Well after about a month or so of searching for a new exhaust system I opted for the dynomax #19430. Installation went pretty smooth everything fit good and it sounds great. I was kinda concerned if it was going to be to loud with the straight through muffler and the 4" tail pipe. It sounds about the same at idle and has a nice growl when you hammer it. Took me about 3 hours to complete. . I ordered it from rockauto.com got it in 3 days. Found a discount code online for 5% off. I originally ordered it from a place with free shipping but they said 2-3 weeks to get it I toldem to keep it.
Ed

 

how does the butt-o-power meter read? any gains in power or mileage? post up man

I'd really appreciate it if you could post up some pics on your install. The site doesn't give a good discription.

 

The butt-o-power meter I'd say its a little better on acceleration. On the milelage I'm in process of checkin that now, I'll let you know in a week or so. I've been anticipating putting on a free flowing exhaust so I've been keeping track of milage. I was getting just over 17 mpg's prior to install. Thank god for cruise otherwise I'd have my foot in it all the time. . Pics I'll try to get some tommorrow and see if I can get them posted. Ed

 

Thanks tuke, I look forward to seeing the pics.

Enjoy your exhaust!

 

Heres some pics clicky link http://pg.photos.yahoo.com/ph/edsaws...n%3as,13%3af,0

 

Tuke,

What year/engine?? Looks good from the pics. I'm thinking about doing the same and am interested in what you see in mileage etc...

The DYNOMAX system you put it is it a 3" system??

 

It's a 92 7.3 non turbo. It goes from 2.5" from manifold to 3" to muffler and 4" out muffler. Don't know about the mileage yet.

 

does the kit include a y pipe??

 

yep heres a pic of what I got all clamps included the only thig you don't get are new rubber insulators for the hangers but they may not be needed mine were good.http://www.rockauto.com/ref/Walker/D....html?5359.jpg

 

How does the new Y pipe look??? is it less restrective than the factory garbage one???

cheers
Bob

 

Well it looks like it may enter the pipe with more of an angle but not much. The down tubes are 2.5" the drivers side comes around like the stock one and then transitions into a 3" pipe. The passengers side comes down into the 3" pipe. In that respect I would think it less restrictive. It doesn't have a smooth flow design which I think is what your wondering.

 

This seems to be the norm on these exhausts - they start (relatively) small and get bigger and bigger as they go back. To me that seems backwards.

I've read several articles on "tuning" exhaust flows (as it applies to gassers anyway) and the prevailing school of thought seems to be that for maximum flow and minimum backpressure (which isn't always what you want in a gasser, but supposedly is exactly what you want in a diesel) your exhaust should start out as big as is practical. This is to give the hot (expanding) gasses as much room to expand as possible. But the farther you get from the exhaust ports - and therefore the cooler the gasses get - the smaller the pipe needs to be (within reason of course).

The theory behind this is that as the gasses cool down they contract, and therefore require a progressively smaller pipe to keep the cooler gasses moving at the same velocity. That high speed helps with the scavenging effect. Think of it as the speed and momentum of the gas rushing through the pipes creating a vacuum behind it and kind of sucking the exhaust gasses behind it along for the ride.

Does anyone know anything about how or why this principle would somehow not apply to diesels? Is there a good reason for the exhaust pipes to get progressively bigger as you get further away from the engine?

 

not sure about diesels or gassers but listen to this... I dont think gasses cool down when they contract(maybe contract isnt a good word to describe it) gasses cool when pressure decreases. that is why you dont put aerosol cans in hot places (the pressure increase may cause it to explode) also, try this out. say your easy cheese or your shaving cream runs out of pressure. fill the sink with hot water and put the container in the hot water for about 3 minutes or so. then you should get some more out of the container because the increase in temperature. likewise, if you take a warm sandwich and put it into a ziplock bag with all the air pushed out, and put it into the freezer, it will act like a vacuum sealer and contract the bag even more. here is the reason why:


temperature changes adiabatically with pressure.. higher pressure, higher temperature. the main reason our engines don't melt is because of the exhaust. as the exhaust runs out of the cylinder the pressure decreases and the temperature decreases dramatically. going to a bigger and bigger exhaust actually decreases velocity and increases pressure. google a convergent and divergent duct. I dont believe there is much if anything beneficial about an exhaust that gets bigger and bigger. although, your engine wouldn't have to push the same exhaust out through 15 ft of 2" piping or whatever. you dont use a hose that gets bigger and bigger and bigger for syphoning water do you?

if you want to know more about exhaust scavenging and things like that look into an X-pipe. http://www.pypesexhaust.com/pictures.html im not sure the difference this would make for our lower rpm engines, but it might have an effect.

velocity increases as it enters a duct, proportionally decreasing pressure, and visa versa as it exits. I dont think ram air ducts/funnels do much more than the diameter pipe they go into.

the x pipe uses the flow of ones side of the engine to create a low pressure area in the other pipe that practically draws out exhaust from the other side of the engine.



all out, the best exhaust there will ever be for our engine is headers, with the pipes the same diameter as the collectors. I dont think there will be much gain from 3" collectors to 4" pipes. The increase in pipe size decreases velocity. Velocity is what does work (kenetic energy) and pressure doesnt do a thing (potential energy) until it is released from a tank or whatever. When pressure is released as airflow the speed of that airflow is defined as velocity. velocity and lower pressure is what we want in our exhaust.

