Tommywrig

I’m a 17 year old with a 1988 Mazda rx7 convertible!
I really want to spend some time and build my car and gain power in a safe way. I just don’t know where to start and I’m hoping I can get some guidance! Please help me out and give me some ideas.

j9fd3s

iTrader: (3)

hmm i've been thinking about a thread like this for a while, and the first place to start is just to make sure the thing is running right in the first place.
this assumes you caught up on the servicing, so fluids, filters, spark plugs, stuff like that. i approach things like the car is a stock class race car, and there are enough adjustable things on the FC where you can make a huge difference in how it feels just by getting everything dialed in.
1. clean the windows, this is an old mechanics trick, and a placebo, but its a strong one, every car runs better with clean windows.
2. get a good tire pressure gauge, and set the tires cold to the number on the door jamb sticker. Mazda's test course is a race track, so their pressures are a good starting place. should be when the tires are cold
3. the NA cars have the spark plug wires all bundled together, and this is wrong. either separate the leadings from the trailings, or make sure they all cross each other at 90 degrees. this is worth a longer post, but there is a thing called inductive crossfire where one spark plug wire can fire an adjacent one, so they either need to be run separate or crossing them at 90 degrees cancels the signal. there are aftermarket plug wire holders for this although you can just route the wires and use a zip tire here and there.
3b, if the wires are not new, check resistance, they should be around 8K Ohms, and the limit is about 16K. the more resistance you have in the wire the less ignition power you have, so you want them low (too low and the RFI gets bad)
4. check the timing. i usually find that an S4 likes a couple degrees of advance, and the S5 doesn't. it may depend on the gas you have though
5. on the intake there are two 6 port actuators. push on them you should be able to move them by hand. if they are stuck, pop it off and see if you can move the sleeve. tools are ok here but be gentle, you don't want to break anything.
6. find a boost, or other pressure gauge and tee it into the little hose that does the 6 ports, run it into the cabin, and if you see more than 2.75psi the exhaust needs to come off to look for plugged cats or other damage. the 6 ports need ~2.75psi to open, and anything more than that is hurting power.
7. i like to run the belts as loose as i can get away with.
8. if you haven't already adjust the TPS and the idle mixture, no power here, but car will run better
9. loose some weight. clean out the trunk, keep the spare tire and jack at home. the stock cat back weighs a TON. use a lighter battery.

j9fd3s

iTrader: (3)

part II the chassis. so making power is nice, but we can drop some weight and improve the suspension too, none of it does a lot by itself, but when put together it can be big. or if you like a bunch of small changes add up to a big one
1. look everything over, we're looking for loose stuff, check for play at the wheels, etc. can be pretty quick, raise the car and try to shake the wheel, simple. if there is some play, it needs to get fixed.
2. tire pressure, we covered it, but its important the tire has a spring rate, and its floppy, so having a consistent pressure makes this consistent.
3. go around and torque all the chassis bolts to the high end of the spec. Mazda's competition prep book recommends this, and its free. i would add that most of these cars have an unknown history too so its nice to know that all the bolts are tight when you throw it in a turn. if you have some long extensions you can get to just about all the bolts without having to take anything else apart
4. replace the engine, trans, and front diff mounts. this one costs $$, but it makes a huge difference.
5. rebuild the shifter, and replace the boots. again another money item, but its worth it.
6. the front strut tops are eccentric, so you can make some small gains by rotating them to max negative camber and max caster (the strut is to the inside and rear), just with this you can get about -0.5 degrees of camber which is great in a street car
7. align it! like i say the stock parts can give you about -0.5 degrees of camber in the front, which is good on the street. i felt the best steering feel was zero toe in the front. in the rear zero toe feels great if you can be on the gas in a turn, but often you can't, i liked it one mark in from zero, ymmv. i did my last one with toe plates, its also possible to use an alignment machine, if you do setting the rear thrust to zero is the important part.

the bonus: brakes only slow you down... the pushrod between the booster and the master cylinder needs to be checked, and set correctly it makes a big difference in brake feel.