Never ending quest for the best C4 ZR-1 exhaust system- Stainless Works

[XfireZ51]

Originally Posted by emmvette

That looks like a great set up. Thanks for sharing!

What is the reason for the drone? I've got the drone in 6th at 65-75, which is unfortunately normal cruising speeds. Is it just a resonant frequency?

Is there anything that can change this on an existing set-up? I've got a nice exhaust with headers, so no reason to spend more $ on mine.

Here in FBIland, we 've been using the Z06 exhaust control valve. It seems GM decided it was cheaper and weighed less than a resonator to control drone at cruising speeds (on mine that's anywhere from 1400-1800 rpm). I think there are several factors that can help mitigate drone:

1. A too flabby (rich) tune will give the exhaust more of a blub blub blub sound particularly on an incline when the MAP goes higher and RPMs drop.
I like a bit of a leaner AFR for cruise. Found it tightens up the exhaust sound bringing it into a higher frequency.

2. I think the double walled construction of tips like the Z06, Corsa, MagnaFlow also help. The exhaust opening of these tips is shaped more like a trumpet while the outer portion of the tip is cylindrical. IMO, this cuts down any resonating the tip would generate. The B+B for example are single wall. AL has driven my car and BobGs car, different CIDs but both using the Z06 tips. Meanwhile Pete and Al use the B+B tip w the control valve.
AL has noticed that even tho each car uses the control valve, Bob's and mine seem quieter and less resonance.

3. I think the tips should extend at least just a bit past the rear valence panel. This avoids dumping the exhaust towards the rear panel and setting up a resonance.

The above are strictly based on observations involving my car and some of the other FBI ZRs. Your results may vary. Also, I have used:
1. stock exhaust
2. B+B 3rd Gen
3. Magnaflow C4 catback both w and w/o resonator
4. SW Xpipe w Magnaflow mufflers and tips/no resonator
5. Current system is Watson headers, 3" SS pipe, SW Xpipe, DynoMax
Ultraflow muffs w Z06 tips and exhaust control valves. I have posted vids of the exhaust previously.

[tomtom72]

Sahweeeeet! Nice job Mike! The tips are killer and thanks for the install tips.

Man those OE ZO6 cats look like our cats. Are they brick or spun s/s?

To many miles of smiles! Here's to ya!

Tom

[mike100]

Originally Posted by tomtom72

Sahweeeeet! Nice job Mike! The tips are killer and thanks for the install tips.

Man those OE ZO6 cats look like our cats. Are they brick or spun s/s?

Tom

They look to be typical oem substrate (brick) internally with a tight pattern that looks restrictive, but they work pretty well on a 7 liter Z06 and they are compact. My other theory is that oem Cats usually have more of the rare earth metals and work better than the typical universal. I forgot to take a camera when we cut the cats out of the factory mid-pipe, but they look like the honeycomb on the LT5 cat and pretty much the same as an LS2/LS3 cat if you have ever seen one. As a matter of fact, I have a pair of those also (much easier to buy as take-offs). They are sort of a flat package with a 2.5" pipe inlet. I suppose you could maybe use those adapted to a Corsa catback, but the shape might not lend itself well to fitting underneath the slave cylinder.

[mike100]

Originally Posted by GOLDCYLON

Concur. I would have had em coated as well but that might have been stealth enough for CA

Bingo

I'm also considering dually out with a pair of conventional tips because the best way to make these c4's stop resonation from the back hatch area seems to be stopping up dual outlets to a single one...like Corsa's do and GM as well with the factory fake 2nd outlet. I think it's about time to figure out how to get the NPP valve hooked up on my car. Also very likely will go to some quieter muffler type as mentioned in my first post.

The main question I have on GM's NPP system is what controls the valves to open up at roughly 3500 rpm besides low manifold vacuum? If there is electronic control, how do you adapt it to older cars?

[vilant]

Wow, sweet job. Have any video of how the new exhaust sounds?

[XfireZ51]

Originally Posted by mike100

Bingo

I'm also considering dually out with a pair of conventional tips because the best way to make these c4's stop resonation from the back hatch area seems to be stopping up dual outlets to a single one...like Corsa's do and GM as well with the factory fake 2nd outlet. I think it's about time to figure out how to get the NPP valve hooked up on my car. Also very likely will go to some quieter muffler type as mentioned in my first post.

The main question I have on GM's NPP system is what controls the valves to open up at roughly 3500 rpm besides low manifold vacuum? If there is electronic control, how do you adapt it to older cars?

The exhaust valve is controlled by vacuum. They are closed at idle and open up approaching WOT. The valves are controlled using the Charcoal Canister vacuum line. You can go further and install an electronic control to allow vacuum to pass or not. Should be pretty simple to install although I don't see a need for it.

[mike100]

Originally Posted by vilant

Wow, sweet job. Have any video of how the new exhaust sounds?

I'll try to make something on Saturday when I return home. It does sound great when you are going for a 10 mile drive to open it up and play, but difficult to travel a highway in for any length of time in 6th gear.

[mike100]

Originally Posted by XfireZ51

The exhaust valve is controlled by vacuum. They are closed at idle and open up approaching WOT. The valves are controlled using the Charcoal Canister vacuum line. You can go further and install an electronic control to allow vacuum to pass or not. Should be pretty simple to install although I don't see a need for it.

The reason I ask is because I wouldn't want it to work below 4000 rpm or so. I took a spin in a friends C6 and kind of disliked how much attention the extra noise brought me. My C6 doesn't have that option. I found it distracting (along with the HUD too).

[BigJohn]

What's New?

[KFoster]

Good info. I bought mine with a two into one big flowmaster, then two out and the pipes split into dual tips each side. Sounds surprisingly good. I usually don't care for mixing the exh like that. Many times it sounds like a UPS truck. I've been looking around to see what is out there in stainless. Might even change to long tube headers. Your pics look really good.


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