Fuel Injectors
11-04-2004, 02:24 PM
#2
6th Gear Member
Join Date: May 2004
Location: las vegas, nv
Posts: 9,092
RE: Fuel Injectors
bigger injectors just supply more fuel. if you arent already running the max hp for the size you have, you wont notice any performace change...ex. if you have 200hp going to 24# injectors wont make any difference. you may notice something but thats only cause your switching from old injectors to new ones. if your running 300hp on the 19# injectors, you should notice a change when going to 24
11-04-2004, 03:03 PM
#4
I ♥ Acer
Join Date: Sep 2003
Location: United States
Posts: 8,826
RE: Fuel Injectors
OB things like fuel pressure will affect the flow of injectors, for example a stock set of 19# injectors will max out at a 90% duty cycle at 304 hp, whereas bumping the pressure to 45 psi you can squeeze 345 hp outta em.
But, I suppose if the injectors were run at the stock 39 psi then:
19# = 304
24# = 384
30# = 480
36# = 576
42# = 672
Now this assumes a bsfc of .45 - a supercharged car is gonna consume more fuel - more like a .55 bsfc (because you'll be running a much richer a/f ratio) so in the case of a supercharged car then your only gonna get 314 hp out of 24# injectors.
Also, remember this is flywheel horsepower - and that you ideally wanna be around 70% duty cycle, not 90%
If you wanna figure it up yourself its pretty symple. Just remember that Ford rates their injector flow at 39 psi, so if an injector flows 19# of fuel and you have 8 cylinders then if they were stuck wide open you'd flow 152 #'s per hour at 39 psi. You've got a max duty cyle of 90% so you take 152 x .9 = 136.8 #'s into the cylinders max. A na performance motor usually has a bsfc (brake specific fuel consumption) of .45, a supercharged car around .55 ... so take that 136.8 / .45 for a na performance engine and you've got 304 hp. If you increase fuel pressure from 39 psi to 45 psi then you've increased it by roughly 13.5%, so you can support 13.5% more hp, or 345 hp.
Class dismissed.
But, I suppose if the injectors were run at the stock 39 psi then:
19# = 304
24# = 384
30# = 480
36# = 576
42# = 672
Now this assumes a bsfc of .45 - a supercharged car is gonna consume more fuel - more like a .55 bsfc (because you'll be running a much richer a/f ratio) so in the case of a supercharged car then your only gonna get 314 hp out of 24# injectors.
Also, remember this is flywheel horsepower - and that you ideally wanna be around 70% duty cycle, not 90%
If you wanna figure it up yourself its pretty symple. Just remember that Ford rates their injector flow at 39 psi, so if an injector flows 19# of fuel and you have 8 cylinders then if they were stuck wide open you'd flow 152 #'s per hour at 39 psi. You've got a max duty cyle of 90% so you take 152 x .9 = 136.8 #'s into the cylinders max. A na performance motor usually has a bsfc (brake specific fuel consumption) of .45, a supercharged car around .55 ... so take that 136.8 / .45 for a na performance engine and you've got 304 hp. If you increase fuel pressure from 39 psi to 45 psi then you've increased it by roughly 13.5%, so you can support 13.5% more hp, or 345 hp.
Class dismissed.
11-04-2004, 03:07 PM
#5
6th Gear Member
Join Date: Jan 2004
Posts: 5,836
RE: Fuel Injectors
Heh, didn't even think of having to run richer=less hp out of the injectors...
Thanks
That's why my injectors arnt flowing enough for the 150...
Bleh
Had to up the Fuel Pressure a bit just to run the 75 with my current mods
Oh, well buying new injectors soon anyways
Thanks
That's why my injectors arnt flowing enough for the 150...
Bleh
Had to up the Fuel Pressure a bit just to run the 75 with my current mods
Oh, well buying new injectors soon anyways
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