Attention: TDR Forum Junkies 
I keep reading where members are suggesting the Mighty Cummins Turbo Diesel doesn't need 4" exhaust, and 3" is good up to 350 hp.
Also that factory air filters are ok for modified engines.
These statements are a Big mistake!
Here are the facts.
We took a completely stock 98. 5 24 valve 3500 quad cab dually 4x4 7400 lbs.
Added a set of gauges and set out to do some testing.
Near my shop exists the Dream test hill, 1 mile long flat (Non Rolling) 9% grade.
We put out markers 4 total so we could track where we picked up power i. e. low end, mid range, top end.
Made 3 runs stock and averaged the numbers.
Then made 3 runs with each modification again averaging the numbers.
The K&N air filter in the stock air box was worth 1/2 lb. boost, 25 degrees drop in EGT, and 1 mph faster from the second marker on.
The 4" exhaust was worth an additional 5 mph at the second and third markers and 3 mph on the top end, 75 degree drop in EGT, 2. 5 lbs. boost, and achieved top speed in 2/3 the distance.
We also did 0 to full boost testing and to get more accurate results it was necessary to do 10 runs stock and 10 runs with the 4" exhaust.
Stock exhaust with K&N; the boost went from 0-18 lbs in an average 3. 2 seconds.
With 4" exhaust and K&N; the boost went from 0-21 lbs. boost in an average of 2. 5 seconds.
An improvement of . 7 seconds and at 3 lbs. higher.
We did the math and came up with a 30 hp increase to the rear wheels.
All my customers report better fuel economy, more pulling power, less smoke, quicker turbo response, higer average boost, faster cool down, Plus it sounds awesome!!!!!
Fact! a 3" pipe can only support 200-250 HP
That is if the pipe is mandrel bent, 2000 and up Dodges have compression bent down pipes, this drops the pipe size down by 10-15%.
Any time you modify an engine, take care of the support systems first then add power.
Air flow, fuel supply, then fueling increase.
With out the support systems you will never achieve full potential.
Also that factory air filters are ok for modified engines.
These statements are a Big mistake!
Here are the facts.
We took a completely stock 98. 5 24 valve 3500 quad cab dually 4x4 7400 lbs.
Added a set of gauges and set out to do some testing.
Near my shop exists the Dream test hill, 1 mile long flat (Non Rolling) 9% grade.
We put out markers 4 total so we could track where we picked up power i. e. low end, mid range, top end.
Made 3 runs stock and averaged the numbers.
Then made 3 runs with each modification again averaging the numbers.
The K&N air filter in the stock air box was worth 1/2 lb. boost, 25 degrees drop in EGT, and 1 mph faster from the second marker on.
The 4" exhaust was worth an additional 5 mph at the second and third markers and 3 mph on the top end, 75 degree drop in EGT, 2. 5 lbs. boost, and achieved top speed in 2/3 the distance.
We also did 0 to full boost testing and to get more accurate results it was necessary to do 10 runs stock and 10 runs with the 4" exhaust.
Stock exhaust with K&N; the boost went from 0-18 lbs in an average 3. 2 seconds.
With 4" exhaust and K&N; the boost went from 0-21 lbs. boost in an average of 2. 5 seconds.
An improvement of . 7 seconds and at 3 lbs. higher.
We did the math and came up with a 30 hp increase to the rear wheels.
All my customers report better fuel economy, more pulling power, less smoke, quicker turbo response, higer average boost, faster cool down, Plus it sounds awesome!!!!!
Fact! a 3" pipe can only support 200-250 HP
That is if the pipe is mandrel bent, 2000 and up Dodges have compression bent down pipes, this drops the pipe size down by 10-15%.
Any time you modify an engine, take care of the support systems first then add power.
Air flow, fuel supply, then fueling increase.
With out the support systems you will never achieve full potential.
. Sam
I'm getting gauges done this month (December)... finally
