I want to upgrade my exhaust from the block to the y-pipe in the form of a RB header/collector and, either a RB presilencer or just a piece of test pipe with a tube for the 6pi.

My question...how hard is it to make custom testpipe to run the 6 ports work off of?

I was thinking i'd just cut a hole in the pipe about halfway down, and run a small tube into the pipe and angle it forward to help "scoop" more exhaust into the 6 port tube.

 

I think that you are asking if you can weld a small pipe into a set of headers and go from there to the auxiliary ports.

It is easy to do (if you can weld.) Drill a hole in the header, find a 18-24 inch piece of small steel pipe to connect to it (small enough to connect line to the ports to.)

The reason for the length is so that hot exhaust won't melt the line.

Of course the modified exhaust probably won't make enough back pressure to ever open the port actuators, but the line can be connected.

I have had pretty good success with springs on the actuators to allow them to still operate with 0.5 psi backpressure instead of 1.6 psi (you could do this to, but they are difficult to get adjusted right.)

Good luck on the project.

 

ok i was told that it was, exhaust velocity that caused the ports to open. And if the piece of test pipe was a little smaller than the rest of the exhaust, wouldn't that increase the exhaust velocity enought to open them?

 

or you could just not mess with all that and make an RPM switch like this \/

https://www.rx7club.com/2nd-gen-archive-72/how-diy-rpm-switch-6th-ports-vdi-233381/

 

is it just me or is that link completely usless as the diagrams no longer exist?

 

lol, my bad, I didn't check to see if the pics were still there. I'm sure it's not that hard though.

maybe somebody who has done it would be kind enough to repost a diagram or 2?

 

Electronic air pump to open the ports with is superior to relying on exhaust backpressure.

Do you want to *hope* your ports open all the way, or do you want to *know* that they did? The Cadillac air-ride pump provides you with lots of *know*, as it makes a soft PFT sound as soon as you hit that oh-so-desirable RPM.

 

The ports are actuated by exhaust backpressure. This is caused by Exhaust velocity (approximately proportional to the square of the velocity) THROUGH the pipe and mufflers. High velocity in a small section of the pipe will actually cause lower pressure (the venturi effect.) The test pipe size is not important, it is a pressure signal (not a velocity signal) that is carried up the feed from the fresh air pump and causes the ports to open.