Exhaust Science Demystified

[Pinhead]

Exhaust Science Demystified

For me the first really serious look at how to muffle a high-performance race engine without loosing a significant amount of power started in 1980 when I built a 400lb-ft, 404hp 350 to replace the very lame 158hp 305 in my California-spec Pontiac Trans Am. Having worked very hard to build a pump gas fueled engine (gas was really bad in those days), that would cross the 400 hp barrier, I was very disappointed to find that, regardless of what mufflers were used, the output dropped by some 20 lb-ft and 25 hp. Having had some experience designing a no-loss system for the original style British Mini Coopers, I felt confident I could pull off the same stunt for significantly bigger V-8 engines. The result, aided by an acoustics expert friend, was the Sonic Turbo. This design went on to be manufactured by Cyclone (now a division of Walker/ Dynomax). After the smoke cleared from a big muffler shootout (done at Gale Banks facility and published by Hot Rod magazine), a pair of 2.25-inch Sonic Turbos (the 2.5-inch ones were still a couple of months off) sunk everybody else's 2.5-inch items. This, it seemed, was just what the hot rod fraternity wanted and they sold by the hundreds of thousandths. That was good, but more importantly, it appeared to spark the industry into aggressively pursuing significantly more functional mufflers and exhaust systems. The result is that 20-some-years later, all the necessary components to build a highly effective, no-loss system are at hand, and not necessarily that much money either. All that appears to be lacking is widespread know-how as to what is needed to achieve this happy state of affairs. As of now, we are going to make a start on putting that right.

 

[wallaka]

 

[Lazy JW]

Pinhead,
Thanks for the link, that was very informative. Reckon most of us go too large on the pipes
Joe

 

[Pinhead]

Pinhead,
Thanks for the link, that was very informative. Reckon most of us go too large on the pipes
Joe

Perfect example: look at the Civic Rice Rocket fart can exhausts LOL.

 

[wallaka]

Pinhead,
Thanks for the link, that was very informative. Reckon most of us go too large on the pipes
Joe

Perfect example: look at the Civic Rice Rocket fart can exhausts LOL.

That's just the tip, haha. The real exhuast is stock size.

 

[80broncoman]

Pinhead,
Thanks for the link, that was very informative. Reckon most of us go too large on the pipes
Joe

Perfect example: look at the Civic Rice Rocket fart can exhausts LOL.

That's just the tip, haha. The real exhuast is stock size.

Ya that how the ricers get that oh so sweEEeet sound :!:

It goes like 1.6 engine, 10 feet of 1 3/8 pipe and 6 iches of coffe Can :!:

 

[XPC66]

Another typical article from one of the venerable oracles that pretty much says, that every situation requires it's own set of rules. Really just a tongue wag,trying to make a science out of trial and error IMO.

 

[jamyers]

Another typical article from one of the venerable oracles that pretty much says, that every situation requires it's own set of rules. Really just a tongue wag,trying to make a science out of trial and error IMO.

I wouldn't completely dismiss it, though. The basic guidelines are good, we used them on my Buick 455 - shorty headers into 3" collectors with 3" pipes into chambered mufflers, then 2.25 id pipes out the back. The effect is a really long collector, then the exhaust "thinks" it hits open atmosphere at the mufflers. Works like a champ, at 4000rpm there's no measureable exhaust pressure (psi at the header collector) and it makes gobs of power across the rpm range.

What I gathered from it is the same thing I've learned regarding the rest of engine building: It's the combination that matters.

 

[XPC66]

That's true, I've always approached every build I've done with and overall plan and copius calculations, but from there on it's iterative steps.

I am constantly bemused at how frequently article writers have epiphanies about the bleeding obvious, embellished with some moderate narcissism.

There is no doubt Vizzard has provided good reading to the magazine loyalists, but that tends to be about as far as it goes. Joe Average car mag enthuisist probably never goes past putting bling and turtle wax on his beastie, but will hold court at a barbeque with his vast knowledge of all things automotive. Of the remaining 10% , 7/10ths of them are lego mechanics who go out to retail outlets and buy offshelf bolt ons. The last 3% pour copious time into practical development, that invariably has a tenuous resemblance to the one size fits all solution from the performance shop.