NefMoto

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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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

Latency goes up a very small amount with pressure.

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...

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

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?!

Please supply a proper log.

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%.

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.

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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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...

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.

See attached Log 1

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

Before even talking about what the pump can flow, I'm sure no one here has actually checked an FPR with a compressor and a pressure gauge and actually seen that they ALL max out at 5.4 bar and that they can't increase fuel pressure above that. even if you feed it 3 bar of boost, it will still only give you 5.4 or 5.7 bar max.

I have been thinking about this and and came to the conclusion the larger injector are required sooner or later. Now i am waiting on 550cc EV14 and i will post back after install, will initially install with 3 bar fpr and if required will increase to 4 bar

Just to finish this up, purchase 550cc Ev14's and installed and never had an issue since, i strongly recommend to this method instead of increasing fuel pressure.

Definitely a worthwhile upgrade