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Author Topic: Stock injectors and 5 bar fpr KRKTE  (Read 396 times)
streacy
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« on: November 10, 2019, 06:51:38 AM »

Hi,
I have installed a 5 bar fpr to get a little bit extra from stock injectors. With the larger cc per injector due to more pressure am I to calculate a new KRKTE or use stock and change TVUB values or both. Or what changes should I make?

Any help appreciated


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dilly
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« Reply #1 on: November 10, 2019, 05:44:35 PM »

someone correct if wrong but krkte is the constant which you will need to adjust. tvub is the voltage offset which shouldn't have to be changed because it is still a stock injector
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nyet
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« Reply #2 on: November 10, 2019, 06:04:34 PM »

Latency goes up a very small amount with pressure.
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dilly
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« Reply #3 on: November 10, 2019, 10:08:54 PM »

Latency goes up a very small amount with pressure.
calculated? or manually fine tuned until it is correct?
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nyet
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« Reply #4 on: November 10, 2019, 10:59:31 PM »

calculated? or manually fine tuned until it is correct?

Some injector sheets have a scaling constant vs pressure with their latency specs. Some don't...
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streacy
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« Reply #5 on: November 13, 2019, 08:13:43 AM »

Thanks for the replies,my calculated krkte is as follows

original 349cc = .0975
5 bar FPR (400cc) = .085
(just for info the car has a Bosch 044 fuel pump and a crushed 4bar fpr to 5 bar)

I have inputted this into KRKTE and am getting lean on both banks partial load (23%) and idle (-10). This is after trying to rectify the issue with FKKVS which made no difference.

I have found a spreadsheet (attached) to calculate a given krkte and tvub based on fuel trims and the resultant krkte and tvub is as follows:

KRKTE: .1110

TVUB :
7.04 : 1.28
10.07 : 0.46
12.04 : 0.28
14.08 : 0.21
17.88 : 0.13

I know that the KRKTE is wrong as it should be lower if using larger injectors but I inputted the values and drove the car around and now the fuel trims are perfect and car is running great on idle and part load, although a lot of banging off throttle (too rich with high KRKTE)

Should I log a run and see how car is running or refrain from going WOT? Very confused as to how this is happening

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adam-
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« Reply #6 on: November 13, 2019, 08:49:19 AM »

What boost pressure are you targetting?  5 bar + boost pressure could easily be 7 bar.  Can your pump actually support a good flow at 7 bar?!
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nyet
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« Reply #7 on: November 13, 2019, 09:40:42 AM »

Please supply a proper log.
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prj
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« Reply #8 on: November 13, 2019, 10:21:40 AM »

I don't see how you go from 349cc to 400cc.

If 349cc is given at 4 bar pressure:
% expr sqrt(5.0/4.0)*349
390.1938620737133

KRKTE should be:
% expr 0.975/sqrt(5.0/4.0)
0.872066511224918

3 bar pressure:
% expr sqrt(5.0/3.0)*349
450.5570626087962

% expr 0.975/sqrt(5.0/3.0)
0.7552317525104463

No reason to touch FKKVS, TVUB will need a bump of 2-4%.
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Blazius
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« Reply #9 on: November 13, 2019, 11:38:53 AM »

I've seen injectors with 0.20 ms @ 14v to 0.40 ms increase on lower voltage when going up in pressure , obviously not stock injectors but something to keep in mind. Regardless,calculated values and fuel trim adjustment should get you in the 5% stft area.
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streacy
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« Reply #10 on: November 13, 2019, 03:00:33 PM »

As suspected PIG RICH,

Thanks prj for the KRKTE values, I was incorrect. I inputted the new value and upped tvub by 4%. I will post a full log but it does still look like partial trims are +10 on both banks. Can I adjust tvub on certain voltages to account for this?

EDIT: went for a drive but couldn’t get a log but checked fuel trims on vagcom and they were -5 idle and +18 partial

Any hints on what could be causing this?

Will post a log tomorrow

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adam-
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« Reply #11 on: November 14, 2019, 02:18:09 AM »

... a crushed 4bar fpr to 5 bar)
Have you measured static pressure?  Is it actually 5 bar?  Also, can your pump sustain +7bar at a decent flow?

Flow rate PLUMMITS when you ask for loads of pressure...
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streacy
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« Reply #12 on: November 14, 2019, 04:00:31 AM »

Static pressure i have checked without vac (gauge inline reads 5.2bar)

The fuel pump is a genuine Bosch 044 delivers 200LPH at 5bar and has a max working pressure of 12bar, so i would assume its within its capabilities though i have not ran the car with the gauge attached to see pressure while driving.

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streacy
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« Reply #13 on: November 14, 2019, 09:14:10 AM »

See attached Log 1

« Last Edit: November 14, 2019, 09:18:02 AM by streacy » Logged
streacy
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« Reply #14 on: November 14, 2019, 09:23:34 AM »

See attached Log 2

Apologies on the two post's, could not upload the two logs on the same post for some reason.

Log 1 is done with calculated prj's krkte 0.875 (after run vagcom 032 showed partial +22)

Log 2 is krkte + 15% primary via lemmiwinks (after run vagcom 032 partial is 7%)

I know i do not have a wideband which is needed but still confused at the whole lot because injectors arent maxxed (duty cycle 75% max). But partial trims are still looking for more fuel. Can anyone shine a light on it? Is this a hardware issue i.e. fuel pressure reg or fuel pump or mad MAF?

I also have a few questions about engine load being so low along with MAF values being low & boost not sustaining 18psi (wg duty cycle dropping off). Are they being regulated by knock or AFR?

Any help appreciated
« Last Edit: November 14, 2019, 09:49:24 AM by streacy » Logged
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