Carter BBD rebuild - Page 10 - JeepForum.com
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post #136 of 151 Old 03-15-2014, 01:52 PM Thread Starter
moto450r
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For fun.....

Me and my DMM enjoying the Las Vegas Strip



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post #137 of 151 Old 03-15-2014, 02:45 PM
86cj74.2L
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I guess that's as fun as taking your pet rock for a drive.

No lean out the needles.
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post #138 of 151 Old 03-15-2014, 03:13 PM Thread Starter
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Quote:
Originally Posted by 86cj74.2L
I guess that's as fun as taking your pet rock for a drive. No lean out the needles.
I didn't touch the needles before going to work. I adjusted them when I got to work so the ride home will be telling.

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post #139 of 151 Old 03-15-2014, 05:35 PM
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I followed the instructions printed in the rebuild kits as to which way to turn the Allen screw to rich or lean out the mixture.
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post #140 of 151 Old 03-15-2014, 05:42 PM Thread Starter
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I adjusted the vacuum piston assy before I left work, full lean. What I saw gave me confidence that it is working. The picture was at steady mph, no load just a flat road.



.
.
.
Now I see what that frigg'n thing is doing! And I now know where the 'stops' are for lean/rich

Any time I would get on the gas or had load on the motor, the reading would go right back to .8+v. Still a little rich

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post #141 of 151 Old 03-15-2014, 07:51 PM
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You want that when you step on the throttle. Its the accelerator pump squirt.

And you also want that .8+ at wide open throttle.

At .11 what did it sound like. Grammys exhaust had a buzzy resonance to it.

Start out shooting for .6 and see how you like it for a few trips. Under different conditions. Take your time.

Then repeat at .50 and .45 and again at .40 paying attention to mpg and throttle response when you just touch the throttle to accelerate a little faster. (Where you would not give enough throttle for a decent pump shot to richen the mixture)
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post #142 of 151 Old 03-15-2014, 07:52 PM
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And don't run it too long that lean.
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post #143 of 151 Old 03-16-2014, 07:53 AM Thread Starter
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Quote:
Originally Posted by 86cj74.2L View Post

At .11 what did it sound like. Grammys exhaust had a buzzy resonance to it.
could not hear or feel any difference, not what I excepted when I saw .1's.

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post #144 of 151 Old 03-16-2014, 08:10 AM
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moto,

FWIW, here's what the wideband A/F numbers show on my engine....

Upon cold start the numbers start in the low 13s with the choke fully engaged. As the engine warms, and the choke opens, the numbers slowly climb to around 15. When I kick it down to normal idle the numbers drop to around 14.3. That seems to be where it idles the best.

At partial throttle cruise, the numbers stay in the 14.3-14.8 range. If I mash the skinny pedal, it drops to around 13, then recovers to the mid-14s in just a few seconds. Coasting down a hill will produce numbers as high as 15.5-16.

I have no idea how those numbers compare to narrow band numbers, but I bet 86 could tell us.

Matt
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post #145 of 151 Old 03-16-2014, 09:33 AM
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Matt, I had a lot of experience tuning a 95 Miata I added a turbo to. It had a narrow band O2 sensor, and fully adjustable timing and AF maps. Those numbers you have are dead on correct, as I am sure you realize. The problem with narrowband O2 sensors is that they are really only accurate within a narrow range around 14.7 which is the theoretical ideal fuel air ratio for a complete burn.

And you get that with a carb!
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post #146 of 151 Old 03-16-2014, 09:49 AM
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Thanks Lee,

I enjoy tinkering with carbs, and now that I've used a wideband, I can't imagine tuning without it.

The wideband is also one heckuva a diagnostic tool. A few weeks ago, I noticed my numbers had shifted to the lean side. Minutes later I realize I had a few loose exhaust manifold bolts. I tightened them up and the numbers were right back to normal.

Really enjoying this thread.

Matt
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post #147 of 151 Old 03-16-2014, 10:02 AM
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Tuning a carb with a narrowband is not like a narrow band used with fuel injection.

The reading is not always going high and low. Its a nice steady number relative to current carb metering.

.93 ish is 12.7 or the good wide open throttle number. Though anywhere from 13.1 to 12.7 is good.

.40 to .60 is a good cruise mode number. Its around 15:1 at .4v and around 14.1 at .60v
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post #148 of 151 Old 03-16-2014, 11:44 AM Thread Starter
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Quote:
Originally Posted by Matt1981CJ7 View Post
moto,

FWIW, here's what the wideband A/F numbers show on my engine....

Upon cold start the numbers start in the low 13s with the choke fully engaged. As the engine warms, and the choke opens, the numbers slowly climb to around 15. When I kick it down to normal idle the numbers drop to around 14.3. That seems to be where it idles the best.

At partial throttle cruise, the numbers stay in the 14.3-14.8 range. If I mash the skinny pedal, it drops to around 13, then recovers to the mid-14s in just a few seconds. Coasting down a hill will produce numbers as high as 15.5-16.

I have no idea how those numbers compare to narrow band numbers, but I bet 86 could tell us.

Matt
Thanks.
I want to install a A/F gauge but can't swing the 200 bucks for the wideband right now.

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post #149 of 151 Old 03-17-2014, 08:19 AM Thread Starter
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Small step this morning.

Started the Jeep for the kids this morning so I could find out how the choke plate needed to be fine tuned. The engine is starting perfectly when it's cold. As it starts to warmup it stumbles for a short time. I found that the choke plate is not opening fast enough. Simple thing to check and adjust, if it's cold enough outside.

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post #150 of 151 Old 03-17-2014, 11:02 AM
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Quote:
Originally Posted by moto450r
Small step this morning. Started the Jeep for the kids this morning so I could find out how the choke plate needed to be fine tuned. The engine is starting perfectly when it's cold. As it starts to warmup it stumbles for a short time. I found that the choke plate is not opening fast enough. Simple thing to check and adjust, if it's cold enough outside.
It a little more air gap on the choke pull off.

Where mine is set. there is a slight ruff idle when its warmer outside. But it lasts all but 30sec and is gone.

I have the tamper proof unit so I can't tell where its at with regards to the lean or rich marks.
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