i got some 450s and yes, i searched for an hour and i only found idle pressures. im thinking 16-18 idle. i ran 70psi@ 9psi with 30# and good til 13psi on the wideband. i no longer have access to a wideband so what fuel prs. do i need @ what boost for 450s?

got that megasquirt!

This is too broad of a question. Basic concept is lowering the pressure of the injectors makes them flow less than their rated amount. 450cc are flowed at 43.5 psi. lower pressures make them operate as if they are smaller size.

Pressure all depends on what you are using for tuning. If your just installing the 450s and lowering the pressure, then you really re not tuning and ned to find a real way to tune the fuel map.

its a simple question. i read that i needed 20-22psi to idle 30# and 70psi @ 9psi of boost. i hooked up a wideband and it showed good. so my ? is can i get a easy answer to a quick question. what pressures for 450's? i know how this process works i just need numbers.

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i'm sure there are lots of you using theese injectors, does anyone know right off hand what fuel pres. i should have @ 13-14 psi. of boost?

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what are you using to tune with? are you simply fuel pressure tuning? the general idea is that bigger injectors require less fuel pressure to flow the same amount or more fuel and you tune by changing duty cycle. asking "what presure should i run?" is in fact a very broad question. since you seem to know so much about how this works, i wont offend you by asking if you are using a 1:1 regulator now. you want an easy answer, 25-30 psi at idle. you want a slightly more correct answer, set you pressure at idle by pulling your vacuum line from the regulator and set your pressure to around 40-43 psi then hook your vacuum line back up. to give you any better answer than that you need to give more info.

ok fine, im using an sfmu and utilizing "fuel pressure" instead of "duty cycle". i'm idling @ 22psi with 30# injectors. why would i put in bigger ones and idle even higher press? i'll prolly jus try to get ahold of a wideband and forget the bicoring. i guess i just assumed that you all knew i had an sfmu cause 90% of us do. do some of you run the gst 450's or am i taking crazy pills? so is that aprx. 40psi static? and if wher on 14psi of boost, what fuel pressure should i see. if you need more info, ask away.

got that megasquirt!

There used to be a fair amount of people running an SFMU but MSnS is the new crack that every one wants. You do have a resistor pack for the 450s right?

the reason why you would run more pressure is because you would turn down the duty cycle. since you dont have a way of doing that then yes you are going to need to run very low pressure at idle. so low the injectors probally arent going to work correctly. theres really no correct science to say "this is the pressure you need to run", you might just need to play with it until you get it to idle. when i put bigger injectors in i usually just kind of do it by adjusting pressure until it smooths out. like i said, not an exact science, at least not with me. if your car is running fine now with the 30#'s, why are you going bigger? id wait to put them in until you at least get a wideband to tune with, or at least some dyno time where they have a wideband. and its usually not a good idea to try to run that big of injectors with only an sfmu. like i said, why screw with it if its running fine with the 30#'s anyway.

the only reason i'd fix it when its not broke, upgrade. i'm limited to 12psi on the 30# and don't want to kill them. sorry, i got perfect instrucions for the 30#, i was just looking for the same "easy out". oh, yeah. i got the impedance thing worked out. i've spent hours resurching.

got that megasquirt!

Since you dont want to discuss the issue like a rational individual and want to tell us how things go then I am locking this. Do what you want and have a nice day. Find a real way to tune while your at it.