Poll: Whats More "Restrictive" - Sidepipes Or N11 for Midyears Whose Got The Evidence

[65TripleBlack]

Poll: Whats More "Restrictive: Sidepips Or N11 Fer Midyears" Whose Got The Evidense

Okay all you. Whose got the dyno tests to proov it. Im tired of all the bs abbout chambered verses 3 baffled (not 5 baffled) pips. chambered 1 7/8" insid daimeter , verses 2 1/2 diamer N11. Allens aluminide.
I bet you gotto be an enginer to figgur the acoosticks inside the pips, an the backpresser between the chamberd N14 and 3 baffels N11. I think a lots of pipple try to hurt the sidepips peppol because there jellos. So they say N11s are better than N14s...................sooooooooo, whwere your numbers prove it.

 

[Tom Bryant]

:argue :crazy

Only your dyno man knows for sure. You would have to run both types on a dyno on the same car with no other changes. Who wants to offer up the guiney pig ( Corvette).

 

[Vettewine]

chambered vs. baffled pipes

I have underbody chambered by Walker (the orig sidepipe mfr now available through Mid America) on my '65 roadster and it flat screams at WOT but is very nice and rumbly at low RPMs. BTW, it's 2 1/2 inches in dia all the way back to the tips...!

 

[Tom Bryant]

Re: chambered vs. baffled pipes

I have underbody chambered by Walker (the orig sidepipe mfr now available through Mid America) on my '65 roadster and it flat screams at WOT but is very nice and rumbly at low RPMs. BTW, it's 2 1/2 inches in dia all the way back to the tips...!

I have the same thing for my '69 Stepside (Project C10R). I will be thrilled if it sounds like Corvette side pipes.

Tom

 

[65TripleBlack]

Undercar Chambered Exhaust

Tom:

Aside from the sound, which, of course is also a function of engine configuration, I am more concerned with the construction.

Some folks say, "duh sidepips are to restrictiv becase dey ain't 2 1/2" dameter"
Hope I got the quote right. Anyway, my sidepipes, which are GM, as original, are 2 1/2" diameter, end to end. The "chambers" are formed by swaging the pipe at approx. 8" intervals to create the dimpled "chambers". Some say that undercar chambered exhaust are "true" 2 1/2" diameter, and so, "not as restrictive" as sidepipes. If so, then how are the chambers created? I am clearly missing something.

Joe

 

[Vettewine]

sidepipes vs. underbody chambered exhaust

Joe has it correct as the chambered portion of the exhaust system, whether it's sidepipes or underbody, will still have a slightly reduced ID due to the "dimples" that create the chambers. However, when compared to baffle-type systems, the flow-through capabilities are greater in the chambered exhaust (see this link on MId America's website: http://www.madvet.com/shop?store=1&category=36&frame=1293 ).

 

[Tom Bryant]

Here is a picture of my chambered mufflers. Walker sells them under the Turbo Tube brand name and they are available for most anything popular. These came from NAPA.

These are 2 1/2" in and 2 1/4" out. The chambered section has a perforated lining that allows the exhaust to do it's thing with the swedged outer casing. The lining is 1 7/8" diameter but being perforated the exhaust can flow freely through it and there are no baffles. It can't be near as restrictive as a 1 7/8" solid pipe would be.

 

[65TripleBlack]

Thanks Tom And Al,....But.....

...I never saw the inside of my GM (Walker?) sidepipes, but Tom, are you saying that there is an inner pipe of 1 7/8" dia running thru the swaged area. If so, do you know whether it is perforated like yours, or solid?


Joe

 

[JohnZ]

Yup, the (perforated) inner pipe is 1-7/8" diameter; I have an SAE Paper filed away somewhere written by an engineer at GM Research in the late 60's which stated (with lots of empirical dyno evidence) that the turbulence created by the pressure waves induced by the protrusions into the inner pipe reduced the flow of hot gases and created more backpressure than an ordinary non-perforated pipe of the same diameter.

I participated in a day-long "A-to-B" comparison on a '69 Camaro Z/28 with factory chambered exhaust which was being changed over to the standard factory conventional dual exhaust two years ago. Same car, same day, same chassis dyno, no changes to the car except swapping the exhaust system. Made three pulls with each system, and the standard factory dual system made 25-30 more peak rwhp than the factory chambered system did. Didn't have instrumentation to measure system backpressure differences, just the dyno numbers.

