So heres the back story. 2005 Altima, VQ, using Uprev Osiris. Ran my other stock block super lean because i didnt have an AFR gauge to monitor it. Was running 14.1ish @ wot when targets were set to 12.5 @ WOT. This is N/A, not FI. Figured the stock crap fuel pump was going since i have full bolt-ons, custom intake manifold, and cams. This was with the completely stock fuel system that this happened.

So i bought an AAM stage one return system, made it work on the FWD platform. Also installed an Aeromotive 340 pump, and replaced the entire assembly because i thought maybe the fuel filter was clogged also. The fuel pressure maxes out at around 55-56psi, which I think it low for maxed out, without vacuum. Anyway, the difference between the target and actual AFR then went down some, but still wasnt perfect but was very close last time i checked it.

Since then, put in my built low comp block for boost this winter. Broke it in finally, did a few pulls and checked the log. Found my AFR is AGAIN off by about 1.5. Target was set to 11.8 and it was damn near 13.3 AFR. So i set it to 10.3 So it runs high 11's @ wot, even thought im going to stay away from that until i get this problem figured out. The lower the fuel pressure is, the bigger the gap between the Actual AFR and Target AFR is. Its at 56psi now, if i put it to 50 its more like 2 AFR off instead of 1.5..

1. Only thing i can think of is that the wiring to the fuel pump is too small and cant carry enough amperage to get the pump to run at full capacity, causing the fuel pressure to drop @ wot. (wish i had a gauge inside the car for this too) or

2. The stock injectors cant handle what the engine needs, even though they are only at 83-84% duty cycle on the logs, so they should be fine i would think.

Anybody got ideas to try? I may try just running a wire from a better power source to the fuel pump and see what happens, but can i run a power wire straight from the alternator/starter distribution point and not fry the fuel pump or wires in doing so?

 

All this means is you need a full tune not just playing with the target map. You have to make changes to K, MAF and compensation tables to bring the actual close to target.

 

Why would it happen when it was on a completely stock map with the entire stock fuel system too? Shouldnt the K vaules be nearly the same since its running on stock injectors still?

I know theres alot more to tuning then i really know how to get into and mess with, but i would think if it did it stock and now, that there may be a problem somewhere. But i do agree that tuning is the key. Forgot to mention before, that it intermittently starting having hot starting issues when this started happening(extended crank before it started), and it still does have them, which i know thats tuning, but i never changed anything when it starting doing it stock, which is kind of weird i think.

 

Even OEM stock down to the bone the actual AFR is never close to target. Most VQ's with a slew of bolt-ons and no tune are in the high 13's low 14's as well. You have to keep in mind the ECU is shooting in the dark on those targets -- it's completely open loop at WOT. I would recommend reading the uprev 101 thread in the tuning section.

 

i dont really remember what it was when i first logged it when i got it, but it was rich. It was pretty much right on target after i adjusted the target and made the compensation 100% for a few months, because i checked it periodically and it was fine, then of course when i stopped checking it, it went wrong lol. I believe you that it probably is the tune, i just find it weird how it happened.

You think that 56psi is fine from the pump without having boost pressure to up the pressure?

 

Like DJ said, target isn't even half of the battle.

As for 56psi base with no boost reference... depends how much boost you intend to run. I would be ok with it for a 10psi or so setup, but wouldn't recommend 20psi etc

 

In open loop it doesn't use a target map. It will run the directed injector pulse (or whatever the weird input is) on the base fuel map.

 

ok. Glad its just a tuning thing and not an actual problem with the car, that was my concern. I'll let the professionals, like Hal, tune it when it is boosted. I have way less of a clue what im doing then i thought i did lol.

And yea i only have the fuel pressure so high now due to the tune and AFR being off. Once its boosted it will be running a lower base pressure, like 45 or something.

Thanks for the input guys

 

Actually this is incorrect. It still uses the target map as part of the variables to come up with the final IPW no matter what (the full equation is in one of the Osiris manuals..). It just won't do any corrections at WOT to bring it closer to target if it happens to be off for whatever reason. Side node - A cool thing about the GTR ECU is that it's full time closed loop.

