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Discussion Starter #1 (Edited)
Morning all,

I'm running SARD 800cc injectors, numerous other mods, no idea of top power yet, but thats kinda by the by, when running 800cc injectors or anything big, what duty cycles are people hitting, at high powers, only asking as I'm still mapping the dam thing, but at only 1 bar boost im using 80% + duty cycles, and im not running that rich ! mix is bang on, but im needing that high to fuel it, seems a lot more than i anticipated.!!

Stu
 

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Discussion Starter #4
mods, yea lots, all done by me hehe, but power no not yet..!
head work, pisonts, plenum, managment, boost controlelr, turbo, etc , normal stuff, im more interested in what duty, people with known quantities have, e.g a dyno'd 550bhp enigne, on such a size injector running 70% etc... just seems mad im nitting 80 on these 800's already, whihc either means shes a LOT more powerful than i thought or, i have a issue.!!
also means as im limiting boost at min, these aint going to be big enough if its ok.!

Stu
 

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thats probably normal for the power you are putting out. i have 850s in my rx7 and that see's high 80s for short rev ranges but unless in the 90s im not worried. im getting 1600s in that.

a wideband will tell you if you have a problem or if its using the fuel.

how sure are you that they flow that high?
 

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Discussion Starter #6
ive got a wide band display and its not overfueling, so its presumable its burning it.!
they are SARD 800's and I flow tested them,,,
 

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from what i can remember the stock injector (340mm i think) runs at 80% to make 300hp approx

so for yrs running at 80% i would guess its either 600+bhp or you have a problem



As an example if yrs are 880 injectors it would be 50% for each cycle as you would get twice the amount of fuel as a standard injector. Thererfore you only need 50% of the new injectors volume to flow the same fuel if that makes sense.

check here bud...http://www.skylineowners.com/forum/showthread.php?t=65436&highlight=injector+duty+cycle
 

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Discussion Starter #10
up to around 4 to 5 Krpm, and a bar boost it is, but after there no not really, and im already hitting sodding 80%..!!
 

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Could be just your fuel pressure. You should be running 3bar, if it was lower your injectors would run harder to make up the extra fuel needed
 

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Here's some quick calculations for you with an online calculator. Bear in mind I'm no expert but have been swotting on this alot of late in my spare time (would love to do mapping course in the future)...

Power: 400 horsepower
Number of injectors: 6
BSFC: 0.60
Duty cycle: 0.85
This combination will require 494 cc/min injector (47.1 lbs/hour)

Power: 500 horsepower
Number of injectors: 6
BSFC: 0.60
Duty cycle: 0.85
This combination will require 617 cc/min injector (58.8 lbs/hour)

Power: 600 horsepower
Number of injectors: 6
BSFC: 0.60
Duty cycle: 0.85
This combination will require 741 cc/min injector (70.6 lbs/hour)

as said - possibly fuel pressure regulator and/or fuel pump maybe?
assuming all else is sorted and you can get the power down to the hubs lol, you should be able to get:

Injector size: 800 cc/min injectors(76.2 lbs/hour)
Number of injectors: 6
BSFC: 0.60
Duty cycle: 0.85
This combination will supply fuel for 647 horsepower

you didn't mention what turbo your running etc? What bhp figures have you had it at so far with the 1bar/80% duty? You mention friends are running 550bhp @ 70% with similar mods?

interesting this - finally techy geek thread on here lol! :drivin:
 

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Discussion Starter #13
Yea pressure is fine, sitting at 45 Psi....
turbo is a hybrid T3/T4 item... whihc would struggle past mid 550's I would expect...

Humm will have to keep playing...!
 
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