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  1. #1
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    Sep 2004
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    MEFI IV Worth it?

    Looking at the other thread on here about the MEFI IV has me wondering what the advantage would be to updating from MEFI 3 to 4. I have a ramjet in my car now and it runs just fine but the price of $450 approximately for a controller and wiring harness seems reasonable if it actually makes an improvement. Has anyone made this change or know about the benefits i.e. more horsepower, torque, better mileage.....whatever? Also does it use a single O2 sensor?



  2. #2
    Join Date
    May 2001
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    Mesa, Az.
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    MEFI 4 upgrade

    If you are thinking about making the upgrade I would say go for it. I have used a III with and without the O2 and am now using a IV with the O2 in it from the factory. The biggest thing that I like better about the IV is not only does it include the O2 but also contains a IAT sensor (Intake Air Temp.) which really helps with cold starts and other tunning.
    BTW, the O2 is good for about 5 mpg on the highway.

  3. #3
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    Nov 2004
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    Quote Originally Posted by PhillipM
    If you are thinking about making the upgrade I would say go for it. I have used a III with and without the O2 and am now using a IV with the O2 in it from the factory. The biggest thing that I like better about the IV is not only does it include the O2 but also contains a IAT sensor (Intake Air Temp.) which really helps with cold starts and other tunning.
    BTW, the O2 is good for about 5 mpg on the highway.

    OS and IAT can be programmed into the MEFI 3.

  4. #4
    Join Date
    May 2001
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    Conversion

    Absolutly it can be, if he would like to send it out and converted. What is the cost on conversion, and the sensors? It may be better just to sell that one and buy a IV. If you can sell the III that is.

  5. #5
    Join Date
    Aug 2004
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    5mpg? Thing must've been running like a pig before

  6. #6
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    May 2001
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    On the R/J 350 I was getting around 20 on the highway with a Richmond 6 and after the O2 I was getting around 26 or 27 on the highway consistently and around 14 or 15 around town under normal driving of course. So it did okay originally, but the O2 really does make a difference.

  7. #7
    Join Date
    Aug 2004
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    I wasn't doubting you, just saying that it's extremely rare to see a 30+% improvement, the previous calibration had to be pretty awful in both fuel AND spark (unless you were cruising at 11:1, in which case your eyes would have fallen out by now). Sure you were getting into 6th gear before? J/K

    My only real purpose is to point out that, while ram jets specifically may have a calibration issue (and from all that I've read, they do), most people doing EFI swaps should not expect such an improvement simply from adding closed loop unless they are replacing parts that were way out of tune. A well adjusted carb will do better than most people give them credit for.

  8. #8
    Join Date
    Sep 2004
    Location
    Prineville, Oregon
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    Thanks for the posts you guys. It would probably be cheaper to just go with the IV than to send mine in to someone like AS&M for reprogramming. Where would the IAT go? Is there a fitting somewhere that exists for that on the older ramjets?
    '79 Z28,White w/camel tan interior,Cowl induction hood,TKO-500 5SPD,350 RamJet (polished),Jet-Hot coated Hooker Headers,Magnaflow dual exhaust,11" Ram clutch,10 bolt 370 Posi,Rock Valley fuel tank,Vette Brakes monoleaf suspension,AGR quick ratio steering,Baer 4 wheel brakes,17X7 Alloy Cragars w/245/45X17 AVS Sports in Front & 17X8 Alloys w/255/40X17's Rear.

    Chris

  9. #9
    Join Date
    Jan 2005
    Posts
    1
    Quote Originally Posted by hotrod
    Thanks for the posts you guys. It would probably be cheaper to just go with the IV than to send mine in to someone like AS&M for reprogramming. Where would the IAT go? Is there a fitting somewhere that exists for that on the older ramjets?
    Hotrod, I too, have the MEFI 3 on my RamJet 502 and am looking to update it. Just not happy with performance being consistant. I do have some data logging / monitoring capability using a beta copy of TTS DataMaster and the ALDL OBD1 cable, which will not work for the MEFI 4. For some reason I get a surge letting off the throttle after hard acceleration. The MEFI seems to be chasing the correct throttle setting.

    I am leaning toward an aftermarket ECU like the Accel Gen 7 where you get all the latest capability ( WBO2, sequential, etc.) while still having the flexability for diagnostics, data-logging and re-calibration. The cost would be about the same as a MEFI 4 and Rinda Diacom PC SW and you still can't calibrate the MEFI 4 Just thinking out loud

    Bullshark

  10. #10
    Join Date
    Aug 2004
    Location
    Central Florida
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    217
    Bullshark

    I had MEFI4 i replaced on my Ramjet502. I also have the Rhinda Technoligies software (if I can find it). I replaced my setup with a FAST XFI and I love it. The Mefi4 still hunted like your 3 does and no way to fix it. I did find a guy who has the software to tune the mefi4 but it was after I switched out mine. He posts on Turboride.com and he says he could get me the software to tune the mefi4. The Fast is sweet though its like I got a new engine. It even sounds different with a proper tune on it.

  11. #11
    Join Date
    May 2001
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    MEFI 4 Tuning

    If anyone is looking for another tuner of MEFI 4's look to UMI also. They are awesome. If you want some proof head to LS1 tech and look at Katech's LS7 that the tuned using a MEFI 4B controller! I think their website is something like umiracing.com. But not sure. Phillip