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Author Topic: Boost lower after raising LDRXN  (Read 4166 times)
SlashProm
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« on: November 08, 2020, 09:08:04 AM »

Hey guys, I've been running stage 2 on my leon 180 auq for a while now.

I have LDRXN tuned to spike at 20 psi around 3k rpm and it quickly tapers off to around 12-13 psi at redline.
I recently installed a decent front mount intercooler so I thought I'd add a little bit more boost.
Just for fun I thought I'd go nuts and have a 26 psi spike and have it taper to around 16 psi at redline, just to push the limits of the setup and see what it can do.

Here's my problem, I put the tune on the car and holy cow it's fast, spinning the wheels at max boost. But my boost levels are now lower? max I've seen with this tune is 16 psi. How can my boost level have gone down by raising LDRXN? I also made sure to also raise the higher load lines of KFMIRL as well. I don't understand how it can be faster but show lower boost?
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« Reply #1 on: November 08, 2020, 09:21:56 AM »

Hey guys, I've been running stage 2 on my leon 180 auq for a while now.

I have LDRXN tuned to spike at 20 psi around 3k rpm and it quickly tapers off to around 12-13 psi at redline.
I recently installed a decent front mount intercooler so I thought I'd add a little bit more boost.
Just for fun I thought I'd go nuts and have a 26 psi spike and have it taper to around 16 psi at redline, just to push the limits of the setup and see what it can do.

Here's my problem, I put the tune on the car and holy cow it's fast, spinning the wheels at max boost. But my boost levels are now lower? max I've seen with this tune is 16 psi. How can my boost level have gone down by raising LDRXN? I also made sure to also raise the higher load lines of KFMIRL as well. I don't understand how it can be faster but show lower boost?
everything is so wrong i dont know where to start lol. the factory charge pressure sensor so anything over 22 psi youll have no closed loop boost control unless you do the 5120 and install a larger charge pressure sensor. odds are you fucked up your load scaling and its suck at a lower load row hence the lower boost. lower load cells have more advanced ignition timing so thats why the car feels strong with less boost. this is just a guess based off the extreemly limited info you provided. if you want actual help upload me7logger csv of a 3rd gear pull and ill have a look. also good luck trying to get 26 psi on a stock turbo and wastegate. back pressure in the exhaust manifold is so high it will surly blow the gate open.
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SlashProm
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« Reply #2 on: November 08, 2020, 09:30:11 AM »

I know about the 22 psi limit for the map. Does that mean it can't physically try to make more that 22 psi? Or does it mean that it can not efficiently control boost above this level?
« Last Edit: November 08, 2020, 10:14:27 AM by SlashProm » Logged
SlashProm
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« Reply #3 on: November 08, 2020, 09:45:01 AM »

I'll start with my original tune and build up in small increments. I was under the impression that the car could boost over 22 psi as I've read that people are "spiking" a lot higher. I'm assuming that you can't physically go over 22 psi without the hack. I was under the impression that you could, but it just wouldn't have full control over the boost via the ECU. Is it likely that people are asking for a 22 psi spike and the reason they are seeing 25, 27 etc is just overboost?

Edit. My laptop broke a while back which is why I have been absent for so long. I rooted a netbook out of my cupboard and it has a dead l-ion battery so I wont be able to do any logs until it arrives. I just took a look at the file I took off my car before re-flashing which was a slightly different revision of the one I was using as a base. It turns out that the tune I was running on the car had a maximum boost request of 16 psi tapering to 10 at redline. So according to my boost gauge it's boosting a few psi higher than I was requesting, so it would explain why it wasn't happy with the last map I tried with stupid high figures.

I have a 3" decat downpipe and a 2.25" centre silencer style backbox with a centre res delete pipe and a ported manifold so the exhaust system is pretty free flowing, healthy 710p DV and an uprated silicone tip, as well as the front mount which has 2" piping out of the turbo stepping up to 2.5" the rest of the way. I made 2 tunes a while back, a "stage 1" and a "stage2" I was under the impression I was running the stage 2 because of what my recently installed boost gauge was showing, but thinking back, I put it back to stage 1 levels because at the time i didn't have a front mount.
« Last Edit: November 08, 2020, 10:16:23 AM by SlashProm » Logged
vwaudiguy
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« Reply #4 on: November 08, 2020, 10:52:21 AM »

Tuning issues aside, it's common in my experience to have less boost after a FMIC install with the stock 1.8T turbo, especially if the turbo is maxed out to begin with.
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SlashProm
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« Reply #5 on: November 08, 2020, 10:56:58 AM »

My boost stayed the same after installing the front mount to be fair. I think it's because people go overkill with the core sizes that they lose some boost trying to fill a massive core and end up with a pressure drop. I'm stuck atm anyway, I just went out to put the old map back on the car and my flasher isn't working. After about 5 seconds of connecting it disconnects its self and comes up with a "no response from tester message"

I had this problem a few times when I flashed in the past and I always thought it was because my lead wasn't connected properly to the obd2 as if you push too hard the obd comes off it's mount and sinks into the console, but I think it's just an intermittent problem with the 032HN ecu's because It's a brand new lead and I've pulled my obd out of the housing so I can physically push on the back of it to get a good connection. Worked first time doing it earlier, this time tried about 20 times with no luck :/ Even tried different baud rates, just not my day today.
« Last Edit: November 08, 2020, 11:24:47 AM by SlashProm » Logged
nyet
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« Reply #6 on: November 08, 2020, 12:31:55 PM »

I'm assuming that you can't physically go over 22 psi without the hack. I was under the impression that you could, but it just wouldn't have full control over the boost via the ECU. Is it likely that people are asking for a 22 psi spike and the reason they are seeing 25, 27 etc is just overboost?