I seriously think it would hinder our exhaust by stepping up in size because the pressure would increase and the velocity would decrease, and its the velocity that does the work with carrying the exhaust out.
I know bigger is better, but...

I cannot prove that stepping up the exhaust in size at the pipes go along is bad, good, or negligable. Theoretically there are two points. bigger exhaust less backpressure, but the velocity is a factor as well..

maybe this will get the brain juices flowing. ok, I'm done playing professor...

 

You just proved the opposite of your point. The can of shaving cream creates additional pressure when warmed up because the contents expand as they get hotter. It is the expansion within the enclosed space of the can that creates additional pressure - which is what pushes the contents out when you depress (open) the valve. IIRC ALL matter expands when heated. That is why a hot air ballon rises and why cooler air is better for engine performance. As the temperature changes the density (unit volume per unit mass) changes. Hotter air is less dense because it expands (the molecules get farther apart). Being less dense than the cooler air around it makes it rise because it weighs less than the denser, cooler air around it.

Conversely, cooler air is better for combusion because it is more dense (more oxygen molecules per unit of volume). It is condensed - therefore in terms of volume it has contracted (opposite of expanded). The exhaust gasses don't cool down because they have contracted - the cause and effect relationship is just the opposite. Cooling down caused them to contract. Which is what I said earlier


You have that right. As the pipe gets bigger, the same amount of mass (gas) trying to move through it will result in the gas moving at a slower velocity. Because it is being moved through the pipe by pressure, a bigger pipe results in less pressure and therefore slower speed. Again, just like I said.

I understand the concept of an X-pipe. While it is true that our engines run at slower RPMs, the sheer volume (420 CID), and pressure (21.5 CR) makes up for the lower RPMS in terms of total flow - compared to a 300 or 350 CID engine. The X-pipe would probably provide a fair benefit - but plumbing one to go under our trucks would be rather difficult. Heck even a standard configuration dual exhaust system (one pipe per side) is very difficult to do.

I disagree. The "scoop" effect of a larger frontal area funneled into a smaller area (the pipe) actually provides some compression of the air as well as increasing its velocity down the duct. That translates to more air stuffed into the intake plenum and therefore into the cylinders. This is a well-proven concept.

Agreed

Most of that is correct, with one exception. Stepping up pipe size does decrease velocity, but it also decreases pressure - not increases it as you said above.

We are mostly in agreement. Starting big (at the point where there is the most pressure trying to expand), and ending smaller (to maintain velocity) makes more sense than starting small and getting bigger as you get farther from the engine. Which was exactly the point of my original post. All the systems out there seem to be built backwards - 2.5" pipes to 3" pipes to 4" pipes, and sometimes even ending with 5" pipes......

 

Conversely, cooler air is better for combusion because it is more dense (more oxygen molecules per unit of volume). It is condensed - therefore in terms of volume it has contracted (opposite of expanded). The exhaust gasses don't cool down because they have contracted - the cause and effect relationship is just the opposite. Cooling down caused them to contract. Which is what I said earlier

I think we are on the same page. I know cooling causes stuff to contract. but when you let stuff expand, it looses pressure, which would drop the temperature. gases exposed to a greater area will expand and decrease in pressure(like letting the air out of a balloon) this decrease in pressure is what cools the air. its not the cooling of the air that decreases the pressure, unless your refridgerating your exhaust.

Your explanation is backwards in my opinion. it is good for the intake I know, what your saying applies to things like cooler climate = better performance and intercooling the air before it enters the intake. you cool it and it becomes more dense, which would mean more oxygen and more medium(nitrogen) to be effected by the heat. this medium expanse and pushes the piston down. more medium to absorb the heat makes more power (hence why vapor injection works in some cases) as far as exhaust goes you are backwards. pressure decrease will decrease the temperature, not the other way around, unless like I said, you intercool or refridgerate the exhaust.

not trying to flame, or argue remember. we are just debating. keep the smiles on our faces

oh and about your increase velocity and increase pressure thing, you are completely wrong there for sure. I took two years of aviation maintenance classes and am a certified A&P Mechanic. If you were right, planes would not fly. http://www.aoxj32.dsl.pipex.com/NewF...TWPhysics.html

bernoulli's principal