3.8 MPFI injectors on a 3.1 MPFI

[CorvetteBeretta]

Long story short I had a conversation with some wacko on craigslist the other day, he basically told me he is running 3.8 MPFI injectors from a Camaro or something on his 91 Beretta 3.1 MPFI with no ecm mod. He told me you can use any MPFI injectors and the computer will recognize them. Is this possible or is this guy out to lunch?

[3X00-Modified]

Run them yes... computer recognize them, no... It will treat them as the factory injectors and will over run at idle and the O2 will register that and then your BLM's or trims aka fuel learning will be way off since it will be pulling fuel all over. This is bad because at WOT it may also lock in at that learned negative trim which will then trim WOT fuel and may bring that too lean...

Basics in ECU tuning is when you swap injectors you should modify the injector flow constant in the ECU... Then you can tweak the air flow characteristics in the ECU as well to get your BLM's as close to optimal as possible. 128 is the sweet number... With that being done you then modify the open loop fueling and whatever you enter there you KNOW will be used at WOT... and wont get trimmed back by a bad BLM learned value.

Car ECU's have a level of correction built into them to allow for changing conditions and aging parts but you should not take advantage of that when swapping in larger capacity parts because that learning section of the ecu for one is limited and second that learned or corrected value for one driving condition could be detrimental to another driving condition.

[CorvetteBeretta]

That's what I thought thanks