4 GB Limit for Powerpivot text file imports via ACE text data source driver

We have been investigating reports that large text files are not completely imported into Powerpivot. And indeed a thorough investigation showed two unexpected things happening.

1.The text import is cut off at 4 GB 2.Import is shown as successful.

This applies to the SQL Server 2008 R2 and the SQL Server 2012 Powerpivot add-in for excel in both, 32 and 64 bit version.