He said "Would this apply - Reduces back pressure and hurts drive pressure at lower speeds"...

This would lead one to believe that they are two seperate things... They are not, they are the same thing...

Drive Pressure is Back Pressure...

 

I agree with you to a point because isn't one factor the cause and the other the effect ? Yes there are the same but doesn't it depend on what side of the turbine wheel that pressure is as far as what it is called?? I don't know??
Actually as I try to think this though it is back pressure before it gets to the turbine wheel. Then when that pressure is in the turbine wheel it is drive pressure. Then as that pressure leaves the turbine wheel it is again back pressure. And please correct me if I am wrong. And I am sure you will. And for the sake of learning goes thanks for your input.
Sorry about the

 

Well... there are those who would call the difference in sound from a 5" exhaust a "benefit"... just saying (no other point intended or implied).

 

Go back and reread my original post. The second sentence states that they are the same.

 

With all humility and respect to CSIPSD, I must respond to this for the sake of accurately conveying useful information to the readers.

A common garden spigot has a 1/2" pipe feeding it, usually as a spur from a larger common pipe. Put a 1/2" garden hose100' long on the spigot at full flow, then swap it out for a 3/4" garden hose 100' long - you'll see a difference in flow out the nozzle. Now, take 1/2" garden hose 3' long and a 3/4" garden hose 3' long and you won't see squat for difference - except the distance the water ejects out the nozzle. One of the many ways I get my geek on.

Going to a 4" downpipe and going big on the rest, or going 5" downpipe (if possible) will make a difference with big CFM numbers. Bends count as restrictions, and there are plenty of those under a truck. Larger diameter pipe will compensate for restrictive bends, plus don't forget the muffler. There is also a point to be made that I've stated in order to justify the 5", mega-mods are needed - and that dink of a turbo ain't gunna stay with a mega-mod.

I'm just sayin'

 

With all due respect, I think you need to get out more...

Here are some pictures of the 19cm housing I have for my H2e... I have not installed it because I just dont care but it is a housing that on a modded H2e is capable of about 650-700hp as a single.









So tell me what size turbo has a larger then 4" outlet... Only thing I can think of is LARGE secondary turbos that would be used in a twin set up...

I'll repeat myself, since it got missed the first time...

THERE IS NO POINT IN WHICH A 5" EXHAUST IS NEEDED.

 

I see in your photo that the outlet on your turbo is 3 1/2" in diameter. By the logic you've proclaimed here, my 1/2" hose comparison holds no merit, and a 4" exhaust would be a waste of money on a 650-700HP diesel engine because it's bigger than the turbo outlet.

I won't say you're wrong, incorrect, or mistaken - I just made my case and you made yours. The readers now have mulitple sources of input and observations to consider when making their purchasing decisions. Thank you for contributing to the thread, it's all useful information.

 

I am not master or claim to be, and hardly ever get into debates. But i would think:

If the fan had an output of 4" and a 100 foot run of 4" pvc pipe. The pipe run(distance) would be the restricting factor.. The air would bottle neck because it would run out of power to continue its journey the rest of the way and have to be "pushed" Using a 5" pvc or 6". Would be lesser a restriction. That is why Fans have specs on min size and max distance, As such of a dryer vent. Or Sub pump. before they loose efficiency.

Same principles in running ac/furnace duct work i believe. I would think the question would be what would be the max length of the exhaust pipe before you start restricting

Heck, almost not quite the same thing with electrical wire.. 10 gauge 30amp? But what if 5000 foot long run?

So i would think, 5" exhaust is better than 4" Lessening the restriction (length of pipe)

 

What is the going price of a 4" exhaust?

 

Did some other reading.
4" is plenty for up to 500 hp.
Shown that 5" looses some torque and slight Hp drop. at different RPM's.

Exhaust, Ah, A whole science in itself. If you going to be through money at the tail end of the exhaust, There is a point of wasting money without throwing money in the air intake side.

I have a 4" in my future. But that is it. Just to help a bit from towing. I don't have any mods on the intake side except a 6647.

 

4" is plenty for 1000hp... Dont know why that is so hard to understand. The only reason to go with a 5" system is sound.

 

Tugly, what is red line disconnect?

 

I went with 5" because I got it and a 4" downpipe for $75...so there is another reason besides sound!
My truck absolutely runs better now than stock.

Mike

 

Hey Ed, I hope you keep the cat when you changed your exhaust out.

 

Oh yea I kept the cat because at some point the wonderful state of Indiana might make me put it back on. CYA I also kept the down pipe just incase someone might need it.