Question about stock exhaust:

[BillyGman]

Now that many of us have realized that there is more power to be obtained by improving on the stock exhaust configuration of our MM's, and are rushing to get an after market exhaust on our cars before the winter comes, I've been pondering about what changes in the exhaust will actually contribute to HP and acceleration gains, and what wouldn't. But I think that to fully draw some accurate conclusions about that, I would first need to recognize the inadequecies of the stock exhaust on the MM. So the obvious things are those that restrict exhaust flow, and cause exessive back pressure. Which ofcourse are, Exhaust manifolds, having 4 cats, small diameter muffler pipes, and stock mufflers.
Now this brings me to the question at hand. What are the reasons why all these restrictive exhaust conponents were installed on the MM by the factory? So let me fish through this in an attempt to sort this out:

REASON FOR EXHAUST MANIFOLDS- ease of installation during assembly line manufacturing, as well as the cost of exhaust manifolds being less than that of headers.

REASON FOR HAVING 4 CATS- increasingly stricter emissions standards for new cars.

REASON FOR THE STOCK RESTRICTIVE MUFFLERS- It's more difficult for a dealer to sell a loud car to the majority of their costumers than it would be to sell a quiet car. (SALES)....

So I believe this answers any questions that can be asked about the reasons for the MM exhaust being the way that it is from the factory. EXCEPT FOR ONE........why does the muffler pipes on the Marauders which are between the cats and the mufflers, shrink down at one point to a mere 2" diameter, while the tailpipe increases in diameter to 2 1/4"??? I can't think of any reason why this is done.

[TAF]

Originally posted by BillyGman
........why does the muffler pipes on the Marauders which are between the cats and the mufflers, shrink down at one point to a mere 2" diameter, while the tailpipe increases in diameter to 2 1/4"??? I can't think of any reason why this is done.

I don't know the answer, Billy...but if I were to venture a guess...it would be due to the fact this car was assembled with mostly "off-the-shelf" parts from other FOMOCO products, and it could be as simple as that was what was available for a "true duel exhaust". But, I'm just guessing.

[TripleTransAm]

My wild guess would be:

the 2 1/4 tailpipes are mostly for show (very believable, do notice how far back in the system the tailpipes are situated... the exhaust has cooled a great deal by that point).

The 2" diameter shrink *might* be for clearance purposes as well, but I'd have to check (wish I'd seen this thread earlier, my car was in the air for an oil change just 2 hours ago).

[Mikeenh]

Steve,
What weight oil did you use? Was it synthetic or blend or the cheap stuff?

[Haggis]

Mikeenh I use the new synthetic Hershey Chocolate Syrup in my engine. It will come in real handy if I ever get into an accident with a milk truck.

Didn't you ask me in Hershey to start a new oil thread?

[BillyGman]

it's because the exhaust gases have already started to cool by the time they get past the mufflers that I'd understand it if the tailpipe was smaller than the muffler pipe. But on the marauder exhaust it's the other way around w/the muffler pipe being smaller.

[TripleTransAm]

Originally posted by Haggis
Mikeenh I use the new synthetic Hershey Chocolate Syrup in my engine. It will come in real handy if I ever get into an accident with a milk truck.

Oh man! ROFLMAO!

[joflewbyu2]

COST !! 2" PIPE IS CHEAPER THAN 2.25"

[TripleTransAm]

Originally posted by BillyGman
it's because the exhaust gases have already started to cool by the time they get past the mufflers that I'd understand it if the tailpipe was smaller than the muffler pipe. But on the marauder exhaust it's the other way around w/the muffler pipe being smaller.

Precisely my point... I think the tip size is just for show. Meaning, the choice of outlet size was in no way related to what the intermediate pipe was sized at. Most likely the two Ford employees who worked on each respective item didn't know the other person existed, much less consulted with them...

(all my humble opinion and nothing but, of course, I wonder what the real story was behind the exhaust engineering)

[BillyGman]

your theory must be correct because from a mechanical engineering standpoint it doesn't make any sense.
BTW, I believe that because the exhaust gases are colling off already by the time they exit the mufflers and are in the tailpipe as you've pointed out, there might not be any performance gains at all to be had by opening up the tailpipe to 2.5" once I already have the Headers,X-pipe, hi-flow cats, 2.5" muffler pipes, and straight-thru mufflers.

[SergntMac]

Originally posted by BillyGman
BTW, I believe that because the exhaust gases are colling off already by the time they exit the mufflers and are in the tailpipe as you've pointed out, there might not be any performance gains at all to be had by opening up the tailpipe to 2.5" once I already have the Headers,X-pipe, hi-flow cats, 2.5" muffler pipes, and straight-thru mufflers.

Changing out the 2.25" tailpipe with all it's beutiful bends, is wasting your time and money, Billy, IMHO.

I suspect that 2.25" pipe was used to stabilize the mating with the 3" Megs tip, a 2" pipe would be too small and most likely crack inder flex.

When the exhaust system was first designed, the tailpipe stopped at the mating with the Megs tip. Just before production began, it was decided to quiet the tone by extending the tailpipe 18" into the tip, where it sits today on OEM exhaust. No need to change the diameter of the pipe, just the length ot the tailpipe to comply with instructions from above.

I have a demo tape of the MM sent to dealers before production began, it has the original exhaust tone and tenor. It's delicious.

[MapleLeafMerc]

So if us BSO get the tailpipe the h**l out of the Megs tips on our BSM, it'll sound like it should, right?

[jgc61sr2002]

Originally posted by joflewbyu2@aol.
COST !! 2" PIPE IS CHEAPER THAN 2.25"

Sounds like typical FMC always trying to save a buck.

[cyclone03]

I think the 2" section is shared with the crown vic police cars and there 2v engines.

[BillyGman]

pretty much agree w/everything that's been said here. Some good points have been brought up by everyone. The way I see it, the power to be gained by an exhaust change will be due to getting rid of the stock exhaust manifolds in exchange for reworked manifolds or headers, ripping off the 4 stock cats in exchange for 2 hi-flow ones, and tossing that wimpy 2" diameter section of muffler pipe for a 2.5" diameter one, and let's not forget the X-pipe. I never did understand why any "X-pipe" would offer a performance advantage over an "H-pipe" but everyone seems to be claiming that it does, so I'll give it a shot since I'm already going to be changing many other things on this exhaust anyway. I'd like to think that everyone who speaks of the gains of adding an X-pipe aren't simply parroting mere sales hype. but I guess that's often the chance that you take w/these things. But I have no doubt in my mind that this overall exhaust package will deliver a noticeable performance gain.
BTW, what I plan to do is save all of the stock pieces of the original exhaust incase the car will not get through the emission tests w/the exhaust upgrades. That will not be until several years from now, but I wouldn't want to have to purchase new exhaust components just to get it through emissions.