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Old 11-19-2012, 03:31 PM   #1 (permalink)
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Arrow A/F understanding

I always thought that o2 sensors were put in the car to keep the A/F at the ratio it Should be. I know that you have to tune a car after doing air and fuel and Turbo upgrades. I know you have to tune it, But my question is Why. I thought That's Why o2 sensors are there.
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Old 11-19-2012, 03:42 PM   #2 (permalink)
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Default Re: A/F understanding

For any small upgrade like a different intake or exhaust the ECU works just fine asis. It's when you start installing bigger turbos and need to add more fuel. Since the ECU is setup to run 360cc injectors even with the o2's un-plugged it will run somewhat "safe" if you change the injector size the ECU still thinks it is running 360cc injectors so it will +\- fuel based on the stock injector size. If the injectors are bigger the ECU needs to be "tricked" because it can only compensate so much before it runs out of adjustment.
At WOT the ECU runs off a internal map thats based off 360cc injectors "open loop" so it does not even look at the o2's

Hope this helps? I am even a little confused after re-reading :-)

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Old 11-19-2012, 03:59 PM   #3 (permalink)
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Default Re: A/F understanding

and unfortunately you can't just make adjustment for the injector size and the map still be right. So you have to add and take away fuel at different rpms in order to achieve and maintain the 10.X to 12.x target you are looking for when running WOT. The O2's will try and hold the car at 14.7 which is great when at idle or cruise, but way to lean when your getting on it.
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Old 11-19-2012, 04:09 PM   #4 (permalink)
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Arrow Re: A/F understanding

Well I recently ordered a wideband AEM, and I was looking at the arc2 system. Is the arc2 a good system? I new to the whole A/F world, just trying to learn How all this works.
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Old 11-19-2012, 09:00 PM   #5 (permalink)
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Arrow Re: A/F understanding

Where can I find A/F for dummies or A/F 101 hahaha. Seriously though.
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Old 11-19-2012, 10:50 PM   #6 (permalink)
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Default Re: A/F understanding

Quote:
Originally Posted by italiano3kgt View Post
Where can I find A/F for dummies or A/F 101 hahaha. Seriously though.
Here, google search, factory service manual, and DSM forums had a lot of great info.
I have seen a lot of books on Fuel injection, and Turbo stuff.

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Old 11-20-2012, 08:33 PM   #7 (permalink)
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Default Re: A/F understanding

Need to fined a good tuning book or start reading about tuning/fuel injection/basic engine knowledge on the internet. Did you get the AEM fail safe gauge? It's better than a regular AEM wideband since it's easier to data log.
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Old 11-21-2012, 03:05 PM   #8 (permalink)
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Arrow Re: A/F understanding

I believe it is the fail safe.

The only thing I don't understand is less than 14.7 is rich and greater than 14.7 is lean. Then Why on an a/f gauge is lean on the left and rich on the right
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Old 11-21-2012, 03:29 PM   #9 (permalink)
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It's the digital read out that matters.
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Old 11-21-2012, 04:11 PM   #10 (permalink)
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Default Re: A/F understanding

standard weights and measures, seems most all guages read in a clockwise direction.
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