Tom73

I have see a lot of statements made basicly saying that chambered pipes are more restrictive than a good set of free flowing mufflers. Does anyone know if a real study has ever been done to confirm this? Any links or library references would be greatly appreciated.

tom...

tnt76vette

One guy told me here that they were "too restrictive". I said, "How can ya tell?" He said, "Just look at 'em." So I looked at 'em and bought 'em anyway and I'm happy (very) I did!!!!! Like you Tom, I've heard that arguement but have seen nothing to back it up. Wheres the Beef (Proof)? :flag

sb69coupe

I seem to recall that someone posted dyno results or 1/4 mile times showing a big difference. Seems that it was dyno numbers from a big block car with sidepipes. Thanks to the poor search capabilities on the forum, I can't find the post :(

Shannon

Sigforty

I have not seen any study on this topic, but being in school for Chemical Eng. can help me understand the belief. I think the dimples in the chambered sections help create more friction to the air moving by them. This would slow down the max velocity at the center of the pipe. The dimples would also create turbulent flow. Turbulent flow creates eddies of gas that would just sit and swirl behind the dimples. It seems like a simple fluid mechanics problem, but the only way to know would be to test flow some chambered sections.

Mark B.

fauxrs

Many years ago - one of the peterson publications did a study of turbo mufflers vs. your basic striaght through glasspack - they found the glasspacks to be incredibly restrictive - especially since you can see right through them.

The reasoning seemed to be the very small perforations in the core that sit in the slipstream of the exhaust gasses create turbulent flow similar to that mentioned in an earlier reply.

Since the dimples are much larger than these perforations I could see some reasonable argument that they would be restrictive. at least compared to a smooth pipe w/ hi flow mufflers at the end.

However I dont believe any kind of study has been done specifically on these pipes.

MELVIN

On my 68, I had hooker sidepipes. When I replaced them with the chambered, there was a large, noticable diff in seat of the pants

J Winkeler

Melvin,
Was that a positive or negative SOTP difference?
John

Jughead

When I switched from Headers and a 2 inch exhaust/muffler system(previous owner installed) to the 2.5 inch chambered/ram horn manifold system my Vette was a different vehicle. It had better throttle response and ran much, much stronger.

I don't think the crimped section of pipe has anything to do with the air flow. A straight pipe runs right thru the chambered (crimped)section. I don't remember see any perforations in the pipe, but there was fiberglas aroung the 2.5 in pipe.

Here's a page from my site which I wrote soon after my install http://temp.corvetteforum.net/c3/the...t/index4.shtml. I waited a long time to legally run essentially a "straight pipe" system and don't think I'll be going back to mufflers.

Interesting comments from MELVIN though, I curious as to whether the results were (+) or (-). I was thinking about using the Hooker side mounts next!

7Bob3

I don't have any scientific evidance or dyno sheets to confirm, but I do have a set of chambered exhaust that I purchased, mounted and drove straight to the muffler shop. I wasn't the first one to say just look at them but I will say it. You have a 2 1/2 in pipe choked to a 2 in solid ring opening, then a 2 in perforated pipe through the chamber, then a 2 in solid ring back to 2 1/2 in. That's 20%. Sigforty can probably explain the dynamics of this restriction on flow. I have never held a chambered side pipe in my hand so I cant comment on their construction. They were probably very hi tech in 1965, but they cant compare to the Flow Master, Dynomax, Manaflow and others for making power. They do sound cool!


[Modified by 7Bob3, 1:37 PM 11/30/2001]

MassVette

I think chambered pipe i.d. is 2". Not a sufficient size for breathing efficiency on a Big Block; How do I know? Well, I have Hooker sidemounts on my ZZ/502, and I had 2" dia. Hooker glasspacks inside the tubes. On the dyno testing, there was a 90 HORSEPOWER DIFFERENCE with the mufflers connected!!!!!!! Chevrolet recommends a 3" exhaust system for a H.P. Big Block- after that, I knew why! I installed JCL spiral turbo baffles after that; end of problem!
:yesnod: :chevy :yesnod:

glen242

I may be wrong, but.... I believe my 2 1/2" chambered exhaust goes from 2 1/2" to something greater at the dimpled section. This added diameter, I thought, was to compensate for the dimples. In no way does it choke down to 2''.

I'll measure the chambered section O.D. next time I'm under the car, if anyone is interested.

