Ronac

I have a stock 89 n/a execpt for a cold air box mod. I'm just wondering how much a S-AFC would help the car. Hp wise and fuel economy wise. Also, how would i get it tuned properly?

Ronac

is 10hp a number thats just written on the box or is it a dynoed number for a almost stock fc?

Scott 89t2

worse millige? how do you figure that? you will be leaning it out....

ilike2eatricers

Yea you would get more power and better gas mileage it tuned correctly. Not many mods will have power and better gas mileage.

Dan H

I agree, if tuned right, should get even better mileage. Only reason it will get worse if it is tuned to run in very rich settings. The flexibility of a piggyback ECU is a welcome benefit.

Ronac

Hey Scott
in the other link you told somebody it was $60 to tune the S-AFC. Is that one a dyno? and how long does it take?

ilike2eatricers

It would differ for each car and I believe most dyno shops charge by the hour. It would be good to have a wideband o2 sensor while tuning as well.

Ronac

If i get it tuned on the dyno, do i still need to buy a air/fuel meter to go with the s-afc?

ilike2eatricers

Where is your stock AFM? I dont think your car would run without one.

Ronac

i meant a guage..
sorry

Scott 89t2

no dyno. driving around on the street with a wide band pluged in. tunning by www.lr-racing.com great guy. it's like $60cnd/h should take an hour. dyno is probably $100cnd/h

he was building a single turbo 3 rotor FC vert when I was there a year ago. probably still there.

a/f gauges are garbage. you can't tune with them anyways. so no. you tune with the wide band above.

you just need to figure out what A/F ratios you want to be hitting. I have no idea for N/As

Ronac

and now my second problem. Where can i get one? cheap.

Scott 89t2

try ebay should be around $200usd now

Ronac

alrigh thx
and how do i figure out what a/f ratio i need?

Scott 89t2

you wait for people with N/A's to answer

or start another post asking

bingoboy

i have talked (not seen dyno sheets or watched them tune) to 2 people with NA's who actually had dyno'd their cars with mild bolt on mods. exhaust, intake, no emissions etc. one went from i believe he said 140 to 148 rwhp for an 8whp gain with his safc. the other guy went from 140 to 150 rwhp for a 10rwhp gain with his safc. the guy who picked up the 10 hp also claims his cars gas mileage improved by several mpg (maybe as much as 5 which i would think would imply he has a rather heavy foot). when i dyno'd my car a few weeks ago, i got 151 rwhp. my a/f ratio was around 12:1 at 5500rpm to 7000rpm and from 7000rpm to 8000rpm it went from 12:1 to 10:1. i have an intake, header, no emissions and exhaust on the car. they told me my car ran rather strong for the bolt on mods done to it compared to other S5 NA's they had dyno'd (most are around 140 apparently with intake and exhaust). by looking at how rich my a/f was, the guy that ran the shop told me with an SAFC or something similar i could probably see 10-15 more hp at the wheels by leaning it 10-15% after 4000-5000rpm up to 8000rpm. can't be very exact without dyno tuning for that.

bingoboy

~200 bucks on ebay is about as low as they go if you want a new one. if you search around the net a few shops have similar prices as well.

BDoty311

Why do people feel the need to post false info? With intake and exhaust you should get about a 10 rwhp gain, well worth the money. And you dont get worse gas mileage, you get even bette mileage because you are leaning out the mixture so you are using less fuel, and it burns better.

And please from now on not post bad info because some n00b might think that you actually know what you are talking about.

Ronac

So no hp gains? or just less?

RylAssassin

The S-AFC's job is to modify the airflow signal so that the user can controll how much fuel is being used at particular rpm's. So by adjusting your fuel to exactly what you need for certain rpm's how can this cause lower gas milage?? IT CANT!
Another great thing about this mod is that you can add MORE fuel at rpm's that would add more hp!!
So bottom line is its a great mod that can not only improve gas milage but add power if tuned properly.
Goes great with TII's and bigger injectors

Josepi

Why didn't you tune it for leaner than 12:1?! Unless I'm mistaken, there's no turbo on your car...

Scott 89t2

because he didn't have a S-afc or anything to tune with.... he just dynoed it.

Roy James

Thats just the numbers he pulled in by dynoing the car. He didnt tune it for that.

I need a WBO2 as well for my S-AFCII.

Ronac

so is 10:1 a good ratio?

Roy James

The lower the first number, the richer (more fuel) there is in the mixture. I think Stoich is 14.7 which is when fuel is perfectly Atomized in the air (someone back or chop me on that if wrong). Anything leaner than that will certianly most likely detonate and you dont want to be close to that number at WOT or you will have a good chance of detonating.

If you are not sure what detonation or spark knock is, its when the Air/Fuel mixture is too lean, like say 14.5:1 when it starts to get compressed in the compression stroke (similar principle of a rotary, just triangled out) and the pressure itself ignites the mixture while the piston/rotor is on its way to TDC and the explosion is working against the rising rotor/piston, instead of helping push it down/around. The reason being is there wasnt enough fuel to keep the temperature down and when compressed (*anything getting compressed will put off heat, just as releasing pressure cools down) it pre-ignited the fuel.

Your question about is 10:1 a good ratio, well it depends on the compression and pressure of the incoming a/f mixture. Typically for an N/A Rx7 that is a good bit too rich. Nothing bad will happen from having a mixture too rich, other than heavier carbon biuld up, lower gas milage, and lower performance, but it wont ping or damage that rich. Usually I have seen some N/A Rx7 guys shoot for about 13.0:1-13.5:1 range with not any problems at WOT. Turbo is another story, since the air coming in is already A-hot from the turbo and B-hot from being pressureized so quickly, that the mixture will want to be a little richer in order to keep it from detonating. Most people I have seen on here aim for about 11.5:1 give or take or maybe even 12.0:1. Richer/leaner depending on the set-up, compression ratio of the motor, and the amount of boost running ect ect.

Hope this helps you and maybe some others out.

Charles