts and figured while I had everything apart, I could do all the Banzai block off plates as well as port match all of the manifolds and gut the throttle body. Would it be worth the time and money to do this or is completely beating a dead horse? I saw that Pineapple saw 8hp gains with the inserts and figured that with how poorly the manifolds seem to line up, port matching might help a lot. Any suggestions are welcome.

 

look up "Beefy N/A thread".

 

Personally, I think that's all a waste of time and effort.
Even if you see the full effect of the inserts and port matching, you're still getting what, about 150 hp at the wheels?
Hold on, homie!

Unless you go really crazy on the motor, the NA is always going to be the loser in a drag race with almost anything.
Spend the money on suspension and tires, put her on a road course and things even out (depending on the course...you'll still die a slow death someplace like Road America but would be OK at Roebling Road).

The 2nd gen was more of a sports/tourer and it's quite good at that but the NA versions will never be out and out sports cars unless you fully commit to it becoming a racecar.

 

I already do some autocrossing and am starting to get hooked but really, I've got a bunch of spare time right now in school and could probably do all the machine work in one of my Manufacturing Processes lab. and seriously, $40 for those inserts is nothing. I mean, thats like $5 per horsepower. Where else are you going to get that? I've done a tune up (still needs wires though), full synthetic in transmission and diff, exhaust and rx7.com intake kit. Just looking for a little bit more was all.

And I have read most of that thread. Thats what inspired me for this.

 

Build a custom intake box and mod the front bumper to allow fresh cold air to go directly to the intake filter, that will help with the overall flow of the engine.

You should find a local exhaust shop to build a header for the car, if not, Racing Beat and Corksport both offer bolt-on header.

There are other things you could do, but would involve a lot of modifications and tuning if you stay with NA. One of the few would be porting the engine to a larger street port or bridge port to increase power.

If you're getting hooked with AutoX, do all the suspension upgrade and brake upgrade first. Those will stay with the car whether you stay with NA or swap a turbo engine in, so may as well get those done and go to AutoX again; if you have fun then there's no real need to get more power.

 

I saw the Mariah box, and since I work with a metal a bunch (built a custom four link in the rear of my Jeep Cherokee this summer) then it shouldnt be too difficult to build. Do scooped headlight covers help much? I would imagine a combination of the 2 would help a bit right?

 

Look at the headlight in the closed position and explain exactly what the scoop is feeding.
Also, why is the Mariah airbox any better than the stock airbox...to me it looks like a snazzier version of the same thing.

Finally, do you know that the stock intake is actually choking down your power?
I think it's tempting to make changes like this (and I've certainly done my share, so I'm not immune) because "different" somehow equates to "better" but that is usually not the case.

 

What do you mean that the stock intake is choking down power? Like the tube going to the throttle body? I known that is. Anything ribbed like that is creating extra turbulence.

And why would a scooped headlight cover not be beneficial? I looked at mine earlier and thought how well it would work. Especially if you had somewhat of a sealed off heat shield then the only sir to come in would be somewhat ram air and it would be cold air from the exterior. I don't see how it couldn't be beneficial.

 

Exhaust upgrades, port inserts and a working S5 intake manifold will be the most effective modifications (short of porting the engine) . Just about anything else will net almost no gain, be too expensive to justify, or be a combination of both.

The stock airbox pulls from the bumper area, which already sees "cold air". You could replace the tube between the AFM and throttle body with cheap ebay tubing and couplers, but I'll bet the "gain" wouldn't show up on a dyno.

 

Well so far I've got a K&N 3" cone filter off the MAF, Bonez stainless race pipe and 2.25" piping from the race pipe back to Trust quiet series mufflers. I'd like to open up the exhaust more but I know that it will get obnoxious quick. Headers are about all I wanted to add (for now at least and I know that will already make it louder) but don't really wanna go cut up that Bonez pipe. I will if i have to and add a flange further down to meet headers but wanted like a short tube header that would bolt in with near stock dimensions. I suppose I can make my own if I buy the flanges but its a lot of bending and cutting and welding.

 

1. the stock exhaust manifold isn't that bad, it has a much better port match to the engine than the off the shelf headers, the engine outlet is 48mm, the manifold inlet is 50mm, and the Rb headers are 44mm... if you buy headers port match them.

2. the atkins or pineapple sleeves are a good idea. while its apart, i think it would be a good idea to smooth any casting flaws, and a port matching might be a good idea.

3. tuning! even with the stock ECU there is a noticeable seat of the pants difference if you're willing to play with timing a little, i like to advance it about 2-3 degrees, on the S4 ecu.

4. consider the S5 upper intake, the VDI extends the hp curve at the top.

5.to go much further, you either need to rebuild the engine and or buy an ECU, not cheap

 

^^^^ This is what I was hoping to hear! That makes sense then about the headers and that is fine because making them would suck and buying them to cut them up would suck even more.

How much tuning can I do? I've played with the variable resistor and the brass screw on top of the throttle body. Also, I've heard stuff about ignition timing but what gains can be seen there? Will advancing it make it run rough and stumble at low rpms?

 

Both things you messed with did nothing. Variable resistor affects fuel at idle and the screw affects idle air a smidge. I laugh when I see threads asking for big hp gains with an NA on a small budget. Ain't happening. I used to have the same mindset.

