i’ve been driving my rx7 fc 1990 non turbo sadly and i feel like i’m needing a little bit more power, is there any mods i can do that won’t lead me far from stock but also give me a little extra horsepower for pretty cheap? i’m not looking to turn it into a full fledge track car, i just want it to have a little bit more power as it is my daily.

 

nothing dramatic, but there are a few things you can do.

0. work on your driving skill, if there are turns a good driver in a so/so car will be way faster than a bad driver in a really fast car...
1. run shorter tires, going from 205/60/15 to 205/50/15 makes a big difference....
2. loose some weight. the stock cat back is HEAVY the steel hood is HEAVY, changing both is about 80lbs!
3. tune up the engine. new plugs, replace or check the plug wires, new fuel filter, new pump sock, new air filter. i like to check the timing, S5 likes to be stock, but S4 likes a couple degrees of advance. set the tps.
4. make sure the 6 port valves move freely (you can push on them by hand) and the VDI too, if these don't work, you loose big
5. exhaust. the S5 has all the exhaust pipes welded on the inside of the pipe, and this makes the ID of the pipes really small at the flanges, if you're bucks up RB makes a nice down pipe, if you're bucks down, you can grind the welds down.
6. get an alignment, i like as much camber and caster as you can get in the front with zero toe. in the rear i like a little toe, about half of the spec.
7. lighter flywheel helps a lot, although this is $$

if you do all that you basically still have a stock car, but its much sharper than what the average FC is... if you like its basically a showroom stock race car...

going further requires pulling more weight out (AC, bins, seats, battery), and adding cost, ECU, headers, intake.

 

thank you so much!

 

+1
Adding to:
After header install and air pump/emissions removal, block off plate on intake manifold and gotta wire open the 5th and 6th ports and if vdi is stuck wire that open too. If you do this instead of just mashing the throttle to go fast, progressively move your foot down. It will give you some of that torque back but will really give you that top end. I can definitely attest to the full exhaust!!! I got the RB header that is more curvy (more equal length imo). This all was pretty pricey for me tbh, RB Header then full custom 2.5" and bought mufflers and then either labor or DIY. I probably spent $600+ after 2 revisions. long story.. don't bite off more than you can chew lol.
-I was running 91 or 93 (even tho its really not worth it) and I messed with timing pretty hard and I think it did add power (or placebo effect). Cool nights... she pulled hard for a 30 yo n/a car. Would actually put me in the seat. Gapped on 8th gen V-6 Accord, decent race with modded Cobalt SS and pulled on civic hatch.
-I'm making a true cold air intake rn for mine out of fiberglass (basically just a cylinder large enough for a large cone filter + 1" air gap) and then route a pipe to it that sits in nice cold air (just route it down into pass. brake duct not blocking air stream to pass. brake). - Price of Filter, Fiberglass and Resin (you can also use for other projects)

-Check for vacuum leaks by taking apart intake manifold completely (good practice anyway bc its complicated). Replace hard vacuum hoses.
-Fuel filter and injector cleaning. Rusty gas tanks.
Add extra protection of an e-fan (I have only e-fan so i'm bias) and maybe a better radiator but don't get cx racing (fragile)
-Bushings are junk replace them with something stiffer (delrin bc poly squeaks)
-Toe eliminator bushings or replacement $80 + use of a press aka labor
-Clean plugs = max power but good fkin luck keeping plug a clean lolol.
-I used Amsoil Powerfoam on my engine to hopefully help with any built up carbon deposits. DON'T USE SEAFOAM coolant seal will swell if you do
- Removing any weight that you deem unnecessary (spare & tool kit, airpump, a/c, ps,brackets)
Find some really lightweight wheels that aren't ebay specials and will look good. Example: I'm going to be running Evo 8 wheels I picked up for $300 quality and sharp. (with these wheels you need longer studs,)

This is all i can think of
Dunno why I'm getting all in-depth lol
If there's something your afraid to do or have questions just ask and search cause its definitely been done before.
Mods add up very quick with these cars, $$ wise.

 

don't gotta, its a fast way to make the car slower....

 

Yep, even though I removed my air pump years ago, I did for a time run a header and the air pump with functioning aux ports and VDI. Removing the ACV and air pump doesn't make the car any faster. Probably shaves about 15lbs off the weight of the car at the cost of losing some low end torque.

 

Sorry yeah your are correct. What I mean't is I had to because mine were stuck. Who needs torque when you have gears am I right lol.

My plan is to make a little setup that opens up the ports with an rpm switch and and a small motor. For the distant future though.