 

True, but I was basing my response towards the knowledge level of the person asking. So technically yes but it does not use the target a/f map in order to adjust a/f to reach a desired a/f. Does that satisfy your doctorate level education in engines?

I don't talk to my patients about the inhibitory effects of gabapentin on the posterior horn of the spinal cord when they ask about why they have elbow pain either.....I answer in a manner that they would understand.

 

Well written binder. Another advantage of the Haltech i guess, having closed loop.

Thanks for the info guys.

 

No need to get pissy. Just trying to reduce possible confusion.

 

Also something to keep in mind is that both banks can run different AFR's, probably not related to your situation but worth mentioning for when your tuning. I too have a FWD block.

 

I was just hunting around for anyone with the above issue actually. My Haltech Dual widebands were properly calibrated but I have as much as 0.03 Lambda difference in readings.

Initially you'd assume this is due to injector flow or difference in banks, but the kicker is the difference inverts randomly. By this I mean in one logged, held MAF value I'd receive:

Left bank- 0.95
Right bank- 0.97

Then it would invert:

Left bank -0.97
Right bank- 0.95

So this tells me that it could be an issue with sensor accuracy? Not something I expected from brand new Haltech units. 0.01-0.03 difference may seem minimal, but that's a full 1-3% when you're doing calculations and calibrating your MAFS, etc. It's a HUGE difference when you're trying to accurately tune/calibrate.

I am completely stuck on this one, and it's holding up my calibrations, which is halting my tuning. Can anyone help with some insight on this one? Sorry for the longwinded post, just trying to clarify.

 

Quite a few high hp full stand alone guys on other platforms run closed loop the entire time as well. I actually have a full closed loop map built on my haltech. It works really well. I have been running my open loop setup recently because I'm fine tuning some boost controller settings but most of the summer I ran closed loop in the boost cells. Rich (str8dum1) suggested it to me since I was switching between e85 and pump gas. With +/- 40% correction allowed I didn't have to worry about the percentage of mixture. I guess that's how a lot of flex fuel vehicles work if they don't utilize the fuel sensor like GM does.

Not really being pissy just giving you a hard time about going into too much detail with someone who doesn't have near the background in cars and tuning. Between us and other people that tune I was over simplifying but it sounded like the OP here needed a simple explanation. No hard feelings meant by it.

 

Most likely its not the calibration, its the actual reading. I still do not know the reason, I just tune banks individually. Here is my AFR for both banks:

 

Mine is about 0.5 a/f different between banks in boost... had to adjust the bank cyl trims to get them in line. By doing so I caused the reverse issue in closed loop but the ECU is able to correct them (you can see it adding a little fuel to one bank and subtracting from the other).

 

as for closed loop at WOT, yea I know standalones do it but it's not very common for stock ECU's to do it especially with boost. It's new for nissan.

About the pissy comment, no problem, I was thinking more of the community as a whole reading the thread not just the OP. It seems he already understood that the target map was affecting his open loop a/f, but your statement just didn't seem like the best way to explain it at least for others who might not be on the same page as the OP.

 

Mine was only at certain load cells as well. Usually happens on boost spool and once the boost equalizes it's normal. With the haltech I can adjust it bank to bank and only in certain load cells so it didn't affect my vac map. Bonus features for spending all that extra money

Ya, it's not common at all and I didn't know about it until Rich told me.

And I understand the reason for your detailed explanation.

 

Matt @ haltech is saying this is fairly normal (1-3%) difference in banks on a V-engine.

So my question is how to correct this. I'm using the Haltech also, Platinum Red Box. Haven't seen bank-bank tuning option, just specific injectors, is this what you guys are altering?

Any advice and help here would be awesome, I was really trying to get the MAFS(air flow) into calibration before even touching fuel, but now I'm feeling a little lost because I have to alter stuff just to get my Air flow Calibrated.