Thread: What is down side to high boost

On my recent trip to Qld on the way home my D2 TD5 EU3 auto suddenly started boosting to 24-25 PSI on my aftermarket gauge. I had an alarm set at 21PSI, as this was supposed to be when the ECU would cut and it annoyed the crap out of me until I was able to silence it.

This would happen all the time on cruise control and I would disconnect it and try to keep boost down to 20-21PSI.

However the EGTs would peak at 500C at 24PSI rather than the usual 700C plus at 20-21 PSI. This was on a cool day of about 19C.

I found the problem today as one hose from modulator to controller had popped off and the hose from the inlet manifold boost side had a hole in it. Yet it hadn't had any high boost before. amazing.

The ECU program has been modified by Offtrack to increase the intervention limit and MAF limit and my telltale says 26PSI as the max. It only once stumbled at these PSIs. ( BAS program, Serck intercooler, egr delete ,ceramic manifold, no cat, lower restriction muffler, snorkel.)
I checked the gauge with my Nanocom today and the boost on the gauge and Nanocom were pretty close. I got it to 1.49 ATM just accelerating locally with the gauge reading about 22PSI.

So my question is
What is harder on the engine , high boost and low EGT or lower boost and high EGT?

I have a manual boost controller that I can fit and set to 21PSI or say 24PSI both of which seem to accepted by the ECU. I agree with earlier threads that with the wastegate closed the boost at part throttle is higher than with modulator enabled.

I believe that there would be no harm done by running higher boost at part accelerator but I am concerned about what such high boost on flat out acceleration such as cruise going up a hill. Is it harder on the head gasket with high boost , but low EGT's, or easier?

Regards Philip A

I might be wrong but I don't think 24-25 PSI on a sorted TD5 is an issue
A tired old 10P with a floating head and 25 PSI not such a good thing though