sweet928

Email sent.

PC-85-928S

could a Y-pipe be used on an early 85, and then fitted with a 78-82 BORLA system?

U-928

I think that would work.

James Bailey

Yes it will fit....the exhaust manifolds triangular flange ends up in the same place so the Y will fit..... and I put the dual pipe 85 exhaust and dual cat on the 79 which my wife drove....no problem fitting. You might however be restricting the exhaust since you now have a full two pipe exhaust and dual flow cat....Also some say the two downpipes into the cat are bigger

NC928S4

Why Y versus X pipe? I thought the X pipe increased HP because of the mix in point downstream?

Also, why is 100cpi better than 300cpi or is it the other way around?

My questions are both performance and price related.

Sorry for the newbie questions on exhaust, I've been doing repairs else where the past year.

James Bailey

I think he wants to run the Borla rear exhaust system which is a single pipe system and with the Y pipe it is a simple bolt on....plus a Y is cheaper as I recall.

danglerb

I'm not sure the X is inherently better than the Y, but in practice with an X you can use two cats which are likely to flow better than an equivalent single cat. To get the same flow out of a single exhaust you need larger diameter pipe, and that can have issues with bending and fit. Best performing exhaust right now I think is Greg Brown's dual pipe.

PC-85-928S

I have an early 85 which is 2 small dual pipes that run into one mid muffler and then both into the rear muffler.
I recently installed an x- pipe and removed the cats.
I have to be honest, I don't like the sound.
It is not very exotic or super car like.
My friend has a similar set up on an 86 with the two rear mufflers and I think it sounds much better.
I think totally removing the rear muffler would be to loud, so I was considering replacing it with the borla tailpipe. However it has only one inlet and my system would require two.
A y- pipe would allow me to run the older borla system, which would replace the mid muffler as well. I am not concerned about a few hp. I'd rather get a sound I like and remove the heavy ugly rear muffler.

SMTCapeCod

I don't think you'd find the Borla that much more to your liking. They are straight-thru mufflers, whereas the final muffler you have now is intended to really clamp down on the sound.

Tossing the cats, was the thing.

To avoid reducing flow, I would definitely encourage getting S4 mid mufflers and then an 86.5 final muffler or high flow cats.

PorKen

I ran a Y-pipe into a '84 single cat-back with a gutted pumkin on my old '85.

It made over 300 rwtq/hp with early versions of my chips.

The single gave it more of a 16V sound. I liked it.

rdisney

On the early cars, Is the mid muffler more like a muffler or more like a resonator?

PorKen

All years, the mid muffler is a resonator.

S4-up, the rear muffler is also a resonator (straight through).

Only the big pumpkin muffler is a true muffler that dead-ends.

SMTCapeCod

Well, can't argue with Ken's BT/DT regarding output.

The single could help low end torque a tad and the 'squeeze' will help a bit with sound cancellation in its own right. I still suspect you'd find it too loud. But it is wholly subjective.

Seems likely there could be some Borla youtube vids cat/no cat to help build your frame of reference, though admittedly likely 16V.

FWIW, when I had an '85 years ago I had a dual in/dual out muffler with a perforated pipe and packing made to fit in place of the center resonator. No difference- not much space to work with in the paired dual setup.

PC-85-928S

Dumb question:
What is the difference between a resonator and a muffler?
On the old Borla set up is the mid piece a muffler or resonator?

James Bailey

over simplified mufflers have baffles which cause the exhaust to have to turn corners even reverse direction to pass thru the muffler. While resonators will have a direct tube/path with perforations in the tube allowing sound/pressure to pass into an outer chamber before bouncing back. They are for tuning the tone of the sound more than reducing it....Mufflers reduce sound but also influence the tone of the sound.....
Again greatly oversimplified and terms are often misused....basically if you can see thru it, it is a resonator. Even if it is sold as a muffler