Okay So Im putting on my exhaust manifold and I notice that the little port on exhaust manifold towards the rear of the engine in the lower left hand corner is blocked off. Heres a pic for reference I drew a red box around the hole. The hole is blocked of on the manifold but its still there on the engine.


Now my question is what does that port do and is it important and will it effect my main cat. I do not have pre-cats anymore.

I have called 2 different shops and had two different answers. So now Im asking you guys. One shop says it will effect my main cat and another said it won't now im here .

Im going from s4 manifold to s5 manifold. the car is a 87 TII.

 

none of my j-spec motors have that passage on the manifold.

 

have you used cats on them before and do they hold up.

This thing about it having to do with the cat is starting to like really throw me off. Because looking on the forum for so long I have never heard of anyone talking about this passage before or anything having to do with smog besides the Split Air pipe,Air pump, and ACV

 

Ok..I was gonna just Pass this by..But I had to Pop in and Tell you..the Gasket..you can use it..It doesn't matter if that hole is ther or Not.The Manifold you are putting on is an S5..that's OK..It's Been done..NOW,I have a S4 N/A,that uses the Same gasket.It has the same hole.I am running a Header that Doesn't have a Hole on the Flange.My Exhaust ports open from Down below,on a part Made on the collector...I think you are asking IF the Cats will hold up.The Simple answer is I don't Know.It depnds on How much Power you will be running,Engine Exhaust Temp,Location of the cat.What kind of Catalytic.Rotary engines make Mincemeat out of Catalytics real quick,So the Question is How long do you want it to last,or even if you want one at all...my question to you is Do you need a Catalytic..and if it's just t pass Emissions,then Use it just to pass,then find an Alternative,and save your Catalytic for Emissions testing only.....hope that Helps ,STYX.

 

The main reason Im using a cat right now. Is as means of prevent over-boosting. The waste gate is ported and all. But I don't want it to overboost cause Im gonna drive it like that for a while before I get supporting fuel mods. also I do not want the cat to clogg up and create excessive backpressure and heat.

When that happens then I will be just running a test pipe and FCD/Rtek 1.7