sunkenkarma

Im getting my 88 RX-7 Straight piped pretty soon, the cat is gutted, car is N/A and completly stock, along with the pipes, ill be getting 2 mufflers thrown on aswell....What I was wondering Is what Size Piping should the 13b go could with? I heard they need a good amount of back pressure to operate decently, and the Shop Im going to kinda needs to know haha.



All help is appreciated, thanks!

Aaron Cake

iTrader: (1)

Back pressure is always bad, always.

The only reason the 2nd gen requires some backpressure is to provide a pressure signal to the aux port actuators, which open the aux ports around 3800 RPM. However, this can be easily converted to use air pump pressure so you can run a proper open exhaust.

I think you will be surprised as to how loud the car becomes. It is almost not worth the trouble for the few HP gained, because unless you go to a header, your gain will most certainly just be noise. The stock exhaust manifold is where about half of the restriction lies so even if you are running a free flowing catback, the engine is stick breathing through a bathtub drain.

Controlling noise on the NA is a real issue. Once you gut or replace the cats, the mufflers have to handle all the noise and that doesn't work very well. I'd suggest instead of running a straight pipe, run at least a resonator in place of the cats. It won't hurt flow but will significantly cut down the noise.

funkjaw

iTrader: (3)

Straight pipe it with 2 1/4" piping. The first thing you will notice is how awesome your throttle response got AND they sound awesome with straight pipes.

Do it.

TheAbsence

iTrader: (19)

You're going to need a presilencer of some sort in between the engine and the mufflers. The one exception to this would be if you have stock mufflers, Racing Beat, or some other brand non-straight-through mufflers in the rear.