Carb Tuning with O2 Sensor
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Joined: Jan 2007
Posts: 62
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From: LaGrange Georgia
Carb Tuning with O2 Sensor
I've read many of the procedures for obtaining proper idle mixture for your carb, and it all seems very hit or miss. So I am thinking about getting straight to the source with a wideband O2 sensor.
1. Is this the most surefire method to tune carb?
2. Better or worse than the vacuum or rpm methods?
3. What is the best way to determine proper idle rpm?
Any other useful tips. By the way I have an 81 with summit carb, vortec heads, Comp Cam XE268H.
Thanks
1. Is this the most surefire method to tune carb?
2. Better or worse than the vacuum or rpm methods?
3. What is the best way to determine proper idle rpm?
Any other useful tips. By the way I have an 81 with summit carb, vortec heads, Comp Cam XE268H.
Thanks
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
Setting idle mixture isn't really hit-and-miss at all, and you don't need an A/F meter to do it right.
For carb tuning overall, I have an Innovate LM2 and I wouldn't try to tune without it.
For carb tuning overall, I have an Innovate LM2 and I wouldn't try to tune without it.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
Race Director
Joined: Apr 2000
Posts: 17,676
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
You can't tune a carb properly without one. I have 2 an LM-1 and LM-2. Your engine can run great but you have no idea what your real A/F is until you can see it on the meter. I get 24mpg on the highway with a 600HP 427ci
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
Get the one with the 02 sensor that goes in a collector bung or one installed at the front of the head pipe.
Didnt have great luck with the LM1 that clips in the tailpipes
Didnt have great luck with the LM1 that clips in the tailpipes
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Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
I have that thing - in a pinch it works OK, but it's not great. Key thing is that the sensor has to be powered if it's installed...so the bung needs a plug for when it's not in use.
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
When I hear someone say they get 8 mpg with a big block or 10 mpg with an L48 they are running too rich and it is impossible to tell unless you have an O2 sensor because the motor is running fine. A chevy V8 will run fine at 10:1 or so and you have no idea why you are getting crappy mpg.
The O2 meter will pay for itself in a year no problem
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
You may want to head out to the Innovate forums to do some background reading.
http://www.innovatemotorsports.com/forums/index.php
I'd love to see the D/A download
http://www.innovatemotorsports.com/forums/index.php
I'd love to see the D/A download
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Le Mans Master
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From: Canada
Burning Brakes
Joined: Feb 2006
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From: Regina Saskatchewan
I seem to recall that some of the cylinders are naturally lean compared to others. If I weld in a bung (s) , which cylinder (s) would I want to hit for sure, and how far from the heads is optimum ?
Pro
Joined: Jun 2004
Posts: 543
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From: Miami FL
St. Jude Donor '11, '14
A single cylinder "pulses" too much to get an accurate reading. A typical install is at the header collector or collector extension.
Melting Slicks
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From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Neal
Le Mans Master
Joined: Jun 2004
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From: Seattle WA
St. Jude Donor '14
The bung should be in or near the collector on a header (you can buy collectors with the bung already installed) or near the bend in a stock exhaust. Doesn't really matter which side. The bung should face at least slightly downward to keep moisture off the sensor.