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Author Topic: Someone please explain and LDRXN question I have.  (Read 14472 times)
littco
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« on: February 08, 2012, 08:40:49 AM »

I looked at a pro tuned 06A906032hn last night its a stage 2 map and compared it with the stock equivalent . I used the full damos so it was easy to see which maps where changed by the tuner, however on both files LDRXN was identical. I thought I had made a mistake so compared the files in mapanalyser using to map address to locate the map and again it was the same. KFMIRL was tuned.

My question is , LDRXN is a limit so how can the pro tuned file produce more power if they are the same, surely it'll be limited by the same as stock?

have I missed something here?

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phila_dot
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« Reply #1 on: February 08, 2012, 09:10:56 AM »

If specified load from KFMIRL is less than LDRXN then you would see gains by just raising KFMIRL.
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TTQS
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« Reply #2 on: February 08, 2012, 09:16:50 AM »

If specified load from KFMIRL is less than LDRXN then you would see gains by just raising KFMIRL.

I was going to suggest the same thing but phila_dot snuck in first, along with the caveat that increasing power lower down the engine speed range seems to be the way forward for most pro-tuners resulting in a larger peak torque as on my tune. This can be achieved either by increasing KFMIRL as the delta or margin to LDRXN is probably lower at lower engine speeds, but also (but not in your example) by increasing LDRXN lower down (which doesn't necessarily affect the peak output that most people focus on).

My tuned peak power was hardly changed 254/259 bhp on the dyno before and after but because of the additional mid-range power, peak torque increased enormously to 359 lbft on the dyno.

TTQS
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littco
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« Reply #3 on: February 08, 2012, 09:54:25 AM »

Ok

So assuming KFMIRL is lower than LDRXN then increasing this will result in an increase in torque performance .. If KFMIRL where to go above LDRXN then you are then limited by that instead.

In this case then all the pro tuners have done is increase KFMIRL and left LDRXN and created the increase. It's interesting as pretty much all the talk on here so far has been about increasing LDRXN and setting KFMIRL as the limiter, where as this is opposite.



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nyet
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« Reply #4 on: February 08, 2012, 10:10:39 AM »

I always use LDRXN to limit req torque.
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nyet
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« Reply #5 on: February 08, 2012, 10:13:07 AM »

by increasing LDRXN lower down

Assuming we are ONLY talking about WOT, the wastegates remain closed, and the throttle plate stays open until peak boost in a proper tune.

I don't why *anybody* would be limiting torque via LDRXN or IRL in this region.

Conversely, if you increase LDRXN too low in the RPM range, you'll eventually throw a positive deviation code and go soft limp.
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Tony@NefMoto
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« Reply #6 on: February 08, 2012, 01:04:59 PM »

Don't forget that the tuner could have also underscaled load by playing with the MAF and injector scaling.
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TTQS
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« Reply #7 on: February 08, 2012, 02:22:44 PM »

I assume the additional low down torque arises from reprofiled KFMIRL and LDRXN.

If that assumption is incorrect, may I ask how would you tune to achieve my power & torque profile nyet?

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nyet
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« Reply #8 on: February 08, 2012, 03:34:12 PM »

You pretty much want LDRXN capping IRL if IRL is higher than what your turbos can make at low RPM... you want req load to stay low enough to not cause positive deviation faults

After you hit peak boost, you want to use LDRXN to prevent overspinning your turbos.

for part throttle below cracking pressure, and wherever your turbos can keep up, you can rely on IRL (i.e. wg fully closed, torque governed by throttle plate)

basically, tune LDRXN based on turbo and wastegate limitations.

IRL should be whatever your IDEA of ideal throttle response is, without regard to turbo/wg limitations.
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nyet
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« Reply #9 on: February 08, 2012, 03:37:06 PM »

Don't forget that the tuner could have also underscaled load by playing with the MAF and injector scaling.

not sure this is really relevant for the purposes of tuning LDRXN, unless you are depending on LDRXN to prevent IOP weirdness... which you shouldn't.

IRL should be tied to IOP ... if you have that set up right, no matter how f'd up your actual load is, a higher LDRXN can't make it any worse, and a lower LDRXN shouldn't be required.
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masterj
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« Reply #10 on: February 08, 2012, 03:39:07 PM »

I always do everything with KFMIRL (easy with my generator Wink) and then just reflect load limit via LDRXN
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fredrik_a
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« Reply #11 on: February 09, 2012, 04:48:56 AM »


My tuned peak power was hardly changed 254/259 bhp on the dyno before and after...

