Troubleshooting - what is 'load control'??

[muckipup]

Hi,

I am hoping that a 'techy' can help me work out what I believe is a running problem with my car.

In short, I see erratic AFR plots on the Dyno which has been described as a problem with "load control" by the experienced mapper who did the remap for my car. On the road, the car runs great up to about 5000 rpm then appears to run out of puff as it accelerates.



This got me thinking about this "load control" that was mentioned. I don't have a clue what this is other than what the name suggests or what hardware/sensors directly influence this. Despite this, I went out and logged the Specified vs Actual Engine Load in VCDS.



Does this look right?

I logged a bunch of other stuff and can see no issue with misfires (coilpacks and plugs seem ok), actual vs requested boost (tracks very closely although requested is lower than I would like for a Stage 2+), MAF values are a bit low for an ITG intake (200 g/s max) but not sure if this is cause or effect, fuel rail pressure actual tracks very close to requested (although requesting about 10 -15 bar less than the Autotech HPFP can produce) and low pressure stays up well too.

Any ideas please??? Does anyone alse have figures for actual vs. requested load that I could compare with? Is this likely to be hardware/sensor on in the map?

Thanks

[Richn83]

Mines a standard K03 mate but see logging graph, the engine load specified and actual is clearly off on yours also very odd that the values have such a dominant plateau to the graph nothing is normally that perfect.



 Also just done you a graph of my load specified vs actual

[muckipup]

Thanks Rich,

This is the first comparison of engine load that I've seen. As you say, my figures appear to be way up there and almost look like they are hitting some kind of limiter. I have still got no idea what 'controls' load control.

[Richn83]

When i did my logging I tried to look into what engine load was but I couldn't find a decent explanation, do you have any of the other figures to go along with your load values such as boost fuel pressure lambda etc to see if there is any that looks off in those values?

[muckipup]

Hi Rich,

Was out tonight and did a bit more logging. A bit tricky as I had to do 4th gear pulls (third just ended up with wheelspin) - thank heavens for the disused airfield in my back garden 

I'll post up some graphs from one of the runs as plotting out the others showed them to be almost identical in every respect. Will get these posted tomorrow when I get a moment 

[vRSAlex]

The K03 just cant always make requested.  The load will ask for max, but the turbo can produce max load throughout the whole rev range.  Just as if you logged boost requested vs actual.  I get full fuel pressure throughout so it may be worth checking the follower and changing to an RS4 pressure return valve.  It looks like you are getting a small flat spot around 5.2k which is then picking up again.  Its also interesting that you have an autotech pump fitted?  Im worried that these are causing the flatspots on 2+ cars.

[muckipup]

Thanks Alex,

I have certainly considered the RS4 valve although I am not seeing anything with the rail pressure that would suggest that the actual rail pressure is venting before it gets to the requested rail pressure. I still haven't ruled it out but am delaying partly because I want to suss out this 'load control' thing and partly because it is an awkward job to fit the valve.

Do you know what the engine senses when measuring actual engine load i.e. what sensors come in to play?

Anyway, on the subject of load control, I logged it with several runs last night including 2 fourth gear pulls and I see the same thing (the graph in the O.P. was a 3rd gear pull, this is 4th).....



Rich - I also logged rail pressure, lambda, boost and MAF (and misfires which were minimal so not uploaded). I didn't log timing pull but previous experience showed that to be healthy too. The full 130bar of rail pressure from the Autotech HPFP comes in a bit late in the rev range (do others get the full 130 bar mid-range??) and the MAF seems a bit below what I have seen with others on a Stage 2+ car but doesn't look horrific...It's that load control that has me foxed!.....









 

[Richn83]

Hmmm Something doesnt look good with the air mass flow, again mine is a standard car but dont think you should be seeing such a drop off in requested boost and air flow.  Have plotted my results for boost air mass flow and load.


I guess the question is is this something that was programmed or is the ECU pulling something back?

since the key has been chopped pink is boost specified, yellow boost actual, purple load specified, dark red load actual.

[vRSAlex]

What intake and intercooler are you running on the car?

[vRS Carl]

The full 130bar of rail pressure from the Autotech HPFP comes in a bit late in the rev range (do others get the full 130 bar mid-range??) and the MAF seems a bit below what I have seen with others on a Stage 2+ car but doesn't look horrific...It's that load control that has me foxed!…..

My car requests and makes 130bar (or thereabouts) from around 2800rpm onwards using Autotech internals

As shown here

[Richn83]

The N75 duty cycle isn't showing heavy load as well and I know that when RR turbo crack caused a boost leak he was seeing constant 90% load so not likely to be a boost leak issue.

[muckipup]

Yeah, I notice that the boost and MAF drops off about the same place (or just after) the actual engine load value drops away. I am just not sure what is cause and what is effect. I am told that a failing N75 is not always apparent on the N75 duty cycle and that this could affect load control and the weird AFR plot on O.P. I dunno   

[muckipup]

My car requests and makes 130bar (or thereabouts) from around 2800rpm onwards using Autotech internals

Cheers Carl - I thought that was the case with others.

[muckipup]

What intake and intercooler are you running on the car?

An ITG Maxogen intake and Forge Twintercooler, Alex

[Richn83]

Just read something that suggested engine load (at least on G60 supercharged VW vehicles) was calculated by manifold pressure so rather than the drop in engine load being the issue I wonder if its a sympton?  

Do you know anyone else who has the same map as you so you can compare specified boost?