aftermarket exhaust

[pepsi71ocean]

I dynoed my 98.5 with stock exhaust and then dynoed again with a full 4in system and strait through muffler. Same dyno and exactly the same numbers. The pyro was the only place I saw a difference. It ran a lot cooler. The dyno numbers for hp and torque were unchanged but it sounded at least 50hp better.

yes this is true, but i noticed that when i added a air filter i saw a better response, so i know there is something going on, at least when i did my truck there was.

[dripley]

i dont remember reading that the 4" was going to give me more hp. it was going to allow the engine to breath better allowing for power addons. of course 6 years ago i did not know squat about thewe vehicles and did most of my reading from the advertisements. probably not the best way to educate yourself.

[Mopar1973Man]

I dynoed my 98.5 with stock exhaust and then dynoed again with a full 4in system and strait through muffler. Same dyno and exactly the same numbers. The pyro was the only place I saw a difference. It ran a lot cooler. The dyno numbers for hp and torque were unchanged but it sounded at least 50hp better.

Nice to know the HP/TQ doesn't change on 3" to 4" pipe... Hmmm... Doesn't give me to much reason to upgrade being the 3" I got now is very controllable for EGT's...

[Rogan]

I dynoed my 98.5 with stock exhaust and then dynoed again with a full 4in system and strait through muffler. Same dyno and exactly the same numbers. The pyro was the only place I saw a difference. It ran a lot cooler. The dyno numbers for hp and torque were unchanged but it sounded at least 50hp better.

To be fair: were there any mods done to the truck, aside from the exhaust? The exhaust size increase will only really be noticed once mods are in place (and I don't mean just an air filter, etc.) The difference in a stock/near stock truck, stock boost levels, etc, and the correlation of 3" vs 4" exhaust, is that the 3" exhaust , with it's smaller diameter, allows the expanded (hot) exh. gasses to keep a high exit speed, due to the reduction in diameter. As the EGTs drop, the speed slows down. In essence, you could do a 4" dp, to a 3" exhaust, and this would keep the exit speeds high, promoting a sort of scavenging, if you will. At 20psi boost and 1000*F EGTs, you're at a much lower volume of thermal flow requirement, that you would be at 35-40psi boost and 1000*F EGTs.. If you're 4" system had a 3" downpipe, then you're not really gaining anything, especially if the setup is stock.

[pepsi71ocean]

To be fair: were there any mods done to the truck, aside from the exhaust? The exhaust size increase will only really be noticed once mods are in place (and I don't mean just an air filter, etc.) The difference in a stock/near stock truck, stock boost levels, etc, and the correlation of 3" vs 4" exhaust, is that the 3" exhaust , with it's smaller diameter, allows the expanded (hot) exh. gasses to keep a high exit speed, due to the reduction in diameter. As the EGTs drop, the speed slows down. In essence, you could do a 4" dp, to a 3" exhaust, and this would keep the exit speeds high, promoting a sort of scavenging, if you will. At 20psi boost and 1000*F EGTs, you're at a much lower volume of thermal flow requirement, that you would be at 35-40psi boost and 1000*F EGTs.. If you're 4" system had a 3" downpipe, then you're not really gaining anything, especially if the setup is stock.

this is quite true. Because when your running higher boost you will be pushing more air through the system, which larger pipe will lower the back pressure post turbo and allow for better spool up.

[Rogan]

this is quite true. Because when your running higher boost you will be pushing more air through the system, which larger pipe will lower the back pressure post turbo and allow for better spool up.

sorta.. The deal is, and you have to remember, that it's a 5.9L engine. That means 5.9L of air, period, regardless of how much boost pressure or RPM. You can't put 6L of air into a 5.9L container. ;)

The speed and pressure at which that 5.9L of air is experiencing, is definitely another matter.

[pepsi71ocean]

sorta.. The deal is, and you have to remember, that it's a 5.9L engine. That means 5.9L of air, period, regardless of how much boost pressure or RPM. You can't put 6L of air into a 5.9L container. ;) The speed and pressure at which that 5.9L of air is experiencing, is definitely another matter.

But that is 5.9L of air Per Revolution (i think ) and so if your RPM's go up so does the amount of air coming out, more boost, more air movement, in which the smaller 3 inch pipe will reach maximum velocity. Once that is attained then the system becomes bogged down. Besides increasing boost means your increasing your air into the engine per CID, so you might not have 5.9L of air once your running 40lbs of boost.

[Rogan]

it will ALWAYS be 5.9L, or 360 c.i. of volume, period, regardless of RPM.

This can potentially become a conversation about thermal dynamics and flow, which is one of my favorite discussions

Engine Volumetric Flow Equation

This equation is for finding the volume of air going into the engine. The displacement of the 5.9L is 360 cu.in. We have a four stroke engine; the intake valve on a cylinder opens once every 2 revolutions of the engine. So, for every 2 revs the engine takes in 360 cu.in. of air. How many pounds of air is that? That depends on the pressure and temperature of the air in the intake manifold. But the volume is always 360 cu.in. every 2 rpm.

