federal spec ecu vs california spec ecu.

[allrice4g64]

i was kinda of wondering what the difference between the federal spec md346077 ecu vs the california spec md346673 ecu are. i have done some research and some say its more sensitive so it triggers the cel faster to reduce emissions some say the federal have more aggresive fuel maps some say there isnt a differnce? does anybody know the actual real differnce?

[Ruslik]

thats a good question i always wanted to know too

[99 galant]

Does the cali spec get better mpg?

[allrice4g64]

from what i understand is the california spec does have better gas mileage. i cant remember where i heard this from but i heard that a cali ecu is basically designed to run as lean as possible to pass emissions in california. some say there is a power difference and some say there isnt. theres alota controversy over what the difference is and i want facts.

[jubeiaire]

To be honest if the Cali Ecu does run leaner the its automatically gonna result in less power than a federal Ecu controlled car. The more fuel your car restricts from the engine the less pressure you get from cumbustion(if i described it properly) equating to more lose of power in the transfer from engim=ne tor tranny to wheels.
Now on a CALI Emissions basis the specs in cali DO require all cali sold/owned cars to burn less fuel and create less emissions, so based on that fact its either less fuel burned in engine, or its just the Up graded Cats used in cali or BOTH combined. Id say check the cali Emissions Requirements for your year car against the federal and then look at the specs on the cali G and federal G and see where they made changes and that will tell you if its ECU, Parts Or Both. Fuel Pressure Specs and Throttle Intake specs are the first place to check since ECU controls/Monitors Both also check specs on o2 Sensors.

[DOHCstunr]

running lean actually causes more emissions.
Thats why even prius's don't run lean a/f ratios like 16:1 while cruising.

There are awd eclipse guys getting close to 40mpg with a taller 5th gear and lean burn code in their chipped ecu's

[allrice4g64]

ya i have a cali ecu right now and the thing constantly wants to pull fuel its like its always in a negative fuel trim and its almost impossible to tune out 450cc injectors so im waiting on a federal ecu to see if there is a difference

[mko]

Having an issue has nothing to do with what spec the ECu is. I have cali spec ECU, so did most of the 94 Galants - 2 oxygen sensors and EGR with temp sensor on it.

Lean AFRs cause more NOx emissions, rich AFRs cause more CO emissions. An ECU is not set to get better gas milege, but its set to obey the certain state/country/continent emission laws. You can disable all emissions components on 94-95 Fed Spec Galant and it will run and wont throw a CEL. On Cali spec car it will throw a code cuz it checks if every components is functioning.

You tune with MAFT right? Get the BASE setting right and it should see mid 12s at WOT, around 14.7 at cruise and idle. If it tries to pull or add fuel that means your base setting isnt correct. Also, Id borrow a second wideband to confirm the AFR numbers

[allrice4g64]

yes that is correct i do tune with maft. iv played around with it even with it in a positive trim at idle and with it set lean cruising it stay at 14.7 but no matter what the setting is the ecu always goes to -4.6 thus casuing the ltft to be in a negative. i tryed the 2g ecu swap and that worked for fuel but timing wasnt advancing at all. it stayed between 5 and 7 degrees at idle mid and wot. iv tryed researching that problem and got nothing. so i dunno whats going on one ecu stays lean as hell the other wont advance timing at all but stays rich so whats a guy suppose to do been months now trying to figure this out and still stuck at day one.