Please explain Delta MAP Kpa...

[joecar]

Yes, correct, for an un-referenced FPR, injectors flow more when MAP is less than BARO (100 kPa at sea level), i.e. when vacuum is present.

Yes, injector flow vs injector pressure difference

injector pressure difference = absolute pressure at top - absolute pressure at bottom

The conversion is: 100 kPa == 14.5 psi == 1 bar

so 400 kPa == 58 psi == 4 bar: This is what you will measure with a gauge at the fuel rail.

Also note: 400 kPa gauge pressure == 500 kPa absolute pressure
(i.e. absolute pressure = gauge pressure + baro )

Yes, 460 kPa is 60 kPa vacuum, so injectors flow more.
Yes, 350 kPa is 50 kPa boost, so injectors flow less.

lol, I'm still here

[69camaro5speed]

Thanks I like when stuff adds up lol

[joecar]

Ok, pop-quiz:

What are the MAP values that corresponds to the deltaMAP values 460 kPa and 350 kPa...?

[69camaro5speed]

guess i should log that pid

[joecar]

injector pressure difference = absolute pressure at top - absolute pressure at bottom

460 kPa = 500 kPa - MAP --> so MAP = 40 kPa (i.e. vacuum is 60 kPa)

350 kPa = 500 kPa - MAP --> so MAP = 150 kPa (i.e. boost is 50 kPa)

[joecar]

Why is absolute pressure at top = 500 kPa...?

Hints:
- what is the difference between absolute pressure and gauge pressure...?
- what is un-referenced (constant) rail pressure in psi or kPa...?

[joecar]

Thanks I like when stuff adds up lol

Yes, I like it too...

When stuff doesn't add then there may be a problem.

[Naf]

I sort of understood, but i am lost here. I am tryin to Log the inijector flow base for my E-38 to see if i may repair the tune that way instead of going through the complicated map. What PIDs do i select, so i may log for this Map

I have had plenty of success with my older vehicles using this technique.

Looking forward to your reply

Naf

[joecar]

I thought the pid was E38.INJPDELTA.MAP, in addition to SAE.MAP.

[mr.prick]

My definition of Delta_MAP is the actual (not percentage) difference of
the current frames MAP value from the last.

#Units       Low      High     Fmt       Expression
#------- ---------- --------- -------- -------------------------------------------
psi         -16        16      .0        "({SAE.MAP.psi})-value({SAE.MAP.psi},frame()-1)"
kPa         -105      105      .0        "({SAE.MAP.kPa})-value({SAE.MAP.kPa},frame()-1)"