brownmound

I was talking to my mechanic today about RB exhaust systems. It trust his opinion since he has been racing rotaries since the RX-2....anyways, he says that with the dual pipe "long primary" system there is not enough back pressure to open the 5th and 6th ports, so they would need to be wired open, thus losing some low end.

I don't want to lose low end but I want as much HP as possible from the exhaust. Stock port for now, might street port when she blows.

Anyone with experience?

Right on.

Redwood

Sorry, no experience with that system. But I do have experience with the 5/6 ports. I'd recommend wiring them open to see how it feels for awhile. If you like it, then I'd recommend removing them altogether or putting the pineapple sleeves in there. The stock sleeves are so damn restrictive (and probably dirty). I'm going to run mine for a few months still, but only because they function with my exhaust setup. My sleeves are stewing in engine degreaser as we speak though, until I get to pineapple to buy some new ones.

It's my experience and understanding that you don't lose anything too significant. And with the other mods, the torque shouldn't suffer to heavily.

Manntis

I have the RB 2-into-1 free flowing 'street' exhaust and was plenty satisfied with the HP gains it provided, with any adverse effects yet to be noticed.

The ONLY thing with mine is I've not yet removed the airpump, so when I lift off the throttle after hard accelleration I get a backfire. Once the airpump is off, I'm told, that'll go away.

74RX4

iTrader: (10)

I've got the RB long primary on my GSLSE. Auxilary ports open fine right around 4K. I've got the header with O2 sensor bung and the port for the vacuum line that supplies the auxilary port actuators.
Mazdatrix part # 16-MZTX-4230 . http://mazdatrix.com/r-exh-85.htm

I can't really tell you how much difference it made from stock since the car had fuel problems when I got it and while fixing that I also swapped the exhaust. I never got to drive it with the stock exhaust. Lots faster than my 12A GS.

Ron

WackyRotary

Block off your ACV and run the 5+6ports off the air pump. I have had this mod on my '88 N/A for nearly a 1-1/2 and it works great. Get the lowend and highend power. No change in fuel effiency on low rpm.

Basically run a heater hose from the air pump to a brass ball valve that will fit that hose and somewhere on that hose between the air pump and the ball valve, run a tiny line to the 5+6port tube. Then have a friend rev it to 3500-4000rpm and adjust the ball valve till the port open around 3600-3800rpm fully.

SOme ***** will think the air pump will drag down the power significiantly, but this is not true, as '89-91n/a's DO in fact use the air pump in a simialer fashion to open the ports independant of the exhuast pressure. Any pressure in excess of 2psi is vented to the atmphere past the ball valve I just mentioned, which you can route to the stock siliencer thingy in front under the air box so you don't hear air rushing out of it.

I don't have any connection from the header back to the tail pipe tips. No cats, no acv, K&N air filter, air pump mod. Result: very reliable, no lack of power.

Manntis

No backfires?

WackyRotary

None I'm aware of. I take that back, I've backfired once or twice in a year of driving, and both were a result of mad shifting or a mis-shift if I remember correctly.

Backfire is a result of exhaust leaks and or a bad ACV. My setup utilizes a block off plate for the ACV. I also put in new exhuast gaskets in and made sure there were not any pin holes in any of the wields in the exhuast.