How good is the 91 muffler?

[billschroeder5842]

So, my (continuing) search for a reasonable exhaust mod continues and I'm narrowing it down to a few considerations.

I'm probably going to swap out the the 91 restrictive resonator for a 95 spec (2 1/2 inside diameter) resonator. This is a given as the original has a 1 5/8 interior diameter and chokes the flow pretty bad.

I'm thinking of keeping my stock mufflers because I really like the way they look. Plus, I'm a bit of a purist at heart.

However...

Are the 91 mufflers "reasonable" in performance and back pressure or am I being deceived my the good looks? I realize there are other mufflers that are "better" in performance, but I don't want to change them out for hundred of dollars or for a minimal 5 hp difference?

So... are the 91 Muffs a "go, no or I don't know?"

[RussMcB]

My opinion - Keep the '91 mufflers.

[HAWAIIZR-1]

Bill,
Did you receive my PM last month? I had sent some ideas of what I did. I can't comment about 91, but hearing my car tracked at Laguna Seca had me pull off stock mufflers. The 95 resonator still chokes the stock pipes so replaced with Magnaflow Tru-X to get x pipe with no resonance. Best wishes. Exhausts are so subjective so too many opinions out there. I have Dynomax valve technology mufflers and won't get anything else now.


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[HAWAIIZR-1]

You probably have already seen these, but just in case:

http://www.zr1specialist.com/HAT%20Web/presentations/A%20Review%20of%20ZR-1%20Exhaust%20Systems.pdf

http://www.zr1specialist.com/HAT%20Web/Tech%20Info/High%20Exhaust%20Backpressure%20On%20Early%20Cars. pdf


http://uploads.tapatalk-cdn.com/20161229/342c10f2fb6d7bd0acb0e75c1e5fed0a.jpg


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[billschroeder5842]

Thanks Hawaii-- I had not seen the article but it makes total sense.

I did however see the PPTs from Marc and spoken with him a few times (i bought and installed the chip)

That does make me think a bit....

[DRM500RUBYZR-1]

There is a reason why most ZR-1's that are driven have long since shed their factory exhaust.

Any of the cat back systems appear to offer a significant, and measurable increase over the stock system.

On a completely stock motor perhaps the difference in performance may not be worth the added noise and possible drone, but on a motor with improved flow such as porting and polishing, it would seem counter productive to retain the stock exhaust.

Avoid overly analyzing the options, and remove the stock system.
I would not think of retaining the stock system after seeing the aftermarket systems, simply from the size, material and workmanship differences.
Stock looks like junk in comparison. My guess is performance is likewise.

Not to mention, my 16 year old, since he was 10, says the stock system, which we would re-install for NCRS judging, simply MUST come off IMMEDIATLY after the judging event.

I agree with him fully.

:cheers:
Marty

[HAWAIIZR-1]

Thanks Hawaii-- I had not seen the article but it makes total sense.

I did however see the PPTs from Marc and spoken with him a few times (i bought and installed the chip)

That does make me think a bit....

Hey Bill,

You're welcome. My suggestion is attend as many events where you can meet other Z owners like a Gathering or Carlisle, etc. so you can hear in person. I personally did not like the sound of what was available aftermarket, as well as living in CA at the time and knowing I would move to Japan soon when I designed my system. My theory after seeing thoughts from most respected Marc Haibeck was that 2.5" pipes on a Corsa system makes among the top HP on dyno was the stock pipe diameter of 2.75" is fine. Unless doing performance mods (like full porting or cubic inch, etc.) that benefit from bigger pipes, I wanted to stay with stock pipes itself. I did not care for the sound of Corsa, but did love the look. When I looked carefully at the stock pipes I was satisfied with minimal bends and no kinks despite not mandrel bends. I also saw that the late model resonator was not really a choke point despite necking down, but I wanted to add X flow into the system at that point after consulting with Dr. Gas and other specialists. I almost just put an X pipe there, but wanted to keep the stock appearance for inspections and ensure that there would be no resonance.

I found mufflers that have valve technology to open as pressure increases to wide open mufflers. I wish I had bought the GoPro during XMas sale so I could actually record the sound for you. It is not a "look at me" exhaust sound if that is what you want. It is a deeper tone than stock at idle and while cruising with absolutely no drone at any speed or range of rpm. But at WOT, it sounds awesome since the flap opens to a straight through muffler. Unfortunately I just got it plated so I have not taken to the dyno yet to see actual output and I also would not have a direct comparison to stock. All of that really does not matter to me, but I do have an exhaust that has the look I want, it hardly cost anything to build, and sounds exactly like what I want and envisioned. My car only has 30K miles so it was a shame to take it off or hack it since it looks like new still. I had a stock 90 system and B&B (version 3) on my other Z and hated both. I will be adding SW catted headers soon.

