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Author Topic: Load capping out  (Read 26407 times)
prj
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« Reply #15 on: August 22, 2012, 12:41:58 AM »

It's really simple actually.
ps_w hits 65535.

rlroh_w is fine, it rises as it should.

Yeah, I need to underscale the MAF Sad
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prj
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« Reply #16 on: August 22, 2012, 03:04:16 AM »

Set KFKHFM to 0.66 from 140 load and KFLF to 1.5 from the same point.
Everything is fine now.

This is a pretty annoying limitation though. And I am sure it can be easily circumvented in ASM by doing some divisions by 2...
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prj
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« Reply #17 on: August 22, 2012, 03:26:25 AM »

From the graphs - rl_w now follows rlroh_w and ps_w no longer goes above 2200 mbar, thus load does not max out.

It's back to the age old limitation of 1.5 bar in the ECU. Ah well.
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nyet
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« Reply #18 on: August 22, 2012, 09:30:48 AM »

Wow. Thanks for actually tracking it down.

Someday we'll figure out how to either run an underscaled MAP, or fix the load limitation entirely Smiley

I didn't realize there was yet another limitation (ps_w) that wasn't based on MAP readings.

Would underscaling the MAP prevent ps_w from maxing out? Or is only calculated from load? I haven't checked the FR yet.

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« Reply #19 on: August 22, 2012, 09:33:40 AM »

Set KFKHFM to 0.66 from 140 load and KFLF to 1.5 from the same point.
Everything is fine now.

Yikes. I guess thats one way to skin a cat. Are you sure you can make that big of a discontinuity (even if it is compensated for by KFLF?)

I'd always thought it would be better to just underscale the MAF as a whole, and have load be underscaled everywhere, not just in some regions.
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prj
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« Reply #20 on: August 22, 2012, 11:39:29 AM »

Yikes. I guess thats one way to skin a cat. Are you sure you can make that big of a discontinuity (even if it is compensated for by KFLF?)

I'd always thought it would be better to just underscale the MAF as a whole, and have load be underscaled everywhere, not just in some regions.
This works just fine. I don't see the point to under scale down low, as I would lose fine grained control and blow up part throttle.
Overscaling up top is fine, because this thing has a 1 bar wastegate spring and boost is 30 psi anyway, so the transition is really fast.
That said, I played with KFLF quite a bit just now on the airfield, and I got my fuel right where I want it, because I am linearizing the PID, I also had to do this with 0, 10, 20, 30, 40 etc duty cycle and actual follows requested nicely. This is a narrowband ECU as well.

As for fixing the problem entirely - it will need a simple ASM hack. Before rlroh_w goes into the integrator and gets transformed into ps_w and pbr_w, it should be divided by 2, then multiplied by 2 again.
ps_w is not important, what is important is pbr_w, and keeping it lower until we get back to rl_w. Underscaling the MAP will accomplish nothing at all, because ps_w is calculated from rlroh_w.

When I get some free time (usually in winter, when we have snow), then I will probably write this hack into the ECU. I rewrote tons of stuff on the older motronics to suit my needs as well - factory systems don't really like more than 200hp per liter Wink
« Last Edit: August 22, 2012, 11:42:01 AM by prj » Logged

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« Reply #21 on: August 22, 2012, 12:31:21 PM »

Fantastic. I am VERY glad you found this. I look forwards to seeing your hack.

Then, we get to talk about MAP solutions? Smiley
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DavidG60
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« Reply #22 on: August 23, 2012, 06:51:26 AM »

Set KFKHFM to 0.66 from 140 load and KFLF to 1.5 from the same point.
Everything is fine now.

I didn't think about this solution! (
I agree keeping high resolution at low load is a good idea.
I may have to try it very soon.

BTW, which turbocharger are this logs referring to?
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prj
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« Reply #23 on: August 23, 2012, 08:02:36 AM »

Precision 5857 SP
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silentbob
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« Reply #24 on: August 23, 2012, 09:53:45 AM »

This works just fine. I don't see the point to under scale down low, as I would lose fine grained control and blow up part throttle.
Overscaling up top is fine, because this thing has a 1 bar wastegate spring and boost is 30 psi anyway, so the transition is really fast.
That said, I played with KFLF quite a bit just now on the airfield, and I got my fuel right where I want it, because I am linearizing the PID, I also had to do this with 0, 10, 20, 30, 40 etc duty cycle and actual follows requested nicely. This is a narrowband ECU as well.

As for fixing the problem entirely - it will need a simple ASM hack. Before rlroh_w goes into the integrator and gets transformed into ps_w and pbr_w, it should be divided by 2, then multiplied by 2 again.
ps_w is not important, what is important is pbr_w, and keeping it lower until we get back to rl_w. Underscaling the MAP will accomplish nothing at all, because ps_w is calculated from rlroh_w.

When I get some free time (usually in winter, when we have snow), then I will probably write this hack into the ECU. I rewrote tons of stuff on the older motronics to suit my needs as well - factory systems don't really like more than 200hp per liter Wink

You can't fix this on a specific power output number. Other ECUs have some stepstones that limit you far before that Wink
 
I have wraped my head about this limit as well because my new setup is also excceding the MAP limit and I don't like underscaled load because you fuck up nearly everything with that.
I think the most elegant solution would be to completely underscale the pressures as the flow over the throttle plate is a function of PR before - after the plate. So something similar like running at high altitude with a "bigger displacement" engine. To get it completely right you have to touch some stuff but it will run with no negative side effects.
When my hardware is done in 3weeks I'll start testing and let you know how to do that.
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prj
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« Reply #25 on: August 23, 2012, 11:36:12 AM »

Sure, go on...

For now this solution allowed me to dial in the mixture quite nicely, although I did need to do a lot of tweaking to the KFLF map.
But that might be also because my MAF is not linearized completely right.

Hard to tune unknown injectors with an unknown intake and a MAF where you can only copy paste MLHFM from RS4 and pray Wink
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prj
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« Reply #26 on: August 28, 2012, 04:38:13 AM »

Thinking about this whole thing.

How many things would break just by setting KFURL 2x lower and adjusting the MAP sensor scaling 2x lower?
This would allow the ECU to read 4 bar boost, but at a double loss of precision.

Obviously the zero (atmospheric) point would have to be recalibrated and the relationship between the baro pressure and boost pressure, along with any axes that used boost/absolute pressure and maps, but I don't see anything impossible.

I will wait until my emulator arrives, and then try this on my RS4, and see how far I get before hitting a brick wall Wink
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silentbob
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« Reply #27 on: August 28, 2012, 07:27:54 AM »

It is a bit more complicated but as you said nothing impossible. I have already made a list with stuff that has to be changed (mainly fho and ps-rl/rl-ps related). I'm on holidays this week but I can send you the list next week if you like so things will develope a bit faster as I'm not sure if I will be done with my hardware as planned
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lulu2003
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« Reply #28 on: August 28, 2012, 08:19:41 AM »

do I find a short summary how the other 8-byte limits like MAP in ME7 have been solved?
(I will check with search function meanwhile).

thanks.
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silentbob
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« Reply #29 on: August 28, 2012, 08:45:25 AM »

No. This is all one big picture. You can't really solve one problem properly without solving the other  Wink
« Last Edit: August 28, 2012, 08:49:08 AM by silentbob » Logged
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