ZR-1 Exhaust Cutout Project

[Tony Davila]

This month’s project involves installing custom cutouts on a stock ZR-1 exhaust system. The original system I had was a 3” B&B exhaust system w/ X-pipe. Every time I would drive up to BG I had to wear earplugs because of the drone and it was driving me crazy. I needed a solution in order to enjoy both the sound of the exhaust and lack thereof.


I started looking on the web and eBay and found some 3” vacuum actuator cutouts. I picked up two for $220. I then came up with a game plan on how I was going to get this to work. After trial and error I found that it was a pain trying to get the vacuum actuators to work. The vacuum actuators that came with the system required at least 10 inches of vacuum to close the system. So just going up a small hill would have opened up the system early at part throttle and this isn’t what I wanted. My goal was to run it in the open mode at all times but have the option to close them for long trips for peace of mind and a quite cabin. Lucky for me Daniel McGuffee gave me his old exhaust system to play with.


eBay item Vacuum Actuated Cutouts

I have seen other systems and didn’t want electric cutouts just due to cost and potential for failure. I am also a do it yourself kind of guy. My plan was to install them so that it was not visibly noticeable, the stock mufflers size aided in keeping them hidden. Some of you may ask why use the factory mufflers with their tiny opening and restrictive nature. Answer: The factory mufflers are built with a design called Helmholtz resonance. [The theory of Helmholtz resonators is used in motorcycle and car exhausts to alter the sound of the exhaust note and for differences in power delivery by adding chambers to the exhaust. Exhaust resonators are also used to reduce potentially loud and obnoxious engine noise where the dimensions are calculated so that the waves reflected by the resonator help cancel out certain frequencies of sound in the exhaust.] The factory mufflers are best at reducing sound and resonance and almost every one of you guys probably still have them.

Original Helmholtz design factory muffler.

So come along on my journey and see what I did. I have tested the system and it works bad azz. No resonance in the cabin with the system closed running through the mufflers and it sounds stock. With the system open it sounds like an open header car, loud. I may need to put some bullet mufflers after the X-pipe to quite it down a bit. I’ll be up at BG next month so if your there you will be able to hear it.

First I modified exhaust system by installing a $30 eBay X-pipe then installed a coupler on the passengers side to get rid of the slip fit. I also install my own design high frequency (sort of) muffler. This design is to kill the high pitch a strait pipe makes. It works pretty well, it doesn't sound like a Corsa at wide open.

Custom built high freq killer.


Modified exhaust cutout

I had to place them at an angle that would keep them hidden, still function without interfering with suspension items and not burn anything. R&D came next to make it functional.

More to come.

[Tony Davila]

It took a lot of thought, since I was not using an electric or vacuum actuated type system I had to go back to old school methods of manual cable (Choke cable: $10 at AutoZone).

[Tony Davila]

Still had to do a little more R&D to get the cabling right and the spring pressure to allow a solid open or closing. The pressure from the spring keeps it from rattling when in the closed mode and helps it to seal better.





Next was where to mount the cable levers without creating an eye sore and still be functional and not inconvenient.


Mounting the cable levers in the compartment behind the passenger seat was the easiest shot with the lease hassle.

View of cable coming out of the top backside of the cubby.

[Tony Davila]

The Cutouts are not so noticeable from the rear.
I also cut off the exhaust tips and moved them further out and up in order to get a neater appearance. The gap was horrible.


My impressions of my build are this, A Success!. While driving at 70MPH it is so quite I now can hear all the annoying squeeks and rattles. It still makes noise if you get on it but the sound is outside of the car not in the cab. I will only have it closed during long trips or if I don't want to hear all that LT5 excitement.

when I'm cruising with the exhaust cutouts open there is drone in the cab just like the B&B/X-pipe system and now an even louder race car sound that every one knows your coming. I mean everybody! Even people in different states.

[Kevin]

marc haibeck sells a kit for this. great work and the car looks great

[FU]

Nice ! I can't stand the noise of the non-stock exhaust systems on these cars.

