ThatGuyOnTheGas

Hello all. I've heard that a stock N/A runs a tad rich. And that you can get a bit more power by leaning out the mixture. I couldn't find a guide or write up for it, but I was wondering what kind of power gains would it give, and how to do it. Also, any info on fuel economy before and after would be nice to know as well. I've got a 91 Convertible, under repair, and I was thinking about doing something like this when it's all back together. And if anyone knows of a good computer program for details on the mix, I'd be interested in that as well. Thanks!

barkz

iTrader: (1)

before you start messing with your afr's i suggest you get a wideband o2. and im not sure what you mean by "computer program for details"... theres no piggy backs for us, rtek 2.1 if you want logging/tuning

misterstyx69

iTrader: (142)

All I am gonna say,Look up a thread by SonicRat.

j9fd3s

iTrader: (3)

well first the S5 NA cars do run rich, or perhaps i should say they run richer than the S4's. why you ask? well the warranty on the catalytic converters went from 3/36 to something like 7/70 for 1989, so Mazda (and everyone else) took steps to keep the cats intact. this means keeping the EGT under ~700c, and this means running it rich.

i've put EGT and widebands on the S5 and EGT stays between 500-700c no matter what you do, this just happens to be the temp range the cat wants.

mixture @wot, is about 12.2@4000rpm, and then by 8000 it is about 11:1. the S4 is also 12.2@4000rpm, but then it'll hit 12.6 around 5500, and then its about 12:1 at redline

just by leaning the mixture to be 12.5 from 4000-8000rpm, it FEELS like you gain about 40hp. going leaner gains more hp, but the butt dyno can't tell. 90% of the gain is going from 11 to 12:1, it is better to leave it a little richer than a little leaner.

how we do this is the second part. the stock ecu isn't adjustable, although the rtek is and sonicrat is working on a similar chip. you could also run a super AFC/fcon/other fuel controller.

the AFC is very simple, i actually like the 5 **** one, and you simply just lean it out a little, make a run, and then lean it out again, and make another run, until its as fast as its going to get. on an otherwise stock car i think i was making corrections like 4% at 7000 and 2% at 5000, it wasn't much. no O2 needed for that.

the more complex the ecu, the more you need a wb.

ThatGuyOnTheGas

So would it be worth it to do, since I plan on adding a turbo in the near future, or should I wait until I add the turbo and change the fuel injectors and all the other fun stuff. And if I should wait, is there any other way to make power relatively cheaply?

barkz

iTrader: (1)

just straight pipe it

ThatGuyOnTheGas

I had actually planned on that. I really like how straight pipes sound, especially on a rotary

barkz

iTrader: (1)

i was kidding...

j9fd3s

iTrader: (3)

if you plan on adding a turbo later, i wouldn't bother. to go turbo you'd have to change the whole fuel system anyways, so why do it twice?