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Ok, been meaning to find out about this for a while.. I'm not even sure I'm in the right forum.. but here goes.

At what point in a persons mods does it become necessary to increase the size of the injectors?? I've got 03-04 Mustang GT parts running all the way from the air filter to the heads.. with a Lonnie chip and tune. The 19lb injectors worked for the mustang, as did the fuel pump..

How much further can I go before the 19lb injectors just cant do it anymore?
 

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A side questions since we're talking about injector sizing. Does displacement matter?

Say you have a 4.6L making 300 rwhp and a 7.5L making 300 rwhp. Can they both live on 19 lb injectors?
 

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Ok here is a question.Is my 190lph pump ok to run with my 39lbs injectors? The car seems to run ok for the most part and it is tuned. Sorry to jack travler. Just wanna know how close I am to needed my own upgrade on top of my upgrade. lol
 

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so is there any benefit at all to upgrading to 24# injectors on a stock fuel pump and mostly stock engine if you have a tune to go with it? my injectors are making a faint clicking noise and I feel they will need to be replaced soon.. or can they be cleaned?
 

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so is there any benefit at all to upgrading to 24# injectors on a stock fuel pump and mostly stock engine if you have a tune to go with it? my injectors are making a faint clicking noise and I feel they will need to be replaced soon.. or can they be cleaned?
No.
Injectors make a clicking noise. That is the way it works. If they are injecting gas into your intake then there is no reason to replace them.
 

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I would say 19 #/hr injectors will get you to about 270rwhp, safely, while leaving some margin on the table

as far as displacement, it doest really matter how much, as it does how the engine is producing power in terms of: Naturally aspirated vs Power Adder....it all boils down to the engine's Brake Specific Fuel Consumption, which is a rating of how much fuel is needed to sustain one HP for one hour......a typical compression/efficiency N/A engine is gonna have a BSFC of around 0.45-0.50, while a power adder car will have a BSFC of 0.55-0.60...units of BSFC are #_fuel/(BHP*hr)

how does it factor into everything?....it has to do with general rules of thumb of A/F ratio required at WOT for N/A engines vs Power Adder engines.....typically power adder engines require a slightly richer A/F ratio than N/A engines....that is why they need more fuel for every HP they make in one hour (hence the greater 0.60 BSFC of a poweradder engine--in other words, this figure already factors in the slightly richer A/F ratio that is typical of power-adder engines)

this is how the calculation goes (and is only valid for "typically" used A/F ratios for N/A and power adder of ~12.8:1 and ~11.5:1, respectively, and also assumes a 80% duty cycle maximum)

sustainable BHP= [#_Inj]*[Inj_flow_#/hr]*[0.80]/BSFC

again, this all depends on the engine's actual BSFC (which could easily be lower if it's tuned, has good intake/exhaust, etc, etc), and on how much injector duty cycle you personally are willing to accept (a highly tuned hi-compression engine with efficient intake tuning/exhaust scavenging could easily get down into the mid 0.40s for BSFC, and obviously injectors could be run at a larger duty cycle if the tuner opted to use them as such).......the only half-azz way to find the engine's WOT BSFC (because it does depend heavily on other variables as well), is to get a dyno run, back-calculate the BHP, datalog the injectors pulsewidth to back-calculate the total fuel delivery in (#/hr), and plug those into the above equation, and then solve for BSFC (which will actually be WOT BSFC)

95xbird, 190 L/hr pump is equivalent to ~300#/hr of fuel flow...divided by 0.50 #/(BHP*hr)= ~600 BHP....of course restrictions within the fuel system could (and probably does) reduce this figure substantially...so this is more of a theoretical calculation based on if there was absolutely no restriction on the pump itself (which is obviously not the case with small fuel lines making sharp turns and what not).....so yea, there is no issue to running those injectors (those are what I run personally on a smaller fuel pump)

danalba, no benefit to using 24# injectors on a stock tuned engine, unless the tuner knows how to fool around with the injector timing calculations to get more fuel vaporization from the fuel sitting longer on the closed intake valve (even then its hardly any difference)....i figured out how to work with the injector timing based on cam specs, a/f ratio's, RPMs, engine load, etc....and let me tell ya, theres a reason most tuners dont mess with it: very time consuming to generate even one truly accurate table....because even then it depends on actual physical variables such as actual cam-timing, fuel delivery variations, etc, etc, etc LOL
 

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Thank you for the info Maestro!:thumbsup:
 

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Discussion Starter #10
Ok here is a question.Is my 190lph pump ok to run with my 39lbs injectors? The car seems to run ok for the most part and it is tuned. Sorry to jack travler. Just wanna know how close I am to needed my own upgrade on top of my upgrade. lol
I don't consider it a "jack" in the least.. it was on topic, and a question I'd like to know as well (which guitar maestro answered quite well.. thank you).

So... long story short... the stock injectors and pump will take me up to almost 300 RWHP without too much difficulty..
 

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I don't consider it a "jack" in the least.. it was on topic, and a question I'd like to know as well (which guitar maestro answered quite well.. thank you).

So... long story short... the stock injectors and pump will take me up to almost 300 RWHP without too much difficulty..
yup yup
 

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maestro you deserve an award, period.
 
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