I just bought a 2008 Ram 2500 with the 5.7L and 6 speed manual trans. First off, does this have MDS and how do I tell? The owner's manual says it's an option and I have read conflicting info on the internet, even from the Dodge brochures.

Second, will headers and dual exhaust cause any adverse effects with the MDS system? I have heard it will.

Anyone else have the same engine and trans? I am getting unbelievably horrible gas mileage.

 

I am 99% sure the mds is only on the 5.7 in the 1500 rams and cars, as for duals performance wise you are better off with a custom y pipe and 3 inch single exhaust if your engine is stock internally ( if your set on dual dont go any larger than 2.5 inch as you will lose some power due to a lack of back pressure).

 

you do NOT have MDS.

welcome to DF!

 

2500/3500 Hemi don't have MDS. since you don't have MDS, an exhaust change won't affect it. You do want to make sure you get proper exhaust so you still let the engine breathe.

What is "horrible" mileage? It is a V-8 truck...

 

I know I am from the 4th Gens, but please explain how back pressure is ever good.

Edit: There may be a loss of power, but it is not do to back pressure. It is due to a loss of exhaust velocity/scavenging/etc. Back pressure is a myth; it is always bad.

 

Good deal then. I was just making sure I can get my new one set up like my old 2004 with true duals and headers. And now I don't have the crappy EGR valve like my 1500 had! Always burning that stupid thing up or getting errors from it with my headers.

Why are the only headers that I can find for a 2008 2500 from BBK? I have had great luck with Edelbrock and Flowtech ceramic coated headers and would like to use them again. I assume I have the same heads and could order some for a 2006ish 2500 and they would work?

For some reason I am getting like 10mpg? I figured I would get at least 14 but the truck is barely broke in so I will give it some time to come around.

 

If you change to a new exhaust set up that produces less back pressure, it causes more air to be drawn into the combustion chamber than before. This causes the engine to burn lean. When your engine is burning lean, you can burn your exhaust valves. Added to that, as the fuel/air mixture becomes leaner, the resultant combustion will produce less and less of the force needed to produce torque.

It's a heavy 2500 with a Hemi... expect 10mpg

 

Back pressure and scavenging are intertwined. It's not as simple as one good, one bad. People have written entire treatises on the subject.

 

Holy crap, RF's coming at us with the big words.

 

Running lean creates more power, not less, to certain point. Engines are usually on the rich side for safety.

Here are a few links in case you think I am wrong.

http://courses.washington.edu/me341/oct22v2.htm

Here is a chart showing the proof.


This chart was taken from the following link.
http://www.installuniversity.com/ins...to_tap_faq.htm

When trying to create more power, the loss of back pressure is a good thing. It helps clear the cylinders faster for a fresh air/fuel charge.

You are correct, the effects of a loss of back pressure could be a lean condition. This is why modding a vehicle should consist more than bolting on parts. Reading spark plugs, scan gauges, widebands, etc, should be used to ensure the engine is running safely.