Thats funny because I have a buddy in mechanical engineering (I'm going for structual engineering), and he always WAY over thinks things. He trys to think too hard about it sometimes. Just like you're saying. I know the facts, but he tries to get to into the actual physics of it...

 

Well, I guess if you agree with that statement you quoted, then yes, we finally came to an agreement! As long as you understand from a performance standpoint, the best thing to do is build an engine that doesn't need backpressure to run right so you aren't loosing that power.

Lol, its just a friendly debate! If I didn't like hydrashocker, I wouldn't waste my time!

I can relate to that

 

Lets say we agree that a functioning intake to exhaust must be tuned to run both. A "Balanced Flow Design" to function properly.


To have flow in a regular system there is going to be back pressure or you will lose the low end due to stumbling. This is accounting that there is a "too large of a system". You have to look at what your running, look at what you plan on doing, then account for it. For me, I run some back pressure to keep the system from stumbling on the LOW end but suffer on the HI end. But this is the realm I need and is the best way to build a system.....IMHO.....because of towing, city driving, and hills in my terrane. For your every day driver I believe this to be the best for them on a mass level.

If we go into a higher level of understanding not limited to HI end race machine I would build the system COMPLETELY different. But for the average user that wants a little more punch and better mpg (if you keep your foot out of it) the above systems are going to be your best bang for your buck.


Right now I averagely run 13.5 in the city and 15.8 on the highway with a built 5.9L and 392 gearing in a 46RE Auto transmission and a NV-242-HD transfer case. Max hyw is 17.4 and city 14.2 mpgs here.

 

I will add this to the fray, as this thread was quoted in the 2nd Gen ram section.

The 2001 Ram 318 was increased in HP numbers by DC from 220 to 230HP and the 360 was increased from 230 to 245HP on the official DC spec sheets. The only change was exhaust piping from 2.5" to 3" and I believe the PCV valve was switched from passenger to driver's side valve cover. They actually necked the cat and muffler down to 2.5" with adapters so they could use all there older overstocked parts.

Back pressure is an extremely confusing term to use, and might come from the fact the racing performance cams almost always have a longer exhaust valve duration than intake valve duration, while torquey cams have an even intake/exhaust duration.

The reason exhaust valves are smaller is that the exhaust port has much better flow design that the intake port, the hotter gasses are at higher pressure and exit faster, and the exhaust valves get much hotter and thermally expand more in the cylinder. Nobody ever burns an intake valve.

Hi Hydrashocker!

 

I believe it, but thats not low end! Those numbers are taken from about 4800 rpm! Like I said, bigger exhaust is needed to produce high end horsepower. How was the low end torque effected from that change?

I agree! Most people don't understand what backpressure is. Backpressure is the pressure exerted on moving fluid or gas by obstructions or tight bends in the pipes along which it is moving, against its direction of flow. This means that any obstructions in the exhaust that creates this backpressure slows the velocity of the gas down and creates turbulance and chaos, which forces the engine to work harder to push the exhaust gasses out.

But as me and hydrashocker came to an agreement on (at least this is what I assume we are agreeing on), too little backpressure disturbs the intake flow in a factory style intake manifold that was designed to flow by the engineers that knew they'd be dealing with the backpressures of the factory exhaust. So although you are freeing up power on the exhaust side, you are loosing it on the intake side.

Does this sound about right hydra?

 

I doubt torque was lost at all as the stock cat, water heater, and those nasty dimples in the Y pipe hold back plenty on the system.

It was a cheap performance upgrade for me to have it cut out and replaced with a 3"si/so magnaflow cat and muffler though, thanks Ma Mopar!!!

 

A good all around muffler replacment system is as simple as 2.50'' piping with a straight through muffler.

I personally run a Flowaster on my F-150. It doesn't flow very well. I wish I had went with a glasspack. The Escape has a Magnaflow and no resonator. It sounds good for a Six banger and I noticed it does run a little better.

 

That 4.9L has plenty of torque though lol. You can get away with losing a little low end. (I used to have a 96 F-150 with the 4.9)

I'm probably going to get a Hooker Aero 2.5" single in 2.5" single out. I think that setup will be the best all around for a cheaper system.

 

maybe this tread should be posted in the FAQ's. theres a lot of great info about exhausts, which ever side your on, this might be valuable to others.

 

You may want to rethink any notion of listening to the kid giving you his whole ideology on back pressure, see his quotes he makes about "if you ain't breaking it you aint driving it right." There's two types of drivers in the world....1) the drive it like you stole it and 2) drive it like the manufacturer who has spent 100's of millions of dollars designing and testing it says to. Which do you think knows better. Ask anyone in the world who has a motorcycle of any kind or four wheeler and then put an aftermarket pipe on it. You lose so much back pressure you get that popping when you decelerate. That's why you have to rejet you carb or remap your fuel injection to get more fuel to get more power which equals more pressure to resolve the problem. Look at any aftermarket exhaust sites for motorcycles and they will usually always say "must use jet kit" with a free flowing pipe. Aftermarket auto exhaust makers are not allow to do so due to possible interference with smog and pollution control equipment.