I have put 8000 miles on the TTiD now
One thing that has disappointed me has been the straightline performance. She's fine at motorways speeds, but very sluggish setting off from the lights.
As part of fixing the throttle body that failed, and replacing one of the boost solenoids (not faulty) I ended up doing some monitoring of the boost levels
On tickover the requested MAP is 1.2 bar. Actual is 1 bar, or just a little under
Having read
https://www.uksaabs.co.uk/UKS/viewtopic.php?p=1380777 (thanks wrighar) I'm trying to figure out the best diagnostic strategy as I think the setup for the 9-3 and 9-5 are very similar
The engine essentially has little boost until it gets to 1500 rpm when it's halfway up the gauge and by 1750 rpm it's pulling strongly with the needle in the red. Data wise this corresponds to 2.9 bar MAP or 1.9 bar boost
It appears to me that this is a physical issue. Either the small turbo is underperforming, or the crossover valve isn't working correctly.
I have tried to remove the pipework with the crossover valve with the turbo in situ. Everything came off except the one bolt around the back where I just couldn't get an allen key/ bit into place
Having spend some time trying to understand how the TTiD arrangement works I "think" that the wastegate operates on the big turbo, while the variable vane adjustment also operates on the big turbo. I have also read that the small turbo's have a habit of going "weak", though new ones are only ~ £100
Any advice, knowledge or suggestions much appreciated. If I am going to have to remove the turbo etc, I would really like to be sure of the nature of the fault beforehand so I can simply remove / replace over a weekend.
When she's back to full performance, then I might consider getting her breathed on...
