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Author Topic: Looking for insight on PID tuning. Log attached.  (Read 14221 times)
AARDQ
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« Reply #15 on: April 24, 2014, 07:38:42 PM »

I'm showing the same 2300 mbar/315 g/s flow as you.   My numbers are very similar to yours except that mine peak sooner.

The RS4 WG is set at about 8 psig IIRC.  But as you say, you're happy with it, so don't take this as trying to convince you one way or the other...
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stuklr
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« Reply #16 on: April 24, 2014, 09:26:49 PM »

I'm showing the same 2300 mbar/315 g/s flow as you.   My numbers are very similar to yours except that mine peak sooner.

The RS4 WG is set at about 8 psig IIRC.  But as you say, you're happy with it, so don't take this as trying to convince you one way or the other...

Huh? 315g/sec? The log I posted peaked at 375 g/sec... typo? or talking about a specific rpm?

Do you have a log to post?

I was told by Doug at frankenturbo that to run 25psi+ the gate preload must be kept high because the turbine housing internal pressure would start to push the flap open. I just checked to see if the gates moved in sync and at the same ~15psi cracking pressure before installing. Base WG pressure with the N75 unplugged is roughly 18psi. I left them at the high cracking pressure incase I wanted to run more than map limit at some point. Not something easily adjusted in car after all. In hindsight, setting the gates to less preload would have made my boost control much easier. No big deal. Its working now. 

As for drivability, it is excellent. I scaled the KFVPD axis to match the base gate pressure and its very well mannered at part throttle. No surging or hesitation. I found that info in the big turbo tuning post where Julex had said it worked well for him.

I am not finished with timing by a long shot, but my boost curve is where I want it. Will see a lot better torque curve once the second meth nozzle is in and I can finalize timing. Right now I am running the same settings I ran on 93 pump with my old K03's and a single small nozzle mounted in the driver's bi-pipe.
 
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ddillenger
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« Reply #17 on: April 25, 2014, 11:31:40 AM »

IMO, this is what you should shoot for (I still have a touch of overshoot here).

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stuklr
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« Reply #18 on: April 25, 2014, 11:56:50 AM »

I agree. That DC looks great. Little to no adjustment from the PID.

 I need to redo the DRL map. I think its just starting with the wrong base wgdc and the having to adjust alot to get it right. Second meth nozzle here and i have a free weekend ahead of me to get it setup.

Why is everyone complaining about the boost curve though? I like the current profile. Its a personal prefrence.
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nyet
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« Reply #19 on: April 25, 2014, 11:59:18 AM »

Again, i'd rather keep pressure off the wastegate during spool. maybe its just me.
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stuklr
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« Reply #20 on: April 25, 2014, 12:07:38 PM »

I agree when the spring preload is very low, but in my case with 14psi cracking 18psi control pressure, its not affecting operation.

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nyet
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« Reply #21 on: April 25, 2014, 06:43:24 PM »

I agree when the spring preload is very low, but in my case with 14psi cracking 18psi control pressure, its not affecting operation.



I understand that, but that isn't how PIDs are supposed to work, even one with parameter scheduling.
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julex
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« Reply #22 on: April 25, 2014, 07:14:54 PM »

can you post your P, I, D tables/values.

Your D is really bouncing like crazy initially below 4k when in dynamic mode, most likely due to I not being adequate.
Then you go into static with "P" active and it is a calm period but due to too small of "P" quotient (or maybe KFLDIMX being too small?, or your KFLDRL being all screwed up - most likely this) you deviate below the dynamic regulation threshold again (UMDYLDR) and the ECU switches in dynamic load regulation for PID controller.

I spent too much time tuning this stuff on my car, as you can tell...

edit: I am now almost 100% sure you KFLDRL needs major overhaul... it is stock which with 18psi wastegates will never work smooth. You need to follow "KFLDRL calibration" thread and do some runs with fixed WGDC to figure out how different levels of fixed WGDC result in boost profile which you can then linearize.
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stuklr
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« Reply #23 on: April 25, 2014, 07:45:11 PM »

My DRL is not stock, but needs a major overhaul. Sunday is log and flash day. I am going to redo my DRL. I used values I logged from a friend's GT2552 car. Figured that would get me a lot closer than the factory stuff. I know that's the wrong way to do it, but this is pretty much a base file.

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Snow Trooper
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« Reply #24 on: April 25, 2014, 08:25:36 PM »

Again, i'd rather keep pressure off the wastegate during spool. maybe its just me.

I agree, but there is a limit.  Heavier the spring less you should use to minimize air loss.  For instance I use a 21# tial gate, its true spring flow rate is 23#.  At 3.5% duty cycle I make 30 Psi, at 15% duty cycle I make 36, at 24% I make 42.  25% becomes my max dc for spool region.  0% until spool is possible.  Otherwise its just a line that flows like a boost leak or even vac leak.
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