explain to me how the stock ECU meters fuel and timing

[themadscientist]

OK, this is the situation. I have a bone stock ECU for a CA18DET. I am using a Vein Pressure Converter and a Graphic Control Computer to eliminate the Mass Air Flow sensor. I have used this to adjust the fuel delivery to very good effect but eventually the stock injectors are going the need supplementation. To that end I have an Additional Injector Controller and yet another Graphic Control Computer to start feeding extra fuel when the time comes. If I had the money I would go standalone but I don't so I am using what I got. The problem is I do not know the theory of operation that the Nissan ECU uses to compute fuel delivery and ignition timing.

I have the O2 sensor removed so closed loop is disabled and there is no factory boost solenoid any more. So I guess you would say I am "running off the maps" but without a source of manifold pressure or A/F signal exactly how does the ECU know what to do. I see only the following sources of information available to the ECU to figure it out.

1.Air flow, well the ECU thinks its a MAF when actually it's air temp and MAP translated into a MAF signal2.Water temp3.RPM4.Throttle position

Does anyone know how many map points there are in a CA computer and most importantly what parameter triggers the computer to toggle up and down through them.

What are the X & Y axis of the fuel maps RPM & MAF?

Is it water temp that signals the step up to the next map?

Same question for the ignition maps.

This is an area of concern for me as I have no means of adjusting ignition advance without a ROM tune as I see it, please clue me in if I am mistaken.

I know we have some ROM tuners out there so I hope someone can splain it to me. If I have an understanding of how the stock computer does it's thing I can better set my various piggybacks to back the ECU up.

[Q45tech]

It is not so simple as a single parameter. The ecu creates a fill in the blank multiple equation with dozens of parmeters creating the final injector open time.

Same with ignition advance it builds up a negative number of degrees before TDC to stop voltage to coil which results in secondary voltage.

Load [tps] and rpm along with [tipin= rate of change of accelerator pedal] create a reduction/advance in timing. This was created from dyno tests = what is ignition advance for MAX BMEP then back off a few degrees for bad fuel and coolant temp then back off how much KS system requests.

Battery voltage as read by ecu is a trim.Coolant temperature is an advance trim below 150F and a retard trim above 195-200F.................then IAT trim below and above 77F

Emulating MAF voltage is fine except the limit maybe 4.8 volts

[themadscientist]

dam, that's pretty daunting.

[Q45tech]

Why it's all done in a computer simulation prior to ever applying to an engine then after hundreds of dyno hours of tweaking, then hundreds of hours on the road testing at each interval it gets closer and closer to ideal.

Each different engine gets millions of dollars worth of tweaking. Because of emissions and MPG/tax and fines.

Creating power is the easy part, a 1/10 of a MPG or emission is the costly part.

Why mods ecu reprograms only make changes at WOT and above 2750 rpms.

[FoxFire]

what kinda of chip do you have27c128 or 27c256

this is how to idedentfy your ecu and eprom location http://home.aanet.com.au/nistu...n.pdf

once you find where and what kind of eprom you have

you canA. change the stock eprom out for an already tuned eprom from someone that can load epromsB. buy the eprom programmer (70 euro), tune and load your own, not real time but easyly changeableC. buy an emulatator like nistune or the cheaper procket romulator and tune eproms real time