To calculate Volumetric Flow:

volume of air (cu ft/min)= engine rpm x engine cid

(1728 x 2)

2200 x 360 = 792000

1728 (cubic ft in inches) x 2 = 3456

792,000 / 3456 = 229.17 cuft/min of flow

Ideal Gas Law/Mass Air Flow

The Ideal Gas Law is a handy equation to have. It relates the air pressure, temperature, volume, and mass (ie, pounds) of air. If you know any three of these, you can calculate the fourth. The equation is written:

PV=nRT

where P is the absolute pressure (not the gauge pressure), V is the volume, n is related to the number of air molecules, which is an indication of the mass (or pounds) of air, R is a constant number, and T is the absolute temperature.

What are absolute temperature and pressure? Do we care? Of course we do!

Absolute pressure is the gauge pressure (measured by a gauge that reads 0 when it is open to the outside air) plus atmospheric pressure. Atmospheric pressure is about 14.7 psi at sea level.

Example: a boost gauge reads 0 psi before it is hooked up. Hook it up, boost the car, and it reads 17 psi. 17 psi is the gauge pressure, the absolute pressure at sea level is 14.7 + 19 = 33.7.

A pressure reading is marked psia or psig. The "a" stands for absolute, the "g" for gauge. (The psi stands for Pounds per Square Inch). As we just showed, 17 psig = 33.7 psia. A perfect vacuum is 0 psia, or -14.7 psig.

The absolute temperature is the temperature in degrees F plus 460. This gives degrees Rankine, or deg R. If it is 80 deg F outside, the absolute temperature is 80 + 460 = 540 deg R.

The Ideal Gas Law can be rearranged to calculate any of the variables. For example, if you know the pressure, temperature, and volume of air you can calculate the pounds of air:

n=PV/(RT)

That is useful, since we know the pressure (boost pressure), the volume (which we calculate as Engine Volumetric Flow), and we can make a good guess on the temperature. So we can figure out how many pounds of air the engine is moving. And the more pounds of air you move, the more power you will make.

Here is the Ideal Gas Law rearranged to the two handiest forms, with the required constants:

To get pounds of air:

n(lbs/min)= P(psia) x V(cu.ft./min) x 29

(10.73 x T(deg R))

To get the volume of air:

V(cu.ft./min) = n(lbs/min) x 10.73 x T(deg R)

(29 x P(psia))

To stop the insane thread hijacking I just pulled off, I can start a tech thread on Thermal Dynamics of engine efficiency, flow and such, if we'd like..

(I love this stuff)

[jlwelding]

[Dave3500]

Nice to know the HP/TQ doesn't change on 3" to 4" pipe... Hmmm... Doesn't give me to much reason to upgrade being the 3" I got now is very controllable for EGT's...

With you I bet you would notice a change!

[clutch]

To be fair: were there any mods done to the truck, aside from the exhaust? The exhaust size increase will only really be noticed once mods are in place (and I don't mean just an air filter, etc.) The difference in a stock/near stock truck, stock boost levels, etc, and the correlation of 3" vs 4" exhaust, is that the 3" exhaust , with it's smaller diameter, allows the expanded (hot) exh. gasses to keep a high exit speed, due to the reduction in diameter. As the EGTs drop, the speed slows down. In essence, you could do a 4" dp, to a 3" exhaust, and this would keep the exit speeds high, promoting a sort of scavenging, if you will. At 20psi boost and 1000*F EGTs, you're at a much lower volume of thermal flow requirement, that you would be at 35-40psi boost and 1000*F EGTs.. If you're 4" system had a 3" downpipe, then you're not really gaining anything, especially if the setup is stock.

The first mod we did was the Pinacle exhaust. It was a full 4in. No changes in TQ or HP. Later we bought a Edge EZ and used it on the 40hp setting. Also added a boost fooler. Hp went up 34 on the dyno and the TQ went from 385 ft lbs to 485 lbs. The truck towed our 32' Montana with a flat trailer behind very well. Our next mod was a Fass fuel system after another lift pump failure. Pulling the trailers up White bird hill I couldn't get the pyro past 1100*. I really don't think a 4 in system is necessary until the HP is like 350 and up. My truck was only 234 HP with the mods. The price was right for the exhaust. We won it at Diesel Thunder in Spokane. Second place for most HP stock. LOL lost out to a friends 3rd gen.

[Dave3500]

The first mod we did was the Pinacle exhaust. It was a full 4in. No changes in TQ or HP. Later we bought a Edge EZ and used it on the 40hp setting. Also added a boost fooler. Hp went up 34 on the dyno and the TQ went from 385 ft lbs to 485 lbs. The truck towed our 32' Montana with a flat trailer behind very well. Our next mod was a Fass fuel system after another lift pump failure. Pulling the trailers up White bird hill I couldn't get the pyro past 1100*. I really don't think a 4 in system is necessary until the HP is like 350 and up. My truck was only 234 HP with the mods. The price was right for the exhaust. We won it at Diesel Thunder in Spokane. Second place for most HP stock. LOL lost out to a friends 3rd gen.

