Getting more power
10-12-21, 10:02 AM
#1
Newbie
Thread Starter
Getting more power
I recently acquired a 1988 S4 N/A gxl. I'm looking to increase power, and possibly add a turbo at some point in the future. Any suggestions on where to start. I got the FC with the intention of it being a daily driver / road course runner. Any suggestions would be greatly appreciated.
10-12-21, 11:17 AM
#2
Information Regurgitator
Searching is your friend. To get you started for N/A power. Lots of info here Naturally Aspirated Performance Forum - RX7Club.com - Mazda RX7 Forum
Also decide your eventual power goals and look here Time Slips and Dyno - RX7Club.com - Mazda RX7 Forum Then se what setups the people making the power level you want are running. We'll answer questions to help you along but we can't do all your research for you. Making the sure the car is running good, doing a good tune up plugs, wires, filters, etc. is always a good place to start. After that opening up the exhaust is where most start in their quest for more power.
Also decide your eventual power goals and look here Time Slips and Dyno - RX7Club.com - Mazda RX7 Forum Then se what setups the people making the power level you want are running. We'll answer questions to help you along but we can't do all your research for you. Making the sure the car is running good, doing a good tune up plugs, wires, filters, etc. is always a good place to start. After that opening up the exhaust is where most start in their quest for more power.
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10-12-21, 11:45 AM
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i'm glad you asked! there is a bunch of stuff you should do. FC's are complicated, and there is a bunch of you should check and adjust before you buy any go faster stuff.
sometimes this is called stage zero, get the car up to speed. since there are a bunch of things that are adjustable, when you have all this stuff adjusted right, it makes a big difference.
the service manuals are here Foxed.ca - Mazda RX-7 Manuals
1. oil, use whatever you like, but it should be changed frequently. if you change the oil and the car runs better, its too old.
2. if you're keeping the stock air cleaner, the stock filter is fine. air cleaner is designed for ~180hp so its fine. a cone filter helps, you'd want to put a shield to keep radiator heat away
3. adjust the TPS, the idle mixture and set the speed. if its a new to you car, you should check this quarterly, or when you change the oil
4. new fuel filter, but also the sock in the tank, ND part number 952-0043
5. new spark plugs. stock is fine. these do last 30k miles, but for a high performance car you'd want to change them at like 15k
5a. spark plug wires; either replace or check them. resistance new is like 7.5k ohms, and the upper limit is 16k, the more resistance the less ignition power you have.
5b. its worth a longer post, but either route the wires so that the trailings are away from each other and the leadings, or make them all cross at right angles. the search term is "inductive cross fire" https://www.rx7club.com/build-thread.../#post12481669
5c. set the timing. the S4 likes a couple degrees of advance, the S5 doesn't
6. push on the 6 port actuators, they should move , if they don't pull the actuator off and see if you can turn the sleeve. if its stuck, the intakes need to come off. if you can get it to turn, you're good.
6a. on an S4 you can tee a pressure gauge (boost gauge) into the 6 port hose, go for a drive, if the backpressure is over 2.75psi, then you need to look at the exhaust. (the 6 ports need 2.75psi to open).
7. exhaust. for a street car the stock manifold works great. the S4 exhaust just needs to have any damaged cats fixed. the S5 exhausts were welded on the inside of the pipes, so there are gains from grinding these down
7a. for a street car, stock manifold into one of these https://www.racingbeat.com/RX7-1986-...silencers.html with either a presilencer or cat, and then into cat back of your choice is pretty ideal. you'd get 90% of the power of a header, but it could be quiet and emissions legal, plus its simple.
7b. add a header. the RB header needs to be port matched to the engine to see any gains, the engine is 48mm and the header is like 43mm, there is enough meat to add a bevel but still, kind of why the stock manifold is the better choice.
