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Mefi conversion

Old 11-17-2016, 02:52 AM
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Default Mefi conversion

I've read just about everything on converting from differing Mefi units. I'm having issues with my engine and I'm almost to the point of converting. I have a Mefi 1 but have a spare 4b ecu laying around.

I'm not new to repinning wiring harnesses but I have found very little in detail of the conversion. I have both ecu pinout diagrams and they appear really similar. The biggest thing I know to be different is the Mefi 4 has a crank angle sensor vs the sensor in the distributor like the Mefi 1. But I believe the Mefi 4 also sends a signal from the distributor. Who should I call or contact for a 5 minute phone call to solve my questions?
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Old 11-17-2016, 05:49 AM
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Give me a few to get to my office and I'll send you the service manual. Should have everything you need as far as pin placement
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Old 11-17-2016, 09:24 AM
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Thanks. I think I have everything. The main thing is do I need the CAS for the mefi 4 ecu to operate correctly.
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Old 11-17-2016, 04:34 PM
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Originally Posted by 1 2 NV
Thanks. I think I have everything. The main thing is do I need the CAS for the mefi 4 ecu to operate correctly.
No, I have mefi 4's on several motors without crank angle sensor, Smitty
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Old 11-21-2016, 03:28 PM
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Originally Posted by articfriends
No, I have mefi 4's on several motors without crank angle sensor, Smitty
Thanks. I thought for sure it would throw a code for no signal from the sensor. I thought it would need the CAS deleted from the programming.
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Old 11-21-2016, 07:46 PM
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Originally Posted by 1 2 NV
Thanks. I thought for sure it would throw a code for no signal from the sensor. I thought it would need the CAS deleted from the programming.
its all in how the ecu's program is configured.I've used the 4b on the 496's w/ crank and cam and also on my hei engines were it only has a 6 pin distributor.I could,if I wanted to set it up for dis set up and I believe it will work w/ 24,58 tooth crank trigger set ups.
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Old 11-24-2016, 11:02 AM
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the complete 4 family support 7x 24x and 58x or 60-2
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Old 11-24-2016, 11:28 AM
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I've been searching OSO for quite awhile now. Is there any advantages to a LT4 hot cam on a mefi 1 system? I've found a ton of info on cars/trucks and boats with carbs. Virtually nothing speakable on boat EFI.
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Old 11-24-2016, 01:21 PM
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I've been following your other thread regarding your engine performance. The problems you are having have nothing to do with the series of MEFI computer
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Old 11-24-2016, 01:33 PM
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Much appreciated. I've been milling around the jet boat forums and it seems that my engine is right on par with others. I believe my friends low hour 350 was a factory freak or his tach was off. It's fairly hard to find a 2.9 impeller used. That's my next step.
Don't forget my fuel burn is something fierce. So I'm still sorting through that issue.
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