trailblazer

I recently purchased a 1995 502 EFI Magnum to rebuild over winter. Along with the engine I also got two computers, a mefi 1 and a mefi 3. I am not planning on supercharging the engine so would there be any advantage to using the mefi 3 or would the mefi 1 run it just fine?


Thanks,
Doug

pachangalpina

I guess it depends on which wiring harness you have. The 95 should have been a MEFI1 setup, to change to the MEFI3 I believe that you will have to alter or replace the harness.

trailblazer

The wiring harness has been altered to work with the mefi 3 computer because the previous owner of this engine had a supercharger on it. I'm not going to supercharge it (or at least not for a while) so I could sell the mefi 3 computer, but I won't if it would run my engine better than the mefi 1.




Doug

russ

So if the wireing harness has been altered to work with the Mefi3 thats the one your going to have to use. Unless you change it back to what it was to use the Mefi1. Or buy a Mefi1 harness.

You are going to have to send the Mefi3 off to be reprogrammed if it was reprogrammed for the S/C. Thats another $350. If the program on the Mefi1 has the original progam init and you build the motor up to what it was stock it will work. If that progam was changed in anyway you will have to send it off to be reprogrammed.

There is no advantage if you use one or the other.

Or say hell with the EFI and go carbed! Might be cheaper in the long run and easier to tune. More than likely you will have to send the ECU back a couple of times and to get the program right.

I had a nightmare trying to get a used EFI system working. Wires where spliced when the guy had a supercharger on it. Then the guy programing the ECU couldn't get the program right and took him 5 months to get the ECU's back. So I said the hell with it and went carbed.

poolshrk

Would you be interested in selling your mefi 3? Let's talk. I have the chart that shows how to reconfigure your wiring harness from mefi 3 to 1.
cell 1 707 480- 8183.poolshrk

509 SC

Doug, You could of just asked me since I sold it to you. The MEFI 1 may or maynot of been on my motor originally. The wiring harness was repinned to accept the MEFI 3 since it is capable of reading boost with a supercharger. Don't get nervous from Russ's response above, this harness worked fine with the new computer. I think the easiest thing is to have the computer reset to factory specs, try calling Mark Boos at Precision Marine in Kenner La. I don't think a reflash to factory specs will be $350, call and check. Now, if your going to do alot of mods a carb and manifold might be the way to go if you sell the fuel injection system. These decisions all sound so deja vu like! Steve

russ

I didn't meen to scare him. I thought if he was going to rebuild the motor anyway he would be trying to get more than stock power out of it. And I still think most people charge 350 to add stock program back in. I think for around 800 he could convert it to carbed. I also beleave Merc. will buy back the computers for around $300 to 400 apiece.

Poolshrk

I have 2 Mefi3 that have custom programs in them that we just got back last week that where for my motor. Same program that is in this http://www.hotboat.net/members/artic.../BOLT-ON_s.htm

I don't know if my Mech. sent them to Merc yet or not.

PowerboatsNW

Sounds like you dont know much about fuel injection that is why you are saying put carbs on. Stick with the mefi 3. That is still old news since we are on the the mefi 5.

russ

I'm saying put a carb on because it would be easier to tune.

trailblazer

I would have to have either computer re-programmed as the engine will not be stock. I definitely am staying with the fuel injection because that is one of the reasons I used to talk my wife into the bigger engine Re-pinning the harness is not a big deal at all to me, I just wanted to know if there was any other advantage to running the mefi3 besides being able to read boost as I'm not supercharging the engine (not yet anyway!!!) and there is definitely a market for mefi3 computers.



Doug