AFR problem. Runs lean and fluctuating - Miata Turbo Forum - Boost cars, acquire cats.

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Old 12-29-2013, 02:07 AM   #1
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Default AFR problem. Runs lean and fluctuating

Hi folks, I recently bought a 92' 1.6l turbocharged Miata running a Miata MS2.
I noticed the AFR fluctuating on the gauge and I'm not sure if it's normal.

Have to say I'm all new to efi tuning, read a few books and a lot on the internet but have no other experience.

Here some info:
-Cold idle AFR: Fluctuating 17-17.5:1
-Cruising 4th Gear 2500RPM AFR: Fluctuating 13.9-14.6
-Warm idle AFR: Fluctuating 16.5-17.4

Where does that come from?
I've also noticed when I let of the Gas the AFR first goes rich about 11.9 and richt after super lean >17.5:1. I assume the fast enrichment is for the shifting interruption, is that right? Apparently some setups go either rich or lean for engine break, does this setup make sense? What do you guys recommend?

Thank's I'd really appreciate any info you guys have.
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Old 12-30-2013, 02:24 AM   #2
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You failed to include your wideband sensor. Has it been calibrated properly in Tunerstudio?

A tune file and datalog will help us to help you. Otherwise we can only make guesses.
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Old 12-31-2013, 04:04 AM   #3
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Default Thank's

Thank's for the response. I do not know what programm the previous owner used. I'll connect my notebook sometime soon and get the tune file.

What do you mean by failed to include wideband?

It's really strange, the afr right after the startup is between 14.4 and 15, nearly perfect. But after a bit it first gets richer (probably the warmup enrichment) and then suddenly super lean.
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Old 12-31-2013, 04:27 AM   #4
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Either you are really ignorant about your new car or you are a troll.

For the former case go make an intro thread in the meet and greet section, and start reading about how to tune with megasquirt.
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Old 12-31-2013, 05:01 AM   #5
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You should tune your car...
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Old 01-06-2014, 03:46 AM   #6
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Quote:
Hi folks, I recently bought a 92' 1.6l turbocharged Miata running a Miata MS2.
I noticed the AFR fluctuating on the gauge and I'm not sure if it's normal.

Have to say I'm all new to efi tuning, read a few books and a lot on the internet but have no other experience.

Here some info:
-Cold idle AFR: Fluctuating 17-17.5:1
-Cruising 4th Gear 2500RPM AFR: Fluctuating 13.9-14.6
-Warm idle AFR: Fluctuating 16.5-17.4

Where does that come from?
I've also noticed when I let of the Gas the AFR first goes rich about 11.9 and richt after super lean >17.5:1. I assume the fast enrichment is for the shifting interruption, is that right? Apparently some setups go either rich or lean for engine break, does this setup make sense? What do you guys recommend?

Thank's I'd really appreciate any info you guys have.
I am learning on the go as well so i will pick out some bits to comment on.

Overall though it sounds like your tune is not "tuned".

On zero throttle, de acceleration for instance..the afr would normally go full lean as it would usually not be getting any fuel. You say you see 17 ish..seems wrong. I see 22.5 on my MTX-L.

Warm Idle would normally be 13 - 14...ish.

Cruising would normally be 13 ish (at a guess) but the gauge will fluctuate a little..I believe this is normal...

keep reading, and post specific questions. Eventually someone will drop the sarcasm and make a helpfull post.

It seems to me that your car really should go somewhere for a basic tune though...can you find out if anyone in your area with a dyno can work on MS ecu's.

I am not sure I would be giving the car any "stick" in the meantime....
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