[Tony Davila]

Originally Posted by Kevin

marc haibeck sells a kit for this. great work and the car looks great

He does an outstanding job of it too. But I wanted mine hidden. And..thanks

[WARP TEN]

I had Marc do the cutouts and I love them. But the way he does them requires removing the spare tire carrier. I have been trying to think of a better place to put them so I can restore the spare tire carrier. Your position is great although with the electric cutouts I am not sure they will fit. I will test it when I can. I dummied up something the size and shape or an electric cutout with motor and I think they can be positioned just forward of the "y" in the pipes and a hanger but need to angle down a bit to avoid the pass side storage compartment. --Bob

Here is what I have now and my thinking on a new position:

I also installed a rocker switch hidden under the carpet to activate them:

[Tony Davila]

Originally Posted by WARP TEN

I had Marc do the cutouts and I love them. But the way he does them requires removing the spare tire carrier. I have been trying to think of a better place to put them so I can restore the spare tire carrier. Your position is great although with the electric cutouts I am not sure they will fit. I will test it when I can. I dummied up something the size and shape or an electric cutout with motor and I think they can be positioned just forward of the "y" in the pipes and a hanger but need to angle down a bit to avoid the pass side storage compartment. --Bob
:

I liked your design and it was an inspiration to me... but you are right I had to solve the problem of the spare tire issue that the electric cutouts present. I did look at that same position you are considering as my first position. Due to the size of my cutouts and their simplicity I was able to put them behind the muffler.

[XfireZ51]

Originally Posted by Tony Davila

This month’s project involves installing custom cutouts on a stock ZR-1 exhaust system. The original system I had was a 3” B&B exhaust system w/ X-pipe. Every time I would drive up to BG I had to wear earplugs because of the drone and it was driving me crazy. I needed a solution in order to enjoy both the sound of the exhaust and lack thereof.


I started looking on the web and eBay and found some 3” vacuum actuator cutouts. I picked up two for $220. I then came up with a game plan on how I was going to get this to work. After trial and error I found that it was a pain trying to get the vacuum actuators to work. The vacuum actuators that came with the system required at least 10 inches of vacuum to close the system. So just going up a small hill would have opened up the system early at part throttle and this isn’t what I wanted. My goal was to run it in the open mode at all times but have the option to close them for long trips for peace of mind and a quite cabin. Lucky for me Daniel McGuffee gave me his old exhaust system to play with.


eBay item Vacuum Actuated Cutouts

I have seen other systems and didn’t want electric cutouts just due to cost and potential for failure. I am also a do it yourself kind of guy. My plan was to install them so that it was not visibly noticeable, the stock mufflers size aided in keeping them hidden. Some of you may ask why use the factory mufflers with their tiny opening and restrictive nature. Answer: The factory mufflers are built with a design called Helmholtz resonance. [The theory of Helmholtz resonators is used in motorcycle and car exhausts to alter the sound of the exhaust note and for differences in power delivery by adding chambers to the exhaust. Exhaust resonators are also used to reduce potentially loud and obnoxious engine noise where the dimensions are calculated so that the waves reflected by the resonator help cancel out certain frequencies of sound in the exhaust.] The factory mufflers are best at reducing sound and resonance and almost every one of you guys probably still have them.

Original Helmholtz design factory muffler.

So come along on my journey and see what I did. I have tested the system and it works bad azz. No resonance in the cabin with the system closed running through the mufflers and it sounds stock. With the system open it sounds like an open header car, loud. I may need to put some bullet mufflers after the X-pipe to quite it down a bit. I’ll be up at BG next month so if your there you will be able to hear it.

First I modified exhaust system by installing a $30 eBay X-pipe then installed a coupler on the passengers side to get rid of the slip fit. I also install my own design high frequency (sort of) muffler. This design is to kill the high pitch a strait pipe makes. It works pretty well, it doesn't sound like a Corsa at wide open.

Custom built high freq killer.


Modified exhaust cutout

I had to place them at an angle that would keep them hidden, still function without interfering with suspension items and not burn anything. R&D came next to make it functional.

More to come.

Tony,

You should have read my thread on NPP exhaust controller here:
http://www.zr1.net/forum/showpost.ph...0&postcount=32

or read the latest HOTB issue and the mike100 article on using vacuum actuators w rpm and vacuum switches. If you view the video in the thread I posted, you'll see that I control the actuator w a flip of the switch at my fingertip in the console. Another way to do it. I was interested in the same thing as far as keeping the noise down while just cruising.