RamJet 350 MEFI3

OPMACHINE

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Ladies,

I am looking for some advice on ways to reduce the eye watering fumes that are coming form the tailpipe of my RamJet 350 MEFI3. This engine runs off an open loop system and is known to run rich. The later MEFI4 open/closed loop wiring harness addresses this issue to a certain existent, adds an oxygen and IAT sensors. It is an easy upgrade, but unfortunately it looks like it has been recently discontinued.


Would simply adding a catalytic converter to the exhaust system help reduce the fumes? Anything I would need to be concerned about.

thank you,
350 ram jet new valve covers - Copy.jpg
 
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Not familiar with that setup but my best bet is that you'll have to take it to a shop that specializes in EFI tuning. Even if they don't support that system they could probably point you to someone who does.
 

OPMACHINE

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From the research that I have done, the RamJet 350 computer cannot be tuned or programmed. the MEFI3 setup is essentially a boat motor with no intake air or co2 sensors, no cats or any smog control. The open loop system runs very rich at idle and will literally make your eyes water.

I am trying to figure out if adding a CAT would do anything to reduce the emissions?

I am also trying to see if I can find an NOS MEFI4 conversion kit that will add the intake air or co2 sensor computer.
 

EWheeler

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From the research that I have done, the RamJet 350 computer cannot be tuned or programmed. the MEFI3 setup is essentially a boat motor with no intake air or co2 sensors, no cats or any smog control. The open loop system runs very rich at idle and will literally make your eyes water.

I am trying to figure out if adding a CAT would do anything to reduce the emissions?

I am also trying to see if I can find an NOS MEFI4 conversion kit that will add the intake air or co2 sensor computer.
MEFI4 computers are commonly used in sand rails out west here due to their ability to survive the elements so well. You can buy a MEFI4 harness and a used computer, add in the necessary sensors that you are missing, and then have someone custom tune the computer for you. This could save you months or years of searching for a NLA NOS setup. When i bought my new harness foe my sandcar it was $700 4 or 5 years ago.

The bummer about the MEFI units is the software to tune them isnt cheap and you cannot use EFIlive or HPTuners which most all tuners use. Seeing as you are in FL though, the marine industry is pretty big, so you may have no trouble finding somone to tune it as the MEFIs are used widely in fuel injected boats.
 

EWheeler

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I suspect this harness would work on the SBC even though it says its for a 502.

 

EWheeler

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Also, i know there are at least two versions of the MEFI4, the 4a and 4b. One is preferred over the other, but i cannot recall the differences or why the preference.
 

EWheeler

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There are likely over a dozen ways to add IAT and 02 sensors to make the engine run in closed loop, but they are pretty much all going to involve a new ECM, Harness, and tuning. Holley has some self learning/tuning options that are probably in the $3k range, but when youre looking at that kind of money, an LS swap isnt much more money if you can find the right deal. I sold a nice LS1 with mefi4, harness, and fuel system for $4k a couple years back when i upgraded the engine in my sand car.
 

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EWheeler

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Yes, it is a harness only. The plug ends on the harness will be the same regardless of engine displacement. I was suggesting that harness could be used in conjunction with a used MEFI computer, which you would also need to source on the aftermarket. Finding that NLA NOS kit is certainly possible, but you could build it yourself if you wanted.
 
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I added a cheap cat from summit to my oem carb 1F and it pretty much eliminated the smell even with a tailpipe that doesn’t extend out past the edge of the body.
Put a cat in
 

OPMACHINE

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Thank you everybody for you input!

I would still like to find a MEFI4 ECU and harness, hard to swallow the fact that these were available a few months ago.

For now, phase#1 is to remake the 2.5'' SS exhaust with a provision for O2 sensor and catalytic converter. This will be my first exhaust so I will let everybody know how it turns out.
 

EWheeler

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Thank you everybody for you input!

I would still like to find a MEFI4 ECU and harness, hard to swallow the fact that these were available a few months ago.

For now, phase#1 is to remake the 2.5'' SS exhaust with a provision for O2 sensor and catalytic converter. This will be my first exhaust so I will let everybody know how it turns out.
If it's anything like all the other work you do, it is going to be top notch / best in class!
 

jim land

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Try this place , painless wiring did not care about their mefi kit and told me to call them if i need assistance

 

EWheeler

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Try this place , painless wiring did not care about their mefi kit and told me to call them if i need assistance

These guys are local to me and who I bought my standalone harness from for my sand car. They are one of the top motorsports engine builder/parts supplier in the area. They do marine, street, and off-road engines. The guys at CBM know their stuff.
 

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