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Your logic is off IMO. -------//------//-----------/--- exhaust in a nutshell. 1st // = cat 2nd // = res / = muffler -------//-------------------/--- The less restrictions, the better.  Sure, the resonator is not the ONLY bottleneck, but it is still a bottleneck. There will be lower pressure from higher velocity with the resonator removed. And there is a difference between a bottleneck and a restriction...a restriction can be something in the way (cat honeycomb), but a bottleneck (y pipe/res) forces the flow to go from a 2.25" pipe to a 2" pipe, disrupting flow and creating more pressure/less velocity. Hence the term....bottle neck.
99 SVTC, T-Red, #652/2760-12.8.1998
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Originally posted by CalgarySVT:
No, no, no... it is clearly a restictive portion of the exhuast. I do NOT doubt that at all, I never have. What I am saying is that it is likely not "the" bottle neck, or in other words, not the single most restrictive portion of the stock exhaust system. Meaning there can only be one bottle neck in the system at one given time. I am of the opinion that the cats (both the pres and mains) as well as the Y-pipe joint are probably more restictive than the resonator. Therefore, my position is why remove the resonator when it is not the part (on a stock exhaust system) that is slowing down the gas flow. For example, if 50 widgets of gas can pass through the cats in one second, and 60 widgets can pass through the resonator in one second, removing the resonator will still only allow 50 widgets a second to exit the exhaust system...
first I swear I read that you said your experience is with other 4 cyl cars, and it is obvious that this isn't and many people in the know have replied
i think you missed the fact that the loss is addative, well there are losses from all the parts of the exhaust, but if you remove a part of the sum of losses, no matter how little the total loss will decrease, so it make some sence to remove the resonator, not only from a flow point but a sound stand point
again many have said that the resonator has a much smaller diameter then the rest of the exhaust and the other exhaust components are not as bad, this means the resonator is going to effect the flow also
I also think you missed the point made about people who don't or can't change the rest of the exhaust, changing the resonator will net a little difference letting the exhaust flow better, and since it is easily done more people can do that
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Johnny, I see your logic.
I think that be it a smaller pipe or the honeycomb in the cat a "bottlenck" can refer to any restriction that reduces gas flow the most in the exhuast system. After all if we add up the area in the cat's honeycomb that is "open" to allow gas through, it will equate to a pipe diameter. If that diameter is less than the other pipe diameters in the system then it is a bottleneck.
Maybe we should try an experiment. Say we get a large straw, we crimp a segment of the straw 3/4 closed, then a bit further down the straw we crimp it 1/2 closed. If we blow through the straw we will get airflow that is less than if there were no crimps in the straw, right? Now if we release the crimp that is 1/2 closed and blow will we get more air flow? Try it I bet you won't. This is becuase the 3/4 crimp is the bottleneck in the system. If we released the 3/4 crimp and kept teh 1/2 crimp then there woudl be a bit more air flowing through the straw...
This is why I don't believe that the restrictions are cumulative.
If there is power gains then it must be explained by, not flow rate, but perhaps flow characteristics... who knows?
1999 CSVT #545
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Quote:
i think you missed the fact that the loss is addative, well there are losses from all the parts of the exhaust, but if you remove a part of the sum of losses, no matter how little the total loss will decrease
My point exactly!
99 SVTC, T-Red, #652/2760-12.8.1998
Mother#@%@!* did I sound abstract?
I hope it sounded more confusin than that!
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Originally posted by JonnySVT:
Quote:
i think you missed the fact that the loss is addative, well there are losses from all the parts of the exhaust, but if you remove a part of the sum of losses, no matter how little the total loss will decrease
My point exactly!
Our posts crossed, see my last post above. I don't think it is addative, see my straw analogy.
1999 CSVT #545
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I dunno if this helps explain anything for some of you but maybe we can make a weak analogy to batteries in a series versus in parallel... any electrical engineers here that can help us out with that analogy?
1999 CSVT #545
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You've owned the car for not quite three months and you're picking a fight with members who have degrees and certifications in automotive engineering. Those same members have some of the fastest Contours ever. Inflammatory posts will go nowhere in this context.
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Here is a quote from the isupage on exhuast basics:
"Again, the entire system will only flow as well as the tightest restriction, and regardless of the flow capacity of the header and exhaust system, a two inch catalytic converter will limit exhaust flow to what will pass through a two inch diameter hole going into and out of the catalytic converter."
"Installing a performance muffler onto OEM or OEM replacement exhaust pipe will not improve engine performance noticably and will at best simply increase exhaust noise. The problem is that the small OEM size pipe and its squeeze bent construction restrict exhaust flow to the point that a freer flowing muffler will make no measurable reduction in back pressure. The muffler itself is only part of the problem, the pipe itself is most of the problem."
1999 CSVT #545
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Originally posted by CalgarySVT:
What I am saying is that it is likely not "the" bottle neck, or in other words, not the single most restrictive portion of the stock exhaust system. Meaning there can only be one bottle neck in the system at one given time.
For example, if 50 widgets of gas can pass through the cats in one second, and 60 widgets can pass through the resonator in one second, removing the resonator will still only allow 50 widgets a second to exit the exhaust system...
That is extremely incorrect thinking though.
EVERY time you change the diameter of the piping, add a restriction (resonator, muffler, cat), or have a bend it affects the exhaust flow.
You can't say because the Y-pipe crush flange is the biggest restriction then adding a cat-back will have ZERO effect because it is not the "single most restrictive" part. (which you just stated in the part I quoted btw)
That is completely wrong in thinking and in plain fact!
Even after the crush flange...
The cat slows down velocity and adds turbulence to the exhaust. This uses up exhaust energy.
Then the same thing happens to a factor of about 2 in the ~1.8" I.D. resonator. More velocity and energy is lost and turbulence is generated.
Then comes the rear bends. Since they are mandrel the loss in piping size is fairly negligible so the corresponding velocity loss is as well. However "technically" it is still a loss.
Then the rear y split. This is actually pretty well built (I've had mine apart) However you will always get a loss because you are forcing the exhaust flow to divide.
Then it's the stock BAFFLED mufflers. Again a significant loss because of the multiple 180 degree short radius bends and open sectioning.
All loss is CUMULATIVE! YOU CAN NEVER REGAIN THAT ENERGY!
The more loss the less power produced because of the lower efficiency.
So YES loss does continue to occur after the Single Most Restrictive part. (and before it for that matter)
The very simple proof to this is dyno gains from a cat-back system. That's been done ad nauseam. 
Now a well built cat-back system on a car WITH an optimized Y-pipe would shower a higher NET gain then one without. It's all about overall efficiency as you alluded to with the well known fact about maximum flow being limited by the smallest/most restrictive area.
However either one will still show a gain.
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Originally posted by hetfield:
You've owned the car for not quite three months and you're picking a fight with members who have degrees and certifications in automotive engineering. Those same members have some of the fastest Contours ever. Inflammatory posts will go nowhere in this context.
What are you talking about? Inflammatory is what sense? Picking a fight? It seems I am the one being picked on. I guess an opinion constitutes an insult around here? Now why are YOU attacking me?
The best response I have heard is that the restrictions are cumulative. I disagree.
And what does having a fast contour have to do with this. Anyone who spends the $ can have that....
1999 CSVT #545
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