exhaust

[WARP TEN]

Originally Posted by KILLSHOTS

The stock exhaust was designed to muffle sound, of course. But it was also tuned to eliminate the inherent resonance baked into our cars. It hits hard in the 1800ish RPM range and again in the 3400ish RPM range. The resonator was tuned to help part of it and the mufflers were tuned to help the other part of it. The exact details don't matter, but to answer your question somewhat succinctly, the Corsa system was designed in much the same way, except with much less restriction. What you have in the Corsa is a system that is somehow as effective at quelling resonance at all RPM as the stock system, but still causes virtually NO restriction. It is quiet at part-throttle but straight-pipe loud at full-throttle. Any exhaust can sound throaty or be "open" but in my opinion, the Corsa is brilliant because it just does everything right.

Chris is right. Over 20-odd years of owning ZR-1s, I tested and used a half a dozen systems and the Corsa was the best aftermarket system for flow (HP), sound and lack of resonance. Designed like the stock system to eliminate the resonance at the two rpm points that our cars really have it. Had Corsas for probably 12-15 years total. However as most of you know by now, I finally went back to the stock 95 system with electric cutouts for racing and just making noise when I want to. Usually run with them about1/3 open, but close them when I come back into our subdivision to appease my wife. Really like the set up. Quiet when I want it (say a long trip) and as noisy as I want other times. Headers, no cats, when open basically a straight through system as the stock resonator has little flow resistance. --Bob

[1990 quasar blue]

Originally Posted by KILLSHOTS

The stock exhaust was designed to muffle sound, of course. But it was also tuned to eliminate the inherent resonance baked into our cars. It hits hard in the 1800ish RPM range and again in the 3400ish RPM range. The resonator was tuned to help part of it and the mufflers were tuned to help the other part of it. The exact details don't matter, but to answer your question somewhat succinctly, the Corsa system was designed in much the same way, except with much less restriction. What you have in the Corsa is a system that is somehow as effective at quelling resonance at all RPM as the stock system, but still causes virtually NO restriction. It is quiet at part-throttle but straight-pipe loud at full-throttle. Any exhaust can sound throaty or be "open" but in my opinion, the Corsa is brilliant because it just does everything right.

Thanks Chris. The reason I was wondering was because the guys running the NPP tips on a 3" system with X-pipe all have little to no resonance as long as that one tip on the mufflers stay closed.

Ed, it would seem that the 40 series would be the cheapest way to get more sound. I bellieve they're still aluminum so weight should be similar. Sorry I took this a little off topic.

[KILLSHOTS]

Originally Posted by edram454

true but.... the corsa 1300.00 compared with the two 40 series mufflers at 160.00. quite a difference.. might be worth a shot?

Certainly true, Ed. I felt the same way, so I started making changes to my stock system. I got a great sound but it was pissing-off-the-neighbors loud, and since my only "mufflers" were the cats, the whole system had to go when I installed headers. Those "experiments" didn't cost me a whole lot, but when I finally decided to spend the dough and install the right system, what I had spent on the experiments ended up wasted money. If I had it to do over again, I'd have gone straight to headers and Corsa and saved some time and money.

[OregonDude37]

I went with the cat back Billy Boat 3" X-pipe exhaust system on my ZR - result was impressive. Although I cannot tell you how much improvement in terms of HP, I can tell you the car feels better under full throttle and although there is substantial drone at certain RPM's, the end result makes me smile! The look from the rear is also impressive.Cost was right at $1,000.

[Paul Workman]

Originally Posted by 1990 quasar blue

With the Corsa system is it the resonator that reduces the drone? I ask because it is straight through. I thought what really helped the Corsa be drone free was the fact that they only flow through one pipe in the mufflers....*

If you look closely at the Corsa Resonator (specifically) you'll see a circular slot opening in the pipe section near the front of each of the resonator pipes. Like blowing air over the top of a pop bottle, a resonance is generated, dependent on the internal dimensions of the resonator - not unlike a pipe organ.

