EGT readings, fuel mixture distribution

[biggyr]

Hi Guys,

Has anybody connected exhaust gas temp probes to analyze the mixture distribution? We all know the integral log intake manifold is not the best for gas flow. I was thinking of drilling and taping the exhaust for an EGT probe at each cylinder. Plug the unused holes and take readings; change probe location and repeat at the same throttle/rpm conditions. Might show something useful, or not.

I have an Offy 3 carb manifold and might want to use it. Think that three carbs spaced along the length of the engine would gave better flow distribution.

Any thoughts?

John in Kalifornia

 

[thesameguy]

I think you'd be better served with WB02 than EGT for tuning purposes. EGT is not a direct result of A:F, but also timing and engine mechanical properties. I think if you really want to produce good results you need WB02 and dyno time. Then you can employ EGT for fine ignition tuning.

 

[chad]

I think if you really want to produce good results you need WB02 and dyno time. Then you can employ EGT for fine ignition tuning.

Can't aford dynotime. What gage should I put on the other end of the O2 (and I assume any 'downstream' or the 2nd lower, more expensive O2 is the one to install). I wanna see numbers (12, 13, etc).

Thanx-

 

[thesameguy]

I am afraid I'm not sure what you mean...

 

[chad]

Thank you for the reply!

I understand U can make a bung in the exhaust 'n thread in a wide band O2 sensor.
I assume I would hafta use one sold as the "lower" , secondary, or more expensive ones.
If I did so - how would I read it's out put from my dash or under the hood? What form of gage would read out A to F % so I could adjust the carb.

Temp (EGT) is a lill different...

 

[wsa111]

A wideband is a great tuning tool.
On most carb manifolds remember liquid fuel runs toward the rear of the manifold.
If running a direct mount carb jet the forward jet one size richer.
This is not a new deal.
This has been used on many manifold configurations including dual quads on a V8.

 

[thesameguy]

Thank you for the reply!

I understand U can make a bung in the exhaust 'n thread in a wide band O2 sensor.
I assume I would hafta use one sold as the "lower" , secondary, or more expensive ones.
If I did so - how would I read it's out put from my dash or under the hood? What form of gage would read out A to F % so I could adjust the carb.

Temp (EGT) is a lill different...

There are basically two types of oxygen sensors - "narrow band" which is a traditional oxygen sensor and "wide band" which is a newer technology, commonly referred to as a fuel:air sensor. Narrow band sensors need to be tucked up close to the exhaust as they only work when hot. Newer sensors will include integrated heaters to keep them at temperature, but they are not designed to employed all the time - they're designed to make up the difference in a cold exhaust. They are reasonable indicators, but hardly precise. You can't do much with a narrow band O2 sensor except tell rich from lean. Narrow band sensors output a voltage from 0-1v representing 14:1 and 15:1 AFR - 14 is lean, 14.5 is stoich, and 15 is good. Not much range, not much resolution. You can read the output from a narrow band on something as simple as a multimeter. Widebands run at lower temperatures and in fact can be damaged by excessive exhaust temps. They are typically placed further downstream than narrow bands, but that's not a rule, just a guideline. Widebands provide a much wider band of sensing to give more accurate results. Because they are current driven instead of voltage driven, you need a special device to read what they're doing.

 

[chad]

"...Because they are current driven instead of voltage driven, you need a special device to read what they're doing...."

Thanx.
Wonderin what that device might B?

 

[wsa111]

Go on line to Summit. Im sure they list a wideband dash mount.
The other option is get an Innovate wideband with a tail pipe adapter which you remove after tuning is completed.

 

[thesameguy]

"...Because they are current driven instead of voltage driven, you need a special device to read what they're doing...."

Thanx.
Wonderin what that device might B?

There are three components involved - the sensor, a controller, and a gauge. Commonly the controller and the gauge are built into one unit but that isn't for certain, so be sure whatever you buy has both. Search anywhere (Google, Summit, Amazon) for "wideband o2 sensor gauge" and you'll get a whole list of them. I think the Innovate solution is amongst the cheapest, but they're all in the $150+ range.

 

[bubba22349]

Hi Guys,

I have an Offy 3 carb manifold and might want to use it. Think that three carbs spaced along the length of the engine would gave better flow distribution.

Any thoughts?

John in Kalifornia

Hi John, I think most of your original question has been answered except maybe about the Offy 3 x 1V intake, the answer is yes it will give better flow distribution as well as better breathing. It is a tried and true upgrade that if you are willing to put the time into tuning, it will pay off. Good luck

 

[chad]

"...I think most of your original question has been answered except maybe..."
I'm sorry, I keep jackin threads due to my ignorance.
Thanks to all 4 of you (& those who lurk) for indulging me....