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Old 07-22-2007, 06:31 PM   #1
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so i took my miata to get it tuned it pushed good power but the safc is maxed out to 50% and its runing lean in boost do you guys think i could be a bad safc? or do you think my ecu is reading boost? in boost its runing 13:1 ratio and i am runing 8 psi in boost and the damn thing still runs lean and i have the lite purple 265 injectors! the guy that tuned it is just is stumped as me so any help would be great!!!!!
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Old 07-22-2007, 07:01 PM   #2
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what happens to the fuel after 5K?
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Old 07-22-2007, 07:32 PM   #3
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it goes up like 4 psi
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Old 07-22-2007, 08:52 PM   #4
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no, sorry the AFR.
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Old 07-22-2007, 08:59 PM   #5
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uhmmm. maybe you are running out of fuel? lol. The S-AFC isnt going to make the injectors and pump do more than they're capable of doing. Upgrade the fuel pump and put an RRFPR on there. problem solved. Check the fuel filter too.
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Old 07-22-2007, 09:13 PM   #6
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13:1 in boost and you want it under 12 slos13- i have a 255 walbro and its a full tank of 91
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Old 07-22-2007, 09:19 PM   #7
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so no matter what, once you're in boost you have a 13:1 AFR, it doesn't change at 5.5K or so?
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Old 07-22-2007, 09:19 PM   #8
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You're really not giving us much, if anything, to work with.
What turbo? What was your dyno result? Where's the plot? You don't even tell us what year or motor.

Also slow down when you're typing and proof read. If I have to decipher quasi-english to english, I ain't gonna help ya nun.
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Old 07-22-2007, 09:26 PM   #9
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1.6 turbo is a 16g, 1990 8;5;1 comp wiseco pistons, mazdaspeed miata injectors 256cc,255 walbro
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Old 07-22-2007, 10:04 PM   #10
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is a 250cc injector enough to support 8psi worth of power at stock pressure?

I dont have a calculator on hand but it seems to me as if you should be running either more pressure or a bigger injector.
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Old 07-22-2007, 10:08 PM   #11
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i have one of those cheap afpr off ebay, do you guys think i need bigger injectors?
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Old 07-22-2007, 10:16 PM   #12
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I would get a BEGi FMU, and probably throw away the SAFC and definately throw away ebay crap.

Why would you put cheap *** ebay chineese crap in charge of delivering fuel?
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Old 07-22-2007, 10:23 PM   #13
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so get a begi and a safc 2?

Last edited by 90miata; 07-22-2007 at 10:36 PM.
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Old 07-22-2007, 10:24 PM   #14
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cutting corners is sometimes allowable, but never on fuel delivery. get the real stuff for that. Also make sure your ebay POS isnt hooked up backwards
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Old 07-22-2007, 10:38 PM   #15
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Quote:
Originally Posted by 90miata View Post
so get a begi and a safc 2?
Hell no. No way should you spend $400 between 2 fuel piggies.

Just get a BEGi FMU and be done.

If you want to spend $400 get a vortec and pick up a used emanage blue.

Or a new AEM piggy.

Or build a MegaSquirt.

Or spend a little more and get an MSPNP
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Old 07-22-2007, 10:45 PM   #16
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so what tunes the car then? just the begi? and my injectors are ok? should i make and dual feed rail? could i get a e-manged instead?

Last edited by 90miata; 07-22-2007 at 11:10 PM.
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Old 07-23-2007, 12:46 AM   #17
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on your year miata.....

under 4-5k rpm (not sure what the cutoff point is) the stock ecu operates in a mode where it reads from the oxygen sensor and automatically adjusts inector pulse to keep the engine running stoich (14.7). Above 4-5k rpm (again i forget what the cut off is), the oxygen sensor and ecu stop working together, and the ecu feeds fuel according to a preset fuel map.

Therefore a real rising rate fuel pressure regulator like the begi or vortech, will only give you noticeable results after the motor hits the rpm at which the ecu goes into the preset map mode because at that time, the injector pulse width does not change according to what the o2 sensor and ecu determine should yield stoich....so the rrfpr simply clamps off the return line to your fuel tank, the pressure in your fuel rail increases, injector pulse stays a preset lenght, so the overall amount of fuel going into your motor increases.


to answere your main question...yes, without a piggy back of different ecu, the begi or vortech is what tunes your car (but only after the engine hits a certain rpm). to tune the air/fuel ratio below that magic rpm, you need an oxygen sensor clamp which allows the stock ecu to ignore the output coming from the o2 sensor and you to up the fuel pressure under the magic rpm with your begi or vortech.

if it doesn't make much sense....read up on your miata fuel system and it's return system, braineacks' faq, and corky's book maximum boost, and talk to olderguy about his oxygen sensor clamp.

you're on the right track, just need some details hammered out.

p.s. most of those ebay fpr's only up fuel pressure on a 1:1 ratio (1 pound of boost coming out the turbo only increases pressure at the rail by 1 pound)
the begie and vortechs rise fuel at a 6:1 - 12:1 ratio. that's what you're gonna need to get yourself running not lean.

Anthony
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Old 07-23-2007, 12:52 AM   #18
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Quote:
Originally Posted by s10383 View Post
read up on your miata fuel system and it's return system, braineacks' faq, and corky's book maximum boost, and talk to olderguy about his oxygen sensor clamp.
The above quote was the only factual information from that entire post.

The rest is so wrong I'm not even going to start with it, and should be ignored if not deleated.
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Old 07-23-2007, 01:50 AM   #19
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so all your saying is i need to take the safc out and put on the vortech or begi and a 02 clamp and i wont have problems when i get it tuned
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Old 07-23-2007, 10:30 AM   #20
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if you get a static ratio FMU, there's really not much to "tune".

If you keep the SAFC2, you'll have some level of tuneability by modifying the AFM output voltage that the ECU sees. Now, the FMU works off of pressure while the SAFC2 is reading off of mass so it's not an ideal solution but it'll probably work good enough.

I imagine you could hook up a MAP sensor to the S-AFC and tune by pressure but thats another bag of worms
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