TehMonkay

iTrader: (-1)

BTW, stock cats are worth $150 from the junkyard, dont throw them away or let the exhaust shop keep them.

George84

This is taken straight from the rotary resurrection site,

"Between 3-6psi of air pressure is needed to operate these actuators. ON 84-88 cars, this air pressure came from exhaust back pressure, from stock catalytic converters and mufflers. A tube runs from the main cat back to the engine, and from that pipe a small vacuum hose runs to the lower intake manifold, which applied pressure to the actuators."

It says "this air pressure came from exhaust back pressure"

TehMonkay

iTrader: (-1)

So how does the RB S4 exhaust system open the aux ports, with all of the backpressure thats in the system. It doesn't, the velocity of the exhaust gasses pressurize the split air tube on the presilencer.

George84

OK, this is off the RB website and it says;
"Will the 6-port actuators function with after the header is installed?
Yes, the 6-port actuators are operated by the back pressure in the pickup tube on the Racing Beat presilencer. If you decide to forgo the presilencer and install a "straight pipe" or aftermarket cat converter, make certain that a pickup tube is incorporated into your design or your 6-port actuators will not function!"

here's the link, http://www.racingbeat.com/FRmazda2.htm
Still every site says that the 6-port actuators are operated by the back pressure on the s4. I guess that the RB system makes enough back pressure for them to work correctly.

TehMonkay

iTrader: (-1)

So you're telling me there is between 3 and 6 psi of back pressure in the RB exhaust system? That's great, it takes 3 - 6 PSI at the ports, when cramming 17/lbs of air a minute through a 2.5" in diameter pipe, the air shoots into the split air pipe and pressurizes it. It's easy to make 3-6psi in that tube however there is nowhere near that much in the exhaust pipe itself.

George84

I am just quoting what the Racing Beat is saying and what Rotary Resurrection is saying. They are both saying the same thing though. I am not going to argue with you about it.

b16eg

iTrader: (2)

yeah emissions arent a concern where i live which is very nice...so i dont have to worry about passing the emissions test thing

TehMonkay

iTrader: (-1)

If you dont mind spending money get the RB setup.

b16eg

iTrader: (2)

about how much does that run?

Bob Jr.

What are you talking about? s4 n/a NEEDS backpressure to open the secondary ports.

*TOUCH*

iTrader: (29)

you are right, there isnt that much pressure in the main exhaust pipe. thats why the pick tube is so small in diameter. the smaller the area, the easier it is to increase pressure, per the formula "Pressure= force/area" thats why we have PSI pounds per square inch. thus the same force, lets say 17 lbs like you said, exerts more pressure on a 1/3" pick-up tube versus a 2.5" exhaust pipe. although the velocity of the air that you were talking about does indirectly affect the 6pi actuation, ultimately it is actually the pressure that is created from that velocity that does the job.

*TOUCH*

iTrader: (29)

o, but you are right, generally back pressure is the enemy of power, its just that the setup particular to the s4 rx-7 needs some unless modified. although rb does claim that the 6pi system will remain functional, i think that the timing of actuation might be affected, but im not sure. either way, the system is cheap and easy to mod and either an airpump or electric pump is better than the flawed stock system in the first place.

TehMonkay

iTrader: (-1)

Exactly, that is what i was trying to say the whole time. The air flowing through there pressurizes the split air pipe. However, that doesnt mean there is actual back pressure in the rest of the exhaust.

b16eg

iTrader: (2)

what about an airpump?

George84

what about it?

TehMonkay

iTrader: (-1)

http://www.racingbeat.com/resultset....rtNumber=16420
http://www.racingbeat.com/resultset....rtNumber=16206
http://www.racingbeat.com/resultset....rtNumber=16130

b16eg

iTrader: (2)

someone said something about a stock airpump or electric one or something? remember im new to the rotary world, what does an airpump have to do with the exhaust? dumb queston, i know sorry...

George84

this will help you with the air pump route if you chose to go that way, http://www.rotaryresurrection.com/2n...actuation.html

or you can go this route, ELECTRIC 6 PORT CONVERSION, http://www.rotaryresurrection.com/2n...elec6port.html

Theres a whole lot of good stuff on that site, and Kevin does good work from what I have read.

TheAbsence

iTrader: (19)

I've got a bone stock car, including the intake and most of the exhaust. The only thing I've modified lately are the cats. I noticed I had absolutely no top end, and as the original owner, I know I had never replaced the cats. So I took those out after being told that that was probably the reason I had lost all top end power, because they were clogged. I replaced the three cats with one big high flow cat and that made all the difference.

Cliffs: If emissions isn't an issue, noise isn't an issue, go with a 2.5 all the way to a single exhaust. From what I've heard, that yields the biggest gain in horsepower. Removing the cats will also grant a considerable increase in power.

*TOUCH*

iTrader: (29)

+1^. the best setup for an n/a (power wise) is a full exhaust. HEADERS will give a good increase over the stock manifold, deleting the cats with a staright flow is also a must (dont forget to get a replacement with a pickup tube, or fab your own) and then finish with a single exit (this will also drop like 35 lbs off the rear). make sure its all mandrel-bennt and with as little bends as possible (aka, make the whole system as STRAIGHT as possible)