Best thing you can do? All the regular maintanence, clean your grounds, test everything, replace fuel and air filters, clean the aux sleeves (I went to the Atkins sleeves. And don't think it adds any real hp, maybe a 1-2% increase. It smooths the air flow transition more than anything else.), replace plugs and wires with the NGK replacements, make sure absolutely everything works as it did from factory. I will GUARANTEE you will feel a noticeable difference.

Our cars are all over 20 years old, and I bet a good 85% of them have not been maintained as they properly should be. And we're all guilty of it. After you have all that sorted out, then you can start making useful mods. Without opening up the engine? Custom intakes and exhausts (not just hot air intakes, I'm talking fully custom runners and port matching.), possibly ITBs with larger injectors and a standalone, lighten up the power train, etc. even then, you won't see too much power. So in essence, unless you plan to open up the engine and go to town, just stay close to stock and keep everything well maintained. I may not run a 14 in the quarter, but I don't ever expect it to.

If you want power, go turbo. If you want a fun and reliable daily driver with some pep, keep the NA.

 

^Well said, listen to the man.

I've spent more money restoring the car or upgrading parts that needs replacement, and the results is like what REAmemiya_fan said, noticeable difference, considering that the only two things I did that are power related were Blitz intake and Corksport cat-back.

 

Yea, guess that makes sense. Well, after 152,000, im sure sooner or later it will be time to crack it open.

Why don't rotors respond as well N/A as piston engines do?

 

Because rotaries are more like two strokes than regular piston engines.

You don't have all the easy options of a normal 4-stroke- cams, valves, etc....like a two stroke, the power is in the ports.
Plus, Mazda did a pretty good job initially and didn't leave gobs of power at the design table.

 

they do! what other car can you put a $200 cat delete pipe on, tune it up and make 25 hp?

we just dropped a built B18C engine into the race car, and its basically a blueprinted stock engine, it makes 190WHP, and it is just about as fast in a straight line as my stock Rx8. pretty sure the stock engine + rebuild + blueprinting was at least 5k.

or shoot you can take any 13B, mill 2 more holes in the rotor housings, fill the ports in the irons, power doubles, and you can go to the race track and hunt Porsches.

 

Already did the cat delete. That was a huge difference! I also felt a good amount of power increase from the filter change too (despite what everyone else says...) although it definately made my power band narrower.

 

As per the characteristics of a two stroke when i build my exhaust I'm going to keep the ports seperate until the y pipe split, and im going to to have to think of a way to collect and redistribute the gases in a way that will create good vacuum in the other pipe and keep flowing good. That is the point of the header, create a vacuum in the collector to help pull spent gasses (air moves much quicker in a vacuum than it does under pressure).

 

Mostly beating a dead horse if this is a street car. It should be of no surprise that a car with a 4.6L engine is beating a car with a 1.3L engine in a drag race. Your engine will max at about 200-250hp in a street configuration, and any more power would be too loud unless you go turbo.

See this link for Custom Exhaust Systems
Rotary Tech Tips: Exhaust System Configurations

My car has v-band clamps welded to ends of an aftermarket high-flow cat. I also have a piece of straight pipe of the same length with v-band clamps welded to the ends. This way I can easily swap out one part or the other.

This link shows how to build a good performance intake tract.
https://docs.google.com/file/d/0Bzy-...hl=en_US&pli=1
And see this link to see how it applies to a 2Gen car.
E/P Convertible

 

Thanks everyone for responses. I'm going to get the Pineapple inserts probably this week or next and am looking into the Apexi SAFC, SAFC II, or the NEO for a little fuel control. Does anyone have some recomendations to a good A/F meter that isnt too expensive?

 

I would just spend the money and get a wideband kit. That way if you have the itch to get more power (whether NA or turbo swap) you will have it there and working. AEMs are usually between $150-$200, but I've seen used ones sell on other forums for $75 (a couple BNIB too).

 

I just dont have the money for a wide band and I think that with the right A/F meter and building my own fuel maps on the SAFC or NEO that I can achieve all I need for now. I want to do a high comp turbo build next year but for now I figure I can get a used SAFC and then resell it in the future for nearly what I paid for it.

 

You're suggesting tuning with a narrowband? Narrowband sensors/meters won't give you anything more than an estimate. They're not for tuning. They're only good at reading one AFR: 14.7.

 

ive had widebands on both stock S5's and S4's and the S5 runs really rich* and the S4 doesn't. so on an S5 car you can pick up a big gain by leaning the thing out a little, but the S4 is not over rich to start with, so the gains are really small. if anything the S4 could be a little richer, which can't be done on the SAFC's**

i don't have an S4 right now, but to use the SAFC the stock fuel system would have to deliver more fuel to start with. i would like to try a bigger fuel pump and higher fuel pressure, but that would be a $300 experiment...


*the S5's run rich, because Mazda had to warranty the cats, and so they needed to keep EGT's low(er). i've never tested an S4, but EGT's on a stock S5 stay under 720c, which is piston engine territory.

**the SAFC modifies the signal from the Air Flow Meter. the AFM is close enough to 100% open by 6000rpm on a stock car, and it'll be 100% open sooner on a modded car, because it flows more air. since the AFM is at 0 volts wide open (5v closed), the SAFC can't make it be more opener, as voltage would have to go negative.