How lean is too lean? - Team Camaro Tech
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post #1 of 7 (permalink) Old Aug 30th, 03, 12:21 PM Thread Starter
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Paul
 
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I have been messing with my Qjet again. I have it leaned out at cruise and idle pretty far. It shows 0 on my narrow band air/fuel gauge at cruise and idle, but it doesn't surge or bog and has very good throttle response. I'm wondering is there a point when it's too lean and it could hurt the engine or will the engine surge and bog when it's at that point?

If I put my foot in it the mixture goes rich like it should, but as soon as I get to cruise or idle it leans out again.

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post #2 of 7 (permalink) Old Aug 30th, 03, 01:33 PM
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I don't know about the gauge but too lean is hotter. It can damage valves and what ever excess heat will go after like head gaskets or seals. I remember it as a valve warping prone condition. That is too lean. Lean in the proper adjustment range is alright. Funny as it might seem extra gas cools from the particles taking away heat. Less gas doesn't. More air(O2) to fuel is like adding O2 on the acetaline torch.
Didn't you get instruction with that gauge? I'd ask the seller or manufacturer.
What did it read doing the mixture the regular way?
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post #3 of 7 (permalink) Old Aug 30th, 03, 01:55 PM Thread Starter
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No instructions....It's just a narrow band O2 sensor with a voltmeter reading the output. The narrow band O2 sensor only can recogize readings near 14.7:1....Maybe it has a range of 13:1 - 16:1???

Doing the mixture the regular way? Before getting an O2 sensor I could only guess with the seat of my pants on a test drive. When I put in the O2 sensor I found I was always running rich, way rich!

I have been messing with the rods/jets in my QJet so that it runs lean at cruise and idle and rich at WOT. I could go down a rod size and I would be within the O2 sensors range, but it doesn't run any different just uses more fuel.

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post #4 of 7 (permalink) Old Sep 1st, 03, 08:33 AM
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Jim
 
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Check your plugs. If the plugs are a nice tan color or depending on the fuel you are using, a nice grayish color, then your fine. If they are clean, the mixture is too lean. Also way rich is a clean plug. If you inspect your plugs with a magnifying glass and see any sign of aluminum fragments, ritchen it up one step. A perfect mix will cause the plug ground strap to be clean within 1/16" from the plug base and the plug will be a light tan or light gray in color. I guess you don't have your LM-1 yet?
Jim
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post #5 of 7 (permalink) Old Sep 1st, 03, 08:41 AM Thread Starter
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Paul
 
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I have it....just haven't hooked it up yet.

The problem is that with the QJet, one rod(46) runs off the scale lean(.00 which is around 16:1-17:1) at cruise and the next rod(45) runs in the power range rich(.82 which is around 13:1)

So I have a choice of running in the power range at cruise or really lean. The engine runs fine with either mixture it just uses more fuel when it rich. When it's lean it does run a tad warmer, which is to be expected. I think that with the vacuum advance I am safe from detonation running at 16-17:1 though.

I read an air force study where they ran there engines lean 16-17:1 at cruise with the timing advanced(30 degrees). They found no problems with engine wear and they had a 16% fuel savings!

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post #6 of 7 (permalink) Old Sep 1st, 03, 08:56 AM
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I would be curious to see what the LM-1 says? Remember that the type of manifold you have will determine what cylinders get fuel from which side of the carb. My intake is a dual plane and cyl's. 1,7,4,and 6 get fuel from one side and cyl's. 3,5,2,and 8 get fuel from the other side. This will cause your Oxgen readings to be averaged from bank to bank. a single plane is a different story. Plug color is IMO the final measure.
Jim
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post #7 of 7 (permalink) Old Sep 1st, 03, 11:04 AM Thread Starter
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Paul
 
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I would hook it up, but I have the mixture within the range that the narrow band O2 sensor can see. I guess I'm just lazy!

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