I've built and done some simple tests on a TEVO Tarantula but I've noticed some pretty dramatic under extrusions.
- TEVO Tarantula;
- Jim Brown's easy config fork of Marlin;
- Titan extruder (came with printer).
I've updated the firmware with the 400 steps as advised and calibrated the extrusion with the 100 mm method:
- When I run the calibration with the Titan extruder, only the 400 steps is fine and works as expected;
- When I connect the Bowden tube to the hotend and calibrate (at 200, 225 and 250°C), I see only ~50 mm of extrusion.
I've disassemble the hot end, changed filament and I can't see any signs of blockage. The Bowden tube in the hotend is not showing any signs of melting etc. and it is pushed all the way down to the hotend, as per the instructions.
So, what's going with this?
Summarizing for correct understanding: you measured 100 mm without the hotend heated and attached and about 50mm attached and at temperature but not hearing any clicks using a pretty long Bowden tube?
Bowden setups require a little more torque to push the filament all the way to the hotend. I've experienced this with my own 2.85 mm setup when I converted a 1.75 mm BullDog extruder to accept 2.85 mm filament. Your problem is most probably caused by filament not being gripped by the extruder gear and causing slipping on the filament (this does not necessarily mean that you hear clicking!). The Titan is a geared extruder so you should get more torque than a direct setup; this is exactly why you don't hear clicking, the gear turns but does not move the filament. Please inspect your filament after the extruder by removing the Bowden tube; ideally this should show you a regular pattern of the extruder gear.
What you can do to prevent this is to put more pressure on the filament by adjusting the pressure of the spring. In my setup I use some screws to get the spring out of the equation and clamp it directly only tightening the screws by hand (when switching filament I need to unscrew these).
You should also PID tune your hotend to be sure that the heater is optimally tuned to keep the hotend at a certain temperature level.