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julex
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« on: March 25, 2012, 06:18:22 PM »
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When my car decelerates and enters fuel-cut off condition (b_sa toggles), my car seems to still inject fuel with whatever current TEMIN value holds...
This results in wideband reading high limit for AFR (19.6:1 on gauge, 21:1 in zeitronix) since no ignition takes place but injectors appear to squirt with TEMIN value anyway it is just not visible on the gauge but would explain my lower than average MPG for allroad.
Is that how its supposed to work or legitimate b_sa set should result in 0.00 injector time?
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Snow Trooper
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« Reply #1 on: March 25, 2012, 07:37:52 PM »
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teminva needs to be 0.00
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cartoons?
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julex
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« Reply #2 on: March 26, 2012, 05:45:44 AM »
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It is stock at 0.00
The weird part is that the injector on time seems to be leaning on TEMIN value instead with b_sa set, so I should be getting fuel cut off.
The question is then: does stock unaltered bin go to 0.00 injector time or it also leans on TEMIN?
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julex
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« Reply #3 on: March 26, 2012, 06:56:18 AM »
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Reading the Me7.1 doc is like pulling teeth, even the translated one... or maybe specifically the translated one  However, as far as I can tell, TEMINVA whose usage is triggered by b_va bit, is a minimum injection time during warmup unless I am missing something. As such, the TEMINVA will be used until the engine reaches 60c and then it switches to TEMIN. I heard comments recently (hi Nyet!) that you should see fuel cut off when decelerating but I just don't see it... I would appreciate if somebody could post a short piece of log where it shows injectors activity or lack of thereof on decel. |
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Snow Trooper
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« Reply #4 on: March 26, 2012, 10:20:29 AM »
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I just checked a random log and it confirms what you are saying. At 25% pedal/10% throttle, 3500 rpms in 3rd the fuel injector on time is 1.75-2.2 and desired AFR is 0.999755859375. It dips to 1.1 range on initial throttle lift and desired afr goes to 1.046875, at 0% pedal/throttle and over-run it then hovers ate 2.3-2.5 as the engine should just be acting as an air pump.... hmmm.
this from my car, i do have a bov, yet it isnt open during most over run to my knowledge. I swear I have logged 0.00 INJ before. maybe its something we did in our files?
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cartoons?
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Snow Trooper
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« Reply #5 on: March 26, 2012, 10:24:48 AM »
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I will post logs from a stock m-box and modded in a little bit, on different laptop.
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cartoons?
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nyet
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« Reply #6 on: March 26, 2012, 10:26:37 AM »
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Jared: just had an interesting exchange with julex. Julex if you get a chance, summarize it I'll work on the wiki time permitting. |
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julex
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« Reply #7 on: March 26, 2012, 10:42:26 AM »
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So here is the summary:
TEMIN appears to be used as a wall wetting/lubricating mechanism.
TEMINVA appears to be used for the same purpose when engine is cold. Since fuel doesn't evaporate even closely as violently on cold metal vs one that has several degrees, they keep it at zero.
When decelerating, depending on b_va set (b_va - warmup - TEMINVA used), the minimum injector pulse width will adhere either to TEMIN or TEMINVA. It will never fall below these values, again depending on b_va set.
It makes it then important to scale TEMIN by your injector size factor over stock size not just low enough to stop affecting idle. I believe that too large of TEMIN will give you weird rich off or low throttle, fuel dumped in overrun which will result in AFRs dwelling in rich area for few seconds ending in overshooting into lean once lambda control overshoots and popping when resuming throttle.
How I would calculate TEMIN:
[new injector flow] / [Stock Flow] = X
TEMIN / X = New TEMIN
For example:
1000cc / 350cc = 2.85
0.50 / 2.85 = 0.175 TEMIN
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nyet
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« Reply #8 on: March 26, 2012, 10:47:32 AM »
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Care to comment on TVUB interactions with TEMIN... I assume if you have a "slow" injector, TEMIN might need to be boosted a tad?
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julex
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« Reply #9 on: March 26, 2012, 10:51:32 AM »
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TVUB should take care of all inadequacies of injector IMHO. You could use TEMIN to prevent engine stall but then you sacrifice low load drivability and some economy. Wiki already provides info on what can be done to prevent misfires etc, for some injectors you just have to raise idle RPMs/torque reserve due to their bad low pulse width performance.
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nyet
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« Reply #10 on: March 26, 2012, 10:52:49 AM »
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Stupid question: I thought TVUB doesn't correct TEMIN?
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julex
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« Reply #11 on: March 26, 2012, 11:29:19 AM »
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TVUB is always added to final injector on time calculated for a given fuel mass needed in cylider.
So yes, TEMIN is corrected by TVUB. If your TEMIN is 0.5 and TVUB 0.8, then your final lowest injector on time will be 1.3ms.
Next time log te_w and te2_w variables, this is pre TVUB correction inside KRTI module. They are actual calculated injector on time values for perfect injector without any lag (0.00ms TVUB).
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« Last Edit: March 26, 2012, 11:31:24 AM by julex »
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phila_dot
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« Reply #12 on: March 26, 2012, 12:01:17 PM »
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Fuel cutoff is applied after the calculation of ti_b1(2).
It is applied to ti_ev0...7 in ACIFI.
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nyet
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« Reply #13 on: March 26, 2012, 12:03:40 PM »
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Also, ball park napkin calcs tells me that TEMIN during cutoff is still quite a bit of fuel.
I am skeptical that the injectors are still firing..
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julex
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« Reply #14 on: March 26, 2012, 12:06:29 PM »
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I like where this is going. Let me look it up.
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