How BAD is it?
 

Hi guys, I've been told car is running lean. How bad is it really? I am starting out and trying to learn.

Leaner than I'd want to run between 3400-5900.

I target 11.5 at full boost.

Bad. How long has it actually ran like this?

I'd be more concerned with the lack of control of the AFR's , pretty wild swing there. Mid 12's AFR in itself won't blow your engine but if you're running the timing on the ragged edge then it's a possibility you'll get into detonation. You're already running some serious boost so I would get the tune fixed ASAP and see what else is wrong with it. For example if your inlet temp table is crap you could easily lean out when you're operating on a different part of the table when not on the dyno.

12.7 AFR at peak boost isn't great. Overall it looks like you're running rich -- but you have that lean spike. You drop from 13.3AFR, which is rich out of boost, and you end up at 11.2AFR which is rich in boost.

im assuming you're just running a simple FMU setup on the stock ECU?

Thanks guys for your input.

I haven't been driving the car much because of weather here.

It's MSDIY ecu. Flying miata kit with some mixed parts. 550cc inj.

The guy that did the dyno (not the same people that tuned car) suggested listening for detonation. He couldn't find any. If I am going to re-tune it, what kind of numbers should I aim for? My hp goal would be not crazy, maybe around 200-210.

Go back to the guy who tuned your car and demand him to retune your car or your money back.

Do you have a wideband exhaust O2 sensor installed? And does its output match what's printed on your dyno chart if you log a full-throttle run through 2nd or 3rd on the street?

If so, you can adjust the VE table yourself pretty easily. Small changes in the rows (and rows adjacent to, because interpolation) those corresponding to the MAP you hit at WOT. Once you get that roughed in, you can also do the part-throttle rows. That's the nice thing about learning to tune yourself; dyno operators typically focus only on WOT, and don't have the time to fine-tune everything below it.

I find the VE Analyze function of MegaLogViewer (or the VE Analyze Live function in TunerStudio) to be extremely helpful for this sort of thing. Just make sure you save backup copies of your MSQ file at every step, in case something dumb happens.

(Dumb happens to all of us at one time or another.)

It's ok (but not great) if that's a tailpipe reading from the dyno's wideband. It's not ok if it is a wideband connected at the downpipe.

it would take all of 4 seconds to fix the lean spike and overtly rich top-end since you know, you have a fully programmable ECU...

Damn it would take me a while to digest what you guys just talked about there lol

We'll start at the beginning: Do you have a wideband exhaust O2 sensor installed, and connected to the MS?

I have decided to let a shop do the thing. The same place I did my dyno at. They are going to charge 1-2 hours (most likely 2 hours) but I think what the heck. It's probably better for me to learn from scratch and try to DIY and screw it up or going to forever doubt my "tune". Any pointers you guys can give me dealing with the shop? Appreciate your help guys.

Is this the same shop that tuned it earlier?

If so, why do you want to go back and pay them more money?

No, it's the shop that did dyno for me. They did not do the tune.