4" intake piping - 95MM MAF Tuning

[The1]

hmm thinking this 95mm MAF might be my issue, i scaled the tables down so at idle type low airflow scene it was just under 2000hz then brung it back into line with base injector rate, still flatlining at 8000hz, i went back through my old logs just after fitting and tuning the 69mm TB and with stock MAF it went close to 9000hz no problems, the 95mm MAF is suppost to be 1500hz to 12000hz im guessing the stock one is 1890-10000hz, anyway you'd think it'd still hit the limit at 10000hz rather than 8000hz, any ideas guys?

[The1]

oh and it's not the 300G/S limit no where near it

[The1]

hmm well looking at the stock tables for both maf's there's nothing really in it, only a few G/S between them at the same values it's just got more low end and more high end. So im thinking it's just an issue with this MAF.

[antus]

Im not sure you can move the tables up.. maybe you moved them up in the pc side definition, but i think the breakpoints are hard coded in the ecu. kalmaker workshop added a couple of rows to expand the range, but im pretty sure its a code change. VL400 probably knows for sure

[charlay86]

The PCM should be telling you the actual frequency the MAF is outputting.
Maybe shifting the tables has caused it to make less power than before and therefore it wants less air?

This is how the PCM calculates the frequency and does the MAF table lookup. (note, this is for a VT PCM, but i believe the VS is similar?)
please excuse my dodgy commenting

Code: Select all

loc_7225:					
	ldaa	MAF_pulse_ctr		
	nop				
	ldx	MAF_pulse_ctr		
	nop				
	ldaa	MAF_timer			
	nop				
	ldy	MAF_timer			
	ldd	MAF_timer_last		
	nega				
	negb				
	sbca	#0			;change the sign of the last timer value, so we can add them together to find the delta	
	pshy				;delay	
	puly				;delay				
	pshy				;delay				
	puly				;delay				
	pshy				;delay				
	puly				;delay				
	pshy				;delay				
	puly				;delay				
	tst	MAF_pulse_ctr		
	nop				
	cpx	MAF_pulse_ctr		;see if we counted any more pulses since we last checked	
	beq	loc_725E			;branch if we haven't	
	inx			        	;add that one if we have counted another pulse	
	tst	MAF_timer			
	nop				
	ldy	MAF_timer		;load the most recent timer value	
loc_725E:					
	sty	MAF_timer_last		
	addd	MAF_timer_last		
	std	MAF_timer_delta		
	ldd	MAF_pulse_counter_last		
	nega				
	negb				
	sbca	#0			                        ;change the sign of the previous counter value	
	stx	MAF_pulse_counter_last		;store the new counter value
	addd	MAF_pulse_counter_last		;calculate the number of pulses that occured
	bclr	FLAGS_41 2			        ; clear the low maf frequency error bit flag
	cpd	min_maf_pulses		  
	bcs	loc_7287			                ;branch if we counted less than the min # of maf pulses
	brclr	FLAGS_35 $80 loc_7299 ;	'€'      ;branch if not in mode 4 
	tst	byte_19C0			 
	bpl	loc_7299			 
loc_7287:					 
	bset	FLAGS_41 2		          	  ;set the low maf frequency error bit flag
	ldd	#0			
	std	MAF_Hz_aldl			
	std	word_11E			
	ldd	MAF_default_CALC		          ;load the default (calculated) MAF frequency
	jmp	loc_7326			 
; ---------------------------------------------------------------------------
loc_7299:	ldx	MAF_timer_delta		
	fdiv							;calculate the MAF frequency. ->   (number of MAF pulses)/(time period) = frequency
	stx	MAF_Hz_aldl				; this is the value in the aldl datastream 
	ldd	MAF_Hz_aldl				
	subd	MIN_MAF_F			 
	bcc	loc_72AB			 
	ldd	#0				 
loc_72AB:					 
	cmpa	#$1F				 
	bls	loc_72B2			  	; Branch if  ACCA <= $1F
	ldd	#$1FFF				; 0x2761 (10khz) - 0x762 (min MAF f) = 0x1fff
loc_72B2:					  
	lsrd					  ; divide by 2
	lsrd					  ; divide by 2 again
						  ; 1F/4 = 7
						  ; 0-7 is 8 counts which is the # maf tables, this is used to index the correct table (maf table number index)
	pshb					  ; 
	ldab	#$C				  ; 0xC = 12 bytes per MAF table
	mul					  ; 0xC * (maf table number index) = offset in bytes to the start of the correct maf table 
	ldx	#$531D			  ; MAF tables start address
	abx					  ; add the Start address of req'd MAF table
	ldab	0,x				  
	inx					  
	pula					  
	lsra					  ; lookup value prescaled to 1x9 table
	jsr	LOOKUP_2D			  
	mul					  
	dex					  
	dex					  
	dex					  
	addd	0,x				  ; add table offset value
	bcc	loc_72CF			  
	ldx	#$FFFF				 
loc_72CF:	rora					
	rorb			     
	std	MAF_GSx16_aldl          ;this is the MAF grams / second value in the aldl data stream

[The1]

hey guys, by shifting the tables i mean changing the Reference G/S airflow @ x Hz, the tables are still stock 1890hz up like normal decided not the play around with changing the hz table ranges yet. i ended up upping the table values so ended up with around 50G/S more @ 8000hz than before but still flatlined @ 8000hz

looking at the code above there's MAF pulses / Time Period = FREQ, So i would assume this MAF having a greater range will have different pulses per time period. So it's possible that past 8000hz the waveform isn't recognised by this pcm??

Im also wondering if anyone has used any of these default/airflow tables?

[charlay86]

Which table are you talking about exactly?
There are some default tables which are used as a contingeny when a sensor (ie. the MAF) fails.

[The1]

yeh that sounds like it.

Default TPS Vs Airflow (Would be REF for TB)
Default Airflow Vs RPM & TPS% (Guessing this for MAF Failure then)

These tables im guessing are for variation?

Airflow Vs Coolant
Airflow Vs RPM

[antus]

kalmaker workshop has extended the maf tables up to 10240hz, but its a code change.... but the hardware is capable.

[The1]

doesn't the standard tables goto 10082hz though? ive had the stock MAF up round 9000hz