Fuel Injector Rates - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums
 
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post #1 of 8 (permalink) Old 06-06-2014, 11:19 PM Thread Starter
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Fuel Injector Rates

What flow rating would we set 30lb Bosch 3 injectors at ? (from FIC)

I've done my first log on my 383. The motor went into closed loop and the BLM's dropped to 108 in SD mode (MAF switched off)

My initial figure is too low ( for some reason i've set it lower than i had with the xfi 268 cam).

I think from Soloman's site it says the Ford/Bosch run at 39psi so i should be looking at 31.68 as a figure.
Calculating of my figures i'm at least 10% out so should be looking at 33.02

Do I start with the lower figure and then adjust the VE Tables ?

I think i might have just answered my own question.

Thanks
Mitch

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post #2 of 8 (permalink) Old 06-08-2014, 08:18 AM
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If you haven't found your answer, you might want to pm steveo or bobdec as they are both pretty deep into the tuning thing.
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post #3 of 8 (permalink) Old 06-08-2014, 10:38 AM
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your math is correct for those injectors but fails to take into account that flow ratings on bosch injectors are benched with n-heptane and not gasoline

a better injector constant for a baseline might be sqrt(43.5/39)*30*1.035 = 32.78

you need to find the proper injector voltage offsets too, which can be a pain in the ass to find for bosch injectors

obviously in speed density mode you're going to be way out anyways, since your engine is built. are you even going to end up running it in speed density, or do you just want better VE tables?

having your VE tables kinda rich on a MAF car isn't bad, since they'll only be used for emergency "maf broke in half" fueling, or maybe transitional fueling (never proven they're used for that, but richer in transitions isnt bad)
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post #4 of 8 (permalink) Old 06-08-2014, 10:40 AM
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oh and just fyi, you aren't off by 10% when BLMs are 108. you're out somewhere between 10% and 100%. 108 is the minimum trim, it reaches it and just stops pulling fuel. you can change that if you like, but only if you reeeally trust your o2 sensors...
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post #5 of 8 (permalink) Old 06-08-2014, 11:44 AM
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Also, when doing injector offsets,it's better to have more offset than less. This'll make the injectors fire sooner instead of later if they are slightly off. It's not better than perfect, but if they are off it's better off early than late.


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post #6 of 8 (permalink) Old 06-08-2014, 12:49 PM Thread Starter
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Cheers guys I'll give that a go when i get my new PC battery.
I was just trying to get the motor set close with VE tables etc then go back to MAF tuning.
For some reason i've picked up a lower rating than i'd got to with the previous tune ( a 350 with xfi 268 cam).

Steveo I have an XL file from Jon at FuelInjectorConnection with offsets but it doesn't mean a lot as it needs converting
They were for Modified Bosch 3's with stainless core if you want a look send me an email

Mitch

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post #7 of 8 (permalink) Old 06-08-2014, 12:52 PM Thread Starter
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Steveo :
I realise the 108 is the lowest figure for BLM's it was just as an approximation for the amout out. They were pretty close on my earlier tune with the 350.

thanks
Mitch

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post #8 of 8 (permalink) Old 06-08-2014, 01:15 PM
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if i were you, i'd be working on injector constants and trims with a maf; you're more likely to get the right base constants for injector/cyl vol. then tune VE after.
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