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Loss of boost spike?

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Unfortunately some, or rather many, are not perfectly accurate from the start. Mine when new displayed 1 ohm when turned on and touching nothing. I've spoken with a few techs and it takes a bit of money to find one that is good. It was partly why I said leave the N75 for now and lets make sure it isn't any of the other possibilities.

I say hang on to the N75 for now.
Try a leak detection test with VCDS.
Test for small leaks in the air inlet system.
Perhaps the WG has loosened or just needs a bit of added preload.
 

Whitedemon

Passed Driver's Ed
Location
Miami, FL
In the meantime, I decided to do a 3rd gear pull and log specified vs actual using VCDS, this is what I got:

Group A:'115
Engine SpeedEngine LoadBoost PressureBoost Pressure
TIME(G28)(specified)(actual)
MarkerSTAMP /min % mbar mbar
0​
2200​
86.5​
1950​
1230​
0.07​
2200​
87.2​
1970​
1250​
0.15​
2240​
89.5​
1920​
1270​
0.23​
2280​
91​
1930​
1300​
0.31​
2320​
93.2​
1950​
1320​
0.39​
2320​
94.7​
1960​
1350​
0.46​
2360​
97​
1980​
1370​
0.54​
2400​
99.2​
2020​
1400​
0.62​
2440​
101.5​
2010​
1430​
0.7​
2480​
103.8​
2030​
1460​
0.77​
2480​
106​
2040​
1500​
0.86​
2560​
108.3​
2060​
1530​
0.93​
2560​
111.3​
2060​
1560​
1.02​
2600​
114.3​
2070​
1600​
1.1​
2640​
117.3​
2090​
1640​
1.18​
2680​
121.1​
2080​
1690​
1.24​
2720​
124.1​
2090​
1730​
1.33​
2760​
127.8​
2120​
1770​
1.4​
2840​
132.3​
2140​
1830​
1.48​
2880​
137.6​
2160​
1890​
1.55​
2920​
142.1​
2180​
1950​
1.64​
2960​
148.1​
2220​
2020​
1.72​
3000​
152.6​
2230​
2070​
1.79​
3040​
156.4​
2260​
2100​
1.87​
3120​
159.4​
2290​
2130​
1.95​
3160​
162.4​
2330​
2180​
2.03​
3240​
165.4​
2330​
2220​
2.11​
3280​
169.9​
2390​
2270​
2.18​
3320​
172.9​
2440​
2300​
2.26​
3400​
176.7​
2500​
2350​
2.34​
3440​
180.5​
2540​
2400​
2.41​
3480​
183.5​
2540​
2420​
2.5​
3520​
185​
2540​
2430​
2.58​
3600​
185.7​
2540​
2420​
2.65​
3640​
186.5​
2540​
2420​
2.74​
3720​
185.7​
2540​
2420​
2.81​
3760​
188.7​
2530​
2450​
2.89​
3800​
190.2​
2540​
2450​
2.96​
3840​
191.7​
2540​
2450​
3.04​
3920​
191.7​
2540​
2470​
3.13​
4000​
191.7​
2540​
2460​
3.2​
4040​
191.7​
2540​
2470​
3.28​
4080​
191.7​
2550​
2470​
3.36​
4160​
191.7​
2540​
2490​
3.43​
4200​
191.7​
2540​
2480​
3.51​
4280​
191.7​
2540​
2470​
3.6​
4320​
191.7​
2540​
2470​
3.68​
4400​
191.7​
2550​
2470​
3.77​
4480​
191.7​
2540​
2480​
3.86​
4520​
191.7​
2540​
2480​
3.93​
4600​
191.7​
2540​
2480​
4.01​
4680​
191.7​
2540​
2470​
4.09​
4720​
191.7​
2540​
2480​
4.16​
4760​
191.7​
2540​
2470​
4.25​
4840​
191.7​
2530​
2470​
4.33​
4880​
191.7​
2530​
2470​
4.41​
4960​
191.7​
2520​
2470​
4.49​
5000​
191.7​
2520​
2460​
4.56​
5040​
191.7​
2510​
2460​
4.64​
5080​
191.7​
2500​
2480​
4.72​
5120​
191.7​
2500​
2470​
4.8​
5200​
191.7​
2490​
2470​
4.87​
5240​
191.7​
2490​
2460​
4.95​
5280​
191.7​
2480​
2470​
5.02​
5320​
191.7​
2480​
2470​
5.11​
5400​
191.7​
2470​
2460​
5.18​
5480​
191.7​
2470​
2430​
5.27​
5520​
191.7​
2450​
2420​
5.34​
5520​
191.7​
2450​
2420​
5.42​
5560​
191.7​
2450​
2430​
5.5​
5640​
191.7​
2440​
2420​
5.57​
5680​
191.7​
2430​
2420​
5.65​
5720​
191.7​
2430​
2430​
5.73​
5760​
191.7​
2420​
2440​
5.8​
5840​
191.7​
2410​
2420​
5.89​
5800​
191.7​
2410​
2420​
5.97​
5920​
191.7​
2400​
2410​
6.04​
5960​
191.7​
2390​
2390​
6.12​
6000​
191.7​
2390​
2370​
6.21​
6040​
191.7​
2390​
2360​
6.28​
6080​
191.7​
2380​
2350​
6.36​
6120​
191.7​
2380​
2330​
6.44​
6160​
191.7​
2380​
2330​
6.51​
6200​
191.7​
2370​
2330​
6.59​
6240​
191.7​
2370​
2320​
6.67​
6280​
191.7​
2370​
2320​
6.75​
6360​
191.7​
2370​
2320​
6.85​
6440​
191.7​
2360​
2310​
 

Whitedemon

Passed Driver's Ed
Location
Miami, FL
graph shows the slow spool that I've been talking about, difference in peak boost looks to be of only about 1-1.5 psi though, but notice how actual doesn't catch up with specified until really late in the RPMs.

