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Old 11-15-2007, 09:05 PM   #1
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Default Need boost advice, and AFM adjustment

Ive had a idle problem since a little bit after installing my 1.8l injectors(i redid the intercooler setup around the same time) so i figured i had a vacuum leak. Its been months now and ive searched alot for the leak and never could find one.. so im thinking i need to adjust my afm.. I would just jump right in and mess around with it, but by leaning out the afm im afraid i could lean out my ahave to worry too much?

Ive really been having trouble guessing what boost to run that will make me close as possible to stoich, heres what i got, 1.6l w/ greddy kit, open downpipe, bipes acu set at stock timing retarding 4 deg, (i know i really need to up the timing to 14), stock vortec FMU disk, 1.8l injectors, boost controller, wastegate helper spring.

I make peak boost around 4grand, because of the shitty downpipe. Running around 5-6psi i run way rich, what boost level should i run?

Sorry for all the questions, im hoping to ditch this whole setup for a megasquirt in the near future, but nobody around here can tune it.. might just have to learn myself.


Also, if anyone in the area(Albuquerque, denver, or equal distance from taos) with a wideband would take a day and help me get this thing worked out, i'll pay well.
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Old 11-16-2007, 11:39 AM   #2
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You should give brody at speedlab (ABQ) and chris at the dyno edge (ABQ) a call.

You shouldn't be running anymore boost than you currently are because your bottleneck right now is your fuel pump and 12:1 disk in the FMU. You've gotta be running pig rich right now.
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Old 11-16-2007, 01:55 PM   #3
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You don't adjust boost to accommodate fuel- you adjust fuel to accommodate boost.

5-6 PSI is perfectly reasonable. You could up the boost to maybe 8 PSI or so without much fear, given that you have an intercooler and an ACU. Incidentally, I'd leave the base timing at 10 if you're only running 4 of total retard. In fact, I'd probably run a tad bit more retard since at this point it's obvious that you've got fueling problems in general.

First off, are you basing these observations off of a proper wideband O2 sensor?

When you are not in boost, the engine should be running close to stoich regardless of what disc you have in the FPR, what the max boost is set to, etc.

When you *are* in boost, you want to run rich. And you say that you are, you just don't indicate how rich. If you're using a cheap O2 meter that attaches to the stock NB sensor, then ignore what it's telling you. That thing can't tell the difference between 13:1 (too lean under boost) and 11:1 (too rich under any conditions)


As to the idle- before you mess with the AFM, try removing the I/C pipes and going back to the way it was (or back to the stock crossover tube). You don't want to tweak the AFM to compensate for a tiny leak at idle, other than perhaps turning the idle screw a bit. Do not adjust the spring for this sort of affair. However I'd first try to figure out of there *is* a leak, but swapping out all the pipes and going back to stock.
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Old 11-16-2007, 08:41 PM   #4
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Thanks for the responses,

I most certainly am running rich because of the black smoke coming out of my exhaust just about all the time (not quite AS much at low rpm), also i forgot to mention that i do live at high altitude, about 7400 ft to be exact.

Also, i understand adjusting fuel to accommodate boost but with stock fuel pump, no wideband, and a hardly adjustable fpr i would like to dial in boost as accurately as possible without the purchase of a new fpr, or anything for that matter.

Since i am at altitude i beleive the stock ecu will run rich with stock injectors, and this is why i was thinking afm adjustment might be in order, especially after the addition of bigger(1.8l) injectors.

Ive never once heard an audible knock nor have a run over about 8psi (9 peak).

Also, if there is a vac leak- im almost certain its not in the charge piping, ive done everything i can to try and determine what the leak is, my vac gauge is showing around 17, which should be very close to normal considering my altitude. Im just fed up with it and im running out of options.

Also with the timing, i do live in a mountain town in which the temperatures are pretty goddamn cold, (high in the 60s) so i pretty much figured i should be okay at 14 retarding 6 or so deg of timing if not less.
Also thanks for the warnings, i understand nb o2s are useless, mind i have been lurking/posting for over a year now.

Sorry for the long-*** post but i hope you guys can see why im so fed up.

