After carefully pondering the purchase for entirely too long, I have finally purchased a UTEC, remote switch, tuner regular and VW sensor. That being said, I have had plenty of time to prepare for this. I have read the manuals 5+ times, read tuning threads online, and prepared Excel spreadsheets for logging/adjustments (I am an excel wizard).

At any rate, I need some help with target, or ideal, AF ratios for the 2003 non-revup VQ. I know very well that 13:1 is highly preferred at redline. Most people have found this out. However, what about in the lower band?

Should it start at 15:1 near 2000 rpm and decend to 13:1 at redline? Should the transition be smooth and level? Do I need to account for the CVVT transition point near 3500 rpm?

Any tips you can provide on AFR across the entire band would be great. By the way, I do understand tuning pretty well. However, this will be my first run at it.

Since this thread is more about theory than anything else, I am not inclined to list my mods. However, just in case someone has to know, I have a short intake, crawford plenum, crawford headers, HFC, and exhaust.

I also have benched my injectors with Deatschwerks recently so I know their exact flow rate. By the way, Nissan uses some good injectors. They all flowed 300 exactly.

Thanks everyone.

 

I am no where an expert but I posted my dyno chart with a somewhat large section of the A/F curve if you want to check it out and see how my tuner tuned my Z. search for UpRev review...its a few threads down

 

there is NO standard AFR that will make more power. i own a shop and i dyno tune cars all day. you can bring me two brand new Zs, put the same exact mods on them and one might like 12.5 to 1 AFR with 4 degrees advanced timing and the other might like 13.8 to 1 with 1 degree advanced timing, you really really need to get where you can tune it yourself. make 5 different maps, some high AFR and some low AFR with different timing issues. then go get on a dyno and see what makes the most power. also, on most cars in the world, torque likes fuel and hp likes lean conditions, however, on these cars, its seems to be the opposite for the majority of them. although i have seen some like it leaner up top.


good luck

 

Thank you both for the input. I will definitely check out the UpRev review.

Mayhem,

I completely understand what you are saying. I assumed there would be variances between engines. However, I am looking for good "rules of thumb" as a starting point. I know the stock map from TXS is very conservative and most will need a good amount of tuning on top of it. However, if I know the rules of thumb, then I can get a quick leg up.

Here is my overall plan at the moment:
1. Use street tuning to build at map starting at 15:1 at 2000 rpm and heading to 13:1 at redline
2. Use the above as a base to build a "rich" map and a "lean" map.
3. Dyno all three and do comparison to find which map or mixture of maps yields the best results.
4. After AFR is tuned in, begin dyno tuning small timing changes. This will require small adjustments in AFR since timing changes will cause AFR to wander a little.

Let me know if you can think of anything else that might be helpful. Thanks again.

 

Sounds good to me...good luck!

 

Here is my suggestion for your "Street tuning"

Start out slightly rich, and lean it out in small increments.

Despite what audible said, I would aim for 13.0 all the way from low rpm to redline. If you want to tweak it, you tweak it on a dyno.

Keep timing stock until you get it on a dyno. you cannot tune timing by the butt dyno no matter what anyone says, and it's not exactly safe to do so either.

Be aware of, but don't worry about, slight pinging. The ECU will deal with it.

Just for reference here is the results from my EU tuning
https://my350z.com/forum/showthread....light=ultimate

 

Also, it's flattering to be called out by your thread title, but remember I'm just a guy like you who basically figured out everything I know by reading up on stuff online, as well as in books, as well as testing **** out on my own car.

I'm not a certified expert or something, just wanted to make sure you know this

 

Wired24/7,

Oh, I know you are "just a guy" that figured it out. But that is why I called for you by name. Those that can teach themselves typically have good insights for those looking to do the same.

Everything you stated above is in my plan. I definitely won't try to do timing on the street. That is strictly for the dyno.

However, I am surprised that you said to aim for 13:1 across the board. Isn't that rather rich for the lower RPMs? Then again, if torque loves fuel, then it might make sense.

If I were going to start rich, I would start at 14.5:1 and head toward 12.5:1. Once I get a nice smooth fuel curve, I would then get it on the dyno and start to raise the AFR to make power.