And was this result something that your tuner informed you about prior to purchasing their product, i.e. that top end power would not change at all, and secondly, are you happy with this engine behaviour? To me, it feels like you have received a diesel style engine characteristic that many would not be so happy with. What's your oppinion about this?
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TTQS
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« Reply #12 on: February 09, 2012, 09:46:38 AM »

And was this result something that your tuner informed you about prior to purchasing their product, i.e. that top end power would not change at all, and secondly, are you happy with this engine behaviour? To me, it feels like you have received a diesel style engine characteristic that many would not be so happy with. What's your oppinion about this?

1. Tuner did not advertise anything other than peak power to be expected from a Stage 2 tune (ca. 265 bhp). Yes, the dearth of information from pro-tuners is lamentable.
2. I was well aware of the general strategy of optimising mid-range torque.
3. I was and am delighted (as were other TT 1.8T owners) with the engine behaviour because a large torque output in the mid range makes for rapid in gear acceleration for overtaking, etc. This is perfect for U.K. trunk roads... we don't really do traffic light sprints or standing 1/4 mile shootouts so a peaky tune will not be fit for purpose. Behaviour elsewhere in the rev range is either the same or better.
4. The parting comment from the agent was indeed along the lines of "you have diesel levels of torque/a diesel like torque characteristic".
5. Both my previous cars were diesels and I loved the mid-range torque characteristic.
6. The dyno output is questionable in any case but there is very little I have uncovered so far through my own logging with VCDS and ME7logger that causes me to think that this is anything other than an excellent remap for my car.
7. If I was to attempt my own tune, I would be pleased to emulate this output characteristic.

I'm happy for any pro, semi-pro or amateur tuners on here or elsewhere to compare their 'before and after' 1.8T 225 or 240 PS remapped power and torque curves with mine given the same physical mods.

TTQS
« Last Edit: February 09, 2012, 11:34:11 AM by TTQS » Logged
fredrik_a
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« Reply #13 on: February 09, 2012, 02:02:04 PM »


I'm happy for any pro, semi-pro or amateur tuners on here or elsewhere to compare their 'before and after' 1.8T 225 or 240 PS remapped power and torque curves with mine given the same physical mods.



Thanks for your great input. My reason for asking was actually that I got my hands on a friends 225-version the other week, and there must be something that I do completly different (I must be missing something  Undecided ) as in my case, an increase of boost over the entire range was necessary to acheive any real benefits in performance. I would never come close to 360ft-lbs in torque without running higher boost midrange.

Also, your graph seems faulty actually unless perhaps the different pulls are done in different gears?
As you can see, the power output @ 78mph seems identical but the torque is quite different. Basically the power is identical comparing after 78 mph but somehow the torque is higher for the "tuned run" which of course is both theoretically and practically impossible if the runs are made in the same gear so I'd be hesitant to draw any conclusions from those graphs.
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TTQS
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« Reply #14 on: February 09, 2012, 02:57:44 PM »


Also, your graph seems faulty actually unless perhaps the different pulls are done in different gears?
As you can see, the power output @ 78mph seems identical but the torque is quite different. Basically the power is identical comparing after 78 mph but somehow the torque is higher for the "tuned run" which of course is both theoretically and practically impossible if the runs are made in the same gear so I'd be hesitant to draw any conclusions from those graphs.

Yes, good spot. Of course power and torque curves will always be equal at 5252 rpm because that gives equivalence in the relationship:

torque (lbft) = (bhp x 1.34102 x 60 x 1000 x 0.73756215) / (RPM x 2 x pi)
where 0.73756215 converts Nm to lbft and 0.00134102 converts W to hp

I would also be hesitant to draw too deep conclusions because the dyno deceives. I understand that they measure wheel power and derive/estimate clutch power from the run down. Before I had VCDS, I used the Liquid TT gauge to measure power based on MAF/0.8 and feel that these results more accurately reflect the peak output.

Once I get a new battery for my laptop, I'll log the car comprehensively with ME7logger and try to shed some light on what Revo's strategy is. Some Nefmoto members scoff at pro tunes (with some justification in most cases) but I have confidence they know what they're doing and I can learn from their tune. What I have gleaned so far indicates that their AFR tuning methodology is sound and mirrors what several experienced Nefmoto users do.

TTQS
« Last Edit: February 09, 2012, 03:04:10 PM by TTQS » Logged
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