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Old 06-19-2007, 03:03 PM   #1
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Default will I need a better fuel pump?

Well, I am going to run about 5 psi, and with a 12:1 FMU, that means about 110 psi of fuel. the stock pump can only reach 80 ish psi, so I should get the 190lph HP pump, correct?
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Old 06-19-2007, 03:25 PM   #2
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Yes you will need a HP fuel pump for 110psi but for 5 psi that may be a bit much. You might want to look into a adjustable FMU or as a person who as gone through the FMU, HP fuel pump, Bipes/MSD thing. I strongly recommend going with something like the MS, or EMU, ect.. that gives you have more control of your fuel and timing. It gives you lots of head room. Trust me 5psi will not be enough once the bug really bits you.
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Old 06-19-2007, 03:28 PM   #3
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well I could always get a recalabration kit for the vortec. I do not ahve the money for a MS quite yet. what ratio do you reccommed for a 1.6L engine running 5 to 6 psi?
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Old 06-19-2007, 03:34 PM   #4
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I have a 1.8 but I found that 7:1 worked for me but I have heard that 6:1 worked for others. If you can afford it try and get a wideband a/f gauge. There's a calculator on here somewhere that helps you figure it out.
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Old 06-19-2007, 04:00 PM   #5
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a 1.6L with 1.8L injectors and stock pump should have enough fuel for 170rwhp.

But...\ with sotck injectors you can use Corky's calculation:

Needed fuel pressure = ( PR² x 35) + boost = (1.412² x 35) + 6 = 76 psi
Needed fuel pressure = (1.544² x 35) + 8 = 91 psi

dunno where you got this 110psi number from...technically 110psi of fuel on 230cc injectors is good for another 170rwhp. Which on a T3 will be around 8psi.

so, at wastegate levels...you should have justenough injector...throw in the 1.8L injectors and you'll have plently for a tad more boost, without having to swap the pump or FMU discs.

Last edited by Braineack; 06-19-2007 at 04:23 PM.
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Old 06-19-2007, 10:50 PM   #6
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I'm running about 100psi fuel @12psi boost. If you run that much fuel at 5psi boost, you'll just spit gas out the tailpipe... which might be interesting to watch if you've still got a cat.
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Old 06-19-2007, 10:59 PM   #7
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what pressure is the fuel at at idle?
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Old 06-20-2007, 12:14 AM   #8
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?
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Old 06-20-2007, 12:25 AM   #9
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Are you asking ME? Why are you asking that question at all?

Fuel pressure at idle is not adjustable with the vortech. At idle, the AFPR isn't doing anything, and fuel pressure is regulated by the OEM regulator on the fuel rail. I think mine is around 35psi @~20hg vaccum. I think the only thing that could affect your fuel pressure at idle is a faulty OEM regulator, clogged fuel filter, or bad pump.

At ~0hg, or 0psi if you prefer, my fuel pressure is set per Corky's recomendations in the instructions for the Begi 2025 AFPR that I run. I think it's around 48-50psi.
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Old 06-20-2007, 02:40 AM   #10
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Quote:
Originally Posted by Braineack View Post
dunno where you got this 110psi number from...technically 110psi of fuel on 230cc injectors is good for another 170rwhp. Which on a T3 will be around 8psi.
I think he got it from a post you made on another thread.

Quote:
Originally Posted by Braineack View Post
If you just get 1.8l injectors, you should be able to fuel about 170rwp, if the stock pump is up to it.

That's about the most I could make.

So then, you need a HP pump to pump the pressure up a bit.

Take it to 100psi in the rail and you should have enough (with 1.8l injectors) to fuel 190rwhp.

which will take a good 7-8-9psi or so.

that means with your current fmu disk (12:1), you'll have too much fuel.

12 x 8psi + 50 = 146psi, something most pumps can't even produce.

so along with the pump you need to recalibrate the FMU.....lets try a 8:1 disc

8 x 8 + 50 = 114psi, a bit high but gives you wiggle room....7:1?
7 x 8 + 50 = 104psi, closer to what you want...
So... which formula? I'm so confused!!
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Old 06-20-2007, 04:26 PM   #11
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Quote:
Originally Posted by samnavy View Post
Are you asking ME? Why are you asking that question at all?

Fuel pressure at idle is not adjustable with the vortech. At idle, the AFPR isn't doing anything, and fuel pressure is regulated by the OEM regulator on the fuel rail. I think mine is around 35psi @~20hg vaccum. I think the only thing that could affect your fuel pressure at idle is a faulty OEM regulator, clogged fuel filter, or bad pump.

At ~0hg, or 0psi if you prefer, my fuel pressure is set per Corky's recomendations in the instructions for the Begi 2025 AFPR that I run. I think it's around 48-50psi.
I wanted to know because I need to figure out what FMU I need to get 90 psi of fuel pressure, which according to braineack, is what I need to run 5 to 6 psi on 1.6L injectors. 90 psi is really pusing the stock pump tho, right? So what ratio do I need for the FMU? 8:1?
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Old 06-20-2007, 05:05 PM   #12
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Quote:
Originally Posted by Animal Chin View Post
I think he got it from a post you made on another thread.



