I just got my RB header and presilencer. should I mod it?
 

The presilencer has a tube for the backpressure to go to the 5 & 6 ports on the intake. But it faces toward the rear of the car. my cat back is going to have very little if any back pressure. I was thinking of cutting the pipe on the inside of the presilencer flush with the inside wall. this would increase the amound of back pressure the ports get to open properly right?
what do you guys think? should I cut it or leave it. the cat back is not RB it is a custom 3". so back presure will be very small.

You should leave it in my opinion. RB has done alot of research & testing on their products. When I was looking for a header/presilencer I called RB up and asked if theres would open the aux. ports & they said yes. I then asked if it still would with a aftermarket high-flow muffler & they still said it would.

but at the same time they tested it with their products. and 2 1/2 inch pipe.
I have heard of people whose secondaries didn't open at the proper time after they put on this exhaust.
I don't know I the only thing I can think that would happen is a bit of fire may go up into the tube. at the worst the ports would open too soon. I can either fix that or leave it if I like it. people runn with them wired open.
But I am still unsure.
the tube is also a little restrictive. it si a 1/4 inch pipe in a 2 1/2 inch.

I don't know anyone else???

just leave it and test it. dab a little grease and shift at certain RPMs, like start shifting at 2k RPMs in 1st/2nd gear than at 2.5k....3k RPMs ... closer increments until the grease smears on the actuators (when they move).

If they stay, you are not getting enough pressur so than you can try another way to activate the ports..

I just ordered my racing beat presilencer and so that side pipe better face forward to open my ports cause my air pump is coming off too. I ain't an expert but I think u just have your presilencer backwards.
Just a thought.
Check it out;)

ditto. :)

Nope it isn't backwards. the mount point is right where it is suposed to be.
The thing points bakards.
It isn't so much that I am worried about port timingg but that it is an 1/8" round and about 3" long obstruction in a 2 1/2" tube that is supposed to flow well

Is this your presilencer? If it is, then the pipe should face the front of the car.

You can mount it either way, shouldn't matter, it better not cause mine is coming in and need it to tone the loudness down. Can't even talk to someone normally when on the highway. People ask if wheter I've considered buying a new muffler when I already bought everything new. But anyways does anyone know if the racing beat pre-silencer is really going to silence things up for me?

No cats and straight through cat back

Thanks

Most definitely. My 85 is barely louder than stock at idle and it's a little louder at highway speeds.

Cool, I'm psyched, can't wait for it come in

Thanks

The Pickup tube on the INSIDE of th rb presilencer should be facing into the exhaust stream.

There isn't NEARLY enough backpressure generated in the exhaust to operate the 6P.

The way the RB pickup tube works (and mazda's pickup tube as well) is primarily through flow. As the exhaust flows down the pipe, it is captured and re-directed by the pickup back up to the 6P. This is why the pickup jutts out into the exhaust stream instead of being flush with the sides. RB set up the diameter of the tube and its location based on how much exhaust flow must enter the tube to actuate the 6P. This way, the ammount of BP is not as important to proper opening of the 6P. (Because exhaust flow is the same for a given RPM no matter what)

If your concerned about the pickup degrading your exhaust flow, buy a RB off road header. The 6P pickup is about 2 inches away from the engine on the front header tube. The exhaust pulses impact the pickup directly, so 6P opening is based entirely on flow. You can run an open exhaust w/ this system and still have accurate 6P opening.

Also, if your 6Ps dont open at the right time when you install your exhaust system, you can adjust the 6P actuater dashpots with the screw that extends out from the bottom. (That's what its for)

Remember, the car must be under load for the actuators to open, so you cant see if they open properly by just revving the engine.

Mine open wihtout being under load. Push on the throttle and voila. They need cleaning though which I will do this spring

Mine open wihtout being under load. Push on the throttle and voila. They need cleaning though which I will do this spring

Does the Bonez pipe even have a pickup?

If you have a series 4 (86-88) with no pickup, there is no way your ports are opening.

Are you sure your looking in the right place?

Yup there is a pickup close to the flange which opend them but will be useless when I get my presilencer. Actually I will use both. When I push the throttle down the ports open, one of them anyway, the other is stuck I guess. No load and they open

Well, don't know what to tell you there. They're not supposed to, but I guess if they're opening at the right time, I wouldn't worry about it.

If you do get the presilencer, I'd use one system or the other, not both

Which one would be better?

I guess the factory side pipe off the presilencer would be the way to go!!