I often hear of Fb's and Fc's with the 5th and 6th auxilary ports wired open, and my friend's FC has the mod as well. I noticed there is not 3500rpm hesitation (obviously), but what are the other pros and cons of this mod? Do you guys perform the mod yourselves? Is there a guide on the site somewhere? Thanks.

 

search its covered

 

where, i did search. could you give me a link?

 

https://www.rx7club.com/search.php?searchid=2824063

 

well thats 4 pages of results, im looking for something relevant.

 

First off, the 3800 rpm hesitation has nothing to do with the aux ports, it has to do with the injectors.
Second, to answer your questions, the only pro to the "mod" is that you can continue being lazy and not fix your car properly. The cons are large loss of low-end power and possibly more sluggish throttle response in the low end.
To clarify, wiring open the aux ports (5th/6th ports) is not a "mod" at all. It is simply a band-aid fix for if you did something else to make them not work. On an s4 this would be changing the exhaust to something that no longer operates them, and on an s5 it would be removing the air pump.
On an s4, you need to get an exhaust that has something to coninue to operate the aux ports, like the RB presilencer. If you can't do this for some reason, you can electronically activate them with a small electirc air pump tied to an RPM switch. Search for "electronic 6 PI activation" or similar. It should be in the archives.
On an s5, just leave the damn air pump on. It causes a negligable, probably unnoticable, loss of power (probably 1-2hp) so the only legitamate reason to get rid of it is for aesthetics and a slightly easier to work on engine bay. If you really want the air pump off, you can use the same electronic method described above.

 

Here is the idea in a nut shell..

if u wire the ports open u will loose low end power HOWEVER at like 3K + it will be MAX power since they are completly open.

NOW there is a twist I have talked to some guys who say that they have done this and cant feel a difference.. maybe thats cause they are like me and CRUISE at 3K plus.. I think I will be removing mine but I have not come up with a 100 yes or no!

 

https://www.rx7club.com/showthread.p...ort+activation
There is a long thread with descriptions of how it works. It was on the first page of results from the search that guy posted.
Also, if they are working properly, there is ABSOLUTELY no reason to remove them. There is no power gain, and power loss at the low end. I have personally driven a car back to back with the aux ports wired open, then working properly and there is a very noticable difference. Even if you cruise at 3k like you said, there will always be times when you are below that, even if its just when first starting. You will wish they were working when you have to start on a steep hill.

Edit: To clarify, if they aren'y working for some reason, you will be better off wiring them open. You will be even better off, however, if you just get them working right.

 

alright that clears things up a lot. one more thing though, what effect does a straight pipe instead of a catalytic converter have on the opening and closing of functional ports?

 

if u have an S4 u have to use a pre-silencer in order to open the ports UNLESS u use another method of doing so

Dave

 

if you have an s5 (like me), i believe the exhaust won't have any effect on the ports because the are opened and closed by the air pump. Someone please correct me if I'm wrong.

S4's use exhaust back-pressure, I think...


btw, can I assume my ports are working if I can feel a noticeable increase in power a little before 4k rpm?

 

Yep, you got it.
And yeah, it a fairly safe assumption that your aux ports are working. You can generally tell if they aren't since it just doesn't feel the same up top.

 

alright its all coming together now. which do you guys think is the better(more hp+better value, money is an issue) choice, a straight pipe and wire open ports, or a straight pipe with a presilencer?

 

I have a GSL SE with a 6 port and ran it both ways as a test, and it is better to have them functional! On the S4, if you still have the air pump on you can do the mod to have the air pump actuate them (this works very well actually). You do not need a presilencer to actuate with the exhaust, you will however need a skilled muffler tech modify the exhaust to make the system work. All you need is a small pipe inserted in the exhaust pipe in the opposite direction of the exhaust flow, this will actuate the 6ports based on exhaust pressure.

 

I removed the aux port sleeves when i did my rebuild because they were not opening. This was a big mistake the car idled terribly, I put them back in and it runs perfect i also noticed that i gained more power. At this time the system is still not working but i will hook them up to the air pump. If anyone has done this any help would be great