Bigdeezs

iTrader: (17)

I have been searching this topic through so many different websites including LS1tech and have come by sooooo many different conclusions. I've heard that bosch says they are at 26.5lbs/hr and 28.6lbs/hr at 43.5psi. I think a thirdgen.org member says he flow tests injectors and that he physically tested our injectors at 22lbs/hr-24lbs/hr at 43.5psi. Other than what someone thinks or has heard is there a definitive answer for this and any proof of what they are? Does anyone know where to find it? According to redhardsupras fuel injector calculator and my stock 2000 ls1 injector flow rate table I have a 26.44lbs/hr@58psi injector which would mean my injectors are 22.88lbs/hr@43.5psi. Which means our injectors are rated at 58psi not 43.5psi if that table is correct. I did this same thing with a Z06 injector flow rate table with the calculator and it says the Z06 injector is a 29.15lbs/hr@58psi which makes it a 25.24lbs/hr@43.5psi. Other than what someone thinks or has heard is there a definitive answer for the stock injector flow rating@psi? and any proof of what they are? Does anyone know where to find it?

MeentSS02

iTrader: (11)

Our injectors are rated at 58 psi...I have the 28.8s in my '02, which is exactly how the IFR table is calculated in the PCM. So they are small injectors run at a high pressure.

jimmyblue

iTrader: (11)

Yes, the proof is in the IFR table and the rail pressure.

Bigdeezs

iTrader: (17)

Thanks guys I was definitely leaning that way.

usd2sing

iTrader: (15)

good topic.

adding a question. (just for general knowledge)

if an injector is rated at 33 with 58lb of fp and then installing them into a car with base/idle pressure of 43 makes them a 28lb correct?

same scenario but at wot the pressure is 47 makes the 33lb'ers a 29.7lb injector.

am i on the right track?

Phoenix 5.7

iTrader: (7)

the reverse is the SVO injectors are rated at somewhere around 40psi, so when installed on an LS1, they are higher volume. so a 36lb SVO might be closer to a 40lb on our cars(my numbers are not correct, just an example)

dynocar

It makes them flow at 29.7 either way assuming that the 43 lb fuel pressure was caused by vacuum and you have vacuum compensated fuel pressure. Remember, it is the pressure difference across the injector that determines its flow, so if you have -4 lbs at the output and 43 lbs at the input of injector, the difference is 47 lb thus a 29.7 lb flow rate.

dynocar

Yes, you are correct, a 36 lb at 39 psi becomes a 43.9 lb at 58 psi.

usd2sing

iTrader: (15)

thanks.

my question was based off of learning how diff cars can use diff injectors and trying to figure out how to make the injector from a dif car work in a car that has a lower base fuel pressure.

ex:
car A:
has a static stable FP of 58lbs (from idle to wot). the injectors that came with this car are rated at 33lb.

car B:
uses a static/base pressure of 43.5 at idle, low cruz, low map.
vacuum assisted at higher map it raises it to 47lb at wot.

injectors from car A are now rated at 28.4xx because of the lower (43.5) pressure.
but with the vacuum raised pressure to 47'b it will now be rated at 29.xx.

so taking these 2 diff ratings and put then into the flow settings (low and high end) and then following the map/vacuum increases at throttle increases should be able to find the flow table.

or am i wrong?

(yes, newbie with injector tuning)
thanks

dynocar

As a general rule, injectors are flow rated from their manufacturers (Bosch Lucas, Siemans, Rochester etc) at 43.5 psi differential pressure. In the days of fuel return systems they usually used a fuel pres reg that was vacuum/boost referenced that maintained a constant differential pres across the injector to compensate for the vacuum, ambient or boost pressure at the injector's outlet tip to maintain a constant injector differential pressure so that calculated pulse width changes was the only thing that would alter fuel flow. Then came along non return fuel systems, many like GM with no fuel pres compensation for vacuum or boost. Instead, an injector flow rate table was set up in the PCM's software to compensate for the changes of the injector's differential fuel pressure and the base fuel pressure was increased. With such systems a Bosch injector with a Bosch rating of 19 lb/hr at 43.5 psi became a GM injector rated at 22 lb/hr at 58 psi. The same thing is going on at Ford except that they electronically vary the fuel pressure similar to the old vacuum/boost referenced fuel pres regs. They also use a base fuel pressure of 39 psi so that 19 lb Bosch injector mentioned above now becomes a Ford 18 lb/hr injector. So if you want to use that Ford 18 lb injector in your GM you need to know that once it was a 19 lb injector before you convert it to your 22 lb injector. Hopefully you can see here that the original industry standard of rating injectors at 43.5 psi plays an important role here in these conversions. Hope this helps.

usd2sing

iTrader: (15)

^^^ thanks.

your time and effort is appreciated,

peace,
dan

Old Geezer

iTrader: (3)

Calcs to determine the flow, vs psi.
Most injectors are rated at 3 bars. 43.5PSI.
To determine the flow at another op pressure, the formula is:

NEW flow rate = old flow rate X the sq root, of the new PSI, divided by the old PSI.

IE:
36# inj at 58PSI.

58 divided by 43.5 = 1.3333
The sq root of that is: 1.1547
Thus: 36 x 1.1547 = 41.57#/hr

Back under my injection bench!