8. Fuel control. the S4 has a really old EFI system, and it would benefit from a new ecu. the S4 runs a pretty ideal mixture, so just a fuel controller (SAFC) doesn't do much. the S5 runs much richer (the cat had a longer warranty), so it does benefit a lot from something like an SAFC.
moving on, the alignment makes a big difference, i like zero toe in in the front, and as much camber as the stock parts you can get (-0.5, the strut tops rotate), in the rear a little toe in (about half of stock) and as little camber as you can get (-1.2 to -1.5)
depending on the model you're starting with shorter tires are great, going from 205/60/15's to 205/50/15's really wakes the thing up. i like to check the pedal heights, and spend a long time getting the seat and steering wheel in the right place.
the engine/trans/diff mounts are also usually bad, the competition ones are better in the diff, and trans, the engine is up to you (small NVH penalty)
and then next step is weight loss. the Aluminum hood + aftermarket cat back is an 80lbs savings. (combine a little power, with a little weight loss and better handling is pretty big, its ends up being a really fun street car). i also ditch the spare tire and jack.
and lastly, clean all the junk out of the interior and wash the thing!
sometimes this is called stage zero, get the car up to speed. since there are a bunch of things that are adjustable, when you have all this stuff adjusted right, it makes a big difference.
the service manuals are here Foxed.ca - Mazda RX-7 Manuals
1. oil, use whatever you like, but it should be changed frequently. if you change the oil and the car runs better, its too old.
2. if you're keeping the stock air cleaner, the stock filter is fine. air cleaner is designed for ~180hp so its fine. a cone filter helps, you'd want to put a shield to keep radiator heat away
3. adjust the TPS, the idle mixture and set the speed. if its a new to you car, you should check this quarterly, or when you change the oil
4. new fuel filter, but also the sock in the tank, ND part number 952-0043
5. new spark plugs. stock is fine. these do last 30k miles, but for a high performance car you'd want to change them at like 15k
5a. spark plug wires; either replace or check them. resistance new is like 7.5k ohms, and the upper limit is 16k, the more resistance the less ignition power you have.
5b. its worth a longer post, but either route the wires so that the trailings are away from each other and the leadings, or make them all cross at right angles. the search term is "inductive cross fire" https://www.rx7club.com/build-thread.../#post12481669
5c. set the timing. the S4 likes a couple degrees of advance, the S5 doesn't
6. push on the 6 port actuators, they should move , if they don't pull the actuator off and see if you can turn the sleeve. if its stuck, the intakes need to come off. if you can get it to turn, you're good.
6a. on an S4 you can tee a pressure gauge (boost gauge) into the 6 port hose, go for a drive, if the backpressure is over 2.75psi, then you need to look at the exhaust. (the 6 ports need 2.75psi to open).
7. exhaust. for a street car the stock manifold works great. the S4 exhaust just needs to have any damaged cats fixed. the S5 exhausts were welded on the inside of the pipes, so there are gains from grinding these down
7a. for a street car, stock manifold into one of these https://www.racingbeat.com/RX7-1986-...silencers.html with either a presilencer or cat, and then into cat back of your choice is pretty ideal. you'd get 90% of the power of a header, but it could be quiet and emissions legal, plus its simple.
7b. add a header. the RB header needs to be port matched to the engine to see any gains, the engine is 48mm and the header is like 43mm, there is enough meat to add a bevel but still, kind of why the stock manifold is the better choice.
8. Fuel control. the S4 has a really old EFI system, and it would benefit from a new ecu. the S4 runs a pretty ideal mixture, so just a fuel controller (SAFC) doesn't do much. the S5 runs much richer (the cat had a longer warranty), so it does benefit a lot from something like an SAFC.
moving on, the alignment makes a big difference, i like zero toe in in the front, and as much camber as the stock parts you can get (-0.5, the strut tops rotate), in the rear a little toe in (about half of stock) and as little camber as you can get (-1.2 to -1.5)
depending on the model you're starting with shorter tires are great, going from 205/60/15's to 205/50/15's really wakes the thing up. i like to check the pedal heights, and spend a long time getting the seat and steering wheel in the right place.
the engine/trans/diff mounts are also usually bad, the competition ones are better in the diff, and trans, the engine is up to you (small NVH penalty)
and then next step is weight loss. the Aluminum hood + aftermarket cat back is an 80lbs savings. (combine a little power, with a little weight loss and better handling is pretty big, its ends up being a really fun street car). i also ditch the spare tire and jack.
and lastly, clean all the junk out of the interior and wash the thing!
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