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Gonzo
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« on: September 24, 2012, 06:51:12 PM »
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We are all aware of the equation to calculate KRKTE, however, it becomes cumbersome having to use it all the time.
Something I have found to help me out a lot is make a KRKTE cheat sheet with data I obtained from multiplying KRKTE by the stock injector size.
For example: Stock AWP injector size is 317cc and stock KRKTE is 0.10311
So you take 0.10311 * 317cc = 32.68587 <--- That's your cheat number.
Now if you want to use the newer Bosch 415cc then you take 32.68587 / 415cc = 0.0787612 <-- That's your new KRKTE.
Now go for a spin and drive for a long time. After you are done you will get your long term fuel trim. Its a % number so multiply that % * your KRKTE and add or substract based on your fuel trim and go for a spin again. You should have your long term fuel trim pretty much right on the dot after 2 or 3 revisions.
Now the cool thing is that you can use this cheat number with any decent Bosch injector and it will always get you close enough.
If you use the regular formula/equation, you will still get pretty much the same number, but using this method saves time.
Eg.:
415cc/min x 0.684= 283.86
50.2624*(1.781/4)/283.86 = 0.0788393348833932
vs
32.68587 / 415cc = 0.078761133
I know most of the advanced guys know of this already but it should help a lot of people starting out.
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Bische
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« Reply #1 on: September 25, 2012, 12:21:03 AM »
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Hmm, my stock injectors are 292cc's and stock KRKTE is also 0.103xx. Are those 317cc @ 4bar? I need to double check the partnumber on my stockers, I calculated my KRKTE the way you described and got 0.030xxx. If I use the FR formula I get 0.028xxx, but if my injectors are infact 317cc@3bar that would equal a KRKTE of 0.033xx using this method, huge difference  |
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« Last Edit: September 25, 2012, 12:26:14 AM by Bische »
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Gonzo
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« Reply #2 on: September 25, 2012, 05:40:59 AM »
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Hmm, my stock injectors are 292cc's and stock KRKTE is also 0.103xx. Are those 317cc @ 4bar? I need to double check the partnumber on my stockers, I calculated my KRKTE the way you described and got 0.030xxx. If I use the FR formula I get 0.028xxx, but if my injectors are infact 317cc@3bar that would equal a KRKTE of 0.033xx using this method, huge difference Nope. 317 @ 3bar. What year/model is your car? |
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Bische
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« Reply #3 on: September 25, 2012, 06:53:32 AM »
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Nope. 317 @ 3bar.
What year/model is your car?
02' A4 AVJ |
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Gonzo
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« Reply #4 on: September 25, 2012, 08:00:41 AM »
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02' A4 AVJ
http://www.usrallyteam.com/content/tech/18t_injectors.html You got 205cc @ 4bar according to that page. I used this method to tune for Audi TT injectors on a Audi B6 1.8T and it got me within 9% LTFT right off the bat, but the B6 uses different injectors as well. BTW when you start changing fuel rail pressure, KRKTE seems to get harder to calculate. |
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« Last Edit: September 25, 2012, 08:13:10 AM by Gonzo »
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prj
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« Reply #5 on: September 25, 2012, 08:33:34 AM »
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http://www.usrallyteam.com/content/tech/18t_injectors.html You got 205cc @ 4bar according to that page. I used this method to tune for Audi TT injectors on a Audi B6 1.8T and it got me within 9% LTFT right off the bat, but the B6 uses different injectors as well. BTW when you start changing fuel rail pressure, KRKTE seems to get harder to calculate. That is because pressure and flow are related through a square root curve, rather than linear as well as injector offset is dependent on pressure. |
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Gonzo
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« Reply #6 on: September 25, 2012, 09:05:29 AM »
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That is because pressure and flow are related through a square root curve, rather than linear as well as injector offset is dependent on pressure.
Bingo! Using this method in this thread when changing fuel rail pressures will not work properly. The injector offset changes dramatically as you increase fuel rail pressure and this method does not compensate for it. |
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Bische
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« Reply #7 on: September 25, 2012, 09:42:48 AM »
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http://www.usrallyteam.com/content/tech/18t_injectors.html You got 205cc @ 4bar according to that page. I used this method to tune for Audi TT injectors on a Audi B6 1.8T and it got me within 9% LTFT right off the bat, but the B6 uses different injectors as well. BTW when you start changing fuel rail pressure, KRKTE seems to get harder to calculate. 205cc@4bar lol, if I only knew.. haha But this makes things even more wierd, why is my stock KRKTE 0.10356 if the injectors are infact 178cc@3bar? 178 x 0.10356 = 18.43368 18.43368 / 980 = 0.01881 This is really wierd, and why is it done like this? My injectors cant be as small as that, im going to check the partnumber to verify. Here is a link to the binary I use: http://nefariousmotorsports.com/forum/index.php?topic=1103.0 |
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« Last Edit: September 25, 2012, 09:47:36 AM by Bische »
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Bische
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« Reply #8 on: September 25, 2012, 10:36:52 AM »
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found my error, my KRKTE factor is wrong at 0.000111.
If I put in 0.000167, ~everything lines up at 205cc@4bar.
BUT, according to that site, both the "282cc" injectors used in US spec cars have the same PN as my Euro spec 205cc injectors. And the KRKTE is the same 03A5 from my Euro binary and the US binarys.
Ninja edit #10: Gonzo, they are 205cc@3bar not 4bar.
Something is fishy about those CC numbers on that site, doing the math backwards from my flowtested injectors @980cc using my real world KRKTE would put the stock injectors at ~308cc's.
But thats really rough as my wall wetting is still stock and my injectors are not likely 100% linear at partial throttle.
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« Last Edit: September 25, 2012, 11:15:19 AM by Bische »
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Gonzo
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« Reply #9 on: September 25, 2012, 11:53:09 AM »
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I used 282cc for the Audi B6 1.8T (with the returnless fuel system) with this method and then used 386cc for the new injectors (since they were TT injectors) and this got me super close (within 9% like I stated before). Check to see what injectors you really have. Maybe I'll take a look at your BIN and compare to the North American spec one.
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nyet
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« Reply #10 on: September 25, 2012, 12:10:48 PM »
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I agree. The stock numbers are out of whack given the typical KRKTE values I use for other injectors.
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nyet
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« Reply #11 on: September 25, 2012, 12:12:33 PM »
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That is because pressure and flow are related through a square root curve, rather than linear as well as injector offset is dependent on pressure.
Even given that, I cannot square my KRKTE values with the stock injector flow rate here: http://s4wiki.com/wiki/Fuel_injectors |
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Snow Trooper
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« Reply #12 on: September 25, 2012, 02:18:38 PM »
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I have been saying forever that I am pretty sure we are all wrong about stock injectors specs.
I think they are 319 and not the commonly thought 349
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« Last Edit: September 25, 2012, 02:21:42 PM by Snow Trooper »
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cartoons?
6A 61 72 65 64 40 76 6C 6D 73 70 65 63
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RaraK
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« Reply #13 on: September 25, 2012, 05:59:05 PM »
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b6 a4 is a static fuel pressure, may have something to do with why krkte is the way it is?
fuel pressure inceases/decreases should NOT be handled in krkte when using pretty much anything much bigger than stock injectors, i use tvub to deal with fuel pressure increases
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Bische
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« Reply #14 on: September 26, 2012, 01:26:48 AM »
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Stock injector PN
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