I'd expect the differential to be much higher for a big-block, as it's trying to pump 50% more air than the 302 in the Z/28.

Corvette sidepipes and Chevelle/Camaro chambered under-car systems were NOT engineering-inspired; they were Sales/Marketing-inspired, and generated LOTS of option profit and "street image".

 

[Tom Bryant]

The chambered tail pipes on my '67 442 were perforated on the inside. I was fortunate enough to purchase what was probably the last set of originals GM had in stock in the late 70s and they were as the originals. I feel that the chambered sections that Walker is making now is the same product they made in the 60s. The original Corvette side pipes couldn't have a solid inner pipe or there would be no muffling effect. They would be straight pipes.

Tom

 

[Tom Bryant]

Corvette sidepipes and Chevelle/Camaro chambered under-car systems were NOT engineering-inspired; they were Sales/Marketing-inspired, and generated LOTS of option profit and "street image".
[/B]

I couldn't agree more. I have to admitt that the sound of my '67 442 was a big selling factor over a GTO or SS 396.

Tom

 

[Vettewine]

chambered pipes, etc.

John...

You didn't say whether the factory duals were the same diameter as the chambered and also what was the exhaust manifold - stock cast or headers, etc.?

I know I knocked at least 3/10 off of my best time in the 1/4 when I replaced my duals with the chambered system. Besides, you know, it really does sound so-o-o-o much better...
:J

 

[JohnZ]

The factory duals were the stock 2" system, and the car had stock exhaust manifolds.

 

[Donny Brass]

anyone ever try these pipes ??

http://www.sweet-thunder.com/ses_65-67_vette.htm


I have been thinking about a set for my L-79 car.....

 

[65TripleBlack]

ever try these pipes?

Donny:

That is a great website. It gave me lots to think about, and certainly helped me deduce what's going on inside those chambered pipes. John Z's comments above, about power loss, now come into clearer context, although I would still like to see some backpressure and gas flow data.

In a more practical vein, I would stay away from the 3" O.D. units, because they will probably present clearance problems. If I wasn't looking at "correctness", then I would opt for the "high-perf" units, using the 2 1/4" inner pipe.

Joe

 

[396 RAT]

Truth be told, N11 and N14 are both crap as far as flow & HP.
A modern set of performace muffler's beats 'em both.
And this beats the modern mufflers.
http://www.spiralturbobaffles.com/
Dyno results prove it.
Fit is a trick, but you dont get something for nothing.....

 

[Vettewine]

underbody chambered exhaust system

Joe...

F.Y.I. - I called Mid America and talked to their tech and he said they have bought the tooling from Walker and now make the whole underbody chambered exhaust systems themselves. I asked him what the inside and outside dimensions of the chambered portion are and he replied 2" diameter inside (clear) and 3" diameter outside. This is just for the portion that is chambered. The rest of the system is either 2" or 2 1/2 depending on which one you order. Again, here's the link to that site: http://www.madvet.com/shop?store=1&category=36&frame=1293 By the way, the inner 2" diameter tube is perferated (otherwise it wouldn't be an effective "muffler" at low throttle) but acts as a straight pipe at WOT.

 

[Tom Bryant]

So truthfully, does all of this really make any difference unless you drive your Corvette at 6000 rpms all the time? If I remember right a 3.36 rear gear and normal diameter tires give you about 3000 rpm with a 1:1 top gear at 70 mph. How about a comparison dyno test of these systems below say 4000 or 4500 rpms where our cars spend 95% of their time? Maybe sucumbing to the cool chambered sound over max flow at 6000 rpms+ isn't such a bad thing.

Tom

 

[Vettewine]

Exhaust, etc...

Tom...

On my '65 modified SB the underbody chambered system is just a nice low growl at most cruising speeds so it probably doesn't make a lot of difference until you get on it - then it screams! I love it!:crazy

 

[Tom Bryant]

Re: Exhaust, etc...

Tom...

On my '65 modified SB the underbody chambered system is just a nice low growl at most cruising speeds so it probably doesn't make a lot of difference until you get on it - then it screams! I love it!:crazy

And that's what counts. :cool

tom