As it happens, the wave pulses created within the resonator cancel those exhaust pulses of the same frequency - and it occurs at that slot in the through pipe you see in the resonator.

And, IIRC, the mufflers too have (Helmholtz) resonators in them; shorter than the those in the resonator; designed to address the resonance occurring around 34K RPM.

Google "Helmholtz Resonator" for an in depth reading and how it is used for noise cancellation.

[edram454]

It looks like when I do decide to do a change, I will go with a muffler swap from my 60 series flowmaster to an original 40 series old style flowmaster exhaust. I know I will hear a significant difference in agressive tone and rumble. I will keep the rest of my flowmaster system including the resonators to limit drone somewhat. I drove my car today with flowmaster force II system and it is somewhat loud and under wot aggressive but I just want more. I dont drive her much so when I do, I want the looks, the power and the sound, plenty of sound. I should cost my around 400 dollars to swap mufflers and add tips. I cant believe that tips have become so expensive. they average 60 to 100+ bucks. I think this should work. My car is great and sounds good now but with this new setup it will be very impressive sounding. rumpty-thump!!

ed ramos #3028

[KILLSHOTS]

Originally Posted by edram454

It looks like when I do decide to do a change, I will go with a muffler swap from my 60 series flowmaster to an original 40 series old style flowmaster exhaust. I know I will hear a significant difference in agressive tone and rumble. I will keep the rest of my flowmaster system including the resonators to limit drone somewhat. I drove my car today with flowmaster force II system and it is somewhat loud and under wot aggressive but I just want more. I dont drive her much so when I do, I want the looks, the power and the sound, plenty of sound. I should cost my around 400 dollars to swap mufflers and add tips. I cant believe that tips have become so expensive. they average 60 to 100+ bucks. I think this should work. My car is great and sounds good now but with this new setup it will be very impressive sounding. rumpty-thump!!

ed ramos #3028

Just FYI Ed, when you do this, you will be keeping the most restrictive portion of the Flowmaster system, which is the resonator. Also, since you plan on changing the mufflers, you may experience more drone, as your exhaust was designed as a complete "system" and therefore, Flowmaster probably took the drone characteristics of the LT5 (and the C4, in general) into account. You'll be altering that.

Best of luck with the mods. I hope you find the sound you're looking for!

[edram454]

the flowmaster tech said that the resonator is not that restrictive. He said that in testing that there was not that much difference with or without the resonator. He said that the resonator is in place to change the pitch of the sounds and play them off each other so the noise in the cabin would not be too loud. The resonators are just under the floor in the cabin of the car. The mufflers have baffles inside unlike corsa that is straight through with material around the pipe inside the muffler, maybe it is the muffler where there might be some restriction. The muffler used in the zr1 flowmaster kit is a 60 series muffler. It has 3 chambers so the exhaust gets tossed around quite a bit inside that muffler as noise is bumping off several baffles canceling each other out until it finally exits the muffler. the corsa goes straight through and depends on the material that is wrapped around the perforated pipe inside the muffler to eliminate the noise. Over time, the corsa's material inside the muffler will break down and the exhaust will become louder.

the 40 series is a 2 chamber design so it will be louder and it will have more drone and less back pressure etc.. but it is ok. I believe it will work and its worth the shot. If for whatever reason I don't like it then I will opt for the corsa.

ed ramos #3028

[Schrade]

I just did the first test of drone reduction with the extra-foam / painted top, over glasstop.

I did a recording with each. It was a little quieter with the painted top, and when I played it in a media player with graphic EQ, it IS slightly lower volume.

Next test with cork underlayment under interior cargo carpet area. I don't think it will reduce drone enough more, to take the edge off...

And I can't get over the sound like an exhaust leak. HAS TO be the crossover section. There is no exhaust leaking - of that I'm sure...

[XfireZ51]

I would try some styrofoam or foam over the top of the spare tire so that it deadens any resonance of the hatch floor. Could it be that the spare tire carrier creates a BOOOM Box under the hatch floor?