apex downpipe & thermal catback

[crashed97tsi]

Hey guys,

I'm thinking about getting the apexi n1 or gt downpipe with the thermal r&d 3" exhaust. My question is would this bolt up or would some cutting be involved? I don't think it would bolt up since the themal necks down to 2.5 to bolt up to the stock cat. I would prefer not to weld since i have emissions and would need to switch this out.


Thanks
Dan

 

[Lordmunch]

You could always have a flange welded in like I did so I can swap out my 3 inch cat for my 3 inch test pipe. I did that beacuse there is a visual inspection for me because I my car is registered in PA and you must have a cat.
Munch

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[crashed97tsi]

yeah but would an exhaust shop do that? And the gt downpipe necks out to like 70mm, which is like 2 3/4 or something. Do you think the exhaust shop would have a flange like that?

Thanks for the reply
Later

 

[Lordmunch]

Originally posted by crashed97tsi
yeah but would an exhaust shop do that? And the gt downpipe necks out to like 70mm, which is like 2 3/4 or something. Do you think the exhaust shop would have a flange like that?

Thanks for the reply
Later

Mine did. They cut the neck down off the thermal and welded a small pipe to extend it so it fit right up to my cat. Then they welded a flange on the end and bolted it up. So now my exhaust is 3 inches all the way back.
Munch

 

[crashed97tsi]

ok, What i am thinking of doing is have them weld a reducer on the downpipe so it'll fit on the catback. That way, I'll still be able to bolt the catback up to the stock cat and dp. Now here's a new question. I would be going from 60mm to 70mm, back to 60mm and then to 3". How much would this affect my performance? It would never reduce to less than 2.5" but going from 2.5 to 2 3/4 back to 2.5 then to 3 seems like it would be a major restriction

Thanks
Later

 

[Lordmunch]

It will restrict the flow but not as bad as the stock 2.25
Munch

 

[crashed97tsi]

would it restrict more or less than a straight 2.5 downpipe and testpipe to 3 inch catback?


And thanks alot for the help man, I appreciate it

Later

 

[Lordmunch]

Yes it will a cat will not flow as well as a straight pipe.
Munch

 

[crashed97tsi]

sorry i meant would the downpipe with the reducer at the end of it flow as good as a just a straight 2.5" downpipe. No matter what the cat is coming off, I'm just trying to figure out if i should go with the 2.5 and test pipe or if could get away with the n1