more fuel
 

I am running a street ported S4. I recently had access to a friend's wide band O2 and saw 14.7:1 at WOT from 6,000 - 8,000 rpm. So it would seem that the 460s can't keep up on top. There are other places in the power band where I see readings of 11.5:1, like around 5,000 rpm. Is this caused by mazda's ECU tune, or by my crappy pacesetter header/unequal length stock intake manifolds? Would just dropping 550s in as secondaries be too rich. shoot, I'm gonna go do it anyway. Anyone care to make a prediction?

I'd try cleaning the 460s, then buying an S-AFC.

Id say go for it, tell us how it feels after. clean all 4 before u put them in...
im probly gointo do the same thing with my mild street port S4

The 460s are clean. Megasquirt is comming. Why buy an S-AFC? I need more fuel, not less. Maybe an S-AFC and 550s....we shall see. I haven't cleaned up the upper runners or the chamber or matched the throttle body to the chamber. I am sure there is extra metal there. Need real equal length head pipes with a real collector, and some sort of smoother intake hose with closed box. That could be alot of air, I don't know. I really just wanted to see what people on here would say.

An S-afc isn't ONLY to remove fuel. Guess you didn't notice that part of Apex'i product description. Atleast the MS will take care of that.

okay, this is something I don't get, if I have a MAF that controls my injectors and it pulls the door all the way open, which tells the injectors to have 12V and flow all they can and I am still leaned out from 6,000 - 8,000 to the tune of 14.7 or 14.8, then how is an S-AFC gonna help. How can an S-AFC make more fuel flow from injectors that are already at 100% duty cycle?

the above is one hell of a run-on. I am proud.

The stock ECU doesn't allow 100% duty cycle. I thought that was common knowledge. I thought it was also common knowledge that anything above 80-85% DC on injectors is basically asking for them to fuck up.

THEN I ASK YOU AGAIN, why should anyone who wants more fuel from a mass air flow metered system ever want to use an S-AFC alone? what for that extra 5%?

That's highly unlikely. You need some pretty serious mods to reach the limits of the NA injectors, which you don't have. More likely there's something wrong with you car that's causing the lean mixtures or the wideband you used is suspect.

Well first of all, NZ just backed up the theory that you aren't at 14.7 AFR at WOT. I think anyone that's tuned any FC would tell you that these AFRs would have blow the engine long ago.......



Second of all the AFM is MAX'd out on my car from ~5krpm and up yet I can still increase fuel input with my S-AFC, so yea.......

Nother interesting note is that the MAX'd AFM only reads around 50-60% instead of 100%

How do you know that?

You might want to consult HAILERS about that...

Either way, an Apexi S-AFC allows you to increase fuel enrichment by 50%... Not sure how ACCURATE that % will be, but either way, a SAFC can (of course) be used to 'up' fuel % (not just decrease it).

All other issue's aside, an SAFC wouldn't hurt. It's highly unlikely you're maxing your 460cc injectors out with a "basically" mod'd s4 N/A...

:eek: He got the stock ecu to run 100? *craps pants*

Why would you think you couldn't? That makes no sense.

Here is a little 411 for ya little buddy.. Some ECUs will actually report duty cycles in EXCESS of %100. There is often a large disparity between what the ECU reports and what is actually happening. Hailers took his handy multimeter out and got a reported cycle of 99%. I am definately NOT advocating running at those duty cycles, but the ECU can do it..

I assume you mean aftermarket programmable ECU's because stock ECU's don't report anything about injector duty cycle. This is only a theortical number anyway, since if the calculated injector opening time is greater than the engine cycle time, then the injector is held constantly open and the actual duty cycle is 100%.

Yup.. thats precisely what I meant.

I'd say the wideband your using is suspect.

I've seen, using a Fluke 88, injector duty cycles in the high 90's on a 87turboii. Hard throttle driving, not normal about town driving.

I've easily seen afm openings in the high 90's at full throttle, under load. My definition of load is going uphill at full throttle in third and fourth gear. Using the SAFC readings to read the percent. IF your not seeing the afm at full open, then turn the key to ON and shove the vane in the afm all the way open and see if your SAFC is reading 100 percent.

For a short time I had a wideband in my non turbo 86 and that thing read rich most of the time, especially around 5500 rpm. I never rev'd it in the 7000-8000 range so I know nothing about what happens there.

Actually, reading in the 14's at high revs, I'd suspect the wideband for sure if it were a early TechEdge from OZ. If they don't have a power input voltage of approx 13.5, they'll read 14.6 all the time. They fixed that problem with later models. A halfass alternator or loose belt might cause the reading to default to the 14.6 figure.

I'm aware of aftermarket EMS reporting duty cycles, I was refering to the stock ECU. But if Hailers got 90% then shat.

what are you guy's 1/8 mile times?