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s5fourdoor
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« Reply #15 on: November 06, 2012, 05:50:03 PM »
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somebody help us tie KFLF into this discussion...
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fknbzn
Newbie
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« Reply #16 on: November 20, 2012, 04:03:00 PM »
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"According to Bosch documentation, FKKVS is for compensating for pulses in returnless fuel system. This could be why it is all 1s in M-box, since S4s do not have returnless fuel systems."
Grabbed that right from the wiki. Why is the map all 1.00 in my B5, and in B6s they are not? Not trying to argue here, just genuinely curious.
A4 b5's have a fuel return and b6's have a returnless fuel system. |
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2001 A4TQM - Bolted
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prj
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« Reply #17 on: November 21, 2012, 06:48:43 AM »
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The RS4 has FKKVS corrections because it's injectors are non-linear.
Once again people, FKKVS is used for linearization of the fuel system. Forget this "returnless" business, it has nothing to do with it.
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sn00k
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« Reply #18 on: November 21, 2012, 11:02:50 AM »
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what prj said.
ive named and used this map for injector linearization since about 1.5 year back.
i use FKKVS to counter STFTs.. the lambda-correction.
even tho the LTFTs show 0-0.3% and everything is set up right in TVUB and KRKTE, you can still have STFT fluctuations of +-10% or even more with some injectors without adding to the LTFTs, tuning FKKVS will fix this, and once corrected will generate very linear fueling.
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nyet
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« Reply #19 on: November 21, 2012, 12:03:13 PM »
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I'm still not you are all actually dialing out fuel injector non-linearity. IMO you're generally dialing out MAF non-linearity.
If, on the other hand you have a fuel injector that you KNOW is non-linear and it can't be compensated for via TVUB, then fine.
PRJ: what non-linearity other than latency do you think you are correcting for?
Certainly pressure related non-linearity can't be compensated for by FKKVS anyway.
More importantly, when you are doing fueling corrections based on trims, how do you know if you should correct the MAF or the injector?
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prj
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« Reply #20 on: November 21, 2012, 12:05:40 PM »
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PRJ: what non-linearity other than latency do you think you are correcting for? Injector non-linearity. Please read about injectors and their parameters. Offset is something different to non-linearity... Come on, this is first principles. |
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sn00k
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« Reply #21 on: November 22, 2012, 05:12:22 AM »
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More importantly, when you are doing fueling corrections based on trims, how do you know if you should correct the MAF or the injector?
knowing the oem MAF and injectors were calibrated pretty much "spot on", and then swapping injectors ONLY, with a known MAF, intake tract etc tuned by the bosch-engineers. once injectors = spot on after tuning FKKVS, and fueling is linear, i swap the MAF, tract etc and correct this one.. or the other way around.. one piece at a time. TVUB can never compensate for non-linearity, that is voltage offset and adds to the OVERALL pulsewidth.. yikes. what do you do when 14ms pulsewidth at 3000rpm gives you 10% less fuel then its supposed to.. but 13ms and 15ms gives you the correct amount.. well, you log injector DC, rpm, STFTs and O2s.. and you tweak the FKKVS accordingly. |
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jibberjive
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« Reply #22 on: November 22, 2012, 09:00:12 AM »
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Has anyone here logged a dead stock car with both a wideband and the normal variables? I'm curious how spot on requested is with actual AFR on the stock calibrated hardware. Anyone know?
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prj
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« Reply #23 on: November 22, 2012, 09:59:23 AM »
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Has anyone here logged a dead stock car with both a wideband and the normal variables? I'm curious how spot on requested is with actual AFR on the stock calibrated hardware. Anyone know?
On my RS4 it was bang on. Then again, my RS4 is probably what you guys call Stage 3+. |
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nyet
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« Reply #24 on: November 22, 2012, 10:32:46 AM »
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On my RS4 it was bang on.
On all the stock s4's i've logged, also dead on Then again, my RS4 is probably what you guys call Stage 3+.
Oh please. Stock RS4 is weak. |
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nyet
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« Reply #25 on: November 22, 2012, 10:37:14 AM »
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Injector non-linearity.
Please read about injectors and their parameters. Offset is something different to non-linearity...
No. Latency is one component of non-linearity. For all solenoids, it is the single most dominant source of non-linearity. Look at any injector spec; they're most "wrong" at the bottom of their range, independent of duty cycle, and directly dependent (but also not linearly so) on pulsewidth. Come on, this is first principles.
Yes. So answer the question. It should be easy. What kind of non-linearity? If you *know* what it is, you don't have to tune empirically, which is what I said in my original post (but you edited it out). And, as I pointed out, if you modified your MAF or intake, you definitely can't tune injector non-linearity empirically, because you don't know if your trims are non-zero due to MAF or injectors. |
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prj
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« Reply #26 on: November 22, 2012, 05:19:27 PM »
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Oh please. Stock RS4 is weak. Says the person who probably never drove one :p |
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prj
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« Reply #27 on: November 22, 2012, 05:22:41 PM »
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No. Latency is one component of non-linearity. For all solenoids, it is the single most dominant source of non-linearity. Look at any injector spec; they're most "wrong" at the bottom of their range, independent of duty cycle, and directly dependent (but also not linearly so) on pulsewidth. You really want to tell me that the only characteristic of an injector is flow and offset? I am not going to bother arguing about this. |
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nyet
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« Reply #28 on: November 22, 2012, 05:28:28 PM »
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Says the person who probably never drove one :p
I've tuned them. On 91oct, you run out of injector almost immediately. |
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« Last Edit: November 22, 2012, 05:30:10 PM by nyet »
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nyet
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« Reply #29 on: November 22, 2012, 05:29:17 PM »
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You really want to tell me that the only characteristic of an injector is flow and offset?
No. I said most (not all) of the non-linearity comes from solenoid latency |
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« Last Edit: November 22, 2012, 05:31:05 PM by nyet »
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