So... which formula? I'm so confused!!

if using stock injectors then:
Needed fuel pressure = ( PR² x 35) + boost
PR= 14.7 + boost / 14.7

if anything else it gets a bit trickier. you kinda have to see what an injector can support in BHP at a particular psi level, and get it close.

the formula to see what pressure your FMU will hit in boost is:
Ratio of rise x boost + fuel pressure at 0 ~hg.
ex.: 12:1 x 5psi of boost + 50psi of fuel = 110psi
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Old 06-20-2007, 07:29 PM   #13
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Quote:
Originally Posted by cardriverx View Post
I wanted to know because I need to figure out what FMU I need to get 90 psi of fuel pressure, which according to braineack, is what I need to run 5 to 6 psi on 1.6L injectors. 90 psi is really pusing the stock pump tho, right? So what ratio do I need for the FMU? 8:1?
Your stock pump will only give you 80psi(if it is good shape) no matter what disc you use.
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Old 06-20-2007, 10:25 PM   #14
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ok, braineack, using your formula, for 6 psi of boost, I need 75.4 psi of fuel pressure. Now my car should have 50 psi at 0psi which mean that ill need a 4.2:1 ratio. So I should use the 4:1 recal kit. Is this correct?
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Old 06-20-2007, 11:00 PM   #15
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Maxing out the stock pump like that isn't a good idea. Even the slightest boost spike or overshoot will put you lean enough for just an instant to roast a motor. For $50, you can upgrade to bigger injectors and have a much higher margin of safety. Installing new injectors takes about 10minutes... then you can run lower fuel pressure on the stock pump.

Post a WTB and run through the classifieds here and at miata.net. Bigger injectors are for sale ALL THE TIME. Ebay too.
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Old 06-20-2007, 11:51 PM   #16
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if you're only doing 5-6psi then don't worry about anything else for fuel right now....the stock stuffs with the 12:1 you have is enough.
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Old 06-21-2007, 08:05 AM   #17
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i have got a similar question...

I am looking to boost my miata....

Now i am only missing the fuel bits to complete..

my car is a 1.6...

I am going to run at least 8 psi with a T25 (if that doesn't blown a good condition stock engine)..

What kind of injectors and fuel pump should i use?

planning to put 305cc or 550cc injectors and seems that walboro 190LPH is a popular choice?

Will 550cc injectors haviing troubles when idle?

Is a FPR must for Bigger injectors and fuel pump or i could get away with it?

Please note that i am only running Apexi AFC for adjusting air-fuel mixture.
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Old 06-21-2007, 09:35 AM   #18
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Quote:
Originally Posted by ES86 View Post
i have got a similar question...

I am looking to boost my miata....

Now i am only missing the fuel bits to complete..

my car is a 1.6...

I am going to run at least 8 psi with a T25 (if that doesn't blown a good condition stock engine)..

What kind of injectors and fuel pump should i use?
8psi, now you need to get into the realm of thinkin, "I have X amount of power, I need X amount of fuel."

8psi on a t25 is going to be 170rwhp or so.
265cc injectors 1.8L with 80psi of fuel thrown at them can support that.

I urge you guys to stop saying I have 8psi what can I fuel....every turbo is different. Injectors and fuel pumps dont give a damn what boost you run. The fuel pump flows fuel, the end. the injectors, inject fuel, the end.

the stock pump can output around 70-80psi max.
the stock fuel rail delivers 35psi at idle 50psi at 0~hg. (0 boost, 0 vacuum)

The amount of fuel you need is based on the power you make. Injectors support horsepower. X amount of horsepower needs X amount of fuel. That's the new line of thinking.

Quote:
Originally Posted by ES86 View Post
planning to put 305cc or 550cc injectors and seems that walboro 190LPH is a popular choice?
not for 8psi.

Quote:
Originally Posted by ES86 View Post
Will 550cc injectors haviing troubles when idle?
hell yeah they will.

Quote:
Originally Posted by ES86 View Post
Is a FPR must for Bigger injectors and fuel pump or i could get away with it?
the design of the FMU is for smaller injectors to work as bigger ones so your stock ECU can control them.

Quote:
Originally Posted by ES86 View Post
Please note that i am only running Apexi AFC for adjusting air-fuel mixture.
good luck with that....


I suggest you all go back and read my FAQ: https://www.miataturbo.net/forums/showthread.php?t=4288
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Old 06-21-2007, 09:42 AM   #19
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You guys realy need to listen to us we know a thing or to it isn't like we just made it all up one day.
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Old 06-21-2007, 11:36 AM   #20
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I had read about the FAQ over and over and i just want to make sure that what i am getting is right for my setup....

Anyway i am getting some 305cc injectors from 7MGE engines...

If i don't want pressure to be build up in fuel lines i will just get a Walbro 190or 225 LPH fuel bump...

So the fuel will be good enough to support up to 10-12psi of horsepower...am i right?

For ignition and engine management, i am seriouly considering EMB or EMU...but i had found that no PNP harness for EMU...so i guess i will get a EMB...
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