i talked to uprev awhile back and they told me that i wont get that much gains with my current mods since the computer is able to adjust itself. they saw more gains with long tube headers.

This x1,000,000

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running a car lean will increase mpg's while rich will decrease mpg's. If you run your car too lean the engine runs EXTREMELY hot and will cause a catostrophic failure (so i've been told). example, my wifes altima (yes i know off subject but good for info) afr O2 sensor went out and normally gets 480 before low fuel light comes on, after failure it came on at 515. She got 550 miles out of a tank of gas in a 2.5 S 2008 altima.Downstream O2 was shot as well. Also replaced the evap control valve. 1100 in parts and labor. Hope this helps for info.

I always say this but a dyno should be used for comparison purposes and/or tuning. Doing 1 single run with all of your mods and hitting a magic number doesn't mean a tune isn't necessary.

I really think all he was saying is that a tune isn't necessarily needed to get good gains from aftermarket parts. That's all.

Tuning is absolutely necessary for you to get the most out of your car.

The best part about the tune (to me) is that it made my z much better behaved during city driving. There was a small flat spot in the lower RPM range due to wacky A/F that the ECU never corrected for on its own. I also gained 13 WHP and 6 WTQ. The chart is in a thread in this section somewhere and in my album (from 1.5 years ago).

Goin off topic: I installed the M370 and ART pipes about 120 miles ago and it is now running lean according to Torque app. AFR is about 13.2:1 reading from the stock o2 sensors at WOT and 15:1 at partial throttle. It is my understanding that our o2 sensors report somewhat richer than the actual value as well. Time for a retune!

Well, there's no doubt that in the traditional world, tuning (especially for spark advance and AFR) matters. What's at the heart of this debate for the Z, though, is whether our ECU's ability to dynamically tune spark advance (via sensitive knock sensors, mostly, I believe) and AFR (via the fast wideband sensors the ECU sees just in front of the cats combined with the MAF sensors) is so good that dyno-tuning for advance/AFR is unnecessary for bolt-ons.

Spark advance I believe was well-documented by UpRev to be basically self-adjusting even when set to insane values. You could adjust the target AFR map without a dyno if you want the ECU to attempt a richer or leaner AFR via its sensors at various pedal/RPM points on the graph. That people see gains or AFR changes when they do a quick dyno->mod->dyno cycle could just be that the ECU hasn't had time to adjust yet, and would've arrived at roughly similar numbers eventually. That people see whatever changes on waiting longer between the dyno runs and/or mods... once you wait a while conditions change and these are all relatively small diffs we're talking about.

Personally, I'm inclined to think it's pretty difficult to take this engine anywhere with bolt-ons that the ECU can't adapt to over time, although tuning the fueling maps and/or spark maps on the dyno will keep you closer to optimal right after each ECU reset so that it takes less time to adjust, and tuning the AFR targets without a dyno might be an optimization that's worth it depending on your setup.

Considering our cars do not have true wideband sensors, everyone thinking our cars computers are smart enough to correct them selves I am sure your correct....but it can only correct what it see's...

If your running super lean or rich (which you will with full bolt ons) I would not count on this to give you the optimal tune.

wait, are cars are true wideband from the factory? if thats the case, then why aren't people running a torque app thru their phone instead of doing a gauge setup to read afr's?

They're pretty damn good for on-board wideband sensors.

They aren't dyno-quality good, but they're good enough for government work.

I ran with an innovate on the car for a while and my factory sensors followed pretty well, albeit a little slower.

What people are not considering is the size of piping and air flow. Even though you put a bigger/better exhaust on your car, hfc's and a intake doesn't mean that your car will adjust to those parts. It will max out on its default settings because obd2 was designed to compensate for variations such as temp, altitude, timing, air flow. It has basic pre set settings that are determined by size of stock exhaust tubing, intake design, stock cat cels, etc. If you throw your parts on and don't tune it (as stated before) you aren't getting the performance (not peak hp but rather full band increase in performance) that you paid for. The pre-determined settings are going to be maxed out, which is why a tune helps because it sets new parameters for air flow issues with hfc's or temp issues with cold air intakes. Feel free to chime in if I am wrong, but that is the way that I understand how the uprev helps.

In closed loop the ECU adjusts on the fly based on MAF and O2 sensor readings. It still reads off a target table, and initially starts at that value but then relies on feedback from sensors to make the corrections necessary to hit optimal AFR. The ECU can also log and report how far off the target it was, and how much correction it's making to hit optimal. Tuning the base table allows the ECU to not have to make as large of a correction.

How that affects performance is really up in the air. Supposedly the ECU can learn the correction factor over time, and if that's truly the case, then closed loop tuning is just a matter of driving long enough to have the ECU learn the partial load curves. In this case, tuning the target table would just speed up the process. If it's making the corrections on-the-fly every time, and not "learning", then theoretically at least, there's an associated latency to the correction which could potentially effect part throttle behavior; a tune could be used to clean all this up.

Open loop, or WOT, reads straight from the fuel table based on MAF and load values and doesn't rely on a feedback loop.

The beauty of the MAF sensor is that it alone can pretty much compensate for air temperature and density (altitude). The downside is that it's calibrated for a specific housing diameter. It calculates the flow rate over a very small area that covers the sensor itself, then extrapolates based on the known diameter of the housing to get the amount of air flow.

The O2 doesn't care what the flow rate is, only the oxygen content, and as such can pretty much sample the exhaust in any diameter, just so long as it's relatively close to the exhaust stream.

To add to the above, one of the things I gathered from UpRev's detailed docs that definitely could be worth fine-tuning regardless is the MAF table. Basically, the stock MAF table is a rough approximation, and there are manufacturing variances in the MAF voltage readings as they compare to reality. On the dyno you can adjust those tables to get your MAF tables correct for the exact sensor variations in your own car (not to mention intake diameter changes).

With MAFs being accurate (and with stock intake pipe size, they probably aren't hugely far off), I think it's true that the O2 feedback + MAF is good enough regardless of exhaust setup, and it definitely does learn long-term trims. But yes, every ECU reset it'll have to re-learn, and so that goes faster and smoother if the baseline is closer and less adjustment is needed.

Re: AFR targets, that's not really about compensating for inaccuracy, that's just about deciding what AFR you want to run (safety margin, temps, etc... I even found that bumping my AFR a little richer in the upper left of the table (low RPMs, low throttle) helped a bit with tip-in fueling coming out of the bottom there, at the expense of wasting a little fuel.

The open-loop thing, yeah, not sure how well the car adapts there. Surely the long-term trims learned during closed-loop would apply to the calculations done from the MAF data? Honestly I don't know.

Std is always gonna give you higher numbers..... What was it sae

Sorry DEpointfive0.......i know you're my boy but............ /thread

Dotted lines = before. Green solid = after tune


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