Torque data log interpretation - Fuel Trim, AFR, Timing Etc
 

https://datazap.me/u/butterballz/log...6?log=0&data=5

Stock motor, stock intake, no tunes, stock exhaust system except for track pipe. Just want to make sure my readings are in the normal range.

Some readings look off like AFR in the 20s etc. Thanks.

It isn't possible to determine if your actual AFRs are reasonable as you didn't track throttle position and/or engine load. With a stock engine and map, you will notice your AFR go to 20 anytime you come off throttle (engine braking). On full throttle with very high engine loading, you should see AFRs drop into the high 11s and low 12s. Cruising, constant throttle will result in AFRs around 14.5-14.83.

Your fuel trims look fine (no excursions above +10 summed or -10 summed). I wouldn't expect anything to change with just a catback exhaust.

To be 100% sure, you will need to re-log with throttle position, engine load (if available on Torque - I can't remember), manifold vacuum, MAF voltage, engine RPM, and your short and long term trims.

That's what I interpreted from the readings. Just being OCD I guess.

It's always interesting to log data like this. Recently, I had started to notice a slight dip in my fuel economy (~2 mpg highway, up to 5 mpg city). I logged data for a few days and uncovered slight changes in air flow that led me to a rather significant leak at my exhaust manifold (rusted gasket - I live in the Rust belt). Curiously, the exhaust leak noise I would have expected to hear wasn't very apparent in my situation, probably due to some combination of aftermarket header and catback exhaust. Anyway, replaced the gaskets and am getting the best fuel economy I've gotten in years (~32 mpg on 93 and 27 mpg E85 highway).

Yea that's why I started logging. Noticed the miles I was getting from a full tank to halfway dropped and full to 1/4th dropped. Seems like my fuel trims doesn't show leaks but I bought gaskets just incase. Took my overpipe, midpipe, frontpipe off a couple times to install parts but just reused the gaskets.

Do you calculate your mpg at the gas station? Or have you just observed the tank gauge dropping faster than you might expect? The reason I ask is that the fuel level sending units in this car are not the greatest in the world. Lots of people have issues with the sending units gumming up over time, particularly the secondary sender on the passenger side (for LHD cars) of the tank. There are a couple threads about this but to sum it up, essentially, the sender-B tends to slowly progress towards infinite resistance over time and can cause the gauge to float abnormally slowly or quickly, particularly at the extremes of travel. I had an issue for a long time where my gauge would never show full - others have had issues with the lower quarter of gauge travel would proceed really quickly.

Just based on your log above, I would be confident in saying your trims look pretty darn good. Back when I ran a stock car, I would routinely notice total trims anywhere from -9 to +7, even when the car was only a few thousand miles old. Without the vacuum and load data, it is impossible to be 100% confident, but my bet is you don't have anything that would cause more than a slight (normal wear and tear-related) change in fuel economy.

Another thing to think about is your O2 sensors. I doubt you have an issue with either the wideband or narrowband, but tracking their voltages could be really helpful as well just to be sure. The early narrowband sensors used in the manufacture of these cars were replaced with a new version, I think in 2015. If you have an older car, it's not impossible that the narrowband has gotten contaminated; although, it sounds like you haven't modified the primary cat so it's not too likely in your case. For me, within about 5,000 miles of switching to a catless header, I fouled the narrowband sensor which started messing with my trims (and thus fuel economy) in specific situations.

I reset the trip odo to zero when I fill then compare the miles to the fuel gauge. Noticed some differences from before. Usually, I could get over 200 miles before hitting the 1/4 filled mark. Now I usually get under that. I drive the same route 5 days a week so not much differences with the route. Fuel gauge seems consistent still when I checked the gallons filled during gas up.