I’m looking to get my ecm reflashed, the motor is a 502 mag mpi, edelbrock performer rpm heads, 500efi cam, shortened intake runners, hi-tek stainless manifolds, and the bottom end was rebuilt with all new forged pistons,rods,crank. Where would be best to get it reflashed?
Cheers

where are you located?

Eddie Young, Young Performance Marine.

Padraig

I’m located in guernsey in the UK, so it’s difficult to find anywhere that can do it.

Reflash of the ECM without air fuel ratio (AFR) readings is just a guess. The Merc ECM are programmed on the rich side from the factory, because its safer that way. Putting on higher flow heads and exhaust may not need any improvements. Only way to know is O2 sensors in the exhaust to get the AFR readings

If you get a copy of MEFI Burn then you could reflash it your self if another sends you the file. Might be able to get a file from OBD Diagnostics or Eddie, but as before without testing its all guessing

i was told by the guy that I bought the motor off it wasn’t reflashed, been run like that for a while. Engine has just been refreshed so wanted to get the ecu reflashed as its running very rich, the Rev limiter could do with going higher too. At a guess I’m not running anywhere near the timing advance I should be.

If your ECM is a MEFI, it can be reflashed, even if it has to be wiped and new program reloaded, easy

If its a 555 then harder to do, but can be done, or at least Whipple says they can

What do you have?

I have the mefi 1 ecm. So should be straight forward? The engine mods I think are pretty common so bound to be maps out there? As I’m in the uk though our fuel is 95 octane standard and can go for 99 if I wanted. So the standard timing is not enough for that octane and aluminium heads? Isn’t the ecm set for 87 octane?

Correct the standard file is set for 87
Note, you may know this: the UK octane is straight RON where the USA is RON and MON which is on the anti-knock index. So UK 97 = 91 USA

Should not be an issue getting a MEFI-1 done. The 1 isn't even password protected. I have the MEFI Burn software and its easy enough to change the settings or just use it to reflash yourself. Might try what you have and if not doing good enough then see about changing things. Run, stop and check plugs, then run some more. Best to add so O2 sensors and watch

I was faced with the same scenario and decided to carb my motor. When I get the coin together I will run the Holley hp setup. It simply didn’t make sense to invest in 35 year old parts.