BLT-71

I have a set of Allen chambered exhaust.
2 1/2 ID but the chambered section is 3 ID.
I notice a change in power to the positive, seat of the pants gauge.
The dimpled section gives such an exhaust note that I will only use these on my performance cars.
Some people prefer free flow mufflers but I think it is personal preference over HP or TQ gain or loss.

Ganey

I have done my own tests. Something I may not have posted was that on my first Hot Rods, initially ran glasspacks. Power had been increased greatly. :cool: During a run it blew the glasspacks off & took off like a blower or nitrous had been switched on ! Have run open manifolds & expect anyone who knows the stock fuel pump location would consider this very risky.
This led to the following which has been mentioned in what is sometimes referred to as Ganey's exhaust topic & is on http://www.corvettefaq.com/ .

One way to deal with the live axle cars is to run pipe straight back, add mufflers & forget the tailpipes over axle. I barely attached the mufflers to pipes & suspended the mufflers front & rear so that a hard jab on the throttle would blow the mufflers off & leave suspended out of the way.
This should be done after staging. Too late now, Gotcha!
:cool:

I may have more tickets for loud pipes than all the others combined.

Restrictive is a relative term & the closer you are to stock then the more likely you are to be happy w/ glasspacks, chambered or factory type side pipes.
The next issue is placement so glasspack type mufflers in the stock location at the end of exhaust like Corvette is more acceptable.

Headers, duals, X-over w/Turbo mufflers at the end is a better way to deal w/ a street car.

Anyway I have enough of my own info. for me & do not wish to debate the obvious (like Stingray emblems).

One test you might want to look up is one that Hot Rod magazine mentions in a muffler test about 1985 that "more than 10 years ago" did test showing turbo mufflers to "outperform the straight-through glasspack designs". BTW, this 85 test included the Hemi & Imperial mufflers which some had thought to be good.

:cheers:

ZD75blue

:nono: :nono: I'll have to remember that one :blueangel:

ZD

Tom73

For more info I e-mailed Mike Allen of Allen's Exhaust. He states that his chambered system is not restrictive. Said that the GM chambered system was very restrictive as they were 1 3/4" chamber section while his is 2 1/4" chambers.

tom...

PatsLs1vette

74 vette has the chambered and i just heard them yesterday and boy are they loud but sound really good.They dont sound restrictive. :yesnod:

MELVIN

SORRY FOR THE DELAY GUYS. MY 68 BB 427 ORIGINALLY HAD HOOKER HEADER SIDE PIPES. WHEN I SWITCHED TO CHAMBERED, I NOTICED A DECREASE IN SEAT OF TH EPANTS. IM STILL RUNNING THEM THOUGH, I LIKE THE SOUND

Tom73

Melvin,
When you replaced the Hookers did you install another set of headers or did you go back with the ram horns. If you went back to ram horns that could be the issue rather than the exhaust pipes (since the hookers are a header/side pipe combo). The loss of the headers could be the cause of the decrease in the seat of the pants.

But if you installed another set of headers, then forget the above comment :)

tom..

MELVIN

Tom. I reinstalled the original manifolds, which are the early bb manifolds, not the ram horn type. These types are are fairly free flowing. While I agree, changing back to the stock early bb manifolds, I knew there was no way they would flow as free as hooker headers. But the decrease "seemed" very noticable.

I can only state, chambered exhaust sounds great. But bottom line, the exh flow is restricted by the chambers. To what extent, I cant say. But I do believe it was noticable.

From looking at my chambered exh, it looks as if there about 10-12 chambers on each side. This is probably way more, than say, a good free flowing muffler.

While this isnt a good example, anyone that has riiden dirt bike: I used to run mine wide open, until rules years ago, forced the installation of chambered exh, not just for noise, but for sparks that may exit the exhuast in the woods. I put on a chambered exhaust system, and couldnt believe what I lost. I then reinstalled the stock exhust system, with mufler, and got back some of what I lost with the chambered. But again, I loved the chambered sound.
I like the sound of the chambered though....

Tom73

I e-mailed Mid-America about their chambered system to see what they had to say about it being restrictive. Here is their response:

We have not heard these reports before, but we cannot imagine it being
much if any more restrictive that a standard free flowing system. The
chambered section has a perforated straight pipe inside that only lets
sounds waves cancel into the packing through the perforations. The only
reason we could see it not being as free flowing is because the pipe
bends are not held at the same pipe diameter thoughout the bend and
this may cause some restriction. Unfortunately we do not have any
dyno tests with this system. You may want to check online at the Corvette
Forum to see if anyone else has performed dyno tests. Thank you!

tom...