We just had a dyno day and I was low on torque compared to everyone else. Apparently I'm running very lean. Air/fuel ratio was 19 whereas everyone else was around 14. I have a 2011 S. No mods. I have never had the check engine light come on.

Any thoughts/ideas? I am taking it to the dealer later this week. I don't want them to send me away just because the check engine light hasn't come on. Obviously it's affecting the car's performance.

 

AFR is going to vary depending on the load on the car. Ideally, you would be running 14.7 AFR at idle or at light load. When you start adding load, it will start getting richer, eventually getting to 11.0 or so at full load. Normally the R56 is good at correcting for AFRs, if you were running at 19 under load, your engine isn't going to last long!

 

Thanks, yes, the other cars were at 14.0 or 14.1 when idling. Not sure where they ended up under load. Mine was idling at around 14.9. Here is the photo of the AFR during the dyno. Also dyno numbers comparing my '11 to an '08

 

That cannot be right...

Going that lean under load, for the entire run? I'd be surprised if the motor lasted for the single run if it was actually the case. There would definitely be knocking/pinging as well.

 

Hmmm. Thanks for the feedback. We'll see what the dealership says on Thurs. I agree some things don't seem to add up. The check engine light seems like it definitely would have come on if it were that lean. On the other hand, I should have a bit more power on the dyno results to be closer to all of the other cars (which were all pretty close together). The guy who ran the dyno commented that my car almost sounded like a diesel when it was idling. Maybe that's some of the knocking/pinging you're talking about?

I don't know if this is typical of turbos, but when I drive it, I have very little power until about 3000 rpm and then it seems to pick up significantly.

Thanks for the comments.

 

I agree with Thumper, that can't be right, your car wouldn't be able to run for very long if it was that lean, like just hours, not for a significant amount of time. But at least you would be getting outstanding gas mileage!

 

Thanks. Yeah, something isn't right about that number. I've been driving it hard for a year and it hasn't had any issues yet (average mpg is still about 34 though). You guys have calmed my fears a little bit.

I suspect it is running lean, but not as lean as 19. Why else would the power be low? It was definitely idling leaner than the others (but not by too much). Always good to get second and third opinions. Still want to get it checked out, just in case. I'll make sure it's a senior mechanic on hand when I go in later this week. Will definitely post what I find out. (My guess is that he'll say everything is perfectly normal and send me on my way).

 

Maybe the wideband came out of the tailpipe during the run, or it just died before your run? The power looks pretty good though, maybe a little low.

 

Yea that can't be right...

How many miles on the car?

New air filter?

Good top tier gas?

No rat nests in your intercooler

 

Your graphs look correct... running about 195wtq and 185whp... curve looks about right for a stock car. Are you sure jackie's car is also an S? no jcw tuning kit?

I would guess that there was an issue with measuring equipment... a stock AFR wouldn't even look like that, even if it was flipped upside down... AFR isn't that smooth with the stock tune, and will vary slightly on its way from 15 down to about 12.5 (roughly what the stock range is).

It surely wouldn't just shoot down to 12.5 and stay steady. Its possible the probe wasn't inserted properly or secured properly and just blew out after the run. How many pulls did you do?

Your motor likely would have blown up at that high of an AFR for a whole run. Either that or your water temp warning would have come on after the run/smoking etc.

If you know someone with a scangauge, you can hook it up to your OBD II port and read your AFR while driving since our cars have stock wideband.

 

I really appreciate all of your responses. It has taught me a lot and gave me questions to go back to the dyno guy with. As a result the dyno guy did some more analysis/research. I don't understand a lot of what he said, but basically he said my car is fine and that I should cancel my appointment with the dealer.

He said the AFR can jump up when the car is heat soaked and the voltage is applied to ground. The measurements he showed me were for my third (last) pull only...hence the high heat. He said in high heat, they probably disable the closed loop operation of the sensor and just run open loop to get accurate readings. He went back and checked and one other guy's AFR was at 19 on the last pull as well.

It looks like the chart I attached earlier in this thread was comparing my third (worst) pull to Jacque's first (best) pull. I asked him to send me a chart with all three of my pulls, which he did, along with another chart that compares my best pull to Jacque and to Seth. Theirs are both '08's, manuals, but with lots of mods, JCW tuning, etc. I'm attaching those charts here because I am rather pleased with the results.

Thanks again for the input. It has saved me a few hours of driving and waiting around at the shop.

 

Do you know specifically what kind of mods they have?


Sorry if its a little off topic, I find it interesting how much power a stock n18 makes compared to modded/tuned n14s!

 

Stage 1 JCW. Alta hard-pipe turbo inlet tube and cold side boost tube.

 

Btw, my MINI 07 S Automatic was the other MINI showing high AFR on the last run, it was an equipment malfunction, nothing to do with Bryan's or my MINI.

I am pulling 220/wtq and 195whp on this dyno, warm day 87 degrees, 25-30 humidity and 6800 ft elevation, just a data point.

IMO, the 2011 N18 engines have a better ecu profile and give a bit more HP and TQ when stock, a good amount of that is the updated Vanos Valve train thus the Engine processes fuel better over the RPM range.

Not much better, but better in the stock format.

My 07 S in Stock ECU with a 2010 ecu image, JCW Stage 1 Intake, NO JCW tune, 09 JCW stock muffler fed by a 2 1/2 inch exhauset, no second cat but I have a resonator in place and a Helix IC. Gen 1.

Hope that helps. Currently running no tune, just MINI ECU El Stock.

Don