Anyway, those are just my thoughts of what you could consider or similar since you seem to be going through what I went through. Best wishes in your quest for your ultimate exhaust system.

http://www.zr1.net/forum/showthread.php?t=25422

http://www.zr1.net/forum/showthread.php?t=25353&highlight=stock+exhaust

[billschroeder5842]

Craig, Not a challenge, but a question...

Why did you go with a MagaFlow resonator rather than leaving the stock resonator? I read the articles the Marc reported that the stock resonator had no drag at all and the problem was in the muffler? (I like your muffler with the flapper solution.)

I just (just) picked up a 93 resonator today with the 2 5/8 inside diameter and have an appointment next Friday (January 6) for an install. It is not too late to order a magnaflow like yours and have that installed instead.

I LOVE the way that the Magnaflow looks but am wondering why change from your stock resonator if it really doesn't (or does it??) make a difference?

[HAWAIIZR-1]

Craig, Not a challenge, but a question...

Why did you go with a MagaFlow resonator rather than leaving the stock resonator? I read the articles the Marc reported that the stock resonator had no drag at all and the problem was in the muffler? (I like your muffler with the flapper solution.)

I just (just) picked up a 93 resonator today with the 2 5/8 inside diameter and have an appointment next Friday (January 6) for an install. It is not too late to order a magnaflow like yours and have that installed instead.

I LOVE the way that the Magnaflow looks but am wondering why change from your stock resonator if it really doesn't (or does it??) make a difference?


Bill,

My theory is in the X design of the tru-x muffler. In addition, although the internal stock resonator might have 2.5 I.d. It has necked down inlet and outlet. My purpose was to have a continuous flow with the benefit of X. I thought about going bigger inlet/outlet, but exhaust experts consulted to me otherwise and as shown, the stock diameter did not lose pressure. Hard to say what if anything was gained, but for the price it was worth the experiment to me. In my case maybe $ could have been saved since I have late model resonator, but if you are going to buy a later model resonator and replace early I thought to share an option that has additional benefits. I love to waste money any way and those who know me on here will agree. I don't have to always agree with even Marc too. Again, best wishes in your quest. I am simply trying to share ideas.

https://www.magnaflow.com/products?partNumber=12468&searchTerm=12468



Craig


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[billschroeder5842]

SOLD!

I contacted my exhasut guy this morning and he carries Magnaflow #12468 in stock.

I'll skip my stock resonator and go with the upgrade and see how that works.

I'll look to do something with the mufflers at some point later. I wish I could find something that had the same look as the stock.

Thanks for the direction on the MF!

[HAWAIIZR-1]

SOLD!

I contacted my exhasut guy this morning and he carries Magnaflow #12468 in stock.

I'll skip my stock resonator and go with the upgrade and see how that works.

I'll look to do something with the mufflers at some point later. I wish I could find something that had the same look as the stock.

Thanks for the direction on the MF!


Bill,

Sounds cool. It will be interesting to see results of just resonator change first. I understand your feeling about stock appearance. I'm sure you'll come across a single in dual out than can work. Maybe you muffler guy can open up stock muffler and mod it? Not many choices if trying to keep factory look. You're welcome. Best wishes and have a Happy New Year!

Craig


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[billschroeder5842]

I swapped out the stock resonator for a Magnaflow #12468 as suggested by Craig. You can see from the pictures that there is a BIG difference between the internal diameter. The install was pretty straight forward.

My quick impression after 40 miles is that I'm happy. The idle sounds about the same, I'm getting no drone that I've noticed (even around 1800 and 3600), I can hear a pleasant little "extra" in the back ground while cruising and pretty decent sound when punched- more than stock.

The only down side is that the resonator is about 1 1/4 inches thicker and hangs a bit lower. I'm actually not all that worried about it as I'm careful around speed bumps.

I can also tell that I have a wee bit more in the seat of the pants in the higher RPMs as the resonator is coupled with a just installed Haibeck chip.

BTW... my exhaust guy says the factory mufflers are really pretty decent and not worth a swap for the extra HP vs coin. He said only change mufflers if I want it louder (which I really don't)

Thanks all for the tips!

[HAWAIIZR-1]

Awesome Bill. Thanks fir the update and glad to hear. Love the color of your car too!


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[Z51JEFF]

If I ever get Corsa's I'm going to have a set of tips made that like the OEM part, add the tips to the Corsa's have the muffler PC flat black but first I'd like to remove the resonator and keep the stock mufflers.

[HAWAIIZR-1]

More food for thoughts about mufflers and pipe diameter size.

https://m.youtube.com/watch?v=bXQ-cXeri1Y




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[billschroeder5842]

I'd like to remove the resonator and keep the stock mufflers.

Jeff, I asked my exhaust guy abou that same thing. FWIW, he said that if one were to skip the resonator the "X" pipe is a must have verses straight.

He was unsure of how much drone and said their should be minimal expected, but some drone non the less. The only way to get rid of drone was to do the full resonator with the X pipe.