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Unread 01-23-2007, 11:46 PM   #1
toxin
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Timing and the Nutter bypass the final word!

I have seen many discussions in many forums on timing after the nutter bypass has been done and time after time i see people arguing that you need to time at 1600 rpm.


In 1980 AMC introduced the computerized engine control or cec which was used to control among other things ignition timing and by 1982 the factory timing was being set at 1600rpm.

Reference:
http://library.motoralldata.com/tech.../Jeep_1982.htm


If you look at the above page you will see listings for 4.2l 258 engines notice the difference between the model with the cec and the one with out, the difference is that the non cec model is not set at 1600 rpm.

If you completed the nutter bypass then you have taken the computer out of the loop and you are basically running a pre 1980 version.

The timing may vary from year to year but one thing remained the same, only cec equiped engines were set at 1600rpm

There is no reason to time your vehicle at 1600 rpm if you have bypassed the computer.


Below is a link to the main page with info on many makes and models of vehicles but if you scroll down to the jeep section you can look at each jeep by year also check out the sections labeled Diamler Chrysler Corp because they have listings for amc engines on those pages as well

http://library.motoralldata.com/tech...ication_Chart/

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Unread 01-24-2007, 07:48 AM   #2
lah2420
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Good post Toxin. I've tried to get this across just using my personal experience to no avail. Maybe your way of wording it will convince some people that they NO LONGER HAVE A COMPUTER after a nutter bypass. It is no longer timed like the YJ manual says.
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Unread 01-24-2007, 08:04 AM   #3
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Who didn't know this?
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Unread 01-24-2007, 09:09 AM   #4
drexelsteve
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i timed mine by ear/feel. Works fine for me. just a thought.
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Unread 01-24-2007, 09:40 AM   #5
ElvisV04290
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so you are saying that IF i were to do a bypass on my jeep (90 4.2, auto) then the timing should set it at 550 RPM, not 1600 RPM, right?
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Unread 01-24-2007, 10:08 AM   #6
zeus87gn
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550rpm sounds kind of low, but to answer your question directly, yes.

Once you bypass the computer, set the timing at idle speed.
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Unread 01-24-2007, 10:34 AM   #7
atomicmoose
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Quote:
Originally Posted by ElvisV04290
so you are saying that IF i were to do a bypass on my jeep (90 4.2, auto) then the timing should set it at 550 RPM, not 1600 RPM, right?
Idle speed on my manual is around 800.
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Unread 01-24-2007, 11:39 AM   #8
ElvisV04290
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nevermind this post
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Unread 01-24-2007, 03:03 PM   #9
toxin
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Quote:
Originally Posted by ElvisV04290
nevermind this post

Why never mind the post???

You can search this forum alone and find tons of posts of people asking what rpm to set their timing at after the Nutter and they are being told 1600 rpm which is wrong. Is it wrong of me to post info to try to help people accurately set their timing?
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Unread 01-24-2007, 03:27 PM   #10
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I think he is 'neverminding' his own post...?
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Unread 01-24-2007, 04:42 PM   #11
ElvisV04290
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I had a question but didn't want to sound like a noob, and in any case I'm not going to do a bypass so I didn't want to hijack the thread. The 'nevermind this post' is for me, I posted my question before I thought about it and can't delete it. This Thread is great, I'm sure many people with think what Toxin has found to be great stuff. sorry for the mixup Toxin.
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1990 YJ, Colorado Red with 'Laredo' markings, 4.2L, TF999, NP231, Valvoline Syn fluids, Weber 32/36, Nutter Bypass, Dana 30/35, 16" Electric Fan, Optima Yellow Top, 140amp alt., K&N Air Filter, Cherry Bomb muffler, SRC Front Bumper, CH&F Shackles, KC 100w Daylighters, Homemade Lightbar, Rear Aux lights, Cobra CB/PA/WX, 102" Whip Ant., 400 watt power inverter, 2 fire extinguishers, Mobile Internet & WiFi equipped.
Daily Driver since April 23rd, 2003

Northern Illinois Extreme Jeep Club Member www.extremejeepclub.com
Weber 32/36 Install -> http://www.jeepforum.com/forum/showthread.php?t=382309
Early YJ Club Member #37
For anyone with a 4.2L --> http://groups.jeepforum.com/258s_Unite
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