This is topic Injector size ??? in forum Tech Talk at Northern California Ford Owners  .


To visit this topic, use this URL:
https://californiafords.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=6;t=027179
Posted by SneakyStang87 (Member # 10724) on :
 
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??
 
Posted by 5.0 LsX (Member # 10017) on :
 
just get 80's and get it tuned, then you dont have to swap them later
 
Posted by SteveL (Member # 1241) on :
 
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.
 
Posted by 5.0 LsX (Member # 10017) on :
 
sorry for the bad advice, sounds like steve knows what hes talking about. im just used to bigger motors or more hp
 
Posted by SneakyStang87 (Member # 10724) on :
 
So my car will not run right with the 50lb injectors tuned??
 
Posted by SteveL (Member # 1241) on :
 
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?
 
Posted by KING TUT (Member # 11349) on :
 
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...
 
Posted by SLOWSN95 (Member # 8269) on :
 
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.
 
Posted by SteveL (Member # 1241) on :
 
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?
 
Posted by nitrous_bob (Member # 77) on :
 
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
 
Posted by SneakyStang87 (Member # 10724) on :
 
thanks for the input i am going to try the 50's and tune it and hopefully it will be beastish before boost
 
Posted by Duncan Motors (Member # 7045) on :
 
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.
 




Fueled by Ford Mustang Owners
on CaliforniaFords.com