I'd be happy with that nice 2nd place prize.................What did 1st place win? A new truck?

[clutch]

My friend Skip was first and he won an AFE intake system.

[Dave3500]

I'd be very happy w a new exhaust!:)Now are you not considered a stock truck now?

[clutch]

With the 4" exhaust it no longer qualified for stock class. With my friends new air cleaner he is no longer stock either.

[Dave3500]

With the 4" exhaust it no longer qualified for stock class. With my friends new air cleaner he is no longer stock either.

That's how they git ya!

[KATOOM]

it will ALWAYS be 5.9L, or 360 c.i. of volume, period, regardless of RPM.

This can potentially become a conversation about thermal dynamics and flow, which is one of my favorite discussions

Engine Volumetric Flow Equation

This equation is for finding the volume of air going into the engine. The displacement of the 5.9L is 360 cu.in. We have a four stroke engine; the intake valve on a cylinder opens once every 2 revolutions of the engine. So, for every 2 revs the engine takes in 360 cu.in. of air. How many pounds of air is that? That depends on the pressure and temperature of the air in the intake manifold. But the volume is always 360 cu.in. every 2 rpm.

To calculate Volumetric Flow:

volume of air (cu ft/min)= engine rpm x engine cid

(1728 x 2)

2200 x 360 = 792000

1728 (cubic ft in inches) x 2 = 3456

792,000 / 3456 = 229.17 cuft/min of flow

Ideal Gas Law/Mass Air Flow

The Ideal Gas Law is a handy equation to have. It relates the air pressure, temperature, volume, and mass (ie, pounds) of air. If you know any three of these, you can calculate the fourth. The equation is written:

PV=nRT

where P is the absolute pressure (not the gauge pressure), V is the volume, n is related to the number of air molecules, which is an indication of the mass (or pounds) of air, R is a constant number, and T is the absolute temperature.

What are absolute temperature and pressure? Do we care? Of course we do!

Absolute pressure is the gauge pressure (measured by a gauge that reads 0 when it is open to the outside air) plus atmospheric pressure. Atmospheric pressure is about 14.7 psi at sea level.

Example: a boost gauge reads 0 psi before it is hooked up. Hook it up, boost the car, and it reads 17 psi. 17 psi is the gauge pressure, the absolute pressure at sea level is 14.7 + 19 = 33.7.

A pressure reading is marked psia or psig. The "a" stands for absolute, the "g" for gauge. (The psi stands for Pounds per Square Inch). As we just showed, 17 psig = 33.7 psia. A perfect vacuum is 0 psia, or -14.7 psig.

The absolute temperature is the temperature in degrees F plus 460. This gives degrees Rankine, or deg R. If it is 80 deg F outside, the absolute temperature is 80 + 460 = 540 deg R.

The Ideal Gas Law can be rearranged to calculate any of the variables. For example, if you know the pressure, temperature, and volume of air you can calculate the pounds of air:

n=PV/(RT)

That is useful, since we know the pressure (boost pressure), the volume (which we calculate as Engine Volumetric Flow), and we can make a good guess on the temperature. So we can figure out how many pounds of air the engine is moving. And the more pounds of air you move, the more power you will make.

Here is the Ideal Gas Law rearranged to the two handiest forms, with the required constants:

To get pounds of air:

n(lbs/min)= P(psia) x V(cu.ft./min) x 29

(10.73 x T(deg R))

To get the volume of air:

V(cu.ft./min) = n(lbs/min) x 10.73 x T(deg R)

(29 x P(psia))

To stop the insane thread hijacking I just pulled off, I can start a tech thread on Thermal Dynamics of engine efficiency, flow and such, if we'd like..

(I love this stuff)

Did you ever start a thread regarding this because.....I fully disagree with you. A naturally aspirated engine will normally run at about 80% Volumetric Efficiency with amazing scenarios where a NA engine could reach up to 100% VE. But a forced induction engine will run at 100% VE or more which means that in short, the volume of air within the cylinders is far more than the actual displacement. So therefor the overall volume will increase dramatically. I could also go into great depth with this too but I'm only being short about it here incase you have another thread started.

[clutch]

For the OP. I see you are in Oregon. If you are in the Portland area there is a shop called Source Automotive. Rip Rook is the owner and he has a very good price on 4" exhaust systems. He is on the Washington side of the river. http://sourceautomotive.biz/about-us.aspx

[JAG1]

For the OP. I see you are in Oregon. If you are in the Portland area there is a shop called Source Automotive. Rip Rook is the owner and he has a very good price on 4" exhaust systems. He is on the Washington side of the river. http://sourceautomotive.biz/about-us.aspx

X2, That's a good place Correction; it's in Clackamas, Oregon a couple miles east of I-205.

[rdsutton]

I just finished a 4" MBRP turbo back SS with muffler on a 98 12V CC 4X. It took 1hr. from usafreedomdiesels.com for $375.00 shipped. Cheepiest I could find SS anywhere. Pyro is the biggest reduced tep. change at WTO.