injector size formula

[timucin]

i remember seeing a formula for injector sizing,but cant find... can someone remind me pls..
thnx

[autounion]

I think this one is correct.

(HP) x 6 / (Number of injectors) = cc/min

[timucin]

new turbo calculations show 580 hp max at 8000rpm
assuming that i can receive those hp's
i need around 700cc injectors by this formula?

do i have to put any toleranca like %10 +/- ?

Mihnea any help?

[OZzzt]

Re: I think this one is correct.

Originally posted by autounion
(HP) x 6 / (Number of injectors) = cc/min

I think that's too pesimistic. The Porsche 511cc-injectors manages 500+hp with ease. I know of an S2 which has dynoed 610hp with those injectors at 6 or 6,5 bar fuelpressure.

Looking foreward to dyno my own car with 511cc injectors


OZzzt

[S2central.net]

Timucin - how are you going to run 8000rpm on this monster engine... are you planning on using solid valve lifters cos the hydraulic ones won't be happy at this rpm ?


Paul

[timucin]

yes solid 280 degree from dbilas

[Albert]

You can find all the info on maching the injectors on
http://www.rceng.com/technical.htm

[OZzzt]

Originally posted by Albert
You can find all the info on maching the injectors on
http://www.rceng.com/technical.htm

That calculator can't be correct, or I'm not using it right...

It claims that the stock 346cc injectors can only manage 247hp at stock fuelpressure.

And the 511cc injectors that I am using only is sutable for 377hp @ 4 bar fuelpressure. I have over 500hp now, and no shortage of fuel!

(In the 'Fuel Injector Worksheet':
I am calculating with 0.60 as desired Brake specific fuel consumption, and 0.8 as the duty cycle)

Either this calculator is useless when it comes to the 2.2 T, or I am using it incorrect... If I am doing something wrong, please tell me what


OZzzt

[dkw_dude]

PSIG..

Hi Øystein, Leif-Helge here..

Does PSIG mean that the measured pressure is referenced to absolute vacuum? In that case you may have to adjust your fuel pressure in the worksheet..

[OZzzt]

Re: PSIG..

Originally posted by dkw_dude
Hi Øystein, Leif-Helge here..

Does PSIG mean that the measured pressure is referenced to absolute vacuum? In that case you may have to adjust your fuel pressure in the worksheet..

Hello there mait!

I thought of that too. But after consulting someone with knowledge, I resoned it to be fuel pressure above athmospheric pressure. Althoug I know BARG is used for absolute pressure when talking about boost pressure.

But even if we take the athmospheric pressure in to count, the stock injector only manages 276hp.

But! ...the stock injectors for ABY (and AAN) and the RS2 injectors has it specific flowrate measured at 3.8 bar (55psi). The orange 511cc injectors I don't know the measured pressure for...
In the calculator you have to know the specific flowrate @ 3 bar or 43.5 psi for it to be useful...


To put it simple:

The stock injectors are capable of ~330-350hp
The RS2-injectors ~450hp
the 511cc-injectors ~550hp

This can be stretched a little with very high fuelpressure.


OZzzt

[Albert]

It is just an matematic formula ...

but if You use the second calc You
HP 550
NR of inj. 5
Size 49
PSIG 65
duty cycle .90
You get BSFC .49


so it works for me ...

[timucin]

how come?!?!!?

desired hp:600
injector size:5
bsfc: 0.60
-why cause it says .60-.65 for turbocharged engines
maximum duty cycle: 0.80
fuel pressure rail: 75 psi ( with bosch motorsport+regulator)

result is: 720 cc/min

confused big time!!! what should i get?
orange porsche looks small for my desired hp

pls help

[timucin]

ttt

[Floddy]

720cc for 600hp seems pretty correct from what i know.

(HP*5.1/number of injectors)/0.8=injector size

Chech this out, in swedish but i guess at least the norwegians will understand it ...

http://tote.mine.nu/temp/formler.html

But then, you can make the injector last for more hp by raising the furl pressure and go with a higher duty cycle.

For example, 100% duty cycle and std fuel pressure (3,8 bar) on 511cc injectors would last for 500hp. At 6.5 bar fuel ressure and 80% duty cycle about 520hp.

[timucin]

i am very very sorry for my lack of understanding but i still dont understand:

how come?!?!!?
desired hp:600
injector size:5
bsfc: 0.60
-why cause it says .60-.65 for turbocharged engines
maximum duty cycle: 0.80
fuel pressure rail: 75 psi ( with bosch motorsport+regulator)
result is: 720 cc/min

confused big time!!!

i am just trying to learn, formulas say 720 but real life experts say 511.is there any other formula to calculate this?why there is difference like this

somebody pls-pls explain me this stuff