Injector sizing,duty cycles and efficiency,etc..??
Injector sizing,duty cycles and efficiency,etc..?? I have been looking at injector calculation
plug in formulas and it seems that a lot of people on here aren't running enough injector for their mods or are running at way higher than recommended duty cycles.The formulas I have and use so far all refer to engine hp not dyno at the rwhp as some have mistakenly suggested to me.
Also I understand it is very very bad to go past 80% duty cycle or is it ok for short bursts like quarter mile run as the engine is only at max rpm for a short time,obviously would be different for contiuous wot like some high speed races..silver state challenge stuff like that.Is it possibe to get even 120% on duty cycle for short time..??
Here are some numbers assuming .50 efficiency for the normally aspirated ls1..is this good or is .45 or .40 more applicable?? I hear forced induction use like .60...anyway
400engine hp
assume .50 efficiency for all the following
80% duty cycle recommended 31.2 pounds per hour..keep in mind this is at normal fuel pressure ls1 pressure make these act like bigger injectors so 31.2 becomes like 36 pounds or so.
100% 25 pounds /hr
450engine hp
.80 35.2 pounds /hr
100% 28.1 pounds/hr
500 80 % 39 pounds/hr
100% 28.1 pounds /hr
600hp
80 % 46.9 pounds /hr
100% 37.5 pounds /hr
So if I plan on around 420rwhp with heads,cam intake,headers ,other bolt on which is around
480 engine and 120 shot of nos dry then need from above probably 42 pounders minimum to keep them at 80 % efficiency....is this correct or what.??
plug in formulas and it seems that a lot of people on here aren't running enough injector for their mods or are running at way higher than recommended duty cycles.The formulas I have and use so far all refer to engine hp not dyno at the rwhp as some have mistakenly suggested to me.
Also I understand it is very very bad to go past 80% duty cycle or is it ok for short bursts like quarter mile run as the engine is only at max rpm for a short time,obviously would be different for contiuous wot like some high speed races..silver state challenge stuff like that.Is it possibe to get even 120% on duty cycle for short time..??
Here are some numbers assuming .50 efficiency for the normally aspirated ls1..is this good or is .45 or .40 more applicable?? I hear forced induction use like .60...anyway
400engine hp
assume .50 efficiency for all the following
80% duty cycle recommended 31.2 pounds per hour..keep in mind this is at normal fuel pressure ls1 pressure make these act like bigger injectors so 31.2 becomes like 36 pounds or so.
100% 25 pounds /hr
450engine hp
.80 35.2 pounds /hr
100% 28.1 pounds/hr
500 80 % 39 pounds/hr
100% 28.1 pounds /hr
600hp
80 % 46.9 pounds /hr
100% 37.5 pounds /hr
So if I plan on around 420rwhp with heads,cam intake,headers ,other bolt on which is around
480 engine and 120 shot of nos dry then need from above probably 42 pounders minimum to keep them at 80 % efficiency....is this correct or what.??
Re: Injector sizing,duty cycles and efficiency,etc..?? error made by me..for 500 hp it said 31.5 pounds anan hour I think..here is website.there are others...www.z31.com/software/injector.pl
Re: Injector sizing,duty cycles and efficiency,etc..?? I have heard different things about this as well.. I was told that 28#'s are good up to 440rwhp. There are many 430rwhp cars around with the 28# injectors.. I think if you are going with a solid roller or bigger engine other than the 346ci then 30#'s and above are required to see the engines full potential. Now if you are going forced induction or NOS.. Same say they are the same then you need 30#'s plus.. Thats my take on this..
TECH Fanatic
Joined: Jan 2002
Posts: 1,376
Likes: 0
From: Stuart Fl
Re: Injector sizing,duty cycles and efficiency,etc..?? Ive wondered about this also. My 00 has the smaller injectors. At approx. 480 HP at the flywheel, are my injectors adequate?What size inj. do 00s have?
