carlossus
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« on: March 26, 2011, 05:55:59 AM »
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Can anyone educate me as to the relationship between KVB (cm^3/min) and the mpg display of fuel consumption?
I'd like to re-calibrate and although I can get a decent figure for mpg I'm not sure how to adjust KVB to scale it properly.
Cheers,
C.
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TTQS
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« Reply #1 on: March 26, 2011, 08:32:48 AM »
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Can anyone educate me as to the relationship between KVB (cm^3/min) and the mpg display of fuel consumption?
I'd like to re-calibrate and although I can get a decent figure for mpg I'm not sure how to adjust KVB to scale it properly.
Cheers,
C.
Hi Carlossus. This is an interesting question. I'd like to know how to do it as an academic exercise so I might look into it further if I have time. I recall seeing something in the funktionsrahmen about the displayed fuel consumption. However, if you just want to correct your displayed fuel consumption to more accurately reflect the actual gas mileage you are getting, this can be done easily with VAG-COM/VCDS. Details are in the attached text file because I'm still experiencing truncation of posts. TTQS |
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« Last Edit: October 23, 2011, 02:45:21 AM by TTQS »
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carlossus
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« Reply #2 on: March 26, 2011, 12:47:51 PM »
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Thanks TTQS. That's probably an easier way to go although I'd really like to understand how the constant is used. Unfortunately my engine mount just let go so fuel consumption is low priority now  |
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TTQS
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« Reply #3 on: March 26, 2011, 02:06:04 PM »
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Thanks TTQS. That's probably an easier way to go although I'd really like to understand how the constant is used. Unfortunately my engine mount just let go so fuel consumption is low priority now O.k., I did a quick translation of pages 1593 & 1594 of the funktionsrahmen for the KVA 41.40 module with equations and constants. See attached Word 97-2004 format document. TTQS |
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« Last Edit: October 23, 2011, 02:47:05 AM by TTQS »
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carlossus
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« Reply #4 on: March 26, 2011, 02:43:09 PM »
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Thanks for taking the time to do that. I'll eventually learn to search the funktionsrahmen for myself <insert face-palm here>.
So, that's pretty clear (apart from RKTE_W = Relative proportion tank mixture VENTILATE?). Seems if KRKTE is calculated correctly we shouldn't need to mess with KVB.
So, using the VAGCOM method presumably alters adaptation channels... does anyone know if these get wiped when we Re-Flash?
Ta.
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TTQS
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« Reply #5 on: March 27, 2011, 03:08:47 AM »
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1. RKTE_W = Relative proportion tank mixture VENTILATE?).
2. So, using the VAGCOM method presumably alters adaptation channels... does anyone know if these get wiped when we Re-Flash?
Yeah, I don't think there should be any need to change any of these parameters except KRKTE if, for example, larger injectors and/or a higher pressure fuel pump is used. On point 1, that translation is rough, I'll have another look at some point and tidy it up and add the diagrams for completeness. RKTE_W should be "relative proportion of fuel-air mixture in the fuel tank breather" I think. My laptop is dead at the moment (NTLDR files got accidentally deleted and I don't have a boot CD-ROM because both operating system and applications are on a recovery disk) so I was using my wife's Mac which I'm not used to. On point 2, I would think this is almost certain. I believe these will also all clear if power is interrupted to the ECU, e.g. if you have a flat battery or disconnect it. TTQS |
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« Last Edit: October 23, 2011, 02:47:30 AM by TTQS »
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coreyj03
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« Reply #6 on: March 27, 2011, 09:01:08 AM »
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1. RKTE_W = Relative proportion tank mixture VENTILATE?).
2. So, using the VAGCOM method presumably alters adaptation channels... does anyone know if these get wiped when we Re-Flash?
Yeah, I don't think there should be any need to change any of these parameters except KRKTE if, for example, larger injectors and/or a higher pressure fuel pump is used. On point 1, that translation is rough, I'll have another look at some point and tidy it up and add the diagrams for completeness. RKTE_W should be "relative proportion of fuel-air mixture in the fuel tank breather" I think. My laptop is dead at the moment (NTLDR files got accidentally deleted and I don't have a boot CD-ROM because both operating system and applications are on a recovery disk) so I was using my wife's Mac which I'm not used to. On point 2, I would think this is almost certain. I believe these will also all clear if power is interrupted to the ECU, e.g. if you have a flat battery or disconnect it. Doug the adaption channels wont necessarily reset when power is removed. i took out my ecu and removed the eprom then put it back in and the adaption channels were still they way i had them. but i have also done it and had to reset the adaption channels. |
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carlossus
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« Reply #7 on: March 27, 2011, 09:55:05 AM »
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My understanding is that adaptation is non volatile, stored on EE. it's just that Tony's software warns of losing adaptation info when you flash. I flash a fair bit so it would be a pain to have to keep using VCom afterwards.
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Tony@NefMoto
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« Reply #8 on: March 28, 2011, 10:26:39 AM »
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So, using the VAGCOM method presumably alters adaptation channels... does anyone know if these get wiped when we Re-Flash?
Flashing over OBD sets the adaptation channels to defaults. The way I scaled my KVB, was I got my KRKTE scaled correctly, then I scaled KVB by the same amount. |
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carlossus
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« Reply #9 on: March 28, 2011, 11:05:38 AM »
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So, KVB is the average flow rate of the injectors given the conditions used to calculate KRKTE?
It should then be scaled if FPR pressure is raised?
It should be scaled according to Bernoulli's eqn, hence in direct proportion to KRKTE?
Phew, aaaand breath.
Damn, cant get this to display correctly...
TMAIN
---
\
TKVAG = / (rk_w + rkte_w) * KRKTE [ms] * KVB [cm
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« Last Edit: March 28, 2011, 11:10:03 AM by carlossus »
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carlossus
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« Reply #10 on: March 28, 2011, 11:10:35 AM »
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 sorry nyet, I genuinely tried to use wiki format but lost the will to live. Have TTQS' version instead. |
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« Last Edit: March 28, 2011, 02:29:53 PM by carlossus »
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nyet
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« Reply #12 on: March 28, 2011, 03:18:25 PM »
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Heh. I feel your pain. FYI something like: <math>TKVAG = \frac{\sum_{t=0}^{TMAIN} (rk_w+rkte_w) \times KRKTE [ms] \times KVB [cm^3/min] \times 1000}{Kd [mm^3/s] \times 0.0512 [ms] \times 60000}</math>
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« Last Edit: March 28, 2011, 03:21:15 PM by nyet »
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carlossus
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« Reply #13 on: March 29, 2011, 06:34:50 AM »
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So, to close off the thread: -
KVB is injector flow rate.
If you up the fuel pressure, the new flow rate is calculated by: -
FN = F0 x SQRT(PN/P0),
FN = New flow rate
F0 = Flow rate at old pressure
PN = New fuel pressure
P0 = Old fuel pressure
...BUT if you also up the boost then is the flow rate is affected by the differential pressure across the injector or is this negligible? I have seen differing rates quoted for the EV6 injector at 3 bar.
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Tony@NefMoto
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« Reply #14 on: March 29, 2011, 02:13:33 PM »
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The rising rate fuel pressure regulator handles keeping the fuel pressure the same relative to the intake pressure.
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