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marcellus
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« Reply #330 on: January 25, 2013, 09:44:40 PM »
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It seems like, if the above was true, anybody not running a fuel pump feed to both rails would run one bank lean @ WOT. I say that because I thought the o2 was ignored past a certain load and only MAF and a bunch of maps. Since the hack was to help with STFT/LTFT, dealing with o2 voltages, do you think the car can go that lean enough to cause damage under cruise?
All I am saying is that if this is an issue, I think its an issue anybody running fuel rails with one feeding the other would have.
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Snow Trooper
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« Reply #331 on: January 25, 2013, 10:28:22 PM »
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Im running both banks oem narrow pre turbo, single oem narrow post turbo and single wide band post turbo. I have had the car back going again for a few weeks and I have been testing these new advancements from PD, the hack works perfectly, but this can be a side effect. I played around with both fuel rail setups as I have done in the past. The issue isolates to cross over tube type fuel paths. Like OEM. The ecu has no way to understand that there are two fuel rails with different amounts and pressures of fuel in them and it applies the same injector PW to all 6 cyl. It is inevitable unless you split to have a variation as the first bank removes fuel and pressure yet the second bank fed. Feel free to dispute this through your own testing, be careful. Get your injectors perfect and keep egts in place, or just listen to me as Im pretty sure I am batting 1000 on advice i give about ST setups on 2.7t, i even tell you guys how to unfuck your setups via a customer on AZ sometimes...  |
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cartoons?
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marcellus
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« Reply #332 on: January 25, 2013, 10:36:09 PM »
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Could it be due to not enough fuel pump? I just don't understand how the fuel pressure would be different in what is basically one continuous line being fed on one end and and restricted on the other.
Are you logging NB voltages at WOT pre turbo? Have you logged fuel pressure? How does a stock setup know that one bank is leaner than the other at WOT?
I am not doubting your advice, so don't take it that way. I really want to know how you figured all this out.
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nyet
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« Reply #333 on: January 25, 2013, 10:53:21 PM »
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I'm confused too  If you are running open loop, i don't see how whether or not the system is stereo (or hacked to be mono) matters.. what am i missing? again, not questioning, just would like to learn |
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Snow Trooper
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« Reply #334 on: January 25, 2013, 11:25:08 PM »
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The situation is present at all states, idle with and without trims, part with and without and most importantly WOT.
As usual it goes back to the system really wanting two inputs.
Marcellus, the situation gets worse the more pump you have because then the first bank to receive fuel is getting bombarded with it. It ends up with neither bank being spot on.
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cartoons?
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marcellus
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« Reply #335 on: January 26, 2013, 01:24:43 AM »
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Well, running a "y" in and out of my lines was on my to do list. I just never figured I could be starving one rail. I just can't help but wonder what the straight 6 guys are doing. Seems they would be up against the same problems. Feeding from one end and, and progressively starving the following injectors. They don't run bank specific fueling logically, so how do you deal with that? It's the same thing I see going on here. Maybe I just don't realize how fast injectors can deplete the rails, but I thought my rails being -8 would be enough.
Still pretty confused, but I am going to mod my lines because I don't like feeling unsure about my fueling. Especially the stuff I assume to be ok.
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jibberjive
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« Reply #336 on: January 26, 2013, 10:03:57 AM »
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The situation is present at all states, idle with and without trims, part with and without and most importantly WOT.
As usual it goes back to the system really wanting two inputs.
Marcellus, the situation gets worse the more pump you have because then the first bank to receive fuel is getting bombarded with it. It ends up with neither bank being spot on.
