Please explain Delta MAP Kpa...

[Redline Motorsports]

Couldn't tell you, just knew that it was accurately reporting. In the tank?

Justin

I've had tanks out to install fuel systems and don't remember seeing anything. What data does that pid report??

[dc_justin]

I've had tanks out to install fuel systems and don't remember seeing anything. What data does that pid report??

On this particular truck, right around 43.5psig. Was fluctuating slightly, but pretty stable.

[jfpilla]

So Joe, based upon that, we are only using 6-7 locations of the IFR table when making an injector change. What is all the other resolution for?

No clue Howard and the values in B1210 follow the same pattern.
B1206 might be a reason for limiting IFB values, but I don't see anything that explains the outlying values.
While looking I noticed B4001 and B1210 are labeled MAP, but "injector parameters" offers a choice of MAP or VAC. My file has VAC selected.

[dc_justin]

On this particular truck, right around 43.5psig. Was fluctuating slightly, but pretty stable.

That was an 08 6.2L Sierra Denali. Checked an 07 2500HD with the LY6 6L engine. No pressure sensor on it.

[mr.prick]

Howard,
It would seem so. You know I calculated the IFR for the stock LS7 injectors for my 2003 vette. I doubt if it's a coincidence that the calculated values fit neatly into the 400 to 480 range. The only areas where the numbers change.
Joe

How did you do this?

[69camaro5speed]

so from what I get delta map psi is fuel pressure vs what injectors flow over fuel pressure change
I have a 2010 6.0 suburban motor 6.0 with l92 heads we make them 408strokes they have changed injectors 3 times from 07 to 2010 the 2010s from what i get here have around 55 lbs injectors.
I engine dyno test them befor they leave with a e38 sd tune I made to make sure every things ok I put the first 2010 on and its like 10 to 1 afr I get looking at b4001 it has 55 lbs injectors going off what it seems here I been trying to figure out how that table works for some time (posted while back )seems funny tune says its not flex fuel with that size injectors its over kill for stock great for me.Hear is stock tune

[joecar]

deltaMAP = pressure difference across injector = absolute rail pressure - MAP

note: absolute rail pressure = 500kPa absolute = 400kPa gauge (58psi gauge)

e.g.
deltaMAP=400kPa --> at WOT with NA
deltaMAP=440kPa --> cruise with OEM cam (40kPa vacuum)
deltaMAP=460kPa --> idle with OEM cam (60kPa vacuum)
deltaMAP=500kPa --> theoretical full vacuum (100kPa vacuum)

deltaMAP<400kPa --> boost (MAP > 100kPa)

[joecar]

so from what I get delta map psi is fuel pressure vs what injectors flow over fuel pressure change
...

Almost, not quite...

Stock FPR is set constant to 58 psi (i.e. unreferenced returnless system), fuel pressure should not change... but pressure difference across injector changes as MAP changes...

flowrate is proportional to squareroot of pressure difference across injector,

so ECM has to account for changes in pressure difference across injector due to changes in MAP.

deltaMAP = pressure difference across injector = absolute rail pressure - MAP

e.g.
What happens to pressure difference across injector when MAP is:
40kPa...?
80kPa...?
100kPa (WOT)...?
(absolute rail pressure is 500kPa)

[joecar]

If you have a manifold-referenced FPR (i.e. with return line), then, the FPR will vary rail pressure (as MAP varies) to always keep pressure difference across injector constant...

in this case, the injector flow rate will be the same value regardless of MAP, and table B4001 will be flat static (same value all cells).

[69camaro5speed]

deltaMAP = pressure difference across injector = absolute rail pressure - MAP
ok I see what you are saying maybe lol It takes Into the fact that say 60 kpa its sucking on the injectors harder so they flow more. so if it uses 400 delta map psi as a rail pressure (58lbs )looks like the number to figure injector size thats in the motor.

I understand as vac.goes up the injectors will flow more.Its like a map pressure differance vs injector flow (how it changes injector flow)

but little confusing 400 kpa is 58 lbs. the fuel pressure is 58 lbs but it doesnt change its almost like its a fuel rail pressure table for the injectors

So if I get it 400 kpa is wot injector flow for say 100 kps map and say 460 kps would be high vac. so injectors will flow more say around 4lbs on this tune.
If it had boost then delta map would go down and injectors will flow less say under 400kpa like 350 kpa because you have boost pushing on injectors

ok hope my slopy typing hasnt killed you lol better with wrenchs thanks