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


http://i184.photobucket.com/albums/x...ps6a39da07.jpg

Lol, you didn't let your mods sit on the car long enough, actually at all, lol

HEY! there was 3 days.....lol

Not long enough, lol

After reading the thread most people here don't know how to use Uprev and how are AFR's work,the correction factor is between 75%-125% with 100% being on the money if the ECU moves the AFR toward the 75% it is taking away fuel and toward 125% it is adding so the reason for tuning is to get the car to run as close to 100% as possible so the ECU has full range to adjust rich or lean depending on the information it receives from all the sensors.

If the ECU is not adjusted properly let say it at a giving RPM and load it is running 125% it is maxed out and can not add anymore fuel this is why it is VERY IMPORTANT to get it to 100% so it can do it job.

You guys get the point.:tiphat:

I'm kinda clueless when it comes to gettin' an UpRev tune ...

I don't have alot of mods on my Sport Package ( K&N Typhoon C.A.I., Berk Hi Flow CATS and OEM NISMO exhaust )

Would I need a tune and would it be worth it for this little bit of moddin' and if I did would it void the warrenty ... I've read that yes and no that it would so I'm like :icon14:

I have the 7 year 100,000 mile extended and would hate to **** that up

Thanks !

Well, I think 99.9% of this forum would say yes as you can see from the responses I got. That's why I made this thread.

Your mods aren't a "little", the general consensus on the forum is intake and exhaust (more your HFCs), you need a tune.

As for the warranty, 70%~ of this forum would say that if you have any issues with your car that you can revert your tune and Nissan won't be any the wiser.
I completely disagree, and I think I've dealt with corporate more than anyone else, and I've asked about all these things as well, so do it at your own risk.
There ARE several advantages with only few disadvantages (cost, warranty loss)

All I'm trying to say is that don't believe all the "wow, my car dyno'd 315WHP, and I gained 30WHP because of the tune!" No, bullshít, you didn't let the ECU recalibrate and learn over time, you did a baseline, added parts, dyno'd again, and then tuned it, ECU still thinks it has stock boxes, low flow cats, and a 1" diameter exhaust. That's why the gains were so high.

Tuning levels out the A/F ratio and such. But if the car couldn't tune itself, you'd get a CEL, and if you do have catastrophic failure, hell with it, revert to stock, and they almost can't know you ever modded your car, lol

264 base line with full bolt on's 304 and one at 309 SAE converting to actual power it made 322. ( but that's not the true # ) 304 is.
its a 7 AT and i trap at 114.7 12.342 in the 1/4 mile all motor
.
to run those speed and trap it would have to make 342 rwhp for a 3355 lb car,
i dynoed on a dyno jet with my home made Cobb tune.
I now have uprev and still trying to figure it out.

Z