How to gain horsepower easily and cheaply
 

I have a 1991 convertible. I am very satisfied with the engine. It is a work of art :angel: . I want to know some cheap and easy ways to gain horsepower. All i know about are carbeureted engines, it's pretty easy to bolt on a 4 barrel carb and intake. hopefully this engine will be pretty easy to mod also.

-Thank you, Vasili

welcome to the board. :)

the simple answer is to start with a performance exhaust system.

of course it might also help to know what kind of power increase YOU have in mind.

you could also put an aftermarket intake on it. i did that and seemed to have a change in power a little bit

just any little bit of power i can get and do you know what piping the stock exhaust uses. Is it 2.5'' ?

Where did you get your intake from all I can find is aftermarket air filters

focus on the exhaust. it's the single-most bang-for-buck modification you can make as long as you don't have emissions inspections to contend with.

relatively speaking, the stock air filtering system is not much of a restriction since you wouldn't be changing the MAF system with it. I am skeptical of clams to the contrary, but it may just be me.

I agree. Biggest gains are in the exhaust, dollar for dollar. Unfortunately, keeping it quiet is the tricky part.

More Power, Ease, lower cost

pick two

Unfortunately, your engine is not cheap or easy to soup up, and your car is the heaviest RX-7 made.

Given that, your best bet is the exhaust, as mentioned already. Here are the basic levels in order from more performance/cost/noise to less performance/cost/noise:
A) A full race exhaust.
http://definedautoworks.com/prod2_1.html
B) A full street/race exhaust.
RX7 1986-1992: Exhaust - Complete Systems: Road Race Exhaust System - 89-92 RX-7 Non-turbo - Man Trans -
C) A catback exhaust.
RX7 1986-1992: Exhaust - Cat-Back Systems: Power Pulse RX-7 Exhaust System - 86-92 RX-7 -

Since your car already comes with a "cold air intake", and it is not a significant restriction for your current engine, it will be pretty expensive to upgrade the intake to a point that it will matter. Upgrade the exhaust first, and if you then decide to upgrade the intake then the best performance increase would come from an Individual Throttle Body (ITB), manifold, standalone Engine Management System (EMS), and about $1,000 for professional installation and tuning.
http://www.borlainduction.com/Thrott...carb_vs_fi.pdf

The RX-7 convertible is considered to be one of the best convertible sports cars ever made, so there isn't all that much you can do to improve it cheaply or easily. You can look at this as either a good or a bad thing, lol.

After doing the exhaust (I chose the racingbeat full race duals), I will be going for the apexi safc 2 since the car is supposed to be running quite rich. Also, I have heard an aluminum flywheel is another of the best "bang for your buck" mods you can do. Other than that, I would highly suggest putting your money in suspension. I just finished putting the racing beat sway bars, polyurethane bushings, and stance gr+ coilovers in my car. A little under chassis bracing and maybe a rear upper strut tower brace and you have yourself a fine handling ride!

exhaust definitely a good upgrade but sometimes I love my stock exhaust just less obnoxious and heaty

Not really up on the S5 but how about optimizing what you already have? New set of plugs and wires if your not sure when they were changed last. Maybe auxillary grounds, clean the maf sensor, new O2 sensor with the new exaust? I doubt they'll be any huge gain but a nice base-line is good and assuming the car is new to you...you'll be more familiar with it.

Every car I have seen posted up with an Apexi SafcII has had nothing but Problems.
Try the RTEK 2.1 by Pocketlogger.It is Programmable and not as prone to problems like the Apexi.
it is also a straight swap for your old Ecu,so no hacking of wires is required.

like everyone said, exhaust, intake extractors etc all add up!!

I find giving a car a good tuneup and addressing the wear that has accumulated with age to rank high on bang for the buck. Not only that, it establishes a solid foundation for the sorts of things that people immediately think of, the flash parts like mufflers and such.

Good ignition clean up and exhaust mods

3 rotor!!!

and that is "cheap"?...That's a 6 thousand dollar mod..not to mention he needs an ECU!

Ok now how do i make it just faster overall

Engine swap? Find an old 302 and transmission for less than a grand, granyspeedshop has pretty much everthing else you would need for around 1200. Thats pretty much 230 hp after swap in an engine that weighs only 60 lbs more than a 13b. Not to mention the biggest engine aftermarket.You might piss of purists but the bang for buck doesnt lie.

bring all maintenance up to date first

again, you'll need to provide a guideline to what you're seeking. you are likely to NOTICE the difference the exhaust system makes, but as Evil Aviator mentioned, you have the heaviest Rx-7 ever produced and it's probably still going to be slow - relatively speaking, of course. :( if you can live with that, do it and be done. oh, and it doesn't have to be loud and obnoxious. RB exhausts are very civilized and street-daily-driver-friendly. think maybe along the lines of 15 HP - maybe 20, but that's probably a stretch.

if you actually want the car to be somewhat fast or genuinely fast, then you've graduated to a turbo rotary and my cheap advice is don't even bother working with the 6 port. put a honest-to-goodness turbo engine in it. of course, you have non-rotary options, too. however, neither of these options will be cheap! the 13B-T will just be cheap-ER since it doesn't require fabrication.

intake, full exhaust and a tune

Did rx7 come with dual exhaust

Also will apexi n1 mufflers add power

No it never came with dual exhaust and any aftermarket exhaust system will help better airflow apexi and hks are one of my favorites along with greddy