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Author Topic: Nefmoto community project: Stage1 2.7t ME7.1 S4 (APB 8D0907551M-0002)  (Read 461564 times)
nyet
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« Reply #360 on: June 09, 2015, 05:26:03 PM »

Plus i think environment and car variables are coming into play, at this point I need to figure out the boost spike on first throttle tip in.

Too much IMX, as i've already explained Tongue
Please reread my posts.

You have a non-stock exhaust, which means you can't use the same imx as a bone stock s4 would. You are on your own. If you like, start a separate thread for remote tune help.
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therealnap0le0n
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« Reply #361 on: June 09, 2015, 05:47:25 PM »

Too much IMX, as i've already explained Tongue
Please reread my posts.

You have a non-stock exhaust, which means you can't use the same imx as a bone stock s4 would. You are on your own. If you like, start a separate thread for remote tune help.
yea will do, thanks for the help so far guys
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FlyboyS4
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« Reply #362 on: June 09, 2015, 07:31:48 PM »

Nye, I'm on a non-stock exhaust too.  Realistically I don't think anybody with a bone stock S4 is going to be interested in this site.   A stage 2 S4 usually implies some exhaust upgrades if not IC's.  I'd like to see us try and work through it, and if it proves too difficult then branch off, but companies like APR and GIAC had to account for different hardware when they did this, I think it is at least worth a shot.

Here's the change I made to KFTARX, highlighted in red.  I split the difference between previous value and the column to the right, moving left, to scale the values down so as to have less boost with higher temps.



and the results with these last three changes above [LDRXN, DIMX, KFTARX] incorporated.  78F outside.

Nef-12 Datalog

Interestingly the car felt stronger at the top end despite not showing much difference in the acceleration curve.
« Last Edit: June 09, 2015, 07:33:37 PM by FlyboyS4 » Logged
nyet
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« Reply #363 on: June 09, 2015, 07:53:27 PM »

Apologies for leading you down the garden path - I'd rather not mess with KFTARX just yet.

Hows this: Let's get LDIMX dialed first... bring it back down a bit so you don't get all that overshoot. Put KFTARX back (sorry, my bad) and tweak LDIATA as daz suggested once we get a sane IMX at a given operating point.
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therealnap0le0n
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« Reply #364 on: June 09, 2015, 07:57:09 PM »

given safe limits I'm all for testing the community tune so we can come to a "suitable" for most tune, and then through the learning I've done with this I'll hopefully be able to massage my personal file to my cars needs.

Let's work on LDIMX first and not get too ADHD on the other variables.
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nyet
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« Reply #365 on: June 09, 2015, 08:01:38 PM »

companies like APR and GIAC had to account for different hardware when they did this, I think it is at least worth a shot.

A slight digression here, but I think it is relevant to the discussion:

Their stage 1 was ALL over the map, and if you'll recall, people had all sorts of throttle cut issues when they deviated from the stock exhaust (piggies, high flow cats etc) even a little (APR and GIAC had no idea what KFDLULS was, lol).

Hence, "throttle cut defender", the stupid accel pedal stopper, etc.

The IMX adaptation system was never good enough to compensate for these huge deviations...
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« Reply #366 on: June 09, 2015, 08:12:57 PM »

I don't like the idea of dorking with KFTARX at this point (keep it flat, all 1's IMO). I'd use LDIATA if we're sure it's temperature related, leave request alone, just fix the PID.
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nyet
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« Reply #367 on: June 09, 2015, 08:38:11 PM »

I don't like the idea of dorking with KFTARX at this point (keep it flat, all 1's IMO).

The problem with a flat KFTARX is that you'll have rising req boost as temps go up...

Quote
I'd use LDIATA if we're sure it's temperature related, leave request alone, just fix the PID.

Agreed.
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« Reply #368 on: June 10, 2015, 03:51:16 PM »

I don't like the idea of dorking with KFTARX at this point (keep it flat, all 1's IMO). I'd use LDIATA if we're sure it's temperature related, leave request alone, just fix the PID.

The changes I made by and large were a shift toward 1, so I'll leave KFTARX be for now. 

Next change I'll make will be to drop DIMX a little.
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nyet
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« Reply #369 on: June 10, 2015, 04:00:34 PM »

The changes I made by and large were a shift toward 1, so I'll leave KFTARX be for now. 

Next change I'll make will be to drop DIMX a little.

Feel free to do several iterations. IMX is relatively safe to move around wherever you want at these boost levels.
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Please do not ask me for tunes. I'm here to help people make their own.

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« Reply #370 on: June 11, 2015, 07:02:59 PM »

Here's with DIMX lowered a little and I also slightly altered the LDRXN to not request full load quite so fast.  I'll post those changes soon.

There's three partial third gear pulls, the last is interesting in that it starts at low rpm and boost never overshoots but the two prior that start at a later rpm do.  What's the recommended way to counter that?

Nef 12a data
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nyet
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« Reply #371 on: June 11, 2015, 07:12:21 PM »

the last is interesting in that it starts at low rpm and boost never overshoots but the two prior that start at a later rpm do.  What's the recommended way to counter that?

Tune Q2... now, Q2 is a tricky beast, pay close attention to the axis...

The RPM axis is clear: if you get different overshoot depending on RPM position, vary Q2 with RPM

The other axis (lde, iirc) is not so clear: it allows you to schedule the Q2 gain depending on lde; that is to say, you can make Q2 bigger or smaller long before actual meets requested, or JUST as lde nears zero..

But the D component from Q2 is already proportional to how "fast" lde is changing (e.g. spool), so counter intuitively, if you have a lot of overshoot on fast spool, but not slow spool, you may want to increase Q2 for LOW lde.

Conversely, if you have overshoot on slow spool, but not fast spool, you want to DECREASE Q2 for LOW lde.

You can move the whole thing up and down by toying with IMX, of course. Typically, it is easier to just make IMX very conservative so you dont overshoot, so you can keep Q2 low. You might give up a bit of spool, but it is likely better to have undershoot than uncontrollable boost oscillations (which you will ALWAYS have on overshoot.. that is the nature of PIDs).

Now, keep in mind that on top of this, you also have the IMX trims going on.. but if lde is never that big for extended periods of time, the ECU should not be trimming IMX much.
« Last Edit: June 11, 2015, 07:26:52 PM by nyet » Logged

ME7.1 tuning guide (READ FIRST)
ECUx Plot
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Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
nyet
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« Reply #372 on: June 11, 2015, 07:16:35 PM »

Now that I look at your graphs though:

You can see that D is basically zero when we most need it to control the overshoot....

this is because your req boost is rising just as actual is about to meet requested. That means the slope (derivative) of lde is smaller than if req boost was flat.

This is why it is almost always easier to tune Q2 when req boost is flat near expected overshoot....
« Last Edit: June 11, 2015, 07:21:14 PM by nyet » Logged

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« Reply #373 on: June 11, 2015, 07:22:52 PM »

Ok, it sounds like the first order of business is still to try and get that requested line to flatten out.  I'll keep working LDRXN to make that happen and then revisit the other changes to DIMX, and possibly Q2.
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nyet
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« Reply #374 on: June 11, 2015, 07:28:28 PM »

Please let me know if anything I'm explaining is unclear; it is a complex topic and I am trying hard to make it as layman friendly as possible.

Tuning PIDs is NOT an easy thing; in fact, it is very rarely done by hand... usually automated systems are used...
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ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
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