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3.4 FUEL PSI? by NickD3.4
Started on: 01-20-2008 09:03 AM
Replies: 18
Last post by: NickD3.4 on 01-24-2008 08:49 AM
NickD3.4
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Report this Post01-20-2008 09:03 AM Click Here to See the Profile for NickD3.4Click Here to Email NickD3.4Send a Private Message to NickD3.4Direct Link to This Post
I put a 3.4 swap in, and am wondering if any body has recommendations for what the best fuel PSI would be to run.
thanks!
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NickD3.4
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Report this Post01-22-2008 08:53 AM Click Here to See the Profile for NickD3.4Click Here to Email NickD3.4Send a Private Message to NickD3.4Direct Link to This Post
I put a 3.4 swap in, and am wondering if any body has recommendations for what the best fuel PSI would be to run.
thanks!
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Dodgerunner
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Report this Post01-22-2008 11:23 AM Click Here to See the Profile for DodgerunnerClick Here to visit Dodgerunner's HomePageClick Here to Email DodgerunnerSend a Private Message to DodgerunnerDirect Link to This Post
I'm running the stock 2.8 fuel pressure on my 3.4pr with the 3.4 injectors. Runs very well.
Believe most run stock pressure.

[This message has been edited by Dodgerunner (edited 01-22-2008).]

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avengador1
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Report this Post01-22-2008 12:03 PM Click Here to See the Profile for avengador1Click Here to Email avengador1Send a Private Message to avengador1Direct Link to This Post
I have mine set to 44 psi. It runs fine there.
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Pyrthian
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Report this Post01-22-2008 12:06 PM Click Here to See the Profile for PyrthianClick Here to Email PyrthianSend a Private Message to PyrthianDirect Link to This Post
if you are running the stock Fiero 15# injectors, yes, I'd crank it up a little - if using the stock 3.4 17# injectors, I'd say leave it alone. but - the right answer is to look at the BLM's. adjust accordingly.
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mach1
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Report this Post01-22-2008 12:32 PM Click Here to See the Profile for mach1Send a Private Message to mach1Direct Link to This Post
Normal is in-between 40 psi to 44 psi.
Use this formula to calculate psi and flow ratings:
For example:
17# injector = 16.4lbs/hr @39.2 psi fuel pressure & 17.3 lbs/hr @43.5 psi fuel pressure
New flow rating = [square root of (new pressure /old pressure)] x old flow ratio
To calculate the hp required to support this new injector size we need this formula:
Fuel requirement in lbs./hr = (Max HP x BSFC) / (number of injectors x duty cycle)
17.92 = Max hp x .55 / 6 x 80%
Max hp = (4.8 x 17.95) / .55 = 156.4 hp
The formula is the key.

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NickD3.4
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Report this Post01-22-2008 12:53 PM Click Here to See the Profile for NickD3.4Click Here to Email NickD3.4Send a Private Message to NickD3.4Direct Link to This Post
never have been one for math. I guess ill try it at 40 and see what happens, I cant remember if I used the 15# or 17# any one know how to tell which they are?
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Hudini
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Report this Post01-22-2008 04:05 PM Click Here to See the Profile for HudiniClick Here to Email HudiniSend a Private Message to HudiniDirect Link to This Post
Mine both look the same. You can send them out for cleaning and flow testing. They will flow match then scribe each injector with a number. That is what Cruzin Performance did for me at $12 per injector. Very nice work. Rich is a nice guy too.

EDIT: Did you mix the two together?

[This message has been edited by Hudini (edited 01-22-2008).]

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NickD3.4
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Report this Post01-22-2008 08:44 PM Click Here to See the Profile for NickD3.4Click Here to Email NickD3.4Send a Private Message to NickD3.4Direct Link to This Post
no I put one or the other on. I just cant remember which. I think i used the 3.4 injectors
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sardonyx247
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Report this Post01-22-2008 09:40 PM Click Here to See the Profile for sardonyx247Click Here to visit sardonyx247's HomePageClick Here to Email sardonyx247Send a Private Message to sardonyx247Direct Link to This Post
the free way to tell injectors is simply just look up the part# on the side of the injector.


------------------
"DRIVE IT LIKE A FIERO"
'84 Fiero, engine to be determined
'87Blue GT 3.4L Swap Completed!!!!!!!! Boosted!!!!!!!
Las Vegas Fiero Club
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Hudini
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Report this Post01-22-2008 10:03 PM Click Here to See the Profile for HudiniClick Here to Email HudiniSend a Private Message to HudiniDirect Link to This Post
It took a bit of searching (with a magnifying glass ) since I had not seen any part numbers on mine but sure enough, in very tiny numbers, there are part numbers etched into the black plastic top. They are located on the top half black plastic where the fat part curves over toward the skinny neck. You can just look at the ones out of the car to make sure the ones in it are the right ones.

