I have had the exhaust for about 4 months now (LaBree GB) and I really like. The one thing that sticks in my mind about this exhaust is a post by David Borla on this board. In this post he says "if you placed one ping pong ball inside the pipes on each side (just behind the cat) they will each blow out of the rear without ever touching each other. The ball from the drivers side will exit on the passenger side and vice versa. It's a great design, we're really happy with it".

After coming back from the car wash today I am thinking that this is not quite the truth. I was spraying off my car and I noticed that there was a little soap laying inside the driver side exhaust pipe and when the sprayer went across the passengers side tip, air and water immediately blew out of the drivers side tip. So, I tried it on the drivers side and the same result on the passengers side, air and a little water. Now keep in mind I am not sticking the sprayer into the exhaust, just quickly passing it over the tip. I tried each tip and as I did so, air and a little water blew immediately blew out of the opposite tip. I know that the two sides are connected at the cross-over but that is too far up for the spray action to happen immediately like it did. Anyone else notice this or is there something that I am missing? It seems to me that the two sides may be a little more connected inside the muffler than we were lead to believe.

 

I agree that I don't believe the Borla to be a "true dual" exhaust due to the fact that there may be two individial pipes leading back from the cats, but they both lead to a "common" muffler. I'd imagine that once inside the muffler, it's all wide open between the two sides. Now an Injen is a "true dual" because there are two seperate pipes all the way back and lead to two seperate mufflers. I'm not discounting Borla at all, just making an observation.

-Chrismcagle

 

I believe (like the Magnaflow system) I built for my "G", the Bolra muffler is an X type. That is, no baffles, but has packing with the inlets and outlets crossing each other inside the muffler. Before installation, I confirmed this with my Magnaflow. If I looked thru one inlet or outlet, I could see the two on the other side. I could also see the paths as they crossed each other and emerged on the opposite side. The sound absorbing material was packed to form the paths. Has anyone looked inside the Borla to confirm that they are of a similar design?

Lou

 

The inlets and outlets on the muffler are 90° bends so you can't really see in. Anyone willing to cut theirs in half for "research purposes".

 

May be Mr. Borla himself can provide this for us to prove that it is indeed a true dual exhaust.

When I first saw the system w/ my own eyes, I couldn't see it being a true dual w/ just a single muffler. I thought true dual means two separate exhaust cans. Please correct me if I'm wrong.

 

Keep in mind that if you spray a liquid into your exhaust, it will easily flow thru one "pipe" and into the other because of all the hole/baffles/etc inside the muffler.

A solid ball entering the muffler from one pipe might travel thru it's normal path and come out the correct exhaust tip. There is going to be some cross flow of air (and liquid) between the two input pipes in the muffler but the majority of the flow ought to pass thru the path that brings it out the proper exit.

Dave

 

Well, I think that in order for an exhaust to be labeled "True Dual" there must be a complete separation in the pipes from the headers all the way back to the exhaust tips. The fact that Borla utilizes a "common muffler" makes is not a "true dual" system IMO.

-Chrismcagle

 

So, what is the definition of a 'true dual' system? Are they allowed to have a cross-over pipe, like the Borla? Or does each cylinder bank have to have its own discrete exhaust path? What if a system didn't have a cross-over pipe, but shared a common rear muffler?

 

Well, I don't know the official definition, but here's mine:

A "Dual" exhaust would have 2 seperate pipes off the headers that may or may not lead back to an H or X pipe, then to either a common muffler, or 2 seperate mufflers.

A "True Dual" exhaust would have 2 seperate pipes off the header that lead back to 2 seperate mufflers. There would be no H or X pipe utlilzed.


Going by the above definitions I would say that the Borla is a "Dual" exhaust system, but not a "True Dual" system.

-Chrismcagle

 

Are we going to let this die? Is some enterprising soul going to find a way to look inside a Borla without damaging their muffler? I believe David Borla monitor's these forums. Hey David, can you help us out here? Is the Borla an X type muffler as I have postulated?

Lou

 

yea thats true a true dual does NOT have a X pipe or a H pipe connected.
A dual does.
good point man

 

Well, seems that seems sort of silly to me, H pipes have been used in true dual systems since the seventys. The big three knew that the super cars of the day sounded better and ran better with an "H" to equalize things. Even Harley Davidsons of today (and yesterday for that matter) have a crossever pipe for their dual systems. Anyway, with that sort of logic, the only True Dual we have would be the Injen. The others merely pretenders?