Re: Injector sizing,duty cycles and efficiency,etc..?? I made a run and watched pulsewidths in third at up to 6000 or so and they hit 19..something..I haven't noticed any extreme leaning yet on my 02..they are usually around .890 or so and zero knock retard..I would think I currently have maybe 360rwhp or so with current mods.Hoping for 390 or so when my tts longtubes show up in next little while...and again guys it appears that the forumlas usually refer to engine hp not rwhp
and I guess you can run those injectors at 100% for brief bursts with no apparent ill effects..still probably smart to upgrade .From the charts I would be using probably 36 pounds rated injectors for 480 hp at the flywheel to keep the duty cylcles low and figure our cars make the 36 punders roughly 42 or so??
I plan on 42 for my car as still want to throw that dry shot on top of it and they look like they will work..too bad they are twice the price of 30 pound svos..!!! Ouch..
and I guess you can run those injectors at 100% for brief bursts with no apparent ill effects..still probably smart to upgrade .From the charts I would be using probably 36 pounds rated injectors for 480 hp at the flywheel to keep the duty cylcles low and figure our cars make the 36 punders roughly 42 or so??
I plan on 42 for my car as still want to throw that dry shot on top of it and they look like they will work..too bad they are twice the price of 30 pound svos..!!! Ouch..
TECH Fanatic
Joined: Nov 2001
Posts: 1,190
Likes: 0
From: Las Cruces, NM
Re: Injector sizing,duty cycles and efficiency,etc..?? guys go here to do the calculations www.rceng.com
Yes most people are running 100% duty cycle with hardly just heads cams, but most injectors can handle this for 1/4 mile durations with out problems. Turbo and supercharger have a higher bsfc (.6), NA a lot lower .5 or so.
Better to be a little conservative then blow the engine.
Gary
Yes most people are running 100% duty cycle with hardly just heads cams, but most injectors can handle this for 1/4 mile durations with out problems. Turbo and supercharger have a higher bsfc (.6), NA a lot lower .5 or so.
Better to be a little conservative then blow the engine.
Gary
On The Tree
Joined: May 2002
Posts: 108
Likes: 0
From: Richmond, Virginia
Re: Injector sizing,duty cycles and efficiency,etc..?? In looking at the site that Red WS6 99 lists, I have noticed that at an 80% duty cycle, the stock 28#/hr injectors should be good up to 400 HP. Based on that, most of us can stay with the stock injectors, the guys with the big power have to upgrade the injectors accordingly. I think the best you can get out of the injectors is 100%, I don't think you can get 120%... these are not like a motor you can overspeed, but maybe the software would allow going over 100%. Is there anyone out there that can state for a fact if 100% duty cycle is the limit for the injectors.
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Re: Injector sizing,duty cycles and efficiency,etc..?? No, an injector cannot run past 100% duty cycle. That will not happen unless it is faulty. If it ran past 100% then it would be a larger injector! (i.e. instead of 25# 120% <------theoretically, it would be like a 28# at 80%)
Also everyones BSFC is different per vehicle. I calculated mine to be .45-.47. Also fuel pressure on our cars is around 58PSI - 60PSI. The best way to do injector sizing is on the dyno with a wide band.
Duty cycle is recommended to be tested at 80% because it is standard that companies use for comparison. However it is very possible that some injectors are more efficient then others, right? So when you look at the big picture everyone's setup will be different. You can use the calculations for an estimate, and then "tune" out any differences on the dyno.
Also everyones BSFC is different per vehicle. I calculated mine to be .45-.47. Also fuel pressure on our cars is around 58PSI - 60PSI. The best way to do injector sizing is on the dyno with a wide band.
Duty cycle is recommended to be tested at 80% because it is standard that companies use for comparison. However it is very possible that some injectors are more efficient then others, right? So when you look at the big picture everyone's setup will be different. You can use the calculations for an estimate, and then "tune" out any differences on the dyno.
