Wow, Lots of replies... exciting stuff. I never thought of "rolling / knurling" a pen type tube nozzle.
More details. I am not really looking for more BOOST in this experiment. I have a second engine for that and it burns less fuel that what you guys are thinking Im up to. For now I want to simulate the jet car fire show before I blast off.
I have tried many experiments external to the exhaust cone and none light off on demand and when it does it looks awful. The problem, with at least the engines I have, is the exhaust velocity is to high even at idle to light and sustain flame. Sure I can get the smoke / diesel coming out of the smoke tube to light 50% of the time.... but only before the engine gets to idle RPM and the start is a little wet and studders it's start. I need to make the exhaust wet on demand before the exiting gasses compress to a higher velocity in the exhaust cone. The Jet Car guys call it a Hot Streak. With a good tongue of fire on demand I should be able to light off just about anything a few feet back with the engine at idle. I do not plan on using the injector at any rpm above idle..... I will need to experiment with RPM, but must be cautious of any back pressure to the turbine section.

Although I could roll my own purpose built AB cone, the calculations show the entire engine Starter to tip of AB section to be like 3 foot long.... that is to big and out of the question. My intentions are to not insert anything inside the already small exhaust cone, except a tiny nub just up stream of where the flush mount jet nozzle would be. I plan on welding a threaded block to the exterior of the cone so I can change nozzle sizes till I get it right. I will be plumbing it with stainless smoke tubing running downhill to a one-way check valve, to a fuel solenoid on an adjustable timer relay (about .6 seconds) , to the tank that will be pressurized by the case bleed air.

I have a guy at work that can weld just about anything I throw at him so I dont need to learn that part for now.

The track owners want more excitement beyond the initial WOW when they see me run. It is time to turn up the heat... so to speak.

I would like to see something similar to what is in the picture, but on demand. This happened on it's own with a bad start in in 110 degree humid air. With a flame like this I could light off what ever I spray out of the smoke tubes...


********* Wow lots of good posts while I was writing this one.... Wocketman and I are thinking alot alike... I see. thanks for the confirmation on pressures Sean,