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Exhaust Options-Termination Box?


Ian
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Has anyone tried a termination box for their 2002?  The muscle car guys have been talking about this since an article by David Vizard appeared in Popular Hotrodding a few years ago, with the goal of building an exhaust system that did not contribute any power loss.  (http://www.popularhotrodding.com/enginemasters/articles/hardcore/0505em_exh/).  

 

This was important to the big-block guys for drag racing, but with our little engines I figure we could benefit as well.  My understanding is that if you tune for max power at the header collector and put a large volume immediately downstream, that basically everything after the large volume has no negative impact on power.  So, you could have a quiet muffler at the back of the car and not rob power.  

 

From trolling a few sites, it seems that you want  a volume 2x the engine displacement immediately downstream of the collector.  This is a limitation for the big V8's, because it's difficult to stuff that volume under a car.  But for our engines, it does not appear to be that difficult.  For example, for my 2.3L S14, this translates to 645 cu in.  This volume could be accomodated by a tube 5" diam x 32" length, which could fit in the driveshaft tunnel of our cars.  Or a 3" x 6" diam oval with a length of 11".  

 

With welder in hand, this sounds cheap to make.  The only trick I've come across is that the upsteam inlet should be anti-reversionary, meaning the inlet tube should protrude inside the chamber by a couple of inches to minimize pressure waves from reflecting back up into the header.

 

Has anyone tried this?  As I get older, I appreciate the day-to-day advantage of not blowing my ear drums out, but don't want to leave any power on the table, so I might try fabbing up something. 

Edited by Ian
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Has anyone tried a termination box for their 2002?  The muscle car guys have been talking about this since an article by David Vizard appeared in Popular Hotrodding a few years ago, with the goal of building an exhaust system that did not contribute any power loss.  (http://www.popularhotrodding.com/enginemasters/articles/hardcore/0505em_exh/).  

 

This was important to the big-block guys for drag racing, but with our little engines I figure we could benefit as well.  My understanding is that if you tune for max power at the header collector and put a large volume immediately downstream, that basically everything after the large volume has no negative impact on power.  So, you could have a quiet muffler at the back of the car and not rob power.  

 

From trolling a few sites, it seems that you want  a volume 2x the engine displacement immediately downstream of the collector.  This is a limitation for the big V8's, because it's difficult to stuff that volume under a car.  But for our engines, it does not appear to be that difficult.  For example, for my 2.3L S14, this translates to 645 cu in.  This volume could be accomodated by a tube 5" diam x 32" length, which could fit in the driveshaft tunnel of our cars.  Or a 3" x 6" diam oval with a length of 11".  

 

With welder in hand, this sounds cheap to make.  The only trick I've come across is that the upsteam inlet should be anti-reversionary, meaning the inlet tube should protrude inside the chamber by a couple of inches to minimize pressure waves from reflecting back up into the header.

 

Has anyone tried this?  As I get older, I appreciate the day-to-day advantage of not blowing my ear drums out, but don't want to leave any power on the table, so I might try fabbing up something. 

2.3L = 140 cu in

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  • 5 months later...
.....basically everything after the large volume has no negative impact on power.  So, you could have a quiet muffler at the back of the car and not rob power.  

 

I believe you have misinterpreted some of David Vizard's work. As you know, the termination box terminates the wave of the secondary. Just as primary header length tuning is important, his point is that so is tuning of the secondary length. Though Vizard gives some guidelines on secondary header length, to do it right requires experimentation on the dyno or track. I considered making a sliding section resonator box to test different lengths, but other projects took over.

Vizard's second point is that for *race engines*, minimum backpressure (or zero) is desired. Thus the emphasis on free-flowing mufflers. If you have a 3" exhaust secondary, you cannot put a 1.5" exhaust and a restrictive muffler after the termination box and expect to suffer no performance degradation. The entire exhaust system, from head to exhaust tip, needs to be free-flow. Not all muffler manufacturers publish flow in CFM. Vizard has a rule of thumb for CFM vs. HP, if I recall correctly.

In my experience street engines are different, they like some backpressure. I found this out when once my center reasonator split all the way along the seam. It was loud, and I thought great, now I'll have more power. Nothing was further from the truth, I was amazed on how down on power the engine was. The bottom line is an engine is tuned as a complete system, from air filter to exhaust tip. Tuning and hard parts differ by application, race, street, or other.

Here's some good reading, and do let us know if you do the experiment and find a difference:

 

My previous post on Vizard:

http://www.bmw2002faq.com/topic/109382-need-advice-on-raised-floor-header-install/

David Vizard's How to Port & Flow Test Cylinder Heads

S-A Design (February 15, 2012)

David Vizard's How to Build Horsepower

S-A Design (June 15, 2010)

 

Engine Airflow - A Practical Guide to Airflow Theory, Parts Testing, Flow Bench Testing and Analyzing Data to Increase Performance for Any Street or Racing Engine

by Harold Bettes

HP Books (July 6, 2010)

 

Exhaust Science Demystified. By David Vizard

From the February, 2009 issue of Super Chevy

http://www.superchevy.com/technical/engines_drivetrain/exhaust/0505phr_exh/index.html

Racing Exhaust System - Header Tech. By David Vizard

From the February, 2009 issue of Stock Car Racing

http://www.stockcarracing.com/techarticles/scrp_0704_header_tech/index.html

 

Fred '69 & '74tii

Edited by FB73tii
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Was any headway made on this topic? I am currently researching m2 exhaust options for my own project. 

 

-Ryan

 

 

Still crunching numbers while I work on other stuff. A good bet is a good 2.5" muffler/resonator combo.

2.5in all the way back works very well for my M2.  track is primary application.  fairly loud on street, even with my "street" muffler installed in place of the track rear muffler.

 

and 2.5in is about as big as you can fit along the stock path over the rear subframe.

Edited by mlytle
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