ZL1Killa

iTrader: (17)

well, got to crunching some numbers and :
actual 32lb/hr injectors
36.48853701 lb/hr current 65% duty cycle current


42.5 injectors ordered new duty cycle
49.07477288 0.484183673 48% duty cycle
49

kpa ratio of boost change 14.7 is 101.4kPa
5psi absolute pressure is 19.7
19.7psi absolute to kPa is 135.83

0.642840237 64% on new injectors at135 kPa only

70.06896552 percent duty cycle under boost reference to AFR from 12.7 to 11.6 AFR


but when i crunch numbers from my sticky http://www.rceng.com/technical.htm
I get:
550 BHP
.65 for BSFC (brake specific fuel consumption)I guess this could be played with
.75 duty cycle on new injector
and of course at 58psi at the rail

and it comes up with a 51.6 lb/hr injector rated at 43.5 installed on car this way
so that means i need around a mid 40# injector or even a 50# injector since my fuel pressure is 58psi instead of 43.5


STS kit @5psi with 58psi @ fuel rail and 42.5# injectors...... should i go bigger or just wait and see?

ZL1Killa

iTrader: (17)

don't say motron 60#ers please unless you are running stock internals, stock cam, and just bolt ons and got the 60#ers to work fine at idle in CL and the car not surge
b/c my car is that and the injectors didn't want to stay @ around 14.7 AFR at idle

Urban Legend

iTrader: (5)

OK, how about Siemens 60 lbs. Find yourself a good tuner (see your sig) and you will be fine.

MavrikTA

iTrader: (27)

And this is EXACTLY the reason^^^ I wasnt quick to jump on the 60lb bandwagon. I get more confused every day! LOL!

ZL1Killa

iTrader: (17)

yeh, nick helped me out and the motron 60# injectors wouldn't go below a 1.6ms pulse width at idle... that might be due to the default pulse width and min inj pulse width and small pulse adjust needing to be lowered even more but we played with that and I even helped nick figure out a problem on one of his cars that he is trying to tune that he thinks the injectors are also too large.... LMAO.

60's are going to have another go... but right now I'm having serious issues with the racetronix fuel pump i got that is supposed to be really good. sent them an email and I'm not going to post anything else about it, cept that i might have to buy an actual walbro pump and trash this one

ZL1Killa

iTrader: (17)

now, i must also ask the BSFC number... should I lower that to say .62 since i will only be using 5psi or does that not have anything to do with boost... just demands of fuel?

ZL1Killa

iTrader: (17)

here is some math i did and added some percentage based on the application that might require more fuel for some unknown reason.

came out with 42.5# injectors being fine. 50#ers were even better

calculated the fuel injector rating for 43.5psi and @58psi on
31.6 lucas delphi injectors
42.5 lucas delphi injectors
50 injectors (same as above)
60 motrons

calculated the duty cycle for each at my current N/A setup and for FI setup based on MAP and increased fuel needs (AFR) and then to the right added extra 25% in case of more fuel needs

i do realize that MATH is MATH and an application can require more or less than this equation... its all about what happens when it is applied.

gametech

iTrader: (1)

My injectors came in before the sts kit for my '04GTO. I went ahead and put the injectors on with absolutely no other mods. This was bone stock other than some HPtuning. The 60# Mototrons or Siemens or whatever you want to call them tuned easily and idled fine. I did of course lower the minimum injector pulse width. My neigbor put some on his 434ci holley fuel injected smallblock, and could not get them to idle. I'm not sure if the problem was the holley computer or low alternator output voltage at idle.

ZL1Killa

iTrader: (17)

what all did you change for the 60#ers?
i probably could have gotten them to work just needed more time, but i have already sold them and ordered 42.5#ers that will work fine with no problems; and i'm not losing money from it.
also going to sell my 32# injectors, but i won't post them till i get them off the car.


right now with fuel, i'm having more problems... freakin racetronix 255 pump is kickin in and out, so forget the injectors for now, i want to solve the pump problem

gametech

iTrader: (1)

It has been quite a while now, but all that I recall changing is the minimum injector pulsewidth. If I remember right, there were two tables that I changed that control that. I think I may have raised my idle to 800rpm at the same time, but I don't remember.

ZL1Killa

iTrader: (17)

to 800rpm... what does your car stock idle at?
mine idles at 800rpm... we raised it to 950 and everything was fine

gametech

iTrader: (1)

I don't have my laptop with my stock file with me right now. In a couple of days I may be able to find the exact changes and all other info on the bone stock vs stock with 60's. I'l try to remember and post when I get a chance to compare files. Also, I don't know what differences there may be between my '04 gto computer and yours. And, to add to the previous post, my neighbors 434 idled until the electric fans came on, then the computer could no longer properly control the injectors. This is why I think it may have been a voltage issue. Unfortunately, Holley's fi computers have a lot of software bugs, so who knows.

RedHardSupra

iTrader: (1)

small STS setups usually flow about 68lb/min of air. that warrants about 6lb/min of fuel, which is about 44.5lb/hr. so that makes it sound like a good idea to go with svo 42s, but it isnt', because you'd be running almost at 100%. to keep you at 80% duty cycle you need at least 56lb/hr injectors. there's few choices, some 57's and 60's so just go with that and you should have a nice safety margin.

gametech

iTrader: (1)

The problem is the stock pump and non-boost referenced fuel pressure. I can run just over 10#'s at around 510rwhp all day, but if I go to 13#'sboost, my injectors go from about 80% at 4400rpm to over 100% by 4600rpm. The 60# mototrons bandaid the pump up to a certain point, but I guess that is why I have the aeromotive and racetronix parts in my garage.

ZL1Killa

iTrader: (17)

RedHardSupra where you at man... Marcin...

we will see, you do realize that the 42.5# injectors are rated at 43.5psi... so at our fuel pressure they are actually 49#ers. Marcin.... i see what you mean by tuning on CL without all the OL crap. learning man, learning.


small STS setups usually flow about 68lb/min of air. that warrants about 6lb/min of fuel, which is about 44.5lb/hr

well at 68lb/min (which is not 5psi boost, its higher) and an AFR of 12:1 i get a cylinder specific fuel consumption of .709 lb/min. multiplying the .709lb/min x 60min/hr equates to 42.5lb/hr. So my duty cycle will probably wind up at about (43.5/58), which is 73.3%. This is because the injectors are rated at 43.5psi and they are operating at 58psi.