Pontiac G8 Forum banner

1 - 20 of 32 Posts

·
Senior Member
Joined
·
172 Posts
Discussion Starter #1
I read an article by David Vizard on exhaust science.
Auto Exhaust Science
In the article he talks about a pressure wave termination box that essentially tricks your engine into thinking you have an open exhaust system. Sounded like a fun/cool project that might gain me some horse power, so I've decided to build one. All the materials I'm using are 16 gauge 304 stainless steel. For the termination box, I'm using oval tubing that I purchased from Spin Tech. The dimensions of the oval tube are approximately 3.5" X 5.75", equivalent to a 5" round tube. Since my existing exhaust system is 2.5", I purchased 3.5" to 2.5" cones from Stainless Headers Mfg. to transition from the termination box back to my exhaust system. I notched the oval tube and used two segments of 3.5" round tube to transition into the cones on the outlet side of the termination box




For the inlet side, I machined a cap with two 2.5" holes to merge the two exhaust banks.


The inlet tubes will be cut 2" into the termination box. Here it is mocked up in the car. As you can see, it barely fits between the cross member and the tunnel brace.

The termination box volume needs to be equal to or greater than the cubic inches of your engine. Based on my calculations, my termination box is 22" long for a 376cu. in. engine.

I'll keep you all posted as my project progresses.
 

·
Registered
Joined
·
2,003 Posts
That's a great article, if folks would dare to read it, 3/4 of the exhaust post would not exist.

FWIW, Rick C. built one similar to yours 5? years ago. Not sure what came of it. Think it has changed hands.

BTW, the fabrication looks great.
 

·
Senior Member
Joined
·
172 Posts
Discussion Starter #3
I was going to splice the termination box into my existing Magnaflow exhaust system, but I've decided to fabricate the entire system from the headers to the axle backs from scratch using mandrel bends. I'll use my existing axle backs with Magnaflow 11366 mufflers. So far, I have the system fabbed up from the headers to the termination box. Once it's all tacked together, I'll purge tig weld it all together.
 

·
Registered
Joined
·
588 Posts
That is one clean underbody

Sent from my XT1585 using Tapatalk
 

·
Registered
Joined
·
5,206 Posts
Sub'd
 

·
Naturally as-pirated
Joined
·
360 Posts
the article talks about a pressure wave termination box that essentially tricks your engine into thinking you have an open exhaust system.
For the termination box, I'm using oval tubing that I purchased from Spin Tech. The dimensions of the oval tube are approximately 3.5" X 5.75", equivalent to a 5" round tube. Since my existing exhaust system is 2.5", I purchased 3.5" to 2.5" cones from Stainless Headers Mfg. to transition from the termination box back to my exhaust system. I notched the oval tube and used two segments of 3.5" round tube to transition into the cones on the outlet side of the termination box

For the inlet side, I machined a cap with two 2.5" holes to merge the two exhaust banks.

The termination box volume needs to be equal to or greater than the cubic inches of your engine.
Nice work. I have similar on my daily and worked on others. Where did you find the volume formula from Vizard exactly BTW, I couldn't find that in the link?

A couple of G8 guys have done one big single resonator, and with the benefit of hindsight I do not believe it to be a "volume" deal, rather it is an area change deal. Like a megaphone and expansion chamber.

The effects Vizard "saw" back when were a result of a "chamber" introduced along a long exhaust system that also connected both banks of a v8. It is a large H-Pipe and does a great job of balancing the imbalance from the banks and of diminishing pressure waves into a given static pressure which a given engine might appreciate.

In my experience one large fixed volume chamber affords our car a little increase but introduces a couple of drawbacks for the effort, unless you are looking at building horsepower WOT in a narrow band at peak RPM, hang the noise.

A massive "terminator" box will help a NA engine with a poor set of headers overcome the double-pulse, yes. But consider the drawbacks are loss of low end torque and massive drone (harmonic resonance) throughout the operating range.

I think this is the best video example in a G8:

Also an interesting example of big single resonator and clean fit:
 

·
Senior Member
Joined
·
172 Posts
Discussion Starter #7 (Edited)
Where did you find the volume formula from Vizard exactly BTW, I couldn't find that in the link?
You're right, the formula wasn't in the link. Here it is:

I'm just a guy with a tig welder in my garage who likes to build stuff. If this doesn't work, it won't be the first time I tried something and failed. Vizard's construction details are a bit vague to me, so I tried to copy the system he built for a small block Chevy shown above. When I get my new exhaust system done, I'll go back to the dyno for results and post them here.
 

