Has someone cracked the mpi ecu ?

QBhoy

Rear Admiral
Joined
Mar 10, 2016
Messages
4,721
I know, I know...I’m going to leave myself wide open to being called silly and come in for some comments like “just get a bigger engine” or “it’s too risky”
but
having searched the subject of remapping the GM mpi 555 ecu every other month or so for years, all that’s came up was the silly resistor gimic that presumably tricks the engine into thinking its cold and running rich (dyna something I’m sure was the brand). This is a waste of time gimic for sure...
but just within the last wee while there, a couple of quite reputable U.K. remapping outfits with real credentials and reputation behind them are advertising remaps for the mpi ecu. Mainly for the 350 and 5.0. Some figures quoted see a wee bit of gain. I’m just not sure I’ve ever known any real gain from a naturally aspirated engine ecu tune. Usually forced induction does well as you’ll know.
link to one of a handful of them is below. Any truth in it you think ? Any popped up over the pond and better still...anyone tried it ? Likely optimistic with the figures and also I thought it couldn’t be done ??

https://mychiptuningfiles.com/en/ch...rcury-marine/mercury-marine-5-0-mpi-260hp-all
 

alldodge

Supreme Mariner
Joined
Mar 8, 2009
Messages
31,259
Nice website but I don't believe it. Would be great if someone could take a tune for a 5.0 and reprogram for a 5.7, 6.2, 8.2, etc, but would only want a stock tune. If the 555PCM was able to be reprogramed there would be others doing it.

Each setup is different and there can be areas of slight adjustments to gain performance. Lean out the fuel mix and gain hp, but also can damage the motor. Only way I would want to change the fuel mix or timing curve is with AFR meter and O2 probes.
 

QBhoy

Rear Admiral
Joined
Mar 10, 2016
Messages
4,721
Nice website but I don't believe it. Would be great if someone could take a tune for a 5.0 and reprogram for a 5.7, 6.2, 8.2, etc, but would only want a stock tune. If the 555PCM was able to be reprogramed there would be others doing it.

Each setup is different and there can be areas of slight adjustments to gain performance. Lean out the fuel mix and gain hp, but also can damage the motor. Only way I would want to change the fuel mix or timing curve is with AFR meter and O2 probes.

I’m going to call them on Monday. These have just recently been added to their capabilities. dyno set up apparently on some sellers. I’m 50/50 on it !
 
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