using an apex AFC for fuel under boost

L

liam821

Member
So heres the story, a friend came to me asking me to design him a custom turbo kit for the mazda protege5 wagon. And i have been thinking about the fuel system. I have alot of experience with turbo hondas and i also own a mitsubishi eclipse turbo.

Never the less i run a very cool, cheap, and easy fuel system in my turbo honda.

Here is the parts you will need

Large fuel pump
apexi SAFC (add on fuel computer)
Larger fuel injectors, say 40% larger. I used 450CC eclipse injectors in my civic.

The idea is....with the larger injectors and your AFC set at -40% for fuel, you lower the MAF input signal so far that you extend the maxium allowed MAF input signal. This allowed for 10psi of boost on my honda and im guessing similar results on the mp5.

The end result is very very smooth power, silk like 1/2 throttle driving. For a low boost application (10psi or less) its awesome. Nothing is as good as the stock computer..so why not just use it? :)

The eclipse guys use this same type of setup, increase the fuel injectors and lower the MAF input so they dont hit fuel cut as soon. No reason it wouldnt work on a mazda.

Here is a write up i did on honda-tech.

http://www.honda-tech.com/zerothread?id=137901

What do you all think? :)

liam
 
2 Problems with that....First tha MAF in the Proteges is tamper proof meaning if you fool with it you are most likely going to break it. and then 2 our ECU have a closed loop program at WOT so it would work at 1/2 throttle and all that but once your friend stomped on it BOOM he will lean out due to the computer taking over and disregarding any singal going to it including the signal from teh S-AFC....the cheapest setup for the protege would be a MSD fuel pump and a Vortec 10:1 FMU which is what I am running...oh yeah and another thing the FS engine is only good with stock internals till about 8PSI anything above that and you will need forged internals. Just some advise to ponder so you don't blow up your friends P5...also our fuel systems and requirements are much different than hondas.
 
chdesign said:
2 Problems with that....First tha MAF in the Proteges is tamper proof meaning if you fool with it you are most likely going to break it. and then 2 our ECU have a closed loop program at WOT so it would work at 1/2 throttle and all that but once your friend stomped on it BOOM he will lean out due to the computer taking over and disregarding any singal going to it including the signal from teh S-AFC....the cheapest setup for the protege would be a MSD fuel pump and a Vortec 10:1 FMU which is what I am running...oh yeah and another thing the FS engine is only good with stock internals till about 8PSI anything above that and you will need forged internals. Just some advise to ponder so you don't blow up your friends P5...also our fuel systems and requirements are much different than hondas.
Click to expand...

Now that just cant be right. You dont have to tamper with the MAF sensor, you just plug the SAFC inline between the MAF and the ECU. Even though the ECU does into closed loop mode (which almost all cars do at WOT) it still has to take in account the MAF reading. How else can the car know how much fuel to input into the engine when your at 12,000 feet and there is much less air avaliable, or sea level?

You are correct that the protege uses a set fuel map for closed loop, but it still has to compute for altitude....the most accurate is to read the MAF and compute from that.

If what you say is correct then an apex AFC wouldnt work what-so-ever with the mazda motor...and im pretty sure thats not the case.

thanks,
liam
 
The S-AFC does work to a point on teh Mazda engine but the ECu does not take any signals from the sensors at all at WOT ask any other Mazda guy on here that knows what they are talking about a S-AFC does you no good and that is also the reason superchips and other ECU reprogrammers won't touch our ecu.
 
If you want to try it go ahead but don't come cryin to us when you blow up your friends P5.....Mazdas are not Hondas
 
Sad but true, I spoke to an APEXi mechanic one day, it turned out to be a very informative conversation. He said first off that APEXi has no maps for the Protege at all :(, but the next best thing would be using the base maps from the Miata and tuning "on a dyno" to make it run optimal for the Protege. He said that if the MAF sensors are similar meaning that they operate at the same voltage as the Proteges, then we should be fine. What some one needs to do is get an A/F ratio guage, a dyno, tune with the S-AFC and see what you do.
 
chdesign said:
The S-AFC does work to a point on teh Mazda engine but the ECu does not take any signals from the sensors at all at WOT ask any other Mazda guy on here that knows what they are talking about a S-AFC does you no good and that is also the reason superchips and other ECU reprogrammers won't touch our ecu.
Click to expand...

Then how does the car account for what altitude its at? You dont need as much fuel at 12,000 feet as you do at say sea level. ?

thanks,
liam
 
At WOT our ECU doesn't care what altitude it is at....if you watch the Air/Fuel gauge on a Protege or any mazda when you hit WOT it goes WWAAAYYYY rich.
 
chdesign said:
At WOT our ECU doesn't care what altitude it is at....if you watch the Air/Fuel gauge on a Protege or any mazda when you hit WOT it goes WWAAAYYYY rich.
Click to expand...

Then wouldn't that be a good thing. I would think that being rich is better than being lean:rolleyes:. And going off of what you just stated, the S-AFC will do fine even if it doesn't control the fuel at WOT. Honestly, how many of us smash the gas everywhere we drive. I you think about it, most daily driving is done at part throttle. So tuning the fuel ratio at those part throttle points would be a better thing. Also, isn't the RX-7 considered Mazda and isn't every electonic peice that APEXi makes, excluding the V-AFC of course, work on the RX-7. I guess the only way to fine out for sure is to use the S-AFC and tune, like I stated above.

Anyway, CHdesign is a great addition the ProtegeMP3.com team. His and Spoolins knowledge are greatly appreciated. There are a few things I'd like to add, but since I don't have a turbo'd car, I think most of the guys wouldn't listen to me.
 
THe rich situation is a good thing on a NA engine but you go to turbo and larger injectors and that hard programed cycle comes in it will not deliver a high enough injector signal to give enough fuel under boost and at WOT you have a very high mixture in teh cylinder and if it goes lean under that situation disaster will stirke. Oh yeah and the RX-7 yes A'pex products are used on it but the main one used is a full replacement stand alone ECU. I believe mazda started doing the hard programmed WOT during the transition to ODB-II and I believe the Rex was still OBD-I i could be wrong as I'm not fully up to speed on the rx-7. but I believe i'm correct.
 
Okay, so the ECU reads NO signals at WOT?
How does it know the engine rpm?
How does it know if you're getting knock?

There has to be at least a small set of signals that the ECU is monitoring at WOT.

I can NOT buy into the idea that the ECU is blindly following a set of predetermined maps without referencing something and thus checking itself for proper operation. There's no way the warranty guys would let the car leave the factory like that!

Does anyone own a copy of the manual yet to see what signals are available to the ECU, and how to test the functionality of these signals?
 
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