john563

iTrader: (17)

how much rwhp can 32lb injectors go before maxed out.Lets say youre an A4 with heads and cam doing 390 400 rwhp.How big of a dry shot can you go before it will be maxed out

Robert56

iTrader: (2)

I have answered this question more than a couple times lately, including the math.
Robert

john563

iTrader: (17)

search was not working when i tried it,but thanks

Z284U2TRY

iTrader: (5)

I would say those injectors max would make 500 wheel. Not sugested but it's been done depending on fuel fuel psi those are rated at.

john563

iTrader: (17)

I was asking cuz most places that were reasonable priced were out of stock on the 42lb I wanted,but did have 32lb inj.available.I just ended up buying them from Harris speedworks.They said that they would have them in friday and would ship out that day.I just got a little impatient yesterday and thoufgt about 32lb.inj.cuz my heads are gonna be here anyday,and I know that thats enough for heads and cam,but I will add a dry shot in the spring and did not want to buy inj.twice thanks for your help
john

Robert56

iTrader: (2)

Ok John, sorry I was kinda busy before. Here is the math to get a good idea of what you need.

(Projected BHP x .5) / 6.4 = min inject to meet the 80% rule

So lets say you have 400rwhp as suggested. We now need to convert this to crank hp (bhp). 400 plus 15% drive train lose equals 460bhp. Now lets add a 125 shot to that for a starting point of 525hp.
So.
525 x .5 = 262.5
262.5 / 6.4 = 41.01 min injector

Now you can punch in any figure you want. Also going over 80% really is not a concern when just a short 1/4 mile pass, as this is a wear/tear saver. Just stay away from going static or 100%. Hope this helps.
Robert

john563

iTrader: (17)

thanks for the info.Im def. going dry,its safer,and stealthier,simple,I think you will see more dry hits in the future.Im thinking of a duel stage I dont want to progr.control,cuz dont want to constanly worry about noids.When I get the n20 in the spring Im def. gonna be using it thats why the 2 stage dont want to constantly think"are the noids wearing out"?The heads I got are a winter mod and wanted a little more N/A power,and the nitrous is there for the vipers/and the occasional exotics you'll see in the summer.I want to dual stage it for better traction. /come on smooth.When I get my kit Im gonna set it up right the first time and one thing is for sure its gonna be dry with all the bells and whistles.I already have the fuel requirements(42lb on its way) its just a matter of doing my home work over the winter

Todd157k

iTrader: (5)

This isn't exactly the way you've posted it before (loyal subject that I am..LOL). Your previous post:

"Projected flywheel HP x .5) / 6.4 = min inj to meet 80% DC rule

So we first need to turn your projected hp into BHP. We just subtract 15% from your anticipated 385rwhp + 100rwhp shot = 485rwhp.
485 - 15% = 412.25bhp

412 x .5 = 206
206 / 6.4 = 32.18 injector to meet the 80% duty cycle rule.
Robert


In your first example, you are subtracting 15% from BHP and adding a full N2o shot, whereas in the second post you're subtracting 15% from the TOTAL.
I know, not much difference, just keeping you on your toes.
Also, how is the 6.4 figured? I'm going to put Beer's 28s in today and want to put the 150 shot back in. I know I'll be hitting the mid 90s (dc) again but I'm ok with it since I hardly ever run it for a full 1/4 mile. (I'm usually ahead by then and shut down, if not.. no reason to stay on it)

Robert56

iTrader: (2)

YeaI do that sometimes say subtract when in reality its adding back the percentage lost in the drivetrain. If you could link me to that post I will fix it. I am glad there are guys like you to catch these mistakes, thanks.

The 6.4 is a common denom for 8 cyl motors. Here's the full equation.

(bhp x bsfc) / (No. of Injectors x Duty Cycle .8) = injector

bsfc is the break specific fuel consumption, .5 is normally used except blower/turbos use .6

You can also punch in any DC you like and figure things out from there.

Robert

Todd157k

iTrader: (5)

Got it. Thanks.