jUST CURIOUS IF ROTORIES NEED A CERTAINAMOUNT OF BACK PREASURE LIKE A TWO STROKE, OR ARE THEY HAPPY WITH STRAIT EXHAUST?

 

It depends on the year of your car. 86-88(i think) need backpressure to operate the fith and sixth ports properly because they are operated but the backpressure of the exhast. If you don't have the correct amount they will not open and you will lose alot of HP in the upper RPM. It is possible to wire them open but then you lose some lowend punch.if you get a high- flow cat you should be OK.

Good luck

 

Having variable back pressure on a ported engine helps with low end torque. I was thinking of adding a butterfly valve in the exaust that's partially closed till 3500 rpms.

 

Yea, I had some questions about this as well. I have an 88 GXL which I am going to get headers & the presilencer for soon. How would I make my 5th & 6th ports work properly. To tell the truth I don't even know where they are, lol. I really want to figure this out before I order the headers. Thanks.

 

Well, I can tell you my experience with opened up exhausts. I have a header, high flow cat and cat back. Recently, the gasket between the header and cat let loose, giving me pretty much an open exhaust and I was missing a lot of low end torque. Take it for what its worth.

 

what about the later 2nd gens? I have a '90 tII with dp, cat (stock), and dual exhaust... I think my piping is like 3" or 3.5", and my turbo spools real slow... (i don't know if that's the problem)

 

Come on guys...we need some answers here. I want to be able to get headers & not have to worry about losing low end. How can you make the 5th & 6th ports open when they need to? Thanks.

 

tHANKS FOR THE IMFORMATION THAT i RECIEVED ABOUT BACK PREASURE, IT APPEARS THAT i`VE OPENED UP QUITE A CAN OF WORMS.
I TOO AM UNSURE ABOUT ALL THIS TALK ABOUT FIFTH & SIXTH PORTS, WHAT GIVES?

HUMMER

 

I know that we need some sort of pressure to open the 5th & 6th ports. I know I've seen some solutions before but that was before I was worried about it. I tried a search but could not find anything. Someone please off the best solution. Thanks.

 

Turbo owners dont need bp
NA - if you dont want backpressure then be ready to tie open your ports and lose some low end. If your worried about back pressure that much and want your ports to work then a racing beat na "race pipe" that connects from your exhaust manifold down to your main cat or y pipe connection. It has a presilencer and the actuators do work.

 

How much is the difference between having a high-flow cat & just the presilencer? The high-flow cat will work the 5th & 6th ports, correct? I want the headers & I want the 5th & 6th ports to work properly.

 

Come on...someone has to know. I just want to know if its worth me even gettin headers & the presilencer or what.

 

get the headers
I am running the RB header and presilencer and my six ports work just fine.
you will notice a big difference from the stock feel.

and if nothing else there is a way you can hook up to the airpump to open the six ports.

though ify ou are running turbo get as little amount of back pressure as you can

 

if you get the headers that are for the n/a rex they should have an opening for your actuator hose then your 5&6 ports should work properly if you are looking at a header from a manufacturer other that racing beat or rx7.com then make sure and ask if they have a place to put your actuator hose so you make sure to get the correct back preasure to open them

hope this clears up something

 

Where is the hose that you would need to connect to the headers? Sorry I do not know very much about them. Thanks.

 

Ok....heres some info on backpressure. Backpressure is used to open the 6-ports on 86-88 FC's ONLY! if you have an 89-91, the 6-ports are opened up by air supplied via the airpump and is controlled by the ACV and a solenoid. If you have an 89-91, you can do whatever the hell you want to your exhaust, and your 6-ports will still open fine.

 

And what if you don't have an 89-91?!? I have an 88, what do I do?

 

the hose comes from the back of your 5th port if you look at the passenger side of the engine all the way on the back by the fire wall or as far toward the passenger compartment as possible. if you still have the stock cat in place then the hose will ba connected to a small pipe coming off of the cat if you follow that pipe you will find it pretty easily

 

Ryde or Dye......try this http://home.earthlink.net/~burntoast/6port.html this site shows how to open them, one way. There are more straight forward ways. The dual exaust I got from Mazdatrix(Racing Beat) has a pipe 1/8th inch from the forward exaust port. It builds enough pressure at higher rpm to supply enough pressure to the aux ports to open them. I'm talking 86-88 model here. I've used this method, 1/8 built in pipe from Mazdatrix and two other methods I've played with that open the ports. Buy the Mazdatrix dual from front to rear. Sorry, I did not notice the drop in lower torque described by others (insensitive I guess) but sure as heck noticed the dramatic increase in hp. and much quicker reving to the red line. When you order from RB or Mazdatrix be sure to ask about the aux ports and if the system you are buying has the 1/8 inch nipple on the exaust header to open them. I'm sure they do.