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Old 11-16-2007, 11:38 PM   #1
joe-6STi
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Default How long should you let the map learn before adjusting and reflashing ?

Say I adjsut boost targets and Initial WGDC to get the boost curve under control. How much time should I give it to learn before adjusting things and then re-flashing ?
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Old 11-17-2007, 02:04 AM   #2
dynamix
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You would probably have more success adjusting the max WGDC if you are wanting to keep it under control.

You should do a few runs and then analyse the logs before reflashing. Persoally I wouldnt wait for the ECU to learn to correct your map before correcting it yourself.

If you are modifying fuel trims, then I would leave it longer.
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Old 11-17-2007, 02:30 AM   #3
mickeyd2005
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Originally Posted by joe-6STi View Post
Say I adjsut boost targets and Initial WGDC to get the boost curve under control. How much time should I give it to learn before adjusting things and then re-flashing ?
If you have your MAF scaled correctly and you know that your AFR Learning D is normally pretty close to 0 then you don't have to wait for it to settle.

If you know your tune is close to good then you can set your initial IAM to 1 and then you don't have to do a WOT log to settle it. If you have your initial IAM set less to 1, then make sure your rough knock range is greater than your max load, then do a single 3rd gear WOT. That should set your IAM.

I normally let the car warm up and do a 2nd gear WOT log and then I pull over and stop the engine. Then I restart it. After a reflash, the AVCS becomes fixed until it resets.
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Old 11-17-2007, 02:31 AM   #4
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Originally Posted by dynamix View Post
You would probably have more success adjusting the max WGDC if you are wanting to keep it under control.
If you rely upon max wgdc then it only works in one gear. For example, on my car, if I set my max wgdc to 75% at 3000 rpm, then it will control boost in 3rd gear at 3000 rpm but then it will overboost in 4th gear unless the WGDC initial is set correctly. I would make sure the WGDC initial is set up correctly.

Here's an old plot that I did a while back, 2nd iteration. I missed boost in 3rd gear slightly. It's close enough. I never did get to finish it... It's primarily based on using WGDC initial to control boost.



Here's a cleaner one. This is a stage 1 LGT that I helped my friend tune. Sealevel in Hawaii. Boost is mostly controlled by WGDC initial + turbodynamics.


Last edited by mickeyd2005; 11-17-2007 at 02:38 AM.
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Old 11-17-2007, 09:42 AM   #5
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Originally Posted by mickeyd2005 View Post
If you rely upon max wgdc then it only works in one gear. For example, on my car, if I set my max wgdc to 75% at 3000 rpm, then it will control boost in 3rd gear at 3000 rpm but then it will overboost in 4th gear unless the WGDC initial is set correctly. I would make sure the WGDC initial is set up correctly.

Here's an old plot that I did a while back, 2nd iteration. I missed boost in 3rd gear slightly. It's close enough. I never did get to finish it... It's primarily based on using WGDC initial to control boost.
This is what i was finding. Which makes sense. It would seem like a safer way to set things up is with a suffiecient Max to allow it to hit targets, but a low enough initial that it doesn't over shoot.

Thanks for the info guys. That's actually pretty close to what I was doing. Drive around a bit without WOT and check for knock, and then get on it a bit. A few WOT pulls should be suffieicent then... I was just making sure that I wasn't being too quick to pull trigger on reflashing after making adjustments.

I have it now where it does not overboost anywhere regularly and it coming close to target everywhere. Still have quite a bit to learn but getting somewhere now. No matter how many books you read on riding a bike, they dont mean ish without seat time.

thanks guys
Joe
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Old 11-17-2007, 10:46 AM   #6
MasterKwan
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This kind of leads to another question for me. How much overboost is too much? Should I be worrying about .5 - 1psi of overboost that quickly gets pulled back to target boost?

Mickeyd, I think you've just explained why I'm not getting target boost in lower gears. I reduced my max WGDC from 67 to 60 to reduce overshoot, hit target boost in 3rd and 4th but, don't quite get there in 1st and 2nd. In those gears, the boost is about .5 PSI shy and it hunts a little. This is with a TD04.
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Old 11-17-2007, 02:57 PM   #7
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The way i understood It - you'll never really hit target boost in 1st - rare in 2nd - always in 3rd if things are set up right. Certainly in 4th you should be hitting bosot targets.

Someone said (think it was mickeyd2005) that a .5 psi overboost was alright. In logging my stocker I would set that much at times, prior to ever having touched the ECU.
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Old 11-17-2007, 03:07 PM   #8
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FWIW, there is no long term learning in the boost control scheme. The integral is the only thing that is stored between evaluating wastegate duty, and it resets every time you get off the throttle.
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Old 11-17-2007, 03:22 PM   #9
mickeyd2005
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Originally Posted by joe-6STi View Post
The way i understood It - you'll never really hit target boost in 1st - rare in 2nd - always in 3rd if things are set up right. Certainly in 4th you should be hitting bosot targets.

Someone said (think it was mickeyd2005) that a .5 psi overboost was alright. In logging my stocker I would set that much at times, prior to ever having touched the ECU.
What do you mean? Did you look at the graphs? I can hit target boost in 2nd gear. It's just at a later rpm. The lower load due to the taller gearing results in a faster acceleration of the engine. Spool is affected but you can still hit target boost.

In fact, I can hit target boost in 1st gear if I start my log from a low enough rpm. It's kind of hard to tell though because you only get a handful of data points and the rpm and boost are out of synch. I can tell I hit target boost because my TD proportional is close to zero. In the graph I plotted above, there was some kind of delay in TD integral in 1st gear. I datalogged again later at a very low rpm start (1200 rpm) and the delay in TD integral went away. Not sure what happened but 1st gear datalogs are pretty meaningless...

IMHO, I try not to overboost, at all, but I have to live with some. My opinion is 0.5 psi overboost for a stage 1 or 2 car. The problem with overboost is that TD integral winds down and this causes a dip in boost after overboost. It's better to shoot for a "soft landing."

The way to set up a "soft landing" is to control TD integral. Datalog TD integral and TD proportional and you will learn to control it.

I also datalog a 4th gear transient (start at a high rpm) to make sure that I don't overboost in 4th gear when I punch it at an already high rpm. TD proportional needs to be set up correctly here.
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Old 11-17-2007, 03:36 PM   #10
mickeyd2005
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Originally Posted by Freon View Post
FWIW, there is no long term learning in the boost control scheme. The integral is the only thing that is stored between evaluating wastegate duty, and it resets every time you get off the throttle.

Freon makes a very important point here.

TD integral is supposed to reset every time you get off the throttle. However, it will only reset if the target boost is less than the TD threshold. For example, on the LGT, the target boost threshold is 0.97 psi. If I set target boost to a minimum of 5 psi everywhere in the off-WOT area, the TD integral won't get reset. This could have bad consequences if you then go and hit WOT again.

I've seen some maps that have high target boost populated in the partial throttle region. I don't think that's a good idea. I set my target boost to 0.8 psi in the area where I want TD integral to get reset (during a shift).
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