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Old 07-24-2007, 12:10 AM   #1
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Default Fuel Pump. Which size?

I have my 190HP Fuel pump from walbro, and I was talking to my buddy that does jdm swaps and such in his shop, he said 190 would be too small and that I should/shouldve gotten the 255. What do you think? I have tan injectors and regular vortech disc, I think that would be the 12:1. Would that be good for 8-10 PSI?
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Old 07-24-2007, 12:15 PM   #2
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Don't listen to your buddy. The 190HP is more than adequate at that level.

Hell, I ran 19-22 psi in my DSM with a 190 without issue.
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Old 07-24-2007, 12:42 PM   #3
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your freind is a DSM idiot. the 190 is plenty for 400 or so hp at normal fuel levels the 255 is for people who want to hit 500. Tell him the car did not start with 200 hp and if you hit 300 hp before something breaks on your turbo you will be lucky. So a 190 is a 100 hp cushion easy.
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Old 07-24-2007, 12:43 PM   #4
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cause enough fuel to support around 300BHP @ 100psi in the rail isn't enough....


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Old 07-24-2007, 01:59 PM   #5
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Quote:
Originally Posted by magnamx-5 View Post
your freind is a DSM idiot.
Hey, I resembled that remark!

/former life and all
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Old 07-24-2007, 04:20 PM   #6
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I think brain spells it out pretty good in his faq IIRC.
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Old 07-24-2007, 04:33 PM   #7
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Thanks for the responces guys, And scott, I read that diagram last nite when I searched, but wasnt sure what it meant, but now I get it. Im gonna be printing that out for sure :gay:
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Old 07-24-2007, 04:55 PM   #8
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at 100psi in the fuel rail the pump will still be outputing about 30 gal/hr.

30 x 6 = lb/min

180 x .8 (Duty cycle) / .55 BFSC = 260BHP

I doubt you'll be running a FMU at 100psi at 240rwhp.

so even a 190 regular for someone with an ecu can output about 42 gal/hr at 60psi

60 x 6 x .8 /.55 = 520BHP....so when you start making more than 480rwhp, let me know.
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Old 07-24-2007, 05:05 PM   #9
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I doubt you'll be running a FMU at 100psi at 240rwhp.
.
Scott, are you saying That I shouldnt use my Fmu?
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Old 07-24-2007, 05:09 PM   #10
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no, but most people scrap them after a certain point for good reason.
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Old 07-24-2007, 05:10 PM   #11
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Hm...Can I ask why that is? I though tthe stock FPR would get "overwhelmed" Or well, thats What I read after a search last night at least
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Old 07-25-2007, 02:09 AM   #12
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Quote:
Originally Posted by SlidinMiata916
I was talking to my buddy that does jdm swaps and such in his shop, he said 190 would be too small and that I should/shouldve gotten the 255.
Quote:
Originally Posted by ThirdLap
Hell, I ran 19-22 psi in my DSM with a 190 without issue.
Quote:
Originally Posted by magnamx-5
your freind is a DSM idiot.
On second thought, was this directed at me?

Coincidence or reading comprehension issue?
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Old 07-25-2007, 10:12 AM   #13
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4 High pressure fuel pump

The stock Miata fuel pump can only provide so much fuel (tends to max out around 85psi). ...So you need to upgrade the pump if you plan to fuel past 70-80psi; usualy due to running small injectors on an FMU setup....the fuel pressure raises the size of the injectors.

Other than that, you don't need one. If you have an aftermarket ECU, the stock pump more than enough at 50psi.

For the longest time the Walbro 255 lb/h fuel pump had been the accepted pump for FI Miatas. The 255 flows more fuel at any giving pressure level than is needed. They tend to overload the OEM FPR and cause the system to run rich even in vacuum.
Instead of idling at 35psi and reaching 50psi at 0~hg. It will run closer to 40psi at idle and 55psi at 0~hg.


The ideal pump is the Walbro 190 lb/h HP fuel pump....It is important you get a HP unit if you plan on raising the fuel pressure levels past 90psi. ...The 190 HP unit will not only supply four 700cc injectors with enough flow to maintain 40-50psi in the fuel rail (enough for 400hp), but out flows the 255 HP model after 100psi.


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