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. :hustler:

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.

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.

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.

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.

You should tune your car...

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....

Maybe I'm the noob here, but that sounds normal to me? Perhaps the megasquirts are more precise than the stock ECU, but I didn't think so. On the stock ECU it varies, usually within less than one A/Fr preferably less (eg. 14.0-14.9), because it's constantly adjusting for input conditions, they're rarely ever spot on and stay there. My stock ECU fluctuates from ~14.1 to 15.3 while cruising with a norm between 14.5 and 15.0, drops to between 12.9 and 13.2 on heavy throttle (more precise than cruise) and if I'm cruising in 3rd gear at over ~40 ish and let off the throttle, my A/Fr gauge goes red and doesn't read a value, which I believe is the overrun fuel cut. Your idle A/Fr's seem high to me, so I'd check for air leaks or not enough fuel, but as long as they come down to the 14-ish range while driving normally that's not really an issue and you're saving more fuel at idle.
They meant to include the brand of A/Fr gauge since some give different readings or are known to fluctuate more than others.