Scooter70

Chambered exhaust systems:
I've read through a bunch of archived posts and in almost every thread someone claims that "they're really restrictive" without providing any proof. Then someone else usually comes in and calls BS. Has anyone done any testing to prove one way or the other? Dyno tests, 1/4 mile runs, SOTP dynos? Heresay is not enough.

Thanks,
Matt

BeaterShark

I have looked a little into chambered mufflers. Basically they are glasspacks, but without the fiberglass and theouter tube is crimped to create chambers.

As with glasspacks, "how restrictive" is going to depend on the inner tube size and how the "passages" to the outer tube are created. If the innert tube has a "louvered core", it will be quite restrictive, depending on tube diameter. Here is a pic of a louvered core chambered inner tube:


As you can see, the louvers are in flow of the exhaust, making them more restrictive.

The other type is a "perferated core" inner tube. This is not a chambered or glasspack inner tube, but it does show what a perferated tube looks like:

This is the design of the Dynomax Ultra Flow and Bullet Race mufflers, so I would bet that a chambered muffler of this design would not be restrictive at all, although I'd bet it would be considerably louder than the louvered core type.

marshrat99

My .02, I'd think that for most of us, the difference would be negligable. I'm running chambered from MAD and really like them. However, like you, if someone had a dyno run that indicated a 15+hp loss then I'd have to rethink.

LemansBlue68

Interesting pics!! Thanks. I always wondered what the inside of a chambered exhaust looks like. :thumbs:

Scooter70

Ok, that's pictures but has anyone got any data to prove the 15hp loss? I may just install the 2.5" MAD chambered system on the LS1 with a pair of cutouts and dyno the car both ways just to see how bad (or good) the system is.

70 LS1

Matt,

The MAD system uses a perforated core just like the dynomax pictured above. The inner diameter of the core is ~ 2" on my system. Not only that, but the MAD system does not use mandrel bends, so the pipe gets smaller in the turns. And one more downfall is they choke back down to 2" for the square exhaust tips. Maybe the '73 system wouldn't since the '73 uses 2.5" tips. I think this may actually be insignificant due to the size reduction being so far from the motor. On a slightly modded LS1 like you have, you would probably be looking at a 20+ Hp loss compared to dual cutouts. Of course that is speculation based on what I have read about exhaust on that LS1 tech site.

70 LS1

My vote is go for the MAD system. I know you already like the sound. Take it to the track and see how you do. With your gears and that cam, you should be running mid 12's. And unless you are looking for every last little Hp, you will probably be happy with the MAD system.

billy78sa

I have the 2.5 chambered system on my 78 and it is a great system. It is not restrictive at all (true dual exhaust) mandrell bent with no crimps and my tips are a full 2.5 inches. I also installed headers with this system. I could see all the way through the chambered part before installing. How restrictive could that be? When installing larger diameter pipe, sometimes you will loose a small amount of torque on the bottom side and pick up a few hp's on the high side. The system sounds great and flows very free. I see no way it could cause a net loss in overall engine power.

BIGsteve

billy78sa:

The MAD system is said NOT to have mandrel bends, but you said yours does. Where did you get yours from ??

JJ Deuce

I bought the Allen's system for my car. I believe it is less restrictive than what you've shown here.



It is not mandrel bent, but the overall quality is very good, and some have said it installs easier (better fit) than the MAD system.

billy78sa

I bought my system from mid america direct. The catalog description my not say mandrel bends, but my pipes had smooth,flowing and round bends with no crimping of any kind. If this is not mandrel bent, pipes then I am wrong. I am making this claim due to a cat back mandrel bent system I bought for my camaro and the bends in my vette pipes looks just like the camaro bends; as far as no crimping with smooth flowing bends. And no restrictions with the bends. :cheers:

Mr D.

From a big picture standpoint, 15hp is not that big of a deal on the street. If you are worried about 15hp on the drag strip, I don't think chambered exhaust is what you would want to run anyway.

Scooter70

I just asked if anyone had data. Obviously nobody's going to miss 15hp from a motor that's putting out 425hp on the street. However, if choosing an exhaust system that's 15hp (or more) less than another choice, then there would have to be other factors to make one choose the lower one. I was just asking if anyone had proof to back up the hearsay that's been flying around based on who-knows-what.

That said, the MAD chambered exhaust is cheap, easy, and loud. I think that I'm going to order it tomorrow and install it next weekend with a pair of cutouts before the mufflers. Then I can dyno and run the 1/4 with the cutouts open and closed, compare the gain with other dual exhaust gains for a cutout, and put some data behind whether the chambered systems are a big restriction or not. I will share the results when I get it.
:cheers:

-Matt

AlwaysWave

I've heard these guys are pretty good too. http://www.sweet-thunder.com/index.html

70 LS1

Scooter,

I am very interested in what you find out on the dyno with the cutouts.

zwede

Some years ago (late 90's) I talked to a guy from SLP engineering. These are the guys that made the SS package for the Camaro and WS6 for the Firebird. At the time there were rumours that SLP would release a chambered exhaust system since it was available in the late 60's camaros. I asked the SLP guy about it and he said they cancelled it because it was so restrictive. I asked how restrictive and he stated they lost over 40hp compared to the stock exhaust. Stock Camaros at the time dynoed about 240 hp at the wheels so that would mean a drop from 240 to 200.

crf311

I just put chambered exhaust on my vette. Let me tell you they sound great!. I would not be worried about losing a few H.P.. Put them on and I bet you will like them.

desi

I am very interested in finding out the gain/loss myself. I just bought them from MAD last week, will be installing soon.

:cheers:

BeaterShark

This is where I got the pic of the "louvered core" from. I wouldn't buy it.

I'd love to see what the MA setup does vs no mufflers.

Scooter70

I just ordered the system and should have it on the car within the next couple of weeks. For those who already installed theirs, did it come with all of the hangers that you needed to install it? The picture doesn't show them but the guy who took my order said that it did. :rolleyes:

Once I get the car up and running, I'm going to have it dyno tuned and I'll post the results.