Disco 2 TD5 Overboost

Ok playing with a td5 i have had to repair basically everything on the bloody thing but this is the latest fault. Its an automatic and it all started with a big flat spot when started you can rev - it will reach nearly 3200 rpm flat as a pancake then punch you in the face with boost and from then on boosts from lower revs and behaves normally apart from overboost under higher load.
Vehicle has been mapped its throwing codes 90 and 101 overboost. I bypassed the solenoid same issues checked the waste gate with a pressure test and it opens at 18psi which as far as i can see isn't beyond the capabilities of a Td5. While testing discovered the maf is bushed reading 10kg/hr at idle instead of the 55 ish it should be i am wondering if the ecu is crying overboost due to a mismatch between map sensed and maf sensed.
Gonna rig a t into the boost circuit tomorrow and see what the boost pressure when driving is

What is the standard boost pressure meant to be on a TD5?

With factory setup is around 18.8 psi/1.3bar for Disco 2(MAP =230KPa)) and 16psi/1.1bar Defender(MAP=210KPa) depending on the ambient pressure(average AAP=100KPa) cos the management is working based on MAP(manifold absolute pressure) reading which is = boost + ambient pressure(AAP), on both is possible to shorten the wastegate rod as MAP to grow to max 245 cos the overboost limit is set to 247 by default

great info cheers for that can have a proper session of monitoring through live data tomorrow and adjust as necessary

boost reached 239.9 according to live data on map sensor but still limped with overboost codes. AAP 106 . Fitted a new maf tonight and air flow at idle up to 69kg/hr from 10kg/hr didn't have chance to test drive though.

you should have tried with MAF unplugged then, that MAF reading at idle is a bit high but it's normal if the engine was cold and the revs above 750.

not high from the research i read between 55-70kg/hr and since this has no cat/egr less restriction for turbo,engine was cold and only run long enough to check live data on airflow. Went for a run with maf disconnected but didn't go far then gonna have another proper run tomorrow to see how she performs with proper maf readings
Cheers for the help fella

It's overboosting - 240KPA is too much.Wastegate arm on the turbo needs to be totally sloppy with the actuator arm disconnected. Airflow is top of the shop,but thats OK. You just need to get the wastegate to keep boost below 230...

I have around 240 on mine without any overboost, the factory setting is to reach 230 with 13 threads left on the wastegate rod, i've adjusted to 10 even 9 threads on some and all were above 230 without problems, AFAIK the factory set overboost limit is at 242(referrence 4.36V) and as long as the OP has reached 239 it means the ECM didnt cut fuelling at 230 cos if the overboost limit was there it wouldn't have get to 239 reading ...unless nanocom shows different than the ECM gets

I base my reply on Testbook T4 readings from all the way back to 2003.OK, the refresh rate might not be too good,but 230KPA is where all the problems start.200 or even 210Kpa will give all the performance you need.

Interesting... i dont want to contradict you, i'm just sustaining my own experience and i'm trying to find out as much as possible, that thing with 200Kpa gives good preformance sounds strange to me though especially that i know how mine feels with my newley fitted forge wastegate actuator set as to reach 240 MAP under the highest load, also at 100 AAP that 200 MAP would mean 1bar boost which is a default mode with limited boost for failed AAP sensor so i doubt it can be very good performance

solution to this was modifying remap and detuning a little and reseting the boost again