On mine the 15# numbers- 3276 5235136
17# numbers- 8074 17109826

(Thanks sardonyx247 for making me look closer)
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3.4Turbo
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Report this Post01-22-2008 10:18 PM Click Here to See the Profile for 3.4TurboClick Here to Email 3.4TurboSend a Private Message to 3.4TurboDirect Link to This Post
I run the stock pressure with my 3.4 that runs the 3.4 injectors with FOCOA headers,darrell morse TB, 272 cam, truleo intake and ported heads but I had a custom chip burned with the use of a wideband sensor. I do have the Holley adjustable regulator just in case I want to tweak it a bit.
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NickD3.4
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Report this Post01-22-2008 11:42 PM Click Here to See the Profile for NickD3.4Click Here to Email NickD3.4Send a Private Message to NickD3.4Direct Link to This Post
thanks! I have them out of the car, ill look at the numbers. I just installed a adjustable regulator, so I guess I can tweak it if I need to.
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Marvin McInnis
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Report this Post01-23-2008 10:27 AM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisDirect Link to This Post
 
quote
Originally posted by mach1:

New flow rating = [square root of (new pressure /old pressure)] x old flow ratio



This is correct for "simple" injectors, but the Fiero injectors I've tested are apparently a constant-flow-rate design that are relatively insensitive to pressure. I have done my own testing, and there is very little measurable difference in injector flow rates between 38 and 50 psi.

For reference, the stock 2.8 fuel pressure is 43 (+/- 2) psi, measured with the engine not running. Measured fuel pressure will be about 8 psi lower with the engine running, due to the design of the regulator. The regulator actually maintains a constant (~43 psi) difference between fuel pressure and manifold pressure.
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NickD3.4
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Report this Post01-23-2008 01:06 PM Click Here to See the Profile for NickD3.4Click Here to Email NickD3.4Send a Private Message to NickD3.4Direct Link to This Post
The numbers on my injectors are A 9273 7103007 I dont know what this means though, make sense to any one?
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NickD3.4
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Report this Post01-23-2008 11:40 PM Click Here to See the Profile for NickD3.4Click Here to Email NickD3.4Send a Private Message to NickD3.4Direct Link to This Post
The numbers on my injectors are A 9273 7103007 I dont know what this means though, make sense to any one?
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Hudini
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Report this Post01-23-2008 11:51 PM Click Here to See the Profile for HudiniClick Here to Email HudiniSend a Private Message to HudiniDirect Link to This Post
Using http://users.erols.com/srweiss/tableifc.htm and 17103007 I found 17.7 lbs/hr at 43.5psi (3 bar). Sounds like the right ones.
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Report this Post01-24-2008 01:58 AM Click Here to See the Profile for BizziedudeClick Here to Email BizziedudeSend a Private Message to BizziedudeDirect Link to This Post
I'm running stock fuel pump, rail, and regulator (runs at appx 45 psi) in my 87GT 3.4/Getrag setup.

-seems to work greatn as I have been running 120+ miles a day for the last 6 months without a hitch-

A few more details so you have the whole picture:
Hypertec chip, 160 thermostat, Darryl Morse ported throttle body and plenum, Ocelot exhaust, Ported stock headers, New Old Stock Fiero Cam, 17 pound injectors from donor 94 Firebird, 1.6 roller tip rockers, Rebuilt heads, Billet Steel Flywheel and heavy duty clutch from the Fiero Store, Stock bore and pistons on motor with new moly rings, polished and chamfered crank, shotpeened rods with ARP bolts added (extra insurance).

The 3.4 pulls like a train off the line compared to 2.8 and has only thrown an EGR code a couple of times since the engine changeout. It did this with the 2.8 as well. YEP...every dang sensor and the EGR valve are brand new since rebuild...nothing a piece of folded up paper doesn't fix.

Old top speed=About 120 MPH with a tailwind
New Top Speed=Don't know yet but sure as hell accelerates to 80 much quicker than with old 2.8
Fuel economy=Averages about 27 MPG according to my cell phone calculator...same as I got with the 2.8

I have been extremely satisfied with my efforts and HIGHLY recommend the 3.4 over the 2.8...and it's a super easy conversion
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NickD3.4
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Report this Post01-24-2008 08:49 AM Click Here to See the Profile for NickD3.4Click Here to Email NickD3.4Send a Private Message to NickD3.4Direct Link to This Post
thanks Hudini. I appreciate it. While were on topic, I was going to get my injectors cleaned, but not sure what kind of shop does this. Any one know? I saw cruz performance online does it, but not sure if I want to ship.
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