·
Naturally as-pirated
Joined
·
360 Posts
Cool. The reason I mention volume is because you can get the same effect with less weight and more control using reverse cone megaphone, as per most state of the art sports bikes nowadays.
I start the megaphone at the final merge of primaries and use PipeMax to calculate length and diameter according to engine data / state of tune.
FWIW I use net volume per bank, equivalent volume to one swept cylinder, and X-pipe fitted at tuned length (third harmonic).
http://www.g8board.com/forums/116-exhaust-tech/227418-mid-mufflers-delete-36%94-long-terminator-box.html#post3117522

Similar overall effect just more tuned control over events - possibly quieter, with more streetable torque, I think.
 

·
Registered
Joined
·
348 Posts
great article ,, I have built headers and bike tuned pipes ,, I will be more than likely building a set of headers for my car ,, I know between the material costs and time it takes I could purchase as set for 2/3 of the cost ,but there are some things I want to achieve by building my own set and incorporate a set of high flow cats due to the emissions here,, even tossed the idea 180 headers but the routing logistics would be near impossible , but I like the idea of the termination box ,, I have a corsa exhaust on it now with the stock manifolds and cats , I have all the parts to for the ls3 cam and delete and will do the headers and exhaust to complete the package I am interested in how this will sound keep us informed

Gmonde Performance and Fabrication | Custom Headers-Muscle Car Performance Upgrades-Motorcycle Exhaust-Restoration
 

·
Naturally as-pirated
Joined
·
360 Posts
great article ,, I have built headers and bike tuned pipes ... even tossed the idea 180 headers but the routing logistics would be near impossible
I built and fitted custom 180º recently to synchronise the pulse pattern, yes packaging, heat and tuning was a challenge. Not a cheap solution but definitely the best results I've seen - extending torque down low and coming on strong upper-mid with my 226 VVT cam. Also fitted to an LS3 416 with big cam and really woke it up with nice torque boost and significantly improved down low, sounds good too!
 

·
Registered
Joined
·
348 Posts
I built and fitted custom 180º recently to synchronise the pulse pattern, yes packaging, heat and tuning was a challenge. Not a cheap solution but definitely the best results I've seen - extending torque down low and coming on strong upper-mid with my 226 VVT cam. Also fitted to an LS3 416 with big cam and really woke it up with nice torque boost and significantly improved down low, sounds good too!
what body was the ls3 in?
 

·
Registered
Joined
·
348 Posts
got any pictures of the header build ? I am thinking how the best routing would be ?
 

·
Senior Member
Joined
·
172 Posts
Discussion Starter #15
My new system is done, and I am very pleased with the result. When I fired the car up for the first time after completing the system, it had a terrible resonance coming from the PWTB. It sounded like a tuning fork and it occurred throughout the full range of RPM, even at idle. I left the car running and raised it on the lift and noticed I could make the resonance stop by pressing my thumb (with a glove) on the PWTB. I figured the resonance must be coming from the flat, unsupported walls of the PWTB. I decided to drill 3 equally spaced 1/4 inch holes on the top and bottom (6 total) of the PWTB and tie the two walls together with a 1/4 inch rod welded on both sides. Whala, it worked, no resonance, zero drone.


Here's the completed system. I wanted to try and match the decibel level I had with my Magnaflow system with a mid-muffler, so I installed two 12 inch race mufflers that I bought from Stainless Header Mfg.


More shots installed in the car:




Sound clips coming soon!
 

·
Registered
Joined
·
588 Posts
Nice work!

Sent from my XT1585 using Tapatalk
 

·
Senior Member
Joined
·
172 Posts
Discussion Starter #17
Nice work!

Thank you!


My initial seat of the pants impression of my new exhaust system is that it has given my G8 a performance gain, but I'm probably imagining it because I want it to work. I'll drive it for awhile and take it to the dyno for the results.
 

·
'Mod'erator
Joined
·
4,887 Posts
Helluva thread man. Can't wait to see the results on the dyno...
 

·
Registered
Joined
·
469 Posts

·
Senior Member
Joined
·
172 Posts
Discussion Starter #20
Sound clip video

Helluva thread man. Can't wait to see the results on the dyno...
Thanks Yeti! When I started doing research on this project, I couldn't find much information on build details of PWTB's. Hopefully, the information I've given here will help someone else in their build.

I want to hear it!
Sorry it took so long. I had a long list of honey-do's to take care of for my wife after I finished the exhaust system.


 
1 - 20 of 32 Posts
Top