ok in a pistoin engie, if there is no backpressure present, i.e. only an exhaust manifold then you will quickly blow a valve or two!

in a rotary, what happens if you run the car too long like that?

also if i want just a straight pipe from a header all the way back to a free flow muffler, i.e. a magnaflow that you can see straight through, will it hurt my car or just my ears?

 

bump

Ive got the same question,

 

It doesn't hurt the car, but your ears will start to bleed

 

My car is quite loud right now with my setup, and that's with the stock muffler. There's no danger of damage to the engine, because as we all know, there aren't any valves to bend.