My Foxjet has no jetpipe and I can't get a good smoke density, despite pumping a lot of smoke fluid into the efflux (using 2 of Tam's injectors). The efflux cools rapidly and doesn't vapourise the fluid...so I think injecting it close to the engine and letting it vapourise in the jet pipe would give better density. You could still put scale smoke injector pipes at the back end anyway.

Cheers,

Dick
England