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Author Topic: Hitting max ps_w/rl_w and fueling  (Read 70529 times)
nyet
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« on: October 29, 2012, 12:09:31 PM »

I recall seeing a few posts by somebody (forget who) talking about workarounds for fueling when you hit maximum rl_w/ps_w (another good reason to work hard towards migrating to an RS4 based tune and a bigger MAP).

But I can't recall who it was, or what they said they are doing.

I'm dorking around with FKKVS to compensate, but I really don't like it.

Can somebody point me to the thread? My search foo is failing me.

BTW: thanks to tony for getting the forum back up Smiley
« Last Edit: November 05, 2012, 11:27:20 AM by nyet » Logged

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prj
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« Reply #1 on: October 29, 2012, 12:28:50 PM »

I probably did.

Downscale KFKHFM and upscale KFLF at the same point.
Edit axes to suit.

The problem is not rl_w but ps_w.
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phila_dot
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« Reply #2 on: October 29, 2012, 12:47:45 PM »

Stupid ECU scaling.
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nyet
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« Reply #3 on: October 29, 2012, 01:28:58 PM »

Edit axes to suit.

Are the axes shared by any other maps, or can I just edit them willy nilly
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nyet
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« Reply #4 on: October 29, 2012, 01:44:25 PM »

Oh, also, what is a "safe" value to scale down KFHFM (and KFLF up)?

Also, do you pick a bunch of cells to scale a fixed amount, or do something nice with a linear line?

Are there any possible side effects?
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prj
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« Reply #5 on: October 29, 2012, 03:07:35 PM »

The axes are only for those maps IIRC.

Just make it taper down from say 150 load to 220 load.
And adjust KFLF in the same way.

That will get you close.

After that make some logs and see how far actual is off requested and correct KFLF to suit.

It really sounds a lot more complicated than it is.
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phila_dot
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« Reply #6 on: October 30, 2012, 06:42:32 PM »

Nye,

I'm interested in investigating this a little bit. I can provide RAM variables if you are willing to take some logs of this limit. I have locations now, but it might be a few days before I have time to work out the factors.
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jibberjive
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« Reply #7 on: October 30, 2012, 09:22:10 PM »

When prj first wrote of this, I was curious how this is just now coming to light?  Haven't people on the forums tuned to 600+HP on rs4's before this?

Also, prj, you had this issue on  the k-box, right? So this isn't an issue that can be solved for us m-box guys by switching to the k-box?
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nyet
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« Reply #8 on: October 30, 2012, 10:45:59 PM »

AFAIK they ran super underscaled MAFs, and/or tweaked FKKVS to hell and back to get fueling up.

Why do you think GIAC started with a 100mm MAF back in 2002 lol
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prj
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« Reply #9 on: October 31, 2012, 01:45:44 AM »

Nye,

I'm interested in investigating this a little bit. I can provide RAM variables if you are willing to take some logs of this limit. I have locations now, but it might be a few days before I have time to work out the factors.

Nothing to investigate. rlroh_w gets converted to ps_w and then back to rl_w.
And ps_w has the same hard cap of 2560mbar.

When prj first wrote of this, I was curious how this is just now coming to light?  Haven't people on the forums tuned to 600+HP on rs4's before this?

Also, prj, you had this issue on  the k-box, right? So this isn't an issue that can be solved for us m-box guys by switching to the k-box?
I had the issue on a 1.8T. On the RS4 I am also pretty close to hitting it. My ps_w is 2450mbar right now at it's peak.

The scaling for ps_w on K-Box is exactly the same 0.0390625, making the maximum value 2^16*0.0390625 or 2560.0 mbar.
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phila_dot
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« Reply #10 on: October 31, 2012, 05:10:42 AM »

Nothing to investigate. rlroh_w gets converted to ps_w and then back to rl_w.
And ps_w has the same hard cap of 2560mbar.
I had the issue on a 1.8T. On the RS4 I am also pretty close to hitting it. My ps_w is 2450mbar right now at it's peak.

The scaling for ps_w on K-Box is exactly the same 0.0390625, making the maximum value 2^16*0.0390625 or 2560.0 mbar.

I'm aware, but I would like to look into a possible solution.
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prj
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« Reply #11 on: October 31, 2012, 07:29:54 AM »

I'm aware, but I would like to look into a possible solution.

The solution is pretty much to rescale all pressure in the ECU by a factor of two.
So that it can do 3 bar absolute boost...

ps_w and all the other pressure values are connected.
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phila_dot
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« Reply #12 on: October 31, 2012, 08:06:24 AM »

The solution is pretty much to rescale all pressure in the ECU by a factor of two.
So that it can do 3 bar absolute boost...

ps_w and all the other pressure values are connected.

I know....I've gone through the code some and read the posts, but it is much easier to see with logs.

I think that we can do this and fit a higher bar MAP sensor without too much difficulty. Just ALOT of tedious work.

I don't have the problem (luxury) of maxing out the MAP/pressure variables at the moment and am currently just curious.

Nbd...I can wait on this until it gets in my way.
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prj
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« Reply #13 on: October 31, 2012, 10:29:55 AM »

If you want logs, I have tons of different logs from a 1.8T I tuned recently.
I just upgraded the exhaust on my RS4 so I can try to hit the limit on it as well, but I think 1.7 bar on K04's is pushing it a little...

Basically, I have a functional emulator, a functional brain and a functional car, plus a mile long airfield strip I can go to at any time.
If you want - let's do this ...

My MAP is already maxed as I am running 1.6 bar now.
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nyet
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« Reply #14 on: October 31, 2012, 10:35:23 AM »

As a bonus, the PID (and PID trims) will be a LOT more stable if we have a lot of MAP headroom...
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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.
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