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are 30lb injectors enough for 100 dry shot?

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Old 10-03-2005, 02:15 PM   #1
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Default are 30lb injectors enough for 100 dry shot?

i have a 402 w/ a tiny cam making about 520 flywheel horsepower with 30lb injectors. is it safe to put a 100 dry shot on top of that?
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Old 10-03-2005, 04:44 PM   #2
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I would personally go with some 42 Lbers.

Matt

EDIT: LSX fuel pressure is 58.0 PSI, so a 42 Lb fuel injector will act as a 48.83 lb/hr fuel injector on a LS1.

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Old 10-03-2005, 04:52 PM   #3
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Here's the math,
(Projected hp X .6) / 6.4 = min injector size to meet 80% duty cycle
So,
620hp - 15% drivetrain lose = 527rwhp

527rwhp x .6 = 316 / 6.4 = 49lb injectors

Hope this helps
Robert
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Old 10-03-2005, 05:09 PM   #4
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Quote:
Originally Posted by Robert56
Here's the math,
(Projected hp X .6) / 6.4 = min injector size to meet 80% duty cycle
So,
620hp - 15% drivetrain lose = 527rwhp

527rwhp x .6 = 316 / 6.4 = 49lb injectors

Hope this helps
Robert

Glad you posted that, usefull info.
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Old 10-03-2005, 06:03 PM   #5
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Quote:
Originally Posted by Matt@HSW
I would personally go with some 42 Lbers.

Matt

EDIT: LSX fuel pressure is 58.0 PSI, so a 42 Lb fuel injector will act as a 48.83 lb/hr fuel injector on a LS1.
Yep, that's what I have.
Robert
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Old 10-03-2005, 06:25 PM   #6
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that equation seems way on the conservative side , which is not bad tho
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Old 10-03-2005, 06:34 PM   #7
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Yep, Robert is always conservative. I think that's why he uses the dry kits...he is saving fuel by not using a wet kit.
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Old 10-03-2005, 06:53 PM   #8
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Actually it's an industry standard equation. One addition though, using .6 as BSFC is for power adder cars only, and .5 should be used on n/a figuring.
Robert
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Old 10-03-2005, 07:21 PM   #9
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the BSFC is what concerned me
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Old 10-03-2005, 07:28 PM   #10
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LOL I run some 42lb (48.xx) on my setup...........100rwhp dry shot ..........thats conservative! just wanted a little room to grow!
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Old 10-04-2005, 08:46 AM   #11
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okay....... thanks. that equation IS for 80% duty cycle instead of max... but that's being safe (which is good). thanks for the info.
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Old 10-04-2005, 08:51 AM   #12
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Quote:
Originally Posted by Robert56
15% drivetrain lose = 527rwhp
i have a t-400 trans w/ an unlocked converter, steel driveshaft and a 12 bolt w/ a posi and 33 spline axles.............. more like, 25%+ drivetrain loss.

i only have 371 at the wheels.
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Old 10-04-2005, 08:53 AM   #13
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another thing is that the 30lb injectors actually flow around 36lbs at 4 bar. maybe i'll get new injectors anyways...........i don't have a lot of money and the 30lbs are barley used........
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Old 10-04-2005, 10:45 AM   #14
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Well where did you get 520 crank horse and 25% drivetrain lose? 15% is just a standard base number used, vettes are usually closer to 17% because of independent rear end. Anyway.
371 + 100 = 471rwhp
471 x .6 / 6.4 = 44lb injector at 80%
471 x .6 / 8.0 = 35.32lb injector at 100%

So, you can see that your current injectors are going to be static at your hp level you want. Static is not good. You can go past the rec 80% for short runs, but static I would say stay away from.
Robert
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Old 10-04-2005, 01:01 PM   #15
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15% is for manual tranny's... when i had a six speed the car dyno'd around 440 at the wheels with an aluminum driveshaft. 440 is approx 15% power loss from 520. then i swapped to a t400 trans, steel driveshaft and an unlocked converte and dyno'd at 371 without any changes to the motor or tuning. the motor didn't loose power....... it just got used up by the heavy drivetrain and converter. your 15% standard base is off of factory vehicles. not drag cars. lol
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Old 10-04-2005, 01:05 PM   #16
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Quote:
Originally Posted by Robert56
So, you can see that your current injectors are going to be static at your hp level you want. Static is not good. You can go past the rec 80% for short runs, but static I would say stay away from.
Robert
i understand........ but my runs wouldn't be for more than 11 seconds at a time. i'll try it and see if i have any problems. i should be okay. if not then hopefully i don't break anything and i'll get new injectors with tax return money. thanks for the info guys.
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Old 10-04-2005, 01:17 PM   #17
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Call me stupid, but I never remember hearing a 25% drivetrain lose with anything. That makes absolutly no sense to me to lose 70hp by changing to a auto trans?
Robert
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Old 10-04-2005, 01:57 PM   #18
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it went from a 6spd to a t400 with an UNLOCKED converter and a steal driveshaft. it happens.
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