How is meteors bundled mongo instance configuration different than the default mongodb configuration?

I am using both Meteor and Elixir together. After updating to the latest version of Elixir MongoDB package (added optional replica set support) I am unable to connect to my meteor applications bundled mongodb instance.

Currently my workaround has been to install mongodb locally and to connect both my meteor app and my elixir app to that instead.

Thanks

The bundled mongoDB has a replicaset and oplog set up (pretty much required for Meteor).