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MEGAsquirt A place to collectively sort out this megasquirt gizmo

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Old 05-18-2012, 03:20 PM   #61
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ecu calcuates fuel based on the RPMs and Airflow and whichever formula they are using, with the proper data it command the proper ammount of fuel based on the commaded AFR table as show in the first page.
There will allways be minor issues here and there, over time the injectors start leaking, maf gets dirty, etc of course on stock ecu's there is certain ways they deal with this based off fuel trims.

And yes the emgasquirt can do the same as the factory ecu, I"ve already shown it can.
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Old 05-18-2012, 07:31 PM   #62
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That map is straight from the ROM and is just one of the factors used to calculate the fuel sum. It's several years since I looked at it so I've forgotten most of it, but I pulled this quote from my notes of the time (the reading from that map is stored in location 00F8):

Code:
0102:  Main Fuelling sum  is calculated in a subroutine at A0B2

Start with a value of $0040, then add 8 bit values from 00F5, 00F8 and 00F7 and multiply the result by 4.

Add 8 bit value from 00FB and multiply the result by 8.

Add 16-bit values from 00FC, 00F9 and 0104, multiply result by the (8-bit) value in 0106, producing a 3 byte result.

Multiply that result by 2 then take only the top 2 bytes of the answer.

Store the result in 0102 (limited to $499A maximum).

So the sum is;   
	0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
	0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0
	0 0 0 [ . . 00F5 . . ]0 0 0 0 0
	0 0 0 [ . . 00F8 . . ]0 0 0 0 0
	0 0 0 [ . . 00F7 . . ]0 0 0 0 0
	0 0 0 0 0[ . . 00FB . . ] 0 0 0
	[. . . . . . . 00FC . . . . . ]
	[. . . . . . . 00F9 . . . . . ]
  +     [. . . . . . . 0104 . . . . . ]
				       	


((((($0040 + 00F5 + 00F8 + 00F7) x 4) + 00FB) x 8) + 00FC + 00F9 + 0104) x 0106 x 2 /256



00F5 	This might be acceleration enrichment.
00F8 	This is the reading from the AFR/fuel map
00F7 	might be cold start enrichment
00FB	Just might be lambda correction
00FC	dunno
00F9	dunno
0104	always zero

0106	the multiplier. Seems to be $80 (x 2/256 = unity) or $00 (which would be a fuel cut)
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Old 05-18-2012, 09:29 PM   #63
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Oh wow, that's pretty technical! Thanks!

So it is, indeed, a calculated estimate!
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