Let me know if you have any additional ideas.

Also, any suggestions on the firmware version I should run? 2.6 seems pretty accepted now. I don't think 2.8d is for me. I don't need the turbo solenoid control.

 

I don't have UTEC so I dunno about firmware version.

Optimal air/fuel ratio has to do with the combustion chamber efficiency and so on and so forth. The main reason nissan makes the car run around 14.7 AFR in the lower RPM range is due to emissions consideration (I believe this to be true, but can't prove it)

The catalytic converters have max efficiency at 14.7 AFR... so this makes sense to me.

But look... you should start by tuning at wide open throttle, then just make the fuel curve a gradual change back to stock at partial throttle. You only need that power on demand when you really step on it.


I'm pretty sure you'll make better power with an AFR closer to 13.0ish ... compared to 14.5...

Best torque values come from slightly richer mixtures. Because fuel does not atomize ideally, but oxygen is always atomized (nearly) ideally, you want to make sure oxygen is your limiting reagent for combustion.

I'm sure you know that 14.7 is the optimal number where all the air will combine with all the fuel to burn completely (in an ideal case).

If you are running close to 14.7 you can be pretty certain that you will have a little bit of O2 left over, because even though all the fuel SHOULD combine with all the oxygen (in an ideal world), that will not happen unless your combustion chamber is 100% efficient. That little bit of O2 left over translates to power lost.

If you add too much fuel, then you will be wasting fuel, cooling the combustion chamber down too much, and you won't be getting any added benefit other than slowing yourself down.

To make best torque, you want to make sure you use up every last molecule of O2. For the 350z's combustion chamber, that seems to occur around 13.0 AFR.

For other motors, that "max torque" value will typically fall somewhere around 11.5 - 13.3, where the more efficient combustion chambers will be closer to 13.3... so the Z is not too bad at 13.0ish. I strongly doubt you'll ever have to go below 12.5.

You don't need to burn every last O2 molecule if you're at partial throttle (light cruise conditions) . Actually you'd rather burn every last fuel molecule, for best economy. But you can't run too lean, otherwise you will make too much pollution and risk detonation / knock. So at part throttle you can run at 14.5 no problem.



Then, to make peak power, you want cylinder pressure to be at its peak at 15 degrees after top dead center (ATDC) ... This is of course very difficult to figure out with theory. But this is the key to optimizing timing. So you can only really see the effects on a dyno, which is the most important tool you have to tune. Luckily, the VQ's timing map is not too shabby to begin with. You definitely won't have to advance more than a couple of degrees to get the best HP values. Note: the VQ's timing map changes when the engine is under heavy load. Therefore, it is best to tune timing on a LOAD BASED DYNO. Mine was done on a very heavy load dynapack...

Finally, if you are pinging, the ECU will automatically pull timing, and I don't believe it's a serious problem (many stock motors ping under heavy load from the factory, it says so in the owner's manual). The only seriously bad condition is if you're experiencing repeated pre-ignition, which should never happen if your ECU is working properly. If you are racing or something, you can just throw some 100 octane fuel into the mix. If your octane is about 94-95 you should be fine with respect to knocking, which is only a few gallons' worth of 100.

 

Thanks Wired. Again, great information. A lot of it I am already familiar with.

By the way, my UTEC is installed with the map switch and working fine. The physical install was a bit tougher than I thought it would be, but it is working great.

I do need to finish my install this weekend. I have the route a couple wires and install the Tuner and WB. I will start another thread to cover this process from start to finish.

Thanks again everyone!!!

 

You're telling me. I installed, uninstalled, installed, uninstalled, installed my EU without ever taking off that passenger side dash-underpanel.

Talk about working while standing on your head...

 

Yup it is all installed now and I have collected 7 or so logs with adjustments.

I have started a new thread (linked below) where I will track my progress over the next couple months. By the way, would someone turn off the snow machine? I cannot log WOT runs in the snow, even with snow tires.

New thread documenting progress:
https://my350z.com/forum/showthread.php?p=3311088

 

be careful out there...

sports cars are not meant for snow