ok so im building a custom exhaust for my 13b 6 port. i was going to run a stainless presilencer from mazdatrix but i just was curious whats the diofference between a presilencer and a regular muffler? i understand the high exhaust temps makes stainless steel a must. is there a rule of thumb distance from the exhaust port that the presilencer should be? what about o2 sensor location?

thanks
andrew

 

i was thinking of installing one of these after the collector then an aditional muffler at the tail pipe. http://www.jegs.com/i/Hushpower/526/12512400/10002/-1

 

anybody?

 

The pre-silencer holds enough pressure to open the 5th and 6th ports. You can hook up the 5th and 6th ports to open via pressure from the air pump if you wish to have a straight pipe.

I'm dong something a little similar. My route(if it helps) is modifying my true dual header to a single exhaust pipe, about 1 1/2 feet from the header is the resonator, and straight to another muffler. I'm using the air pump to open my 5th and 6th ports.

To see how to hook up the air pump to the 5th and 6th port, click here!

Hope I helped!
Maybe?

 

In principle there's no difference between a presilencer and a muffler. When people talk about "presilencers" on this board it usually means something installed where the cats used to be, a muffler before the rearmost muffler.

Some of the Racing Beat presilencers that Mazdatrix sells have backpressure sensing tubes for the auxiliary port actuators.

As far as rules of thumb, someone told me one time that you should have your first muffler no less than 6 inches away from the collector. No idea if that's correct, but it sounds reasonable. The O2 sensor should be just after the collector.

 

cool thanks for the info guys. this is for a vw bug getting a rotary transplant. my exhaust space is limited but i want to retain a somewhat quiet exhaust notew as well as significant back pressure for the engine. in the shortest amount of pipe possible. as for the 5th and 6th ports, im going to build a trigger in my megasquirt to activate a relay at 3000rmp to trigger a electric actuator to open them. thanks again