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Author Topic: KFLDHBN - scaling for different turbo  (Read 1968 times)
blairl
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« on: September 06, 2021, 09:53:47 AM »

I was hoping I could get a sanity check from the experts here.  I'm still new to this and this seems like the right place to post this.

I'm working on a tune for my Golf mk4, AWP 1.8T.  The car originally came with a "K03s" (I think K03-053).  It is now equipped with a Borg Warner "K04-001" (p/n 5304 950 0001, compressor map attached).  My car uses a 06A 906 032 HS ECU, xdf and bin are attached.  

My understanding is that the purpose of KFLDHBN is:
  • to protect the turbocharger from overspeeding
  • Overspeeding is likely to happen when air density is low and a high PR is required to meet requested load
  • Conditions like this exist with very high IATs, high altitudes, or both

My intention is that by modifying this map first, I should have a sane PR limit in place so that the turbo is protected if I screw up somewhere down the line.  I do not intend to run close to the MAP limit so I hope these assumptions are valid.

My process for modifying KFLDHBN is as follows:
  • Calculate the flow required for the engine at VE=1 using the inputs for KFLDHBN (n and IAT) and the displacement of the engine
  • Multiply this by the existing PR values in KFLDHBN.  The result of this should be the flow produced at the relevant IAT, engine speed, and PR
  • Modify the PR values used to calculate flow in the above step from the k04-001 compressor map.

Will this at least put me in the ballpark for a sane compressor pressure ratio map? Have I neglected something important?

I couldn't attach the map pack for some reason, I got it from here.
https://nefariousmotorsports.com/forum/index.php?topic=401.0
« Last Edit: September 06, 2021, 09:58:37 AM by blairl » Logged

LAMFAWKR, did anyone else find this variable funny?
prj
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« Reply #1 on: September 06, 2021, 10:13:13 AM »

You will destroy your rods before you do anything with the turbo.
This turbo on stock actuator can run 100% duty cycle forever. It's so soft that the wastegate opens under backpressure before you damage the turbo.

You put a lot of thought into something that is completely irrelevant Cheesy

To fill this map as the OEM does, you need a turbo shaft speed sensor and pressure ratio monitoring just before and after the charger.
It's not an exact science though, especially if the car has VVT.
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blairl
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« Reply #2 on: September 06, 2021, 10:35:52 AM »

Thanks prj! This would explain why I couldn't make heads or tails comparing stock KFLDHBNs to compressor maps.

In that case, I will just move KFLDHBN out of the way if I ever get to the point where boost doesn't follow LDRXN.

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LAMFAWKR, did anyone else find this variable funny?
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