I am unfamiliar with how to scale the injectors on an LS1 PCM, the older LT1 were real easy, this looks greek to me.

I have the stock 28lb/hr injectors and I need to scale them to 69.3lb/hr (60lb Mototron at 43.5 psi, rated at 58 psi fuel pressure)

 

Here you go. These are vacuum referenced so -> 0 kPa is WOT and 80 kPa is equal to 20 kPa absolute referenced.

This follows your IFR table:



KPA 0 5 10 15 20 25 30
8.73, 8.78, 8.83, 8.90, 8.95, 9.00, 9.04,

KPA 35 40 45 50 55 60 65
9.09, 9.16, 9.19, 9.26, 9.31, 9.36, 9.41,

KPA 70 75 80
9.45, 9.53, 9.55,

 

What is the IFR table mean? what are the injectors measured in, values? What does this mean "80 kPa is equal to 20 kPa absolute referenced?"

 

injector flow rate is in g/sec i think and 80 kpa is the vacuum the manifold sees in relation to standard atmospheric pressure of 101.3 kPa. so 80 in the table should be 20 on the map sensor ( i think i actually have a post asking about this )

 

okay g/sec makes sense, but I would like to know about the kpa values

 

im pretty sure that what i was talking about is right, if 0 kpa is the vacuum then that means your at standard atm pressure of 101.3, if you pull an 80 kpa vacuum then

-80+101.3=21.3 MAP

in other words with no vacuum the manifold sees what you see outside of the car, plain old air at about 100 kpa, as you go up, subtract off of that and you get the map reading. so (atmospheric pressure)-(IFR vacuum)=MAP reading

so lets say in the table at 40 kpa vacuum

100-40=60 kpa MAP


did that help or no? lol

 

i got the same numbers he got, you can get it mroe consistent if you check the pressure at the given kpa, if you do that i can plug it in my excel file for you and give you the numbers

 

Could someone post up the stock rates for an LS1 (the gms/s vs KPA) ?
I only have a truck file on this computer right now.
thanks.

 

26.41 26.6 26.79 26.91 27.1 27.28 27.41 27.59 27.72

27.9 28.03 28.21 28.34 28.52 28.65 28.83 28.96

thats 0-80 in 5 kpa incraments

 

*
kPa 100 95 90 85 80 75 70
g/sec 8.73 8.78 8.83 8.90 8.95 9.00 9.04
*
65 60 55 50 45 40 35 30
9.09 9.16 9.19 9.26 9.31 9.36 9.41 9.45

*
25 20
9.53 9.55

 

sorry mine was lb/hr

 

Okay does the table go from 0 kpa to 80 kpa, or 100 kpa to 20 kpa

I know that std atmospheric pressure is 14.7 psi and that is equal to 101.4 kpa, some earlier in the thread said 0 kpa was WOT (no vacuum), is this correct.

Also why do you change the injector constant with manifold vacuum?? I mean wouldn't you wanna keep the injector constant static and then just scale the VE and MAF table??

 

the injecors are really done on a change in pressure basis from what i understand. so at 80 kpa vacuum, thats about 11 psi vacuum, so the rail pressure of 58 plus that vacuum is 69 psi (delta) so that is why the injectors will flow more fuel at 80 kpa vacuum. you want to get this table accurate and then leave it alone

 

The IFR table for my truck is set constant, as is most of what I've worked on, so yes it will work either way you want to do it.
If it's scaled by MAP from the factory, then it's just less work to keep it that way.

I was just trying to figure out the percent increase that was done to that posted table. I figure that the injector size increased by 147.5% over the stock 28 lb.
It looks like he (Bink) roughly added about 162%
Is this what was done here?

 

Depends on if the fpr is vacuum referenced or not...

 

Sorry, I copied the last post wrong - I edited it and it is now correct for absolute referenced values. 100 kPa being atmospheric/WOT = 8.73 g/sec.
If you do the math 100 kPa should be 8.78 g/sec -> But, there is a .05 buffer subtracted which will result in .05 g/sec More fuel for safety.

 

Could you please post the math you used?

I multiply 3.33 * 1.475 and get 4.91
4.91 + 3.33 = 8.24

Did you use a different % gain? or a different formula?

 

F1=60 lb/hr
F2 = New Flow Rate lb/hr
P1=43.51 psi
P2=58.02 psi

F2 = F1 * Square Root (P1 / P2)

F2 = 60.00 lb/hr * square root (58.02/43.51) = 69.29 lb/hr

Remember, the PCM values are in grams/second.

1.000 lb/hr = 0.1260 g/sec

69.29 * 0 .1260 = 8.731 g/sec

Hope this helps some.

 

tonight i went out and logged for my IFR changes for the actuall pressure and was quite impressed with the numbers i got, much more consistent and the VE table seems to flow better now. plus rich idle is eliminated

 

Bink, whatever you used did the same calculation that I did above. you just started with a different base number in the beginning.
You started with 3.33 as the base flow rate with 28lb injectors, and I started with 3.528 as the base flow rate of the same 28 lb injector.

It looks like your formula uses a calculation to convert to gms/sec, and the number I used comes straight from the factory calibration in the IFR table.
As far as I'm concerned, I'd just multiply the IFR table by 147 in Edit and start from there.

Your value of 8.73 is about 6% more flow than my number of 8.24

*Keep in mind that this is the lowest flow rate as seen at WOT, and the difference in values between the two calculation methods will increase as you get closer to the MAP reading for idle.
This could be causing your idle fueling to be a little more off than you think.