Help me make a shopping list!! (injectors, pump)

[ALLstrokedOUT]

Hello everyone, i have a few general questions about some components for fuel injection shopping list. I will be running a MegaSquirt II, (probably with a 3 Bar MAP unless someone has a better suggestion) I have everything pretty much decided upon except for the fuel pump and injectors. The issue is that a year or so down the road after i make some more 'fun' money I plan on building a 'little' twin turbo setup. With how expensive injectors are, on this budget i don't want to have to buy 16 of them over a year's time whether I can recoup something from the first set of 8 or not.

Now, to the math to figure out the injector size: I am assuming i make about 500hp at the crank N/A; the rule of thumb for injectors is .5lb/hr per hp. I am assuming maybe 650hp at the crank for the turbo setup, which is a 0.6 conversion factor so:
(500hp x 0.5)/8 injectors = 31.25lb/hr @ 100% duty.
(650hp x 0.6)/8 injectors = 48.75lb/hr @100% duty.

For the duty cycle, it should be around 45% to 75%. With that being said, what size injectors do you think would satisfy my needs now and later?

If i were to get 75lb/hr injectors that would be a safe 65% duty for the turbo app, but only about a 41.5% duty N/A. Why is there a lower bound to the duty cycle 'rule of thumb', and is 40% too low?

I also need to look into fuel pumps, is there a safe and cheaper alternative to the Aeromotive A1000? ...im not cheap, i just dont want to pay for something that will not be sufficient or will be overkill for my application..
Thanks everyone for your input!

[gui67]

Hello,
I nearly have the same setup:
megasquirt 3 with turbo 383 sbc.
The aeromotive pump is really noisy and with a fixed flowrate. I use a fuelab prodigy fuelpump: 41402 link (http://fuelab.com/prodigy-fuel-pumps/41402-prodigy-fuel-pump-high-efficiency-efi-in-line)
they are much smaller, and you could set it to a lower speed when you have N/A and later set the speed higher for the turbo. I plan on using an output on the MS to set the speed depending on MAP. (you can set the speed with PWM)

for the injectors, I use 83# injectors (but only cause I could buy them very cheap from a friend)
first see how you can wire them with MS2 and if you need low or high impedance (low might need a peak and hold additional driver: jbperf (http://www.jbperf.com/p&h_board/index.html#V1.1A))
for the duty, I now have ~45% (at 6PSI boost) and drive without a problem. I think you could go up to 85-90% duty at max boost, to decrease injector size.
If the injectors are too large, the risk is at idle: the open time would be too short, and the injector flow would be inaccurate if you don't know exactly the opening time: you would have difficulties having a smooth idle and stable AFR.
I would use 65lbs if I were you for the turbo application: you should not have any problem at idle.

[ALLstrokedOUT]

Thanks for the info! ive only heard good things about the aeromotive pumps performance wise, but this car is primarily going to live on the streets, so i would like as quiet a pump as possible. The 65lb/hr injectors sound like a good size, im trying to figure out how much boost i will be running (id like to be around 8-10lbs), playing around with some compression calculators and head gaskets...
With a 0.060 head gasket i should have 9.75:1 compression. There are 'racing' solid copper head gaskets 0.092 thick that can get me down to 9.15:1 compression, but id have to do some research on the reliability of that kind of gasket.

btw, qui67, are you running just MAP on your MS3, or MAP/alpha-n or something else? ..i did a lot of research on the MS systems about a year ago but its all escaped me over time

[gui67]

I am running MAP only.
for the choice of the pump, don't forget that the fuel pressure will be boost related:
you set the pressure to 45PSI, then at boost, the regulator adds the boost pressure: if you have 10PSI, choose the pump to have enough flow at 45+10=55PSI

For MS, I choose the MS3 version which has 8 injector outputs + a lot of other outputs. I run with sequential injection and i could add coil on plug for ignition. (for the moment, I have on MSD coild with a distributor).

[ALLstrokedOUT]

Rite, very cool. I have a pretty big cam with a lot of overlap rite now, so i was thinking id have to run a MAP/alpha-n, but now im thinking of switching to a nice turbo cam before going turbo to help in the initial efi setup. I would like to run sequential injection, but for the extra setup time and cost i dont think i will see a return in performance or economy the way i drive...

Also, Is there a prefferred brand of fuel injectors that anyone uses?

[Six_Shooter]

Using the RC engineering calculator, which uses the same math as I have found from many other sources, the 500 HP estimate at .50 BSFC and 80% DC comes up with 39.29 lbs/hr, for the 650 HP estimate at .6 BSFC and 80% DC, that comes up with 61.29 lbs/hr.

http://www.rceng.com/technical.aspx?UserID=8820294&SessionID=tStgiMOpZDnsuyPhg8hi

If you only wanted to buy injectors once, buy the injectors you will need in the end. You just won't be using the full flow until you need it.

I run a Walbro 255 on my car, and heard of people having great success run a pair on higher power applications.

[ALLstrokedOUT]

Thanks Six Shooter! I never thought about using two Walbro pumps...I looked into it a little bit last night, and it seems like that is the most appealing setup to me now: its more affordable than an aeromotive by like $200, and not overkill for the application. I also have two outlets on the sump of my fuel cell, so it would be easy to plumb for dual parallel pumps.. I need to run a(n) external pump(s)...Ive heard without the voltage regulator on the A1000's they dont last long, but what about the Walbros; do you know how long they last as external/inline pump?

[Six_Shooter]

I've been running mine for about 3 years now, and I drive my car a lot.

IIRC it was fuelpumps.net that I bought mine from.

[ALLstrokedOUT]

Thats good to hear its lasted that long for you..by converting to efi im trying to get the car more consistant and reliable, a crappy fuel pump would kind of defeat that purpose haha. But i think thats the way to go for me, should be more than enough flow when i need it, less current draw when i dont, and for half the price!