So..boost does feel like it's there, it just takes longer than usual to build...specified should be catching up with requested way earlier than that. I have no boost spike at all, just slow building boost.

All this, once again, makes me feel more inclined to suspect it's going to be a pre-turbo exhaust leak, that or the N75 making the wastegate open up too early.
 

Chumeta

New member
Location
Vitoria-España
I see 2 options after all your cheks:
Caudalimeter(flow meter)
All motor load is based on that parameter . I have 3 caudalimeters and with all three I have different turbo pressure peaks and different measurements.
Wastegate
Shorten (regulate) the wastegate rod since it does'nt meet demands on your log, and thus it will be able to arrive at the demands.
Sorry for my bad English
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
If that were my data...I would've already added about 1mm to 1.5mm more preload....or as Chumeta said; "shorten the wastegate rod."

Needing more WG preload does mean something has changed however. That is, if the actual pressure was matching the specified in the past. So, it is possible the WG is loose now.

Have you ever adjusted, add or subtract, WG preload before?
If not, I have a vid or I can explain.
 

Whitedemon

Passed Driver's Ed
Location
Miami, FL
I see 2 options after all your cheks:
Caudalimeter(flow meter)
All motor load is based on that parameter . I have 3 caudalimeters and with all three I have different turbo pressure peaks and different measurements.
Wastegate
Shorten (regulate) the wastegate rod since it does'nt meet demands on your log, and thus it will be able to arrive at the demands.
Sorry for my bad English
I’m guessing you mean the MAF sensor? I’ve already checked that and it’s good. Also checked the MAP sensor as well, good too.
 

Whitedemon

Passed Driver's Ed
Location
Miami, FL
If that were my data...I would've already added about 1mm to 1.5mm more preload....or as Chumeta said; "shorten the wastegate rod."

Needing more WG preload does mean something has changed however. That is, if the actual pressure was matching the specified in the past. So, it is possible the WG is loose now.

Have you ever adjusted, add or subtract, WG preload before?
If not, I have a vid or I can explain.
I haven’t, yes a video on how to do it would be great. Thanks
 

Chumeta

New member
Location
Vitoria-España
The Wastegate over time becomes loose I think simple by use (km) .
Roh Echt you, how do you regulate?
I unplug the N75 and with the VCDS I make log 115 and the value that is repeated the most should be 0,28-0,29max in K03 and 0,34-0,35 in K04
I think it´s the way without disassembling.
To get to the WT rod screw , remove the transmission heat shield(2 of 16mm screws) . The turbo bracket (2 of 13mm screws) and you get to the 2 screws of the WT . Before moving these screws it´s advisable to mark the current position with a marker.
Shortens at first 1 turn
Place everything and make a new log until you get the pressure mentioned before with N75 unplugged.
Be careful , a lot of heat is generated in all parts!!!!
 

ROH ECHT

K04 PLAY
Location
PDX OR
Car(s)
2007 MKV GTI
Chumeta, is
0,28-0,29max in K03 and 0,34-0,35 in K04
the amount of reported pressure by the MAP with the N75 unplugged?

For myself I just adjust the preload. I decide how much is needed on a guess and make the number of turns of the nut on the WG actuator rod to increase or reduce.

I do the adjustment when cold and the heat shield over the long axle removed. I clamp the WGA rod, loosen the outer(nearer the end of the rod) 10mm nut, make the number of turns to the inner 10mm nut, and tighten the outer nut. Go look at data. There are six sides to the nut, so just count the sides as you turn it; 1 turn is 6 sides and 1.5 turns is 9 sides. I cut a 6mm coupler nut in half to add to the end of the rod because it is easier to use a socket with it. Then use something to turn the inner nut. I use a wooden dowel...because it works for me.

This vid I made to show a basic amount of preload. To add preload; just loosen the outer nut. Turn the inner nut away from the WG linkage the number of turns you need. Tighten the outer nut. This vid is better viewed on a larger screen.
 

Whitedemon

Passed Driver's Ed
Location
Miami, FL
Thank you both.

I think I’ll leave that option as a last resort. I want to make sure first I have no leaks anywhere. I’ll be running both, pressurized and smoke tests, and check around the exhaust manifold for possible leaks. If nothing shows then I’ll be adding the preload to the WG 👍🏽
 

Chumeta

New member
Location
Vitoria-España
If that´s the amount of pressure reported by the map with N75 disconnected. This I learned in germany, this measurement is the one that the new K03 and K04 turbos have with the nuts sealed when they are placed on the engines.
 

Chumeta

New member
Location
Vitoria-España
Roh, your video is fine, but the manipulation is easier by marking with an indelible marker to count laps and release as I alredy mentioned the turbo plate support, which are 2screws of 13mm , and you get more space.
 
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