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Discuss all things tuning in this section. News, products, problems and results.
I got the worst of the worst here for a first tune. Recently a customer brought in a 350z for a turbo kit install. I was hesitant to do the tune, but he did not need it right away and I felt that after several months of taking these courses and nearly two decades of automotive experience, I thought that I would give it a go. Plus the customer had purchased the tuner cable and license.
I did not feel comfortable going at an NA stock vq35 with a single turbo strapped to it for my first tune alone. So I called upon a friend with a great reputation for tuning Z cars specifically up to ask him to remote tune for me as I watched and learned.
First question he asked is if I had an upgraded MAF and I replied "no". He then asked if we were running a stock MAF housing. I replied "yes" He said, we'll see how far we get, but we will most like run out of air calibration and be limited.
We were also apparently short on fuel. 440DW to start with running behind it was a 340gs42 pump that we had modified per the turbo kit requirements.
We also did not have a fuel return. So we were working with a "dead-head" setup. He informed that with the 440DW and fuel pump we could at least get "more out of them due to not having a fuel return", stating that it would actually just push more fuel through the injectors and that as long as we didn't go over the 90% duty cycle mark, that we would be fine.
I had talked to several other well known Z tuners and even Up-Rev and the all said the same thing. No chance of hitting 8lbs on anything less than 600cc's So I was skeptical to move forward, but we did.
It actually did work. We did some steady state runs while logging, I wish I would have known that Up-Rev supported Innovate wide-band for aux logging, as I would have talked the customer into that route instead, as I was reporting back to him while tuning what I was seeing on my aftermarket AFR, and he was comparing them to the logs. I believe specifically the fuel compensation values and knock values is among several other logs.
We basically got the car idling great and running 3/4 throttle through the RPM band with no known issues. Of course I would have preferred audible verification, but this was simply not available to me at the time. Zero knock detected on the engine via ECU and the AFR's were looking great, he did mention that he pulled more timing out up in the mid and high ranges until we get a bigger MAF and decide if we want to run bigger injectors. (This was good enough to get it to a dyno and get it properly tuned on the rollers.)
Next we made plans to get a GT MAF and injectors. Then my tuner had a busy schedule until he left for India the following week for 3 weeks! I am stuck here with a car that the customer has already paid for a guy to tune remotely. I thought to myself.. Maybe I can just... tinker with it.. a little.. Right?
So I verified with the customer that it was OK for me to make some minor adjustments.
Popped a set of fresh FIC 775cc's in, had the GT MAF, but was recommended by the the HPA courses that you really want to try and adjust the values for one at a time. So I left the stock MAF in and went straight in to the last re-flash that my tuner left in the ROM files>edit tune snagged the last ROM that was entered in, (I knew this was the tune he had last applied)
I had shit taped to the dash-cliff notes everywhere, I was geared up head to toe with info. Grabbed my injector latency data sheet that came with the new injectors. Previously the night before I had went through the UP-Rev Nissan Tuning study guide and and found that the only things I supposedly needed were the 8v and 14v values, from there I matched the latency presets to as close as I could get them in the presets. SIDE NOTE: I would prefer it if I could just enter in every single value, but apparently that is not how the Nissan ECU of this era functions. So, I entered in those values and flashed it in there. Started the car up and it had a random dead miss. Checked for leaks and went over the engine bay, everything seemed fine. So I said something must be off in the tune, or I should have bought Injector Dynamics lol. Most likey the first one. I checked my short term fuel trims via short term compensation log, seen that they were within around 10 to 20% of the 100% it was trying to achieve. AFR on crank was incredibly rich and even after that, it would be rich and then slowly fall super lean. So I started adjusting the K value slightly, then drastically and same for the MAF. For two days I have been chasing my tail on getting this idle AFR down, as the target is set at stoichiometric 14.7 on 93 pump at idle.
Eventually I started playing with other increment values in latency and the map compensation table, I never touched the Timing table period. I got it to the point where once it was warm it was not missing randomly anymore and the AFR was hovering 14.7 So I went for a light load test drive and logged a the entire time. Slightly playing with the fuel compensation map and just performing simple tests based on percentages against the log.
End of story, I just can't get it.. There is something that I am overlooking and it is probably right in front of my face and cannot see what I am doing wrong. But randomly the car now just starts missing at idle and sometimes at light cruise a few times and I have no idea what is causing it, If there are only two value presets that you can change on the injector latency and I must be having PW issues of some sort. I have monitored knock and AFR and have never been under any heavy or even moderate load while testing on my own adjustments. I just knew that I need to get the MAF about 2v before adjusting the K value to review results. (PER UP-REV)
I have no idea. So any help would be greatly appreciated. I also still don't really understand the MAF values and what the purpose of having a MAF value and K value that work in opposite directions of each other to achieve the same goal towards the BFS. I cannot seem to find the balance theory there.
