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Author Topic: Wideband Lambda PID  (Read 600 times)
BoobieTrap
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« on: April 12, 2019, 01:46:13 AM »

Has anyone played with the wideband Lambda PID control?
I turned off lamdba compensation and dialed in my fueling but when I turned lambda back on, I got wild lambda oscillations!
Most likely I need to reduce lambda PID parameters, I am running high pressure (6BAR) and big injectors (1000cc).
Having looked at FR, these seem to be the likely candidates:
KFLRSG[1-4]
KFLRSP[1-4]

Unless there is an easier accepted way of reducing lambda control??
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aef
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« Reply #1 on: April 15, 2019, 04:57:19 AM »

6bar with 1000cc means your lowest possible opening time (in ms) of the injector will flood your combustion chamber with fuel.

just why?

There is no way to "tune" around this.
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nyet
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« Reply #2 on: April 15, 2019, 08:01:41 AM »

Why are you running 6 bar with 1000cc? That config will never work, ever. You're going to need an idle speed of 2000 rpm lol
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henrique.filho
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« Reply #3 on: April 15, 2019, 10:37:20 AM »

Are the oscillations happening only on low load areas?

If so, zeroing LRSZAML should help you.
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BoobieTrap
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« Reply #4 on: April 15, 2019, 01:50:55 PM »

Guys, I appreciate your feedback but I don't see how running 1000cc at 6 bar is too different from running 1500+cc injectors. This has been done before on the 1.8t with no major issues.
I like the additional headroom that 6 bar gives to turn the boost up plus theoretically there is better atomization/ better burn with higher pressure. When I was first setting these up, the car was idling even at 17-18 AFR with hardly any misfire.
I will need the headroom as I am planning on pushing 8.5k RPM and yes my fuel system can handle it.

I do not have any issues with idle anymore even at stock 760 RPM, as per one of my other posts this is also with an 80mm hemi throttle, badger5 cams and 100mm MAF (see attached).
Yes if I was to start again I may do things differently, but this has made me learn so much more and so much faster than if I stuck to the more traditional routes.

Thanks for the suggestion regarding LRSZAML, I have zeroed that a long time ago though.
Anyway, I have reduced greatly KFLRSG[1-4] and KFLRSP[1-4] and it seems to have helped so far though I still have lots of work to do on the dynamic response.
If anyone has other suggestions though I am always eager to learn more.
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aef
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« Reply #5 on: April 16, 2019, 12:27:20 AM »

But why 6bar?
Dont you have a fuel pressure regulator to increase fuel with boost?
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BoobieTrap
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« Reply #6 on: April 16, 2019, 01:38:49 AM »

It's an adjustable FPR that sets reference pressure at ambient and then keeps the pressure constant with boost/vacuum, if that's what you mean, so at 2BAR boost, the rail pressure will be 8BAR.
Or are you talking about running a rising rate FPR with ratio higher than 1:1? I think mapping that would be ever more of a nightmare?

I chose 6 BAR because that's the limit of the adjustable FPR and with ID1000 gives 1435cc flowrate. Maybe an overkill, but I can always turn the pressure down later on if I can't get it running well. However, I figured that I will start at the limit of the fuel system and then reduce if it causes me issues I can't overcome.
So far I got great idle with no misfire, and good steady state fueling, and working on the dynamic fueling which isn't quite right yet.

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aef
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« Reply #7 on: April 16, 2019, 05:18:18 AM »

weird....

These injectors have a ideal spray @ 3bar. And 4x1000cc@3bar are enough for 650+ hp.
Your 1000@6bar is 1400cc which is enough for 900+ hp.

For 900hp you will need 3+ bar of boost which is 9bar fuel pressure

Which pump will flow 1400x4@9bar lol

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