Pre-muffler (mini-muffler) What's inside?

[Zed Head]

I have a complete original exhaust system from a 1978 Z that I am going to install on my 1976 280Z, non-CA model, to replace the original one, since someone smashed the exhaust pipe up against the differential when lifting, to about half volume. Plus the $30 O'Reilly's Cherry Bomb turbo muffler just doesn't sound right.

Could anyone tell me what is inside the small "pre-muffler" up next to the transmission? The little mini-muffler. It looks to me like a place-holder for the California model's catalytic converter.

Is it just hollow or does it create a flow restriction? If it's hollow I will just get a new muffler and install it as is, saving on gaskets and effort. If it is a significant flow restriction I will replace it with something else before installing.

Thanks for any comments.

[ZCurves]

These 'Pre-Mufflers' were essentially 'Glass-Paks' that provided some primary form of sound suppression before moving on to the Muffler. You are probably correct about it being a 'CAT-filler' for non-California Z's. With all of the exhaust system options available, I would NOT put one of these back on the car unless you were wanting to make your Z as quiet as possible.

If that were the case, you could go 2-1/2" from the collector to a 2-1/2" Glass-Pak and then on to a 2-1/2" Dyna-Flow or other free flow muffler. This would provide the least restriction with the quietest output.

IMHO - I would keep it as simple as possible! I have 2-1/2" all the way out from the collector, but I am really loving the Twice Pipes! You can hear some Z's with Twice Pipes on YouTube - search 'Twice Pipes'. These have the most amazing sound.

After all it is a ZCar, not a Oldsmobile.

[ZCurves]

Since answering the previous post, I got to thinking that I would love to get my hands on a complete set of the OEM Heat Shields from a California Z exhaust. This would include the Pipes and Muffler.

If anyone can hook me up, please PM me! I would appreciate it a bunch!! :laugh:

I am finishing Hijacking now...

[Oiluj]

If that were the case, you could go 2-1/2" from the collector to a 2-1/2" Glass-Pak and then on to a 2-1/2" Dyna-Flow or other free flow muffler. This would provide the least restriction with the quietest output.:

This pretty much what I have on mine. No worry about atracting attention from police, but it still sounds like a sports car.

Nice low "thump" at idle, but fairly quiet on city streets. In fact, I get more engine noise in the cabin than outside at speeds below 35 mph. Above 35, she starts to sing and at 60 mph she sounds very sweet when she passes by.

[Zed Head]

These 'Pre-Mufflers' were essentially 'Glass-Paks' that provided some primary form of sound suppression before moving on to the Muffler. You are probably correct about it being a 'CAT-filler' for non-California Z's. With all of the exhaust system options available, I would NOT put one of these back on the car unless you were wanting to make your Z as quiet as possible.

If that were the case, you could go 2-1/2" from the collector to a 2-1/2" Glass-Pak and then on to a 2-1/2" Dyna-Flow or other free flow muffler. This would provide the least restriction with the quietest output.

IMHO - I would keep it as simple as possible! I have 2-1/2" all the way out from the collector, but I am really loving the Twice Pipes! You can hear some Z's with Twice Pipes on YouTube - search 'Twice Pipes'. These have the most amazing sound.

After all it is a ZCar, not a Oldsmobile.

Thanks for the insights ZCurves. I will try to avoid the Olds sound, but am not ready for Twice Pipes. Baby steps.

[oldhemi]

Weren't these called "resonators" or did I miss the jist of this thread. IIRC, my early 260Z came with one!

[jmortensen]

Yes, they are resonators in the stock system. They knock down the droning that can happen at ~2500 without one. A good replacement would be a "bullet" muffler which is a race thing and is just a straight through tube with holes and fiberglass or stainless packing around it. Your typical glasspack has "teeth" where the holes are in the tube and those create turbulence and back pressure, where a bullet does not.

http://www.dynomax.com/mufflers.php?muffler=racebullet

[ZCurves]

Yes, they are resonators in the stock system. They knock down the droning that can happen at ~2500 without one. A good replacement would be a "bullet" muffler which is a race thing and is just a straight through tube with holes and fiberglass or stainless packing around it. Your typical glasspack has "teeth" where the holes are in the tube and those create turbulence and back pressure, where a bullet does not.

http://www.dynomax.com/mufflers.php?muffler=racebullet

Great Point, Jon. Perhaps I should look into one of those.

[TomoHawk]

Your typical glasspack has "teeth" where the holes are in the tube and those create turbulence and back pressure, where a bullet does not.

The exhaust guy put the glasspack on my car backward so it doesn't make so much backpressure. the engine is happy with that.

[Zed Head]

Just to tie this up and for anyone else that wondered, here are a few pictures. The resonator (actually an anti-resonator I believe, by definition?) does neck down a little at the inlet then back out at the outlet so does create a flow restriction. But the interior is pretty smooth. There are some holes in the interior but no "teeth" to create turbulence.

For those interested in the esoteric Z stuff... (and of course, the obligatory shoe photo - Asics)

Edited May 2, 2010 by Zed Head

[jmortensen]

Glasspacks have the "louvered cores."

Here is an example:

http://www.who-sells-it.com/cy/holley-performance-products-inc-2055/flowtech-airmass-mufflers-9339/page-1-fullsize.html