I feel that I have some understanding of what I am after, but not really sure how to get there, and most importantly get there safely and reliably.
I'm not at all familiar with the system you are using so can't give specific tips or checks for the software but from a general fault finding perspective and the not brilliant feedback i have seen on just about every brand of modified injectors other than ID I would be tempted to start again with the factory injectors to prove it still runs well as you left it the first time and then with the other MAF.
Not being particularly familiar with those cars is there a bypass fuel reg at the fuel tank, or a dead head? How exactly is it set up? Is it manifold pressure referenced or static? Are the dead time for the differential pressure the injectors are actually seeing? Could easily be one injector is a bit lazy to lift or close or has a dud spray pattern, did you go through the process of disconnecting one injector plug at a time when the idle was rough to see if one jn particular was playing up? It's easy to assume you are missing something and that new parts are good but very often, especially in automotive aftermarket they are not.
But when messing with the values would it not miss at certain times if it was dead, it would probably just be dead. I could Ohm them out and double check, but realistically I think it may be an injector minimum pulse width setting issue. Even though it calls for .91. The previous tune had .96 For a simple test, I switched it back to that. There's times where they will run buttery smooth as I am adjusting. Which is why a am leaning towards the tune as an entirety.
Also I noticed that there were six different values depending on fuel pressure to set the 8v and 14 latency values, Since the pressure is rising well above the first column would I use the higher pressure voltage values? shouldn't there be more tables for me to enter in certain latency values at different fuel pump pressure ratings?
To answer your question, yes there is a regulator in the tank. I'm also new to the 350z, so I can not tell you all the specifics. another issue with the 350z is there's nowhere to tap into the fuel rail for fuel pressure. I may be able to find it in the the ECU, but Nissan typically just calculates what the ECU is calling for, not what it actually is, same with timing.. I know my VG30DETT is that way. I wouldn't want to base the latency values of of a theoretical value.
Also, you cannot get to the plugs one at a time to disconnect them, as they are underneath the plenum.
Thank you for your response. I'll keep working on it and check back in daily to see if anyone has a hint.
Also, I have always heard that the higher CC value of the injector, the harder it is to tune the idle. Not sure how true that it is here though.
Yes but plenty of people are running a lot more injector volume:cylinder volume ratio than where your one is at. If you are running non manifold referenced I'd try to fit a gauge somewhere in the fuel line between firewall and engine to see what it doing at idle, add the vacuum it pulls for total differential and use that for dead times (if you have detailed deadtime vs pressure/voltage data) in the ecu as idle is the most sensitive to dead time. They will be out at WOT if there are not multiple ecu tables/3d matrix but it doesn't matter as the difference is a tiny fraction of open time at high load so it won't mess with air/coolant trim linearity much.
I will start there. Thanks for your time.
Any chance you ever found out what the issue was Joe?
I ended up popping the 440DW back in and started over. They fired right up and idled right away. I went ahead and ordered some 600DW as that seems to be what a lot of tuners are familiar with on this particular application, thus way if I could not figure it out myself, I had people that had been there before me that I could pick from. The DW Latency sheet was laughable and not really a data sheet.. Which I was kind of pissed about honestly, as I knew this would entail much more work for me in the long run.
Luckily I popped those in and set the Minimum Pulse Width to what UpRev recommended to start out with, which is half of whatever the stock value is. In my case that was 1.1ms, so I set it to .55 and it fired right up and idled great- made adjustments to the K value to get my idle AFR where I wanted it and had the fuel trims within 5%. I did not even adjust the Injector latency values at all, but I think that may be where my current problems are deriving from. Under load my AFR is quite unstable and very non linear.. Regardless of the the compensation/ interpolation/ smoothing. I may be going through the rpm band and see a 20% drop in trims out of nowhere and detonation for a brief second before I let out of the throttle. The only thing I can do is go up the fuel in that area-(As the timing is already retarded pretty far) From the beginning of my map, I am going from 0 additional compensation, to as much as 67% higher by the time I reach the end of the table RPM/Throttle. This just doesn't seem right to me.
I am going to guess that I am running into the issue that Slides replied with last.
Found the gold for today: https://www.hpacademy.com/previous-webinars/087-injector-dead-time/
Still, what do you do when you don't have an accurate latency sheet with new injectors. Looks like we're going to need a fuel pressure gauge on this thing. Still a ton oh holes in this setup and it's driving me nuts.
There is a table called "Map 1 fuel compensation." Think of it as a speed and throttle angle based correction to the MAF scaling, although "data byte" isn't exactly throttle angle, only proportional to it. Try flattening that table out (reduce correction to zero by setting table to 100) to reduce unpredictable changes in fuel trims.