"Straight" pipes

[KILLSHOTS]

Originally Posted by Tony Davila

If your talking about a stock resonator being replaced with X-pipe it won't get that much more loud because if you ever have seen what is inside of a stock resonator you will see that there is only a small 4" length perforated section at the beginning of the resonator. The rest of the body is a solid pipe. Helmholtz design once again.

I have two stock resonators that I cut off and I was surprised that was all the muffling going on in there. It's design was to kill a certain frequency only that the mufflers didn't. The installation of a X-pipe will just flow better since it isn't at a 2.5" reduction like the resonator.

Hey Tony,

Are you sure you aren't looking at later resonators? My understanding was that GM opened the resonator up A LOT in the 93-95 cars, but that the 90-92 resonators were the primary bottleneck, as they closed down to about 1-5/8" diameter. I had thought that removing the resonator from an early car would make a worthwhile difference. Is that not the case?

Thanks!

[Hib Halverson]

Originally Posted by KILLSHOTS

Thanks Hib. I do have Marc's chip in my car currently...would it need to be recalibrated just to remove mufflers and resonator?

I appreciate the input!
Chris

I've never run a car with cats only. The noise is incredibly annoying, especially on a long trip but...my hearing is really good and lack any particular desire to be loud...not knocking it because there are many others who do want to be loud.

Anyway, the only experience I have which is similar was the Record Run car from way back in the day. It ran with stock manifolds but otherwise open exhaust and it had an aftermarket calibration to optimize the air fuel ratio for that. You'll have a little more restriction than that but you're removing 2/3s to 3/4s of the restriction by cutting off the resonator and the mufflers.

I think it's possible you may need to richen up the motor at WOT, but...check with Marc. My guess is he knows if you need to or not.

The main reason I suggest that is most people these days are running on E10 gas. The 6-7% ethanol usually in oxygenated fuel requires a more rich AFR to begin with–at WOT it goes from 12.5:1 down to about 12.2:1. So right there you're already lean. When you get rid of the restriction of the resonator and mufflers, the engine will go a bit lean and, if you never had the cal redone for E10, then you might end up too lean.

Again, check with Mark.

[mike100]

x-piping the stock exhaust will induce a little resonance at 1700-1900 rpm, but much much less than just slapping a full 3" system on a vette. If you keep the stock mufflers, they still do a good job at keeping things reasonable plus the pipe diameter, bends, and pipe thickness is otherwise unaltered and part of the original engineered quiet system.

I was happy to run around like that for a year until I got greedy and did headers etc.

Something I have never tried, but would be interested in seeing how it worked out:
... those compact glass-pack tube sections in place of the resonator with otherwise stock pipes. Maybe a little quieter compared to and H or X-pipe?

[KILLSHOTS]

Thanks again, Hib. I really do like it loud and I loved my L98 on cats alone (albeit 3 of them) but consensus seems to be that the LT5 on only 2 cats will make a lot more noise than that. Like "race car" loud, which may be OK for me but not for passengers or the local constabulary. I think I'm going to swap the resonator for an x-pipe first and then drive it for a little while before I go hacking off the mufflers. Easier to take more off than to put some back on, I guess!

[mike100]

Also I had loud-azz borlas on an LT1 C4 before with totally stock everything else...very loud and droned in the hatchback badly. The mufflers do all the heavy lifting.

[KILLSHOTS]

Originally Posted by mike100

x-piping the stock exhaust will induce a little resonance at 1700-1900 rpm, but much much less than just slapping a full 3" system on a vette. If you keep the stock mufflers, they still do a good job at keeping things reasonable plus the pipe diameter, bends, and pipe thickness is otherwise unaltered and part of the original engineered quiet system.

I was happy to run around like that for a year until I got greedy and did headers etc.

Something I have never tried, but would be interested in seeing how it worked out:
... those compact glass-pack tube sections in place of the resonator with otherwise stock pipes. Maybe a little quieter compared to and H or X-pipe?

Agreed, think that's what I'm going to start with. You wouldn't happen to have a sound clip of your stock mufflers with no resonator, would you? Lorne just removed his resonator and I'll get to hear it in a couple weeks but he has Borla mufflers, so not really a valid comparison.

[KILLSHOTS]

Originally Posted by Hib Halverson

I've never run a car with cats only. The noise is incredibly annoying, especially on a long trip but...my hearing is really good and lack any particular desire to be loud...not knocking it because there are many others who do want to be loud.

Anyway, the only experience I have which is similar was the Record Run car from way back in the day. It ran with stock manifolds but otherwise open exhaust and it had an aftermarket calibration to optimize the air fuel ratio for that. You'll have a little more restriction than that but you're removing 2/3s to 3/4s of the restriction by cutting off the resonator and the mufflers.

I think it's possible you may need to richen up the motor at WOT, but...check with Marc. My guess is he knows if you need to or not.

The main reason I suggest that is most people these days are running on E10 gas. The 6-7% ethanol usually in oxygenated fuel requires a more rich AFR to begin with–at WOT it goes from 12.5:1 down to about 12.2:1. So right there you're already lean. When you get rid of the restriction of the resonator and mufflers, the engine will go a bit lean and, if you never had the cal redone for E10, then you might end up too lean.

Again, check with Mark.

Hib, are you at all familiar with the muffler eliminators that CC sells? They are 2-3/4" pipe and the hangers are identical to the ones on my 1990 car. CC does not expressly state that they work on a ZR-1 but everything else seems identical to me. Your thoughts are greatly appreciated!

Thanks!
Chris

[Hib Halverson]

Originally Posted by KILLSHOTS

Hib, are you at all familiar with the muffler eliminators that CC sells? They are 2-3/4" pipe and the hangers are identical to the ones on my 1990 car. CC does not expressly state that they work on a ZR-1 but everything else seems identical to me. Your thoughts are greatly appreciated!

Thanks!
Chris

Sorry, Chris, while I'm aware that "muffler eliminator" products exist, I've never used them.

I can offer some instructions on how to build a great exhaust system for a ZR-1. It's the system I've had on my car for about 15 years.

See this web page.

[cadillac531]

On my '91, I have a '94 ZR-1 exhaust system with stock '94 resonator and the stock '91 cats. I cut the mufflers off the '94 system, welded in straight pipes and fabbed up '91-like tips.

It has great sound, but doesn't resonate at cruise. It also picked up 9 rwhp and 19 ft/lb at the wheels.

[ZRXMAX]

My system got good "sound" comments after I built it some time ago.
Watson headers and 3 inch pipe
3" cats
3" x "18 straight thru bullet mufflers in the tunnel leaving room for an x pipe in front of it.
Flowmaster 40s at the the rear with straight tips.

My next system will add the blended X pipe.

I want to dump the Flowmasters and just put straight thru bullet mufflers out back.

If I really get carried away I can put another lenth of bullet muffler after the turn past the differential.

I could also use the tips that also have the sound deadening perforated interior section in them. In spite of how short they are they do seem to have a noise reduction factor to them.

That should give it a tone so low you will think its a big block.

This would essentially make it a straight shot once past the cats.