Torque app and monitoring fuel trim – affects engine performance – acurazine – acura enthusiast community electricity and circuits class 6 cbse


So basically, being at "0" indicates that the ECU is doing a perfect job of providing the exact amount of fuel and air into the cylinder. However, in an imperfect world, it’s almost always going to be at least +/- 3% since adding an absolutely perfect amount of fuel to the cylinder isn’t an easy task for the ECU, even in the day and age of computerized throttle bodies and fuel injectors. Staying -10% to +10% is usually considered acceptable for older engines that naturally have older sensors and cylinder ring or vacuum leaks. If you’re above (+/-) 10% or so there is a significant problem which could affect drivability and should be addressed. A positive fuel trim indicates that you’re running too lean (too much air) with a negative fuel trim indicating that you’re running too rich (too much fuel). There’s a short-term fuel trim which is more of an immediate reaction based on your O2 sensor readings while long-term fuel trim is where the ECU "learns" over time, what the common condition is inside the respective cylinder bank. I believe Long-Term fuel trim is one of those things that the ECU has to re-learn when the battery cable is pulled. But it’s constantly adjusted on a more minor scale based on driving style and the health of the engine.

Before I had an oil control piston ring fixed, I was pulling about a -12% to -15% fuel trim on bank 2 and a +8 to +12 trim on bank 1. So basically out of spec on both, especially considering the mileage on the engine and the fact that the J-series is a pretty well-tuned machine. Too rich on bank 2 and too lean on bank 1. I assumed bank 2 was running rich due to oil burning on cylinder 5. I had no idea why bank 1 was registering lean though. After the mechanic tore the engine apart and replaced the rings as well as all the seals, both trims now only range from about -1.6 to +3.0 which is well within normal operation. After speaking to him about it, he said that removing the intake manifold or runners may cause an air leak in just one cylinder if the bolts are not torqued correctly or if the gasket isn’t in good condition, allowing a bit of air to infiltrate into the runners. I’m guilty of both. I’ve removed the runners from the head and removed the intake manifold from the runners, never having replaced the gaskets and torqueing by feel rather than with a torque wrench. I also learned that overtorquing can be as bad an undertorquing since it can cause the gasket to flex or squish too much in one area, letting in whatever is supposed to stay out.

The reason I added this to the performance sub-forum is because of the significant power increase that the engine put out after having the problems fixed. We tend to concentrate on power adders but also need to make sure the engine is healthy in the quantitative regard – more than just making sure the oil is clean and we don’t have a clogged air filter (see bolded items below) I wasn’t expecting it, but the difference in power, especially low end torque, was definitely significant. Based on the very scientific butt dyno the difference was at least the same as after I did the full exhaust (high-flow cats, j-pipe and magnaflows).

Remember that the ECU’s first priority is drivability and reliability, with performance being 2nd after those other items are addressed. The ECU will rob performance all day long if it’s necessary to make sure the engine runs somewhat "correctly" and doesn’t cause damage (ie. spark knock damaging the engine, bad fuel/air mixture damaging catalytic converters, etc.). The ECU attempts to compensate when running too rich or lean, but having your fuel/air ratio off can result in a loss of power due to a less-than-ideal mixture of fuel and air in the cylinder which produces less power output. Not to mention potential damage to the catalytic converters over time and lower gas mileage.

It’s super easy to pick up a Bluetooth OBD2 adapter on Amazon or eBay. Mine cost $15 on eBay. I got the Veepeak and it works great. Then download the free Torque app which connects to the adapter and provides a ton of info. I purchased the "Pro" version of the Torque app for $10 which provides a lot more features. For $25 total, it’s a great tool to have, and can give you some good info that will help performance with monitoring the following and making changes where needed:

Spark Knock – The "Knock Detector" is a free add-on to the Torque app which will tell you if the knock sensor is detecting any problems, as well as how much timing is being pulled due to knock. When the ECU pulls timing it’s not black and white. It may pull just a little bit or a whole bunch based on the frequency and amplitude of knock that is being detected. Before I had my oil ring fixed I was routinely getting knock, presumably from carbon buildup which was very thick on the cylinder head and exhaust valves. Sometimes it was pulling up to 12 degrees on timing. After fixing it, I’ve managed to get it to knock only a couple of times at very high RPM’s and once with full throttle at low RPM’s with the transmission locked in a high gear using sport mode. The highest I’ve been able to get it to pull timing from knock has only been 0.5 degrees. At that low of a level, performance is hardly affected. Heck, at that low of a level, it may very well be background noise setting off the sensor.

Diagnostic code identification and reset – Not so much a performance issue but is obviously helpful in detecting CEL codes and resetting them without pulling the battery or fuses. Anyway, CEL issues often affect performance (ie. faulty sensors, misfires, stuff like that)

Eh, now a days it seems auto manufacturers don’t provide any info on engine conditions other than the basic alternator light and coolant gauge – which is totally inaccurate since it sticks at the same gauge level as long as the coolant is between 170F-230F. The coolant temp is interesting to monitor. It rarely dips below 168F since the thermostat starts to close at around 170F or so. I get it up to 210F-220F when going up hills. And interestingly enough, it still doesn’t go over about 220F even in the summer. Once the fans kick in, the coolant temp drops very quickly.

The fuel trims are a bit interesting as well. They often drop below 0 during city driving but head back to 0 when cruising. I’m guessing the constant stop and go causes the engine to run slightly rich at times. I monitor intake air temps as well along with catalytic converter temps for both banks since I have high flow cats from RV6 which I’ve wrapped and want to make sure they don’t get over 1800F. So far the hottest I’ve gotten them was about 1750F when I was racing a turbo Kia Optima SX up a hill for about a mile. I got about two car lengths ahead of him but he started closing in pretty good before I shut it down. 100mph in a 55