My guess…
The VW engine compartment is completely sealed. The only air flow to the engine fan is via the vents under the window.
In the TDr, the front of the engine compartment is not sealed, so there is more than sufficient airflow for the engine fan.
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica Roadster
If you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)