I'm with the confused and looking to learn party. So your post says that it is a new issue that crops up because of the 'single input' hack. I thought, by definition, that in open loop (WOT) there is no input. If this is the case, than the issue would be there independent of whether it's a big power single or twin turbo, no? Because the inputs at WOT would be the same, 0 inputs. Or does the stock ECU learn bank specific trims at closed loop operation that it extrapolates into WOT open loop, bank specific usage as well? It does seem that there is bank specific, fuel rail configuration specific calculation/compensation that the stock setup is utilizing, as this guy replaces the crossover with a bigger line and has bank specific issues because of it: http://www.audizine.com/forum/showthread.php/513394-PSA-Don-t-blow-your-motor-because-of-my-stupidity?highlight=fuel+rail |
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phila_dot
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« Reply #337 on: January 26, 2013, 10:11:59 AM »
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Fuel trims are always active
Edit: They only learn under certain conditions
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nyet
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« Reply #338 on: January 26, 2013, 10:41:04 AM »
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In the case of open loop, only the the long term trims are active.. so the issue with mono vs stereo is only if having a hacked stereo is causing your trims to look identical when they should look drastically different? This makes no sense, since IIRC there is no load/rpm based long term trim (other than idle/part) If you are running out of fuel in one bank only at high rpm/load, and your part trims would be the same (if you had a proper stereo setup), how would having a stereo setup save you? Not criticizing, just confused |
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jibberjive
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« Reply #339 on: January 26, 2013, 11:06:11 AM »
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Fuel trims are always active
Edit: They only learn under certain conditions
Yeah, the multiplicative, but if there's a major imbalance at relatively low load (closed loop), it seems logical that it would likely be much worse as it choked off in higher flow (as in not something a linear scalar would fix). That's just my gut feeling though, and that may not be the reality. |
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britishturbo
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« Reply #340 on: January 26, 2013, 11:10:17 AM »
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I have every confidence in my fuel setup.
I have -8 AN rails with an -8 AN hose between them.
The FPR is in the end of the chain and I have more than enough fuel flow. Many many race cars run the same setup with no problem.
And my LTFT is like -2% so there is very little correction being done at WOT.
I do not agree with this theory... but feel free to prove otherwise :-)
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« Last Edit: January 26, 2013, 11:15:35 AM by britishturbo »
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Snow Trooper
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« Reply #341 on: January 26, 2013, 12:28:43 PM »
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Fuel trims are always active
Edit: They only learn under certain conditions
Exactly |
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Snow Trooper
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« Reply #342 on: January 26, 2013, 12:31:42 PM »
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In the case of open loop, only the the long term trims are active.. so the issue with mono vs stereo is only if having a hacked stereo is causing your trims to look identical when they should look drastically different? This makes no sense, since IIRC there is no load/rpm based long term trim (other than idle/part) If you are running out of fuel in one bank only at high rpm/load, and your part trims would be the same (if you had a proper stereo setup), how would having a stereo setup save you? Not criticizing, just confused Yes, the trims should be significantly different on a large pump, cross over rail system and they cannot be different with the hack. |
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cartoons?
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Snow Trooper
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« Reply #343 on: January 26, 2013, 12:33:43 PM »
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I have every confidence in my fuel setup.
I have -8 AN rails with an -8 AN hose between them.
The FPR is in the end of the chain and I have more than enough fuel flow. Many many race cars run the same setup with no problem.
And my LTFT is like -2% so there is very little correction being done at WOT.
I do not agree with this theory... but feel free to prove otherwise :-)
You mean the rails with threaded in AN flares that taper down to approx -6 size at the fitting that expand to -8 hose ID and then contract again at the next fitting? Yeah you will have the problem also, it isnt a theory. You LTFT is based off an average of one rich and one lean bank at this point. Hardly optimal. |
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cartoons?
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Snow Trooper
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« Reply #344 on: January 26, 2013, 12:37:57 PM »
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Well, running a "y" in and out of my lines was on my to do list. I just never figured I could be starving one rail. I just can't help but wonder what the straight 6 guys are doing. Seems they would be up against the same problems. Feeding from one end and, and progressively starving the following injectors. They don't run bank specific fueling logically, so how do you deal with that? It's the same thing I see going on here. Maybe I just don't realize how fast injectors can deplete the rails, but I thought my rails being -8 would be enough.
Still pretty confused, but I am going to mod my lines because I don't like feeling unsure about my fueling. Especially the stuff I assume to be ok.
The straight six guys generally have one long consistent rail. With one long rail or a V setup and big lines, rails and fittings it isnt as much an issue. For the way many of us run our rails, if we have all -8 or -10 sizing we would be better off. All these aftermarket rails like IE and 034 use fittings off the rail that are -6 sized so there are restrictions and then in turn losses from one bank to another. If we split them there will still be restrictions but at least the banks are seeing the same exact flow and pressure. |
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