Lou

 

I think we have a semantics problem. The word "true" has gotten attached to "dual," which implies that there are other systems that are 'false duals,' which further implies deceit, or hype, or some meaure of phoniness.

First of all, granting that there are demonstrable gains to be made from adding a cross-over pipe on American V8s, the main reason for their use is to balance out the left- and right-bank exhaust pulses, which are uneven because of the crankshaft design. (Check out the elaborate cross-over exhaust systems NASCAR uses.)

60-degree V6s, like ours, have a nice natural balance and typically, have an even left-right firing order. An H or X pipe may be advantageous in some exhaust system designs, but, unlike Detroit Iron, a cross-over is not dictated by the engine's nature.

Secondly, a so-called true-dual system is extremely rare, because multi-cylinder engines normally work best when their exhaust pulses are in communication, so to speak. If a true dual was better, then wouldn't a true triple (three pairs) be even better? And, of course, giving each cylinder its own discrete system would be the ultimate -- a true sextuple (don't get excited).

In reality, exhaust system design is extremely complex and, as we all know, losing performance is as easy as gaining performance.

And, finally, I wouldn't use Harley as a reference point in any discussion about high-performance engines.

 

Latepex

Are Harley Engines "Start of the Art" - No. Are they "High Perforrmance" - I've put enough money into mine so that it most certainly is. If you'd like to race for pink slips - Give me a call. I'd bust your chops.

I agreed with the rest of your post however. You do have an understanding of exhaust systems. Thanks for sharing.

Lou

 

Lateapex

Thanks for the educated reply. Reading this thread I was getting angry about so many fellow Z fanatic spewing off on "true dual" and wondering myself if anyone else realizes that a crossover is actually benefitial. As you pointed out, this is common knowledge in the American V8 world.

Too many people here going off on assumptions with little to no research on real world results.

 

Lou,

In the years I was autocrossing OHC Fiats, one of my best friends, and competitor, was a true-blue Austin Healey guy, who readily admitted the short-comings of his engines relative to my and other modern powerplants. Still, he and racers before him had successfully campaigned British machinery, because of their ingenuity and devotion to their marque. He referred to it, memorably, as "the triumph of development over design."

Bill kicked my butt from time to time, as I'm sure you would with your Harley.

 

Not sure, but I believe the Borlas maintain 2 pipes throughout the length of the exhaust. The tubing is perforated within the muffler chamber with packing(nomex?) surrounding the individual tubes. The term "true dual" serves to oppose the (cosmetic only) dual-look of the single pipe systems with duel-exit-mufflers.

And as for noticing exhaust from only one side(I think that's what you're gettin at?)...exhausts are tuned to work best in certain RPM ranges. The H pipe is part of this tuning. At idle, it's not uncommon to see exhaust coming from only one tailpipe. Just watch an older muscle car at a stop light. You'll notice smoke prevailent from one side, but as soon as he gets on it...the smoke will be firing pretty evenly from both sides.

 

I just found a copy of the press release from Borla dated June 6, 2003. The following is an excerpt:

"This system consists of dual 2 1/4" inlet pipes to a 2 1/4" H-pipe assembly. Exiting the H-pipe assembly are dual 2 1/4" pipes to a pair of 14" long by 4" diameter round mufflers. After the mufflers, a pair of 2 1/4" over axle pipes lead to a newly designed X-flow muffler. Our new "True Dual" systems has resulted in gains of 23.5 horsepower and 14.7 foot pounds of torque throughout the entire RPM range which is more than brand "S" who claims 13 hoprsepower and 14 foot pounds of torque @ 5500 RPM and up."

So, in the initial release, Borla claims they use an "X-flow muffler". Unless Borla says otherwise, They use an X flow muffler (which mingles exhaust gases from each side) like the Magnaflow I used in the system I built.

Lou

 

23.5 horsepower gains....... yeah right! why do these exhaust manufacturers make false claims all the time??


I have the Borla Dual and I can assure you ..... it's does not produce a 23.5hp gain.

It does sound great though...... I'd say it's good for about 10hp.

 

That's pretty subjective. How are you able to determine that it's not a 23.5hp gain but in fact about 10hp?