MEFI-1 and MEFI-2 interchanable?

[akorcovelos]

I have a 1996 7.4 Magnum MPI in my Cobalt. Whipple offers a reflash for MEFI-1 that claims 25hp on a stock engine.

I don't want to send them my original ECU, so I'm looking for a cheap MEFI unit to send them as a core (they don't have any).

I've found a few used ones at $500-600, but found a couple MEFI-2 units for $200. I read a few places that the MEFI1 & 2 are interchangeable. Does anyone know if this is a correct statement?

 

[achris]

25hp might yield you another 1 or 2 mph. But it changes the mapping and puts more stress on the engine. It's just not worth the cost, both initially and potentially.

 

[alldodge]

Here is what can be done, a MEFI 1 or 2 can be used on the same motor "provided" they are tuned to that motor. The MEFI 1 and 2 are not password protected so it can be calibated by anyone having software which can change it.

Here is the info about MEFI from BUP at OSO post 10

https://www.offshoreonly.com/forums/general-q/335565-what-years-were-gen-1-2-efis-made.html

MEFI 1993 thru 95 the largest ECM - VST systems

next was

MEFI 1 medium size ECM 1996 thru 1998 and MEFI 1 software in a MEFI 2 case - Some VST systems and 1996 was the transition year for Gen cool fuel for all year models 1997.

Next

MEFI 2 - medium sized ECM - GM 1996 software in a MEFI 2 case with GM part number 16210729 the 729 is the true MEFI 2, if any other part number without the 729 its a MEFI 1 software in a MEFI 2 case. Again the only true MEFI 2 carries GM part number 16210729. This was used on 350 MAG and the L29 454 only, (the true MEFI 2).

Next

MEFI 3 very very late 1998 / for 1999, it was a smaller ECM than all past MEFI's. All MEFI 3 Gen II cool fuel

Hope this MEFI info helps whomever

 

[akorcovelos]

Great info right there. So if I can find a MEFI 2 with the early serial number it's the same as the MEFI 1.

The Whipple tune puts the 7.4 5hp shy of the 8.2, so 410hp which should put me into the low 60s. The boat runs 57mph gps confirmed on the stock 385hp tune, so the extra rpm alone will push me to 60mph.

 

[alldodge]

So if I can find a MEFI 2 with the early serial number it's the same as the MEFI 1.

The 2 is not the exact same as the 1, but it "can" be re-programmed to be used on your motor. Inform whipple what you want done and let them advise if they can do it.

I don't think whipple can do this anymore then they can retune a 555 ECM/PCM without a possible cost later. The 555 is locked down and no one except whipple is saying it can be retuned.

To get more HP from your motor timing and amount of fuel can be changed. The easiest way is increase advance and lean fuel, but we all know what happens if it gets to lean. Each boat is different in design and weight, and the only true way to tune a motor safely for longevity is with an AFR meter and while driving the boat. I hope it works out, all the best

 

[alldodge]

Note: The 454 MPI Mag at 385 hp, the 454 MPI L29 is 310 hp
The reason it needs to be retuned

https://www.perfprotech.com/blog/bo...gnum-mpi-vs-mercruiser-l29-454-marine-engines

 

[akorcovelos]

Yeah I read that before. My motor is a '96 454 Magnum MPI 385hp.

This is the Whipple tune for this engine. I'm familiar with tuning from club racing and building turbo cars with stand alone ecus. This is still probably a pretty conservative tune, and Whipple is a trusted name. I'm not looking for crazy gains, I just want the same performance the 415hp 502 Mag MPI equipped boats came with.