So new member here, just entering the rotary world.

I purchased a close to free NA s4 engine with the plan to tear it apart and learn all about it before I dump money into building one for real, primarily for track use.

started poking around the intake today and realized both my auxiliary port valves were busted. One of the shafts is snapped off and the other valve is tough to operate, ( what I imagine to be more than ~2/3 PSI).

I have a basic understanding of how these aux port work, but not much. From what I have picked up, they offer better performance when opened correct? I am curious if there is some way that I can bypass these ports, or remove them. Or even if somebody can inform me more on how they operate.

I have read that some people switch to electrical RPM switches, but I am looking for an option that won't involve rebuilding and/or replacing both of my busted valves.

I have purchased a workshop manual and done some reading around here, but I am still a little confused on the function of these ports. Even if someone can point me to a well written article it would be much appreciated.

Thanks!

 

Very odd for the shaft to be broken, but very common for them to be gummed up.

Put simply, the aux ports are variable intake port timing. Like the Honda V-tec and really any modern engine with variable valve timing.

After about 3800 RPM under load they open up, delaying port closing considerably (even a little into compression) and offering more port area, both beneficial for high RPM operation.

"Bypassing" them usually means leaving them open. With the ports open, all that area and timing kills low end. By about a 25% reduction in low end torque.

The best bet is to fix the system. By removing the lower intake manifold and unsticking everything. In your case also replacing the broken components.

 

Awesome thanks for the information! It seems like a very failure prone mechanism. It seems like there should be a better way.

When people use an aftermarket lower intake mani (for itbs or something), what do they do about the aux ports?

 

They don't

One thing though, if your going to use this motor for track use, you won't have to worry about the aux ports because you will more than likely be above 3800rpm 95% of the time or so

 

could you elaborate on "they don't"? They don't use aftermarket lower intake manis? or they don't do anything about the ports? just leave them closed? or opened?

I was aware that by leaving them open, my losses would be in the lower range, And also aware for track I would be in the upper range, but would like to find a solution that does not involve any loss. However you are right, It would be a little less damaging for my purposes.

 

Normally when it comes to aftermarket lower intakes, theres very few, and i believe the ones that are out there the aux ports are just open.

Most of the time when people do itbs, the get rid of the 6 port irons and get 4 port turbo irons, then port them slightly for a happy medium between low end and high end (normally street port IIRC)

 

perfect! Just what I was looking for!