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Wideband A/F gauge and tuning SU carbs


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So I’m a total NOOB when it comes to tuning w/o a dyno. Running SU carbs can be frustrating at times, and over time they do fall out of adjustment. I am considering a wideband O2 sensor and gauge for the race Z to help diagnose fuel delivery issues and adjust them in the field. I will be running SM needles, and have been told the A/F will not remain constant over the flow range. Hence, tuning the idle mixture to compensate. 
 

2 questions:

 

1) does anyone else use an A/F meter to tune their SU’s or carbs for that matter?

 

2) any recommendations in make/model of sensors and gauges? 

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4 hours ago, bunkhouse said:

 I don't have any recommendations but what are the fuel delivery issues?

 

Nothing in particular (yet). If the engine has trouble running during a race (or otherwise), the most likely culprit will be fuel with SU's in mind. The float could get stuck, the fuel pumps could die, fuel pressure/flow issues, vapor lock, etc. Not planning on it, but it would be good to have a gauge that would instantly let you know if you have a A/F issue. I plan to go with a crank triggered ignition and eliminate the distributor, so the ignition system should be pretty darn reliable. 

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9 hours ago, Ben280 said:

If you are going to use this for race time troubleshooting, I'd think about running 2, one for each carb. One main one will certainly be an upshot, but two would give you some really good insight into how each carb is behaving. 

 

Personally, I like PLX widebands. 


I was thinking that too! Unfortunately my header is a 6-1, not the 6-2-1 :(. I totally agree though! If I stick with one, il have to remember any change in measurement can potentially be a 1/2 contribution, but it will still show up in the reading. 
 

maybe il start with one, and if it becomes too frustrating I will get the 6-2-1 header and buy another meter/sensor 

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1 is better than none! I'm only using one on my car, but with the ITB's I'd have to go fully nutty if I wanted to tune per cylinder. Paying special attention to keeping the carbs synched up on airflow will pay dividends for you on this. 

 

One thing to remember about AFR gauges too, they measure the combustion gasses. So, if you're running very very rich, with a lot of unburnt fuel, it will read on the gauge as lean, which leads you to add more and more fuel with no change on the gauge. Ask how I know, haha!

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Posted (edited)
4 hours ago, Ben280 said:

1 is better than none! I'm only using one on my car, but with the ITB's I'd have to go fully nutty if I wanted to tune per cylinder. Paying special attention to keeping the carbs synched up on airflow will pay dividends for you on this. 

 

One thing to remember about AFR gauges too, they measure the combustion gasses. So, if you're running very very rich, with a lot of unburnt fuel, it will read on the gauge as lean, which leads you to add more and more fuel with no change on the gauge. Ask how I know, haha!


LOL!!! I think the black smoke and smell of gas might tip me off 😂😂

 

although, that’s a great point because I wouldn’t have thought of that until you mentioned it. 

many reason you like the PLX over, say the AEM gauge? I looked at the PLX unit and the price is attractive! 

 

Edited by AydinZ71
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