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Author
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Topic: Injector size ???
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SneakyStang87
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Member # 10724
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posted
 
 
I am about to drop my engine in an it's a hci 351 trying to 400hp on motor do u think 50lb injectors are to big for motor I am going to boost just not right away. On what I have been looking up they say to run 36lb injectors but I have had ppl tell me the 50lbs would be fine. Any input??
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00 z28-dd
79 Coupe-Project Almost done
93 Drop Top-Got Jacked
87 lx-crashed
89 gt-sold
90 lx supercharged-sold
Posts: 272 | From: 925 to 916 | Registered: Mar 2011
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5.0 LsX
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Member # 10017
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posted
just get 80's and get it tuned, then you dont have to swap them later
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91' Notch
Posts: 1260 | Registered: May 2010
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SteveL
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Member # 1241
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posted
Sorry, that's bad advice.
Use the worksheet at the bottom of this page to calculate the right size injector for the expected horsepower. 36lb injectors should support up to 450Hp.
Let's say you go big. 80lb injectors as suggested. Because they supply (more than) twice the amount of fuel as a 36lb, the injector pulses will be half as short. Fuel injectors are not very accurate at short pulses.
Some injectors will supply too much fuel, others will be too little. There is no way to "tune" this error out. The engine will run but idle and low rpm response will likely be quite bad.
Posts: 578 | From: San Jose, CA | Registered: May 2002
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5.0 LsX
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Member # 10017
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posted
sorry for the bad advice, sounds like steve knows what hes talking about. im just used to bigger motors or more hp
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91' Notch
Posts: 1260 | Registered: May 2010
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SneakyStang87
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Member # 10724
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posted
So my car will not run right with the 50lb injectors tuned??
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00 z28-dd
79 Coupe-Project Almost done
93 Drop Top-Got Jacked
87 lx-crashed
89 gt-sold
90 lx supercharged-sold
Posts: 272 | From: 925 to 916 | Registered: Mar 2011
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SteveL
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Member # 1241
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posted
First off, 50lb injectors is a weird size and not in the Ford Racing catalog.
http://www.fordracingparts.com/download/charts/Fuel_Injectors_and_Adaptors.pdf
It comes down to trade-offs, what's important to you, and cost. Use the chart in that Ford catalog. Just figure that the further you move away from the ideal injector size (by going bigger), that idle and low end rpm response will suffer.
So do you want the engine to run smooth in the configuration you're building it or willing to put up with poor low end response now that will be fixed with an upgrade in the future?
Posts: 578 | From: San Jose, CA | Registered: May 2002
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KING TUT
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Member # 11349
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posted
tuning all has to do with the tuner your using if your on stock ecu or not lol.... just buy the 205lbs injectors so you will need need injectors lol... mine idles pretty good with 2150cc injectors lol...
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mess with the best die like the rest
LS fabrication
FFTEC
-SAVAGE HABITS-
Posts: 264 | From: san pablo | Registered: Oct 2011
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SLOWSN95
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Member # 8269
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posted
It doesn't matter if you use too big of injectors, you can always take out fuel in the tune. If you want to boost later on down the road, I'd recommend running bigger injectors that will support the boost right now while your car is still in naturally aspirated form so that you dont have to change them again later on when you get a supercharger/turbo/etc.. but thats just me.
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94' GT
347 Stroker
MM Suspended
2003 SB SVT Lightning
Pullied and Lowered
89'Hatch-SOLD
Posts: 2214 | From: 510/east bay | Registered: Mar 2008
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SteveL
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Member # 1241
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posted
quote:
Originally posted by SLOWSN95:
It doesn't matter if you use too big of injectors, you can always take out fuel in the tune.
How do you know how much fuel each injector is supplying in the non-linear region (<2mS pulses) of the injector? You flow test each injector or just set the pulse width and hope for the best?
Posts: 578 | From: San Jose, CA | Registered: May 2002
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nitrous_bob
CAFords OG
Member # 77
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posted
i will say 90% of people use way to big of injectors. just like a MAF and TB
i always wonder about the calculators...even they seem to over rate
80% duty cycle and total 300 hp for a nitrous motor it says 27 lber's
i have been spraying for about 15 years, 3 different kits on 3 different cars and have ran fine on 19 lbers with a 190 pump
thats a stock 5.0 running 12.50's on spray
my current setup should net me 400 with a 75 shot, and it says 36 lbers
but i feel fine with a 190 and 24's, based on other combos
it just seems as the years go on....the recommended injector size keeps going up too
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5.0 OG since 1990
Posts: 1402 | From: st clair shores MI | Registered: Nov 2000
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SneakyStang87
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Member # 10724
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posted
thanks for the input i am going to try the 50's and tune it and hopefully it will be beastish before boost
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00 z28-dd
79 Coupe-Project Almost done
93 Drop Top-Got Jacked
87 lx-crashed
89 gt-sold
90 lx supercharged-sold
Posts: 272 | From: 925 to 916 | Registered: Mar 2011
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Duncan Motors
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Member # 7045
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posted
stevel can not of said it any better. cutting a injector down takes it out of its happy spot. just like running a too small injector in sense. run the right size injector. if ur doing to different stages of motor stuff. use 2 different sized injectors for those applications.
Posts: 6310 | From: Vallejo | Registered: Sep 2006
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