potenial boost leak - vcds logs done

[jasongtr]

I've done a vcdd log session to record requested and actual boost pressure, i assume the numbers are supposed to be fairly close across the rev range, i did it with 2nd gear wide open throttle (where I'm testing it i can't really get all of third)

some of the figures are within 200mbar of each other, whilst some are 400mbar, the road I'm testing on has a pretty severe bump in it and flying over that might not be giving a completely accurate reading maybe as the load on the engine will possibly change (thats clutching at straws really)

i can't go anywhere right now but ill do a log on the way home.

Does what I'm seeing at the moment suggest a leak or is it normal, this is the 1st time I've done anything like this

 

[<tuffty/>]

Which way around is the difference?... for a leak actual would be lower than request... although this could also indicate a tired turbo... would need to log N75 duty too... and lambda adjustment to see if the ECU is pulling fuel under boost..

http://www.ross-tech.com/vag-com/m_blocks/

<tuffty/>

 

[jasongtr]

actual is lower than requested, could be a tired turbo the car has done 142k, no idea if the turbo is the one the car left the factory with, just trying to get to the bottom of the slight whooshing sound I'm getting under full throttle

 

[<tuffty/>]

Noise could be due to the worn turbo too tbh... have you done a smoke test?

<tuffty/>

 

[jasongtr]

no mate, not sure i now anyone that has that gear, i did plan to get Bill to map it (with the smoke test he offers), but debating whether to chuck a 3" downpipe / decat / fmic on 1st, the only thing i won't then use on the mk2 golf is the intercooler as i have a custom pro alloy core one on that.

 

[jasongtr]

did a log with the boost pressure N75 control, it was mostly 94.5% - can't say as i really know what the hell I'm looking at though. Lambda % seemed to be -0.8 all the way through (but again might of been looking at the wrong thing - it was Group 032 for that one)

 

[<tuffty/>]

N75 is flat out... lambda isn't taking much out fuel wise so doesn't sound like its leaking out... what it does sound like is a tired turbo...

<tuffty/>

 

[jasongtr]

ok mate, cheers, decision time then, replace, hybrid or tfsi ko4 - rods of course

350-375hp is going to be plenty in the mk2 so i best get thinking


edit, i assume N75 flat out is a good thing?

 

[<tuffty/>]

edit, i assume N75 flat out is a good thing?

... not in this case no lol..

Could also be a tired actuator of course... what boost do you get with the N75 electrically unplugged?

<tuffty/>

 

[jasongtr]

no idea ill have to check

 

[jasongtr]

managed a 3rd gear run, with the N75 unplugged (gutless mode)

lambda was 2.6 at 2600 revs then 0 from there to the redline, actual boost was

revs - actual boost
2880 - 1330 mbar
3240 - 1320
3560 - 1310
3880 - 1310
4240 - 1310
4520 - 1340
4840 - 1340
5160 - 1350
5440 - 1350
5720 - 1380
5960 - 1430
6160 - 1430
6360 - 1470


mean anything?


oh and the whooshing noise was either very little or not there - hard to tell

 

[jasongtr]

and plugged the N75 back in and the noise is back so definitely higher boost related

 

[<tuffty/>]

managed a 3rd gear run, with the N75 unplugged (gutless mode)

lambda was 2.6 at 2600 revs then 0 from there to the redline, actual boost was

revs - actual boost
2880 - 1330 mbar
3240 - 1320
3560 - 1310
3880 - 1310
4240 - 1310
4520 - 1340
4840 - 1340
5160 - 1350
5440 - 1350
5720 - 1380
5960 - 1430
6160 - 1430
6360 - 1470


mean anything?


oh and the whooshing noise was either very little or not there - hard to tell

Actuator pressure is 0.5bar typically... Bill would be in a better position to comment but just literally based on the stuff you have posted so far its pointing towards a tired turbo... can't rule out a boost leak of course but without seeing the car or a smoke test if difficult to diagnose like this...

Tricky one dude... if I was up visiting my brother in Bicester I'd pop over and have a butchers

<tuffty/>

 

[jasongtr]

so even with the N75 unplugged my boost levels are too high then - looks like I'm getting 1.3bar

 

[<tuffty/>]

so even with the N75 unplugged my boost levels are too high then - looks like I'm getting 1.3bar

Gotta take off atmospheric pressure mate... which is 990-1000 mbar

<tuffty/>

 

[jasongtr]

ah righto, did wonder why the car was trying to request over 2bar on a standard ko4 - thought that was bleedin high