P.S. the only reason i haven't taken it to a speedshop are the crazy prices they charge to tune even a simple setup like this one, i am however planning on getting it professionally tuned once i get a real ecu.
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Old 11-16-2007, 09:59 PM   #5
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Quote:
Originally Posted by Fireindc View Post
I most certainly am running rich because of the black smoke coming out of my exhaust just about all the time (not quite AS much at low rpm)
If it's running rich all the time, then dialing up more boost isn't going to help matters because you're not in boost all the time.

That's the basic dilemma. And I would seriously advise you to figure out why you are running pig-rich when not in boost and correct that problem first, before you even contemplate running boosted.

Any number of things could be at fault here. For starters, you mentioned that you were running an open downpipe- depending on where it ends, that right there could be screwing up the whole works. If there's not enough enclosed pipe downstream of the factory O2 sensor (like several feet) then regular air will be running back up the pipe in between pulses, causing the ECU to think that the you're running massively lean and start pouring fuel into the engine to compensate.
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Old 11-16-2007, 10:05 PM   #6
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Put a voltmeter on your O2 sensor and see if it is functioning corectly, if at all.
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Old 11-20-2007, 07:41 PM   #7
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Let me clear up a few things, and add a few things to the equation.

My open downpipe isnt really an open downpipe, it connects to a midpipe which lets out at the rear wheels about.

My car doesnt run so rich at idle that it blows black smoke, sorry for the confusion, it only does so RIGHT at startup after sitting for a while, and romping it on 5lbs around 4grand. Now on 8lbs its not even noticeable.

I havent had a chance to get a votmeter on my 02 sensor yet, but i really need to as i have suspected it for a while now.
I forgot to mention that my car has been throwing a CEL, this cel will come on randomly when im cruzing around 3 or 4 grand, and every single time it will go off as soon as i make enough positive pressure to sound the bov, note i dont have to actually sound the bov to make the cel goes off, but if i make enough boost to sound the bov(around 1psi) it turns off every singe time. The only problem is nowhere local can do diagnostics on obd1 mazdas, and i can jumper it myself and get them to display on my dash, but i cant find out anywhere what 1 long, 7 short blinks, or 1 long, 5 short blinks means.. please link or help me out here. The cel blinks slow once, then fast 5 times in a row. Then it pauses and starts with one slow, and five fast. Im not sure if these are two seperate or one long code.

Also yesterday when i changed my oil, you could deffinately smell gasoline in it.. cylinder wash?

Im going to hopefully work out this whole cel thing first, then figure out why it wont idle correctly(hoping its whatever cel code im throwing) then just go standalone ecu and get it pro tuned. I love diy, but god am i upset with my car right now ><, even though its probably all my fault.

Thanks a ton again guys, and sorry im so late with responses as i have limited time online because where i live there are no internet services available.

- Nate

Last edited by Fireindc; 11-20-2007 at 07:50 PM. Reason: Added more description
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Old 11-20-2007, 08:00 PM   #8
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You are seeing 15 and 17, both of which indicate a problem with the oxygen sensor.
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Old 11-20-2007, 08:02 PM   #9
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Quote:
Originally Posted by olderguy View Post
You are seeing 15 and 17, both of which indicate a problem with the oxygen sensor.
I love you.

Im going to go buy/order one right now.

Edit: this is on a stock greddy downpipe, do you think the original one failed from being overly rich? Im guessing when i was running 5lbs of boost and no intercooler for a while i was running too rich and i fouled it with black nasty?

Just dont want to **** this one up. Hopefully this will fix some of my a/f problems.. Right after i put on the kit(before injectors, intercooler, etc, it ran perfect and idled great.. Perhaps now it will do the same.

Last edited by Fireindc; 11-20-2007 at 08:05 PM. Reason: addition
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Old 11-20-2007, 09:11 PM   #10
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Originally Posted by Fireindc View Post
Edit: this is on a stock greddy downpipe, do you think the original one failed from being overly rich?
I kinda doubt it. More than likely it failed because it was almost 18 years old. But O2 sensors are cheap enough that even if you wind up killing another one it's not gonna hurt too bad. Rather than spending $100 or more for an OEM unit, just go to an auto parts store and ask for a Bosch universal sensor. Should be about $40.
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