In my research , the engine could explode if the following condition exists , any open port an too much unburned fuel in the exhaust gasses, personally that turned the idea sour for me , but , a faux dual exhaust one for the motor an one for "fun" smoke or fire . I still havent had time to build the system "old school style " small scale on my work bench an I am preety sure that in the case of fire it wont work with out the back pressure from the motor . now . on the other hand as YRR found ,smoke, could be fun an significantly safer , c'mon , heres the scene start the smoke an just rev the motor a lil how many folks would be fooled into thinking you were smoldering your tire off the rim an just idle out of a small cloud ? = harmless fun .