97 12 valve...only want to do this once so which is better...4" of 5" exhaust...also what brands do you like...same thing for intakes and cold air setups...will be towing a 30' 5th wheel and need power and fuel economy...thanks
4" or 5" exhaust
- Thread starter Big AL
- Start date
CSARebel916
WMO Burner
First off, do you have any upgrades?
On my mothers 99 24v, I put a complete 4in turbo back free flow exhaust. Pulling our 24' cattle trailer fully loaded, she averages around 22-24 mpg. Her truck sounds like a big rig going down the road!
I have wanted to put mods on it, but she wont allow it, lol
On my mothers 99 24v, I put a complete 4in turbo back free flow exhaust. Pulling our 24' cattle trailer fully loaded, she averages around 22-24 mpg. Her truck sounds like a big rig going down the road!
I have wanted to put mods on it, but she wont allow it, lol
li'l tugger
Registered User
generally, anything over 4" is overkill. i just put a 4" downpipe and freeflow on my 99 psd and love it! if you go to a 5" be prepared for some serious engine droning on the highway. if i had gone bigger, it would be too loud for me. a general rule i think is 1" per 100 horsepower. when you get your downpipe, make sure it starts at 4" and doesn't "taper" up. any brand is about the same i think, but aluminized doesnt stay as cool as stainless. either way you go, you should see a big jump in boost and a big drop in egt's! i picked up about 3 psi and lost about 200-300 degrees in mine
Whit
Registered User
A clip from the latest Diesel Power magazine
Pipe Dreams
Diesel enthusiasts already know the great power potential and more efficient fuel consumption offered by a diesel truck.All that power and economy doesnt come without picking the right parts though. An after market high flow exhaust system has to do more than simply make your truck sound better. Point in case with a 4" vs. 5 or 6 inch system, how big do you need to go? To answer that first we need to go over a few basics.
On most contemporary turbodiesel engines, the exhaust comes right off the exit of the turbo and after market exhaust manufacturers offer more than one tubing size to vent the exhaust more quickly.
One advantage of moving exhaust gasses quickly and efficiently is to reduce buildup of heat. Turbo diesel engines generate alot of heat, especially when the engine is under a heavy load. A high flow exhaust actually allows your diesel engine to run cooler and adds the potential for more boost when towing.
Large diameter tubing also reduces backpressure, making it easier for the pistons to shove that exhaust out of the cylenders and resulting inmore horsepower. Less backpressure allows the turbin to spin more efficiently, therefore it will build boost quicker and run cooler.
Interestingly enough however there is a point where bigger isnt necessarly better. While engine testing indicates that going from 3-1/2" to 4" can reduce backpressure by as much as 98%, ther can be less than 2% reduction above 4" exhaust. SO while a 5 or 6" exhaust looks cool it wont give you much more than just a coolness factor
Pipe Dreams
Diesel enthusiasts already know the great power potential and more efficient fuel consumption offered by a diesel truck.All that power and economy doesnt come without picking the right parts though. An after market high flow exhaust system has to do more than simply make your truck sound better. Point in case with a 4" vs. 5 or 6 inch system, how big do you need to go? To answer that first we need to go over a few basics.
On most contemporary turbodiesel engines, the exhaust comes right off the exit of the turbo and after market exhaust manufacturers offer more than one tubing size to vent the exhaust more quickly.
One advantage of moving exhaust gasses quickly and efficiently is to reduce buildup of heat. Turbo diesel engines generate alot of heat, especially when the engine is under a heavy load. A high flow exhaust actually allows your diesel engine to run cooler and adds the potential for more boost when towing.
Large diameter tubing also reduces backpressure, making it easier for the pistons to shove that exhaust out of the cylenders and resulting inmore horsepower. Less backpressure allows the turbin to spin more efficiently, therefore it will build boost quicker and run cooler.
Interestingly enough however there is a point where bigger isnt necessarly better. While engine testing indicates that going from 3-1/2" to 4" can reduce backpressure by as much as 98%, ther can be less than 2% reduction above 4" exhaust. SO while a 5 or 6" exhaust looks cool it wont give you much more than just a coolness factor
li'l tugger
Registered User
whitmore- i think that pretty much sums it up. those numbers at the end of the article are very interesting.. especially since you could pay hundreds more for 5 or 6 inch system! i cant wait to get home and drive the rig again just to hear that 4" pipe
...thanks for the info...
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