Would there be any advantages to getting an SAFC II and leaning out the AFM some on a S4 NA that is basically all stock? All I have right now is a k&n drop-in, and the most I'd get is possibly the the bonez superflo system which is a pre-silencer then the hi flow cat.

I read that because the ECU runs stupid rich from the factory it can be leaned out for hp and mileage gains though I am mostly looking for mileage gains.

So any input would be great, especially if anyone else has a near all stock NA with an SAFC.

 

*waves* S4 NA, catless exhaust, pineapple inserts, otherwise stock.

Don't buy it for milage gains. You won't see enough to justify the cost. It will help some (and, actually, I find I get better mileage with the O2 sensor disconnected & just running the modified open loop on the highway), but not more than 1-2mpg under normal conditions.

For power gains, I think it might be worth it. I have to pull out a LOT of fuel up high to get near stoich (tuning with the narrowband, I find where stoich is, then adjust from there to go a bit rich). Also, I've noticed that high RPM time burns a lot less fuel now - stock, I could go through a quarter tank in 15 minutes of screwing around.

-=Russ=-

 

That's where the gas mileage comes into play... You just corrected your own statement without even taking a breath...

 

If you lean it out with a cat though the increased temps will likely burn up the cat.

 

Yeah, if emissions aren't a huge deal, try to get rid of the cats first.

 

i thought if you run no O2 sensor it would put your ecu in limp mode

 

I dont have mine connected right now either.

Its an s4... no limp mode

 

Ah. I don't usually consider "high RPM playtime" to be any particular time I'm worrying about fuel economy. It's going to suck regardless at high RPM, it just sucks slightly less.

I tend to consider fuel economy as "cruising, around town driving, highway driving" stuff.

-=Russ=-

 

Well I was thinking about $250~ for an SAFC then get it tuned, gain some hp and mileage would be easier and less expensive than say buying a different car then selling my NA FC. =P

Yeah I'm not looking for huge gains, though if possible I'd like to get 20mpg city if thats possible at all. I get 17-18 right now pretty easily, I just shift when the light tells me too. =P

I was looking at replacing the cats with the RB presilencer and pipe but then you have to block and the air pump and do all other kinds of voodoo... living in California it'd be a pain to do all of that and then have to undo it again to get the emissions working for smog.

 

you are tunning for stoich at WOT?

 

here hoppy:
http://www.racingbeat.com/FRmazda2.htm

the s4 presilencer has a tube to connect the air tube, though you would still have to take it off for smog, but you could pretty much just bolt it on.

plus, i believe they are changing smog to every 4 years, but dont quote me on it, no quite sure.

 

Yeah I've looked extensively at RB's site and rx7.com looking for a downpipe/presilencer solution. =P

Well whatever I do I have to be able to pass smog next year. I would like to do something that would just let me swap out my cats and put something in and swap the cats back in. I know my stock cats will pass smog so I'd just like to pull them out and simply put them back when the time comes.

http://rx7.com/store/rx7/fcexhaust.html

 

No. I'm adjusting tuning at WOT until the narrowband O2 sensor is no longer pegged rich (I see the voltage dropping from ~0.9v down to about ~0.7v), and then add a bit more fuel.

It's a NA. I'm not worried about detonation.

-=Russ=-

 

Temperature question:

So leaning out the air fuel mixture will cause the exhaust to be hotter right?

By how much would it make it hotter, just some or by like, hundreds of degrees?

Mostly I mean would it be enough to say melt the stock cats/mufflers?

 

yes. my friend melted his cat just by putting an aftermarket header on

 

Pre-cat, main-cat or both? Did he have stock mufflers and did those get borked as well?

 

main cat. pre cat was removed. he had aftermarket mufflers, but i dont think it would have any effect on those since there all metal

 

I thought cats were made of titanium?

 

Yeah, but you're assuming everyone drives around with their right foot on the floorboard. I mean, I know I do, but not everyone does.

His statement is right, it won't help much if you shift at 4 grand everytime and don't crowd the pedal.

The monolith (catalyst) in the converters has titanium in it, but it's like titanium impregnated ceramic or something. Icemark has a really good post on how it all works, but apparently cats use a ceramic monolith coated with titanium, rhodium and something else. Maybe MaryTylerMoorium to work well with the Rhodium . The outside is still good old aluminized or stainless steel.

 

back from the dead!

 

just a thought, since it is a S4 NA, maybe get a Rtek?

 

Or a megasquirt for the same price as an SAFC. You need to know more about your car to implement it, but I don't think you'll have too much trouble finding help.

Oh, and the thread was revived because I was searching and it turned up. Since it turned up, I thought I might as well correct the bad information for the next person who's searching.

 

For a normal person it will probably "pay for itself" over a year or more.

 

I guess you can crunch the numbers, and we'll set our assumptions a little low. At $3.00 a gallon, and 15 mpg, and 10,000 miles per year, you'd need 666 gallons (ooh, creepy ) which would be about $2000 over the course of a year. (Seems like a lot, but that's about $160 a month, or $40 a week). If the SAFC gave you 3 mpg better (18 mpg), then you'd only need about 555 gallons. Which would be $1665 dollars a year, saving you $335, which is almost exactly the price of one new. That's pretty sweet!

Although if gas is cheaper, or your starting mileage is better, or the difference is lower, you lose savings. :P

Like if gas is an average of $2.00/gallon, then the difference would only be $1333 - 1111 or $222 dollars savings, so it would take about a year and a half.

Or if you already got 20 mpg and improved 3mpg then, $1500-1304 = $198, so a year and a half again. 2 mpg would be 2/3's of that, so about $130, or roughly 2 and a half years.

But add on the coolness of having that little box on the dash, priceless!