I have two real quick questions about the Flowmaster HP-2 Muffler #12018409 and #12518409.

The #12018409 has a 2" inlet/outlet and comes in T409 stainless.
The #12518409 has a 2.5" inlet/outlet and comes in either T304 or T409 stainless.

Flowmaster HP-2 PERFORMANCE MUFFLERS

(1) Will these fit under a '83 N/A coupe?

It's 5" Wide, 4" Tall, 18" Long.

I'm fairly certain these dimensions will fit in the space where my stock '83 muffler is currently rusting.....er.....resting.

(2) What's the advantage of 2.5" over 2.0"?

I just picked up a set of MSA headers and their outlet is only 2.0", so I don't understand why I would need (or want) 2.5" piping.

Thanks!

 

2.0" for n/a
2.5" for turbo
More flow I guess ....

 

Take measuring tape, measure on your car, compare to muffler size.

Yesh, more flow. Easier to understand when you compare a straw to a water hose to a gigantic water pipe. They carry different amounts, right?

At each collector or at the main collector? 6-1 or 3-2 header?

 

I didn't have the car available when I originally posted my questions, and I wasn't sure of how much room I had to work with. It looks like there's plenty of room and it should work fine.

Yeah, I understand they carry different amounts. My question was why go with a 2.5" when the exhaust is only being pushed out of a 2.0". As it turns out, I went with the 2.5" in hopes it will make the exhaust note more mellow and less noticeable to the local law enforcement (I want the car to breathe -- not collect tickets )

3-2. Sorry I didn't specify that.

Thanks!