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Author Topic: Am I adjusting TVUB correctly?  (Read 31557 times)
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« Reply #15 on: December 02, 2014, 09:00:22 AM »

for that method you must go through couple of cycles of adjusting long term low range and high range LTFTs followed by TVUB to get idle in checks.

Then repeat it.

The problem is that TVUB affects idle the most but it also is a natural component of injection time for any load range albeit the longer the injector is open (higher load and maf flow), the less % wise TVUB affects it.

At idle, if the injector has to open for 0.5ms with TVUB of 0.7ms, the tvub is actually larger then required pulse width of injector to reac proper mixture. If TVUB is off by 10%, it will inbalance the mixture by 0.7/0.5 = 1.4, which gives 1.4 * 10% = 14% off the proper mixture.

At higher load when the injector needs to open for 10ms, the total open time wold be 10 + 0.7 = 10.7 which gives 0.7/10 = 0.07, which gives 0.07 * 10% = 0.7% off the proper mixture.

That's why you want to get the KRKTE by riding the car hard and once you have KRTE honed down to within couple of %, you switch you attention to idle and use tony's method. Eventually you will get it right however not the way you think.

You don't add just 0.01ms across the board since adding 0.01 to 0.01 means upping it 100% while adding 0.01 to 1.00 means upping it 1%.

Instead, you need to divide intended bump (0.01 in your case) by the TVUB value at the voltage you normally operate (14v or so) and get what part of the injection time it is in % at that voltage.

For example, you want to add 0.01 to say value 3 from your example.

0.01 / 3 = 0.00333

Now you want to multiply each TVUB value by 1.000333 and you will get TVUB scaled up by 0.000333 across all value EVENLY.

To properly interpolate TVUB you need to have reliable TVUB specs from injector manufacturer. And remember, TVUB values are always given for 3bar of fule pressure. Audis usually run 4bar FPR which means the injector needs to overcome more resistance and its TVUB needs to be multiplied by some value, usually ~16% for 3 to 4 bar bump but it might vary.

I hope I didn't bore you to death.


Lifting old thread

If idle is off by ie 2% at 14V. Why cant we just add 2% of TVUB value to that row?
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ddillenger
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« Reply #16 on: December 02, 2014, 02:34:03 PM »

If idle is off 2 percent don't touch it.
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« Reply #17 on: December 03, 2014, 12:17:45 AM »

If idle is off 2 percent don't touch it.

I know that, was just an example.
What about doing it this way?
I did some math both ways, the result is almost the same???
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ddillenger
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« Reply #18 on: December 03, 2014, 01:26:07 AM »

I know that, was just an example.
What about doing it this way?
I did some math both ways, the result is almost the same???

The only way you should be adjusting TVUB is if you don't have the data from the manufacturer of the injectors. Is this the case? Otherwise, input the values you have, and use FKKVS.
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« Reply #19 on: December 03, 2014, 01:53:24 AM »

The only way you should be adjusting TVUB is if you don't have the data from the manufacturer of the injectors. Is this the case? Otherwise, input the values you have, and use FKKVS.

I have been working on my fueling a lot.
Idle is off by 6% as now.
I can not effect my idle with FKKVS??? Those tables starts at 1240 rpm. Or can I?
Or does it use first column values for rpm under 1240 as well??
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armageddon
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« Reply #20 on: December 03, 2014, 03:01:29 AM »

My fuel trims are idle -0.1; partial on normal driving are -2.0 but if I give it a spirit driving fuel trims go to -6.0, does this mean that I should adjust  KRKTE? I need this right before go to RS4 MAF
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nyet
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« Reply #21 on: December 03, 2014, 11:32:50 AM »

The only way you should be adjusting TVUB is if you don't have the data from the manufacturer of the injectors. Is this the case? Otherwise, input the values you have, and use FKKVS.

I agree.
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« Reply #22 on: December 03, 2014, 12:47:57 PM »

I know that, was just an example.
What about doing it this way?
I did some math both ways, the result is almost the same???

Remember. Axis can be rescaled. In addition, the for any values UNDER (or over) the axis, the first (or last) cell is used.

In any event, 6 percent isn't the end of the world. It's easily explained by the non-linear nature of injectors running low pulsewidths.
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nyet
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« Reply #23 on: December 03, 2014, 01:05:59 PM »

In any event, 6 percent isn't the end of the world. It's easily explained by the non-linear nature of injectors running low pulsewidths.

Also, O2 sensor accuracy drifts over time.

That said, a known good TVUB that isn't working right is also an indication that something else might be amiss in your hardware, or elsewhere in the tune.
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« Reply #24 on: December 03, 2014, 01:24:51 PM »

Good to know!!
So, TVUB should never be touched if injectors come with right manufactor data.
I had the right data, but i understood the process wrong.
It is all good now.
Thanx guys!!
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nyet
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« Reply #25 on: December 03, 2014, 01:51:02 PM »

Well, also, don't forget there is more than one way to skin a cat Smiley

So everybody has their own way of doing things.. if you can't get anything to work right, but TVUB works for you, and the results are good, well..

These are just recommendations, please take them with a grain of salt!
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« Reply #26 on: December 04, 2014, 06:58:02 AM »

Regardless of a datasheet, if the only consistency during fueling error is battery voltage, then TVUB should be adjusted.

In any event, 6 percent isn't the end of the world. It's easily explained by the non-linear nature of injectors running low pulsewidths.

This is the exact (and only IMO) time FKKVS should be used for correction.

As previously said, everyone has their own methods that will affect how you identify and correct fueling errors.
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ddillenger
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« Reply #27 on: December 04, 2014, 12:32:06 PM »



This is the exact (and only IMO) time FKKVS should be used for correction.



Alright, then how exactly would you recommend fixing fueling? KFKHFM? I've spent the time to dial in a MAF, dial in the injectors, and still needed to clean it all up under open loop.
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« Reply #28 on: December 04, 2014, 12:42:44 PM »

After a lot of logging I can say that TVUB should not be touched if you have right data.
I was chasing my tale, fixing all over fueling, and alog with that I got worse idle.
Than I tweaked TVUB  10-12%, which resulted in leaning up top at WOT.
Changeed back to original TVUB and voala, I got all the fuel all the way and then some.
The rest I fixed with Fkkvs.
So TVUB does effect overall fueling not just idle.
That was my findings.
I also found out, that I make the most power running lean on e85, afr 12.5-13. I would not recommend it though.
« Last Edit: December 04, 2014, 12:44:18 PM by Mocke » Logged
nyet
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« Reply #29 on: December 04, 2014, 12:45:05 PM »

TVUB is for correcting injector latency dependent on voltage

FKVVS is for injector non-linearity

KFKHFM is for MAF non-linearity

Now, you can ignore those guidelines and correct fueling however you want.

But randomly changing things until things are "correct" if you don't know what your underlying issue is probably not the best approach.
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