Boost leak / bad MAF? [Logs inside]

[barelyrelevant]

Hey,
After a frustrating couple of weeks of new ownership I'm sure my car is still down on power. :-(

Recently replaced the DV (rev G), PCV and cam follower. Also had new Bosch spark plugs and 4 genuine coil packs.

I originally bought Torque to diagnose a misfire (turned out to be a coil pack) but whilst messing around I noticed the MAF readings were waaay over what they should be according to what I read on here...turns out that was because the MAF sensor units in Torque were set to CFM rather than g/sec ( ) but I had also noticed peak boost seemed to be on the low side.

I've done a few 3rd gear pulls using Torque and here are the graphs, for some reason Google docs doesn't display RPM along the horizontal axis but they were done from approx 2krpm until 6krpm.

My initial thoughts are that the boost looks a bit lumpy, isn't peaking as high as it should and trails off faster than it should at high RPM? Equally I wasn't sure if an under reading MAF would make the ECU deliver less boost to protect the engine?

Please help, I just want have my car running as it should.

Run 1
Max boost: 9.5psi
Max MAF: 136 g/sec


Run 2
Max boost: 10psi
Max MAF: 134 g/sec


Max boost: 8.8psi
Max MAF: 136 g/sec

[v4rley]

Don't know how to interpret the graphs but could it be a boost leak? Looking at your previous post have you removed the boost tap? Also looks like the outlet jubilee clip might not actually be on the hose?



Looking now there is a a fair amount of oil below so don't think the clip is on the hose

[barelyrelevant]

Yeah the boost tap was plugged when the rev g dv was installed.

Bloody well spotted with that hose, I took some other photos that day so I'll have a look and see if there's a better angle.

[v4rley]

Yeah tbh I was pretty impressed with my spotting of it. Did you remove the boost tap the other end at the top of the bay?

[barelyrelevant]

Yeah that whole lot could be removed when I swapped out the Forge as it's only purpose was to control the solenoid.

[barelyrelevant]

Checked that hose at the weekend and it was solid, was just a funny angle/camera flash which did it.

Any other ideas anyone?

[pudding]

According to those readings, your engine is only producing 165hp!  Does it feel that slow?

Have you got VAG-COM?  If so, verify the MAF readings with that as a second opinion maybe? 

You would be better off doing the pulls in 4th as well mate because that's a 1:1 ratio and will take gearing out the equation and make the engine work a bit harder, so might increase the MAF readings a bit. 

[barelyrelevant]

According to those readings, your engine is only producing 165hp!  Does it feel that slow?

Have you got VAG-COM?  If so, verify the MAF readings with that as a second opinion maybe? 

You would be better off doing the pulls in 4th as well mate because that's a 1:1 ratio and will take gearing out the equation and make the engine work a bit harder, so might increase the MAF readings a bit.

It's hard to say if it's that low, it seems to shift ok but the shove of torque when the turbo comes in always makes cars feel faster than they are. It definitely feels like it's lacking at the top of the rev range, where as when I first got it, it seemed to pull like a train all the way to 6k.

This seems to be reflected in the logging where the boost tails off significantly at the top of the rev range.

I posted in the TFSI tuning facebook group and got this reply:

"Second look if there is correction in injection or ingnition timing .and 3rd look for boost leak or Turbo wastegate actuator not to lazy."

No, not got VAG-COM unfortunately. Will see if I can find any local members.

[barelyrelevant]

Found a small tear in the hose going to the brake booster valve thing, have replaced that and it feels like it's made a difference, did some quick logging this evening and it seems to be reaching peak boost of 10 - 11.5 now which is a slight improvement as well as holding boost better.

However the MAF readings are still only reaching ~135g/sec which is a fair bit lower than it should be.

Also noticed on Torque that my coolant is hovering around 72 - 78c which isn't right either, the fun continues...

[Dan_FR]

Torque is terrible for accurate logging, find someone with VCDS or get yourself a £20 clone and use it yourself

Looking at your logs , boost is tailing off far more than it should be.... You should be holding at least 4 or 6 psi of boost at the redline, not tailing off to nothing, which also explains the low peak MAF figures..... VCDS logging will tell you whether a significant leak is causing this (real time lambda correction) aswell as comparing with the specified boost and N75 control to understand what the ECU is trying to achieve.

Torque can show you the real time fuel trims as well as the long term multiplicative figure which can indicate whether you have a significant leak. My money is on the actuator.

You also need a new thermostat

[barelyrelevant]

Thanks a lot for your input, I was checking the coolant temp again today driving home from work and it was bang on 90c so not sure what is going on there...seems to get up to temperature in a reasonable time. Certainly not ages and ages as if one of the stats is stuck open.

LTFT is about +10% at the moment, however I am running a RamAir intake if that makes a difference.

I have just reset that this evening and will see where it ends up over the next few days of driving. Are there any other checks I can do regarding the fuel trims with Torque until I get access to VCDS?

I thought there is a possibility of the brake booster check valve having failed as well? Allowing boost past when it shouldn't? I noticed one of the pipes running off the check valve does not look in the best shape and could also be letting unmetered air into the TB?

When I was doing some more logging last night I noticed that it felt more like a fuel cut around 6krpm as the acceleration dropped off that sharply.