Yes, but after you hit the limit you run the risk of running lean, since that pressure limit applies to just about every calculation the ECU makes, including fueling. ps_w is not from sensor, it is modeled from MAF, and if you hit its limit all sorts of things go wrong.
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ME7.1 tuning guide
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SlashProm
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« Reply #7 on: November 08, 2020, 12:49:42 PM »

Thanks nyet. I won't be going over the limit then. Hopefully I can get the flash software to connect to the car tomorrow and put things back to a safer level. What Marty said about ignition timing makes a lot of sense as I remember when I logged my tune a while back I was seeing cfs of 6. I put this down to having no front mount and at the time i was getting lower load levels than expected so I've since bought a new genuine maf.

Is it normal for the car to be boosting a few psi higher than requested by ldrxn? Or is this something to do with my boost pid/cheap ebay boost gauge? Hopefully I'll have some logs next week and take out some of this guess work. I will say one thing though. It's so much faster with a peak boost of 16 psi as opposed to the tune with 18-20
« Last Edit: November 08, 2020, 01:09:15 PM by SlashProm » Logged
nyet
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« Reply #8 on: November 08, 2020, 03:47:23 PM »

Is it normal for the car to be boosting a few psi higher than requested by ldrxn? Or is this something to do with my boost pid/cheap ebay boost gauge?

There is a lot wrong with both of these questions, not sure where to start :/

First off, LDRXN isn't PSI or mbar. If you are using the version of the LDRXN map with pressure (and not load) as z units, that is a convenience, not reality. The only source of truth is req boost, not ldrxn converted (poorly) into pressure.
« Last Edit: November 08, 2020, 03:49:18 PM by nyet » Logged

ME7.1 tuning guide
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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 ex
SlashProm
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« Reply #9 on: November 09, 2020, 12:55:04 AM »

LDRXN(Maximum Specified Load) I'm just going off what I read on the wiki. LDRXN x10 +300 - atmospheric pressure. Eg when I request a value of 140 I'm actually requesting 0.7 bar or 10.1526 psi. Or is that not correct?

I spent months reading through the wiki and the stage 1 community thread before even attempting to mess with the car as I didn't want to damage anything or brick my ecu. I'm by no means an expert but I thought I at least had a basic understanding of things. Are you saying that LDRXN doesn't equate to an exact psi, but is only used as a rough guide to get you to a close figure, which then must be fine tuned using other methods? Is that why LDRXN can not be used solely to reach a specific boost level? Or am I way off?
« Last Edit: November 09, 2020, 01:12:48 AM by SlashProm » Logged
BlackT
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« Reply #10 on: November 09, 2020, 02:09:46 AM »

LDRXN(Maximum Specified Load) I'm just going off what I read on the wiki. LDRXN x10 +300 - atmospheric pressure. Eg when I request a value of 140 I'm actually requesting 0.7 bar or 10.1526 psi. Or is that not correct?

I spent months reading through the wiki and the stage 1 community thread before even attempting to mess with the car as I didn't want to damage anything or brick my ecu. I'm by no means an expert but I thought I at least had a basic understanding of things. Are you saying that LDRXN doesn't equate to an exact psi, but is only used as a rough guide to get you to a close figure, which then must be fine tuned using other methods? Is that why LDRXN can not be used solely to reach a specific boost level? Or am I way off?
Sorry for my attitude, but are you blind???

ME7.1 doesn't really have a "boost" table. It does everything based on "specified load".

Approximation
Keep in mind, this is a rough approximation. It can be off by as much as 30% or more. It is dependent on a large number of factors including air density, temperature, elevation, and the alignment of the stars and the moon. Use this formula to get close, then adjust based on real world observations.




It is imposible that you read this LDRXN x10 +300 - atmospheric pressure. and not this

cute boy names that start with d

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SlashProm
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« Reply #11 on: November 09, 2020, 03:39:19 AM »

And the alignment of the stars haha. Thanks i should really re read the whole thing. A lot of it is double Dutch to me but I'm surprised I forgot about that part. I just remembered the ldrxn equation as I'm better with numbers.

I can definitely see why logging is so important on these ecus as it's all guess work without it. I remember when I first started tuning it and I did 4-5 revisions and sometimes it would be a monster and other times so so. And that was just small changes to ldrxn. I think I'll hold off on the tweaking until I get my logging capabilities back. My tune obviously needs some work. The fact that it's running better with less boost makes it pretty apparent i need to be checking out my idcs and cfs
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