chwkrx7

I'm going in for new exhaust in a couple weeks, from the manifold all the way back, 2.5" piping, high flow cat, muffler. but do i read something about this affecting the 5th and 6th ports? or is this only in an s4? the s5 looks like it uses an air pump so i don't have to worry about it?

when it comes to exhaust i know very little. when it comes to exhaust on rotaries i know nothing. is there anything special i have to tell the exhaust place?

My5ABaby

iTrader: (7)

Looks like you have an S5 so don't worry about it. Won't affect you having a new exhaust.

iamsisyphus

Naturally aspirated FCs have a 6 port fuel injection system. The way it works is that 4 ports have long runners and are open all the time. This gives the highest possible volocity airflow and better low end torque (but still not all that much *sigh*). At about 3800 RPM ports 5 and 6 open to increase the volume of airflow and increase higher RPM horsepower. At about 5500 another valve opens to equalize the intake pulsations and increase horsepower. Where the exhaust issues come in is if you have a 86-88 S4 engine. The 5 and 6 ports are actuated by exhaust back pressure. If you buy an exhaust system from Racing Beat, make sure it has the fixture to connect it to the port actuators. If you have an 89 or later S5 FC, then you 5 and 6 ports are actuated by the airpump and you won't have to get the back pressure fixture on your exhaust.

You can find the actuators on the passenger side of the engine below the runners. One is in back and on is in front. They look like old fashioned fuel filters except bigger. There is a similar looking component on the drivers side of the dynamic chamber. That's the valve.

It's pretty easy to drive these cars around and never go over 3800 RPM. Mine was owned by a Dr. who drove it to the country club. If they don't get exercised, they freeze up. You can test them by getting a couple of feet of vacuum hose, disconnecting the one that's on the actuator attaching the longer one and blowing through it gently. You'll see the actuator move. If it doesn't you'll need to remove the actuator and free it up by using penetrating oil and manipulating the lever until its free. It can take a long time. If the actuator is free, the problem could be the solenoid or the port valve itself is frozen I didn't have to fix either of these problems so I can't tell you how to go about it. You should check the other valve also.

Good luck.

MmSadda

iTrader: (2)

The other couple guys have it right; you needn't worry, with your S5 n/a.

I have an s4 n/a, and need to make sure my secondary ports are opening at 3800 rpms if I do anything to the exhaust.

Out of curiosity, do you s5 n/a guys feel like the car instantly gains 50hp or something at 3800? my car feels a LOT faster all of a sudden when my 5th/6th open.

chwkrx7

awesome. so i still need to make sure that the air pump is pumping into the cat? and i'll check that actuator out... i don't feel any power difference at 3800? is it noticeable?

johnmasters

This is an interesting question because I have always wondered if I should feel a little boost in power at 3800 in my NA S5. It is NOT something that I notice. I always figured the 5th and 6th were working as long as I dont feel a 3800 hesitation.

Other S4 and S5 owners observations please...

chwkrx7

ok, so i'm digging around in the fsm, do they call it the 6-port induction system in there? cuz thats what it seems to be. can't seem to find it on the engine tho :S does anyone have a picture?

2slw4u

iTrader: (4)

well in my s5 na i dont really feel a difference eccept that the rpms kinda go a little slow then start to climb real fast around 3800 rpms, i have noticed it make my 4th high end pretty fast, i got up to 135mph in 4th gear at like 7k-8k

iamsisyphus

I know exactly what you mean. These things are so different from a Honda I4, you're staring right at it and you don't know what it is. The 5 and 6 port actuators a way down inside the engine bay. First look at the drivers side of the dynamic chamber. You'll see a valve actuator situated between the two middle runners. It's made of metal and has a vacuum tube going to it. Remember what it looks like. Now go to the passenger side of the car. Look down at the exhaust manifold. Locate the O2 sensor. About 2 inches in front and above the 02 sensor, you'll find a thing that looks just like the valve actuator we located above. The other one is at the front of the engine maybe 8 inches forward of the one you already located.

Another way to find them is to follow the tubes out of the air pump, through the solenoid to the actuator.

I have a convertible, so it's kind of slow anyway, but I don't feel any appreciable pop when the 5 and 6 open. They open rather slowly, so I think they were designed to feel like a smooth increase in power rather than turbo lag. I do get a kind of zing at 5500 when the valve opens though.

You didn't ask this, but the next thing you should do is get the fuel injectors cleaned and blueprinted or replaced. The reason I say this is if you have to remove the upper intake runners to get the 5 and 6 ports functioning, that's when it's easiest to get to the primary fuel injectors. The secondaries are more easily accessible. Did I get that backwards? Anyway, you'd be surprised at the increase you'll get from cleaning 17 years worth of gunk out of your injectors.

Doug