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  • Nutter bypass vs new carb

    Ok, if I do the bypass, I take the computer out of the loop...How do you guys finding it run after the bypass(same Carter carb)? I guess a carb swap means I have to mod the intake and choke? Once the nutter bypass is done, I still keep all the emission stuff. I am now in FLA, non emission state.

  • #2
    the nutter controls spark. the carb controls fuel/air. a crappy carb won't see much benefit from a nutter.

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    • #3
      just two more...

      Mike, more on FUBAR's observation if you intend to stick with the Carter.


      http://4wd.com/kyoung_4wdforums/show...carter+rebuild

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      • #4
        I hate to disagree with anyone, and especially Fubar. But the 1982-90's 6 cyl. Jeeps that had the fuel feedback system had an electric contolled stepper motor Carter carb, and that is what the Nutter Bypass was designed to work with. That bypass procedure fools the computer, and allows you to adj carb like a non-electric Carter BBD. I does not change timing as most people think. This allows you to appear stock for emissions test but it is not running thru computer. if you are non-emissions I would either go to one of the Weber/Interco choices that use adapter plates with the stock intake or use the pre 1982 non electric Carter BBD

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        • #5
          Originally posted by woody
          I hate to disagree with anyone, and especially Fubar. But the 1982-90's 6 cyl. Jeeps that had the fuel feedback system had an electric contolled stepper motor Carter carb, and that is what the Nutter Bypass was designed to work with. That bypass procedure fools the computer, and allows you to adj carb like a non-electric Carter BBD.I does not change timing as most people think. This allows you to appear stock for emissions test but it is not running thru computer. if you are non-emissions I would either go to one of the Weber/Interco choices that use adapter plates with the stock intake or use the pre 1982 non electric Carter BBD
          Wow, this is a complete reversal on what I have been reading.

          So your saying the essensial part of doing the nutter bypass, that is to say, cutting the orange wires and splicing them together, only effects the mixture control on the carburator by deactivating it ? Now I'm not saying it doesn't disable the mixture control or cause the mixture control to become erratic and that's why you have to set the needles to "FULL RICH" position before disconnecting the plug on the stepper motor.

          Just to note the computer feedback system in 1982 on the California CJ's were not connected to the distributor at all and worked mainly off the O2 sensor to control the stepper motor and set the proper mixture. That of course doesn't mean that they didn't changed things in 83 on. These computers were mounted on top of the driver side fender. I'm just "speculating" that the ignition control was added to compinsate for the knock being developed running the engine in such a lean condition to reduce emmisions.

          My questions would be things like why run a knock sensor if the computer doesn't retard the timing when the it detects a knock. I bet a bad knock sensor is the cause most people resort to the 'Nutter bypass" besides the miles of cracked leaky vacuum hoses which causes the carb to run richer than it can compinsate for.

          Why would a vacuum leak cause a rich mixture? The fuel enrichment system in a BBD is controllled by vacuum and when it sees a lower vacuum in the manifold it enriches the mixture thinking the engine has a greater power demand and it operates quite independently of the computer.

          But I've known to be wrong before.

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          • #6
            Hey guys, I'll be the first to say I can be wrong on just about any opinion I have! Except maybe paint and body, but even then its an opinion.
            One reason I say it does not control ign timing is because the Motorcraft distr. they use is mechanical adv./vacumn advance operated,and is the same from 1978-1990 in the AMC 4.2 six cyl engine but fuel feedback/pulse air system was only used from 1982 thru 1990. As per Jeep it is the same distr.
            with a few exceptions like swing weights that change from man to automatic transmissions. I know the fuel feedback computer does control power to the ignition module(again a part that fits 1978-90 on Jeeps) but it does'nt change the timing. I've removed that system by performing surgery on the engine compartment wire harness where the computer harness intersects. I then added a non-stepper BBD and it worked great. Talk to yah later!!

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            • #7
              That emission computer controls spark or timming to some degree. I did not have a "stepper motor" BBD. My jeep lacked power bad. Did the computer bypass and it smoothed out and gained power. Couldn't have had anything to do with fuel, didn't touch the carb.

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              • #8
                In the Nutter article, it says that you need to change the timing immediately or possibly cause damage...is that true as written?

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                • #9
                  My timming was no that far off, only a few degrees. What that means is be prepared to set timming, cause running the engine to far advanced/retarded isn't good for it.

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                  • #10
                    i did the nutter and 2100 and the hei, on my 258. i have been sitting the timing by ear and am not sure where it should be. i tryied to use a timing light but it just didnt seem like it was running right.. i think that with the original bbd car the factory seting was with rpm at a certian degree of timing. my jeep will start up fine but i am stll lacking some power going up hills,i feel it drop from 60 mph to 50 or 55 depending on the grade of the hill, any ideas for me?

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                    • #11
                      Originally posted by brikabee
                      i did the nutter and 2100 and the hei, on my 258. i have been sitting the timing by ear and am not sure where it should be. i tryied to use a timing light but it just didnt seem like it was running right.. i think that with the original bbd car the factory seting was with rpm at a certian degree of timing. my jeep will start up fine but i am stll lacking some power going up hills,i feel it drop from 60 mph to 50 or 55 depending on the grade of the hill, any ideas for me?

                      First set your base idle at about 750 RPM, then adjust your idle mixture using the lean drop method, then reset your base idle back to 750.

                      Disconnect and plug your dizzy vacuum as you normally would and set the timing at about 10 deg. BTDC. (Normally I say 12 deg, but in HI you are pretty close to sea level.)

                      Reconnect all the vacuum hoses and then run her hard up a couple of hills, if she doesn't ping, disconnect the hoses and using a timing light, advance it another 2 degrees, then hit the hills again. Repeat this untill she pings on the hills, then back her off to the last setting that did not ping, see if that helps.

                      If you are really good with a ltiming light you can try to adjust it by 1 degree increments, but that is usually excessive.

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                      • #12
                        there are lots of hills here. ill try your methed,thanks tracraym

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                        • #13
                          There is an alternate procedure in the timing section of the factory shop manual directing you to ground the knock sensor wire. This will set the computer in default mode so that it will not adjust the timing erratically. That way you can set the timing accurately without the extra steps of the normal procedure. I have never had any luck with the procedure and unless a customer is really a stickler for originality, I have always gone with a setup such as the weber carburetor and DUI ignition that permanently eliminate the original electronics - period.

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                          • #14
                            Originally posted by Big Mike
                            Ok, if I do the bypass, I take the computer out of the loop...How do you guys finding it run after the bypass(same Carter carb)? I guess a carb swap means I have to mod the intake and choke? Once the nutter bypass is done, I still keep all the emission stuff. I am now in FLA, non emission state.
                            go to http://www.bustedjeep.com and do yourself a favor with a junkyard TBI system the carter is a pos or buy a howell tbi and weld the dist p/u coil ,use a gm ignition module so all advance is controlled by the ecm get rid of the furt dura spark pos . it's explained in busted jeep.I sold my used howell tbi with the gm hei set up for $550 it got my jeep 18 mpg with power :31 in tires,3.73's,t5.

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