Thread: 300tdi 3inch exhaust required

Originally Posted by rick130

I disagree Wayne, with a turbocharger the only thing stopping you going too large is turbo overspeed, scavenging losses are (mostly) a non issue but back pressure is, unlike a naturally aspirated engine.

One place where maintaining heat and therefore velocity (scavenging) seems to help is in the first couple of feet of the dump pipe.
Back when I built my system I had a good long chat to one of the blokes from Queensland who was making 3" Patrol and Cruiser systems and they'd found that HPC coating the dump picked up 4-5lb/ft of torque and HP over an uninsulated system.
I header wrapped mine from the cast dump to the back of the t/case and can't say it actually did anything, no one is sensitive enough to pick up that type of minor improvement, but it dramatically cut down the temp inside the cabin.



Also the longer a system the lower the flow as you have higher duct losses, even on a straight length of tube.

Rick

The size of the turbo,will come down to the physical and mechanical inefficiencies of having a Turbo that is too large for the engine.And we are talking about a nearly stock 300Tdi.
As far a coating or not coating to give possible increases,this has been a debated point for many years,some swear by it,others deny it.It has to do with Helmholtz law regarding pressure wave resonance in an exhaust allowing better scavenging and efficiencies.Some say that by changing the frequency of resonance by adding a coating (similar to a tuning fork effect)that greater efficiencies can be had.
Backpressure on a typical Turbo Diesel engine is around 3"Hg
I have done a couple more calculations regarding Intake airflow(CFM) and exhaust flow(CFM) on a 300Tdi.Which is dependent on maximum engine temp. and the volumetric efficiency of the engine,and a 2.75" exhaust will do the job nicely.The diameter of the pipe is I.D. as I noticed you were referring to O.D..
These specs could be changed up or down by either increases/decreases in engine temp and changes in engine volumetric efficiency.

And I agree that you need to run a muffler/resonator as it can become very annoying after a while.
I have a 2.5" I.D exhaust on one of my Defenders,and it borders on uncomfortable,even with a muffler.The vehicle is stock apart from this,I haven't got around to turning things up like my other truck,which runs the standard exhaust.

get some side pipes and use em as fancy rock sliders - go onnnnn!
Oh, and then post the pics