ktplotts,

A few years ago you wouldn't be any better off with a cat back vs a turbo back, but the cats that are used to day are very good as compared to the ones of just a few years ago. The flow rates are much higher and the restriction is much lower. The turbo back will get you a 3.5 inch mandrel bent down pipe vs the stock 3.0 non mandrel, that alone is worth some EGT drop not to mention the flow increase.

Mark @ DPPI

 

Mark, i thought i read somewhere that the 05 and up had the mandrel bent downpipe already...not sure where or if even true. The MBRP Turbo back system does not come with a cat..correct?

 

As far as I know, it has provision for a cat to be kept there...

 

OPENED up the intake and exhaust to breath and pass more air thru by just adding a BIG exhaust. That’s a good one.

Large exhaust DO NOTHING to improve air-flow into the engine. It ONLY reduces exhaust back-pressure out of the engine PERIOD.

Volume of air? Were talking about a 6.0L 366 cubic-inch engine. A 6.0L consumes 6 liters (366 cubic-inches) of air every 2 revolutions of the crankshaft. There is only 1 intake stroke per 2 revolutions of the crankshaft.

Hmm, so how are you really getting more air in your 6.0L motor with just a BIG exhaust?

 

Umm...where do you see anyone saying JUST exhaust? Like you quoted...
"The intake and exhaust being opened up" See..."INTAKE" and "EXHAUST"....both, I say opening BOTH. The exhaust is a part of the equation.....just like gasket matching heads, polishing exhaust ports, swirl polishing walves, radius blending valve seats, flowing and reworking the intake manifolds, building a correct camshaft profile......how far would you like to take your engine...thats where it ends. But the very basics are opening the intake and exhaust...the VERY basics. Allow the AIR PUMP under your hood to more easily pump its air, and you end up making more power.

Then you mention Volume of air in a 6.0 and you seem to have neglected that volume is affected by density and pressure. A dense/presurised 6.0 liter chunk of matter has more matter than the same 6.0 liter chunk of matter in a vacume. I apreciate your thoughts, and I will continue to ponder tham for a bit, but I think that your angle of thought is a bit flawed.

 

Looks to me like I see the problem. Your on the wrong web site. GAS dude, happens all the time. I really hope your not spending all your money port, polishing and matching your diesel heads.

While your pondering my flawed thoughts, you do understand gas engines throttle by air and diesel engines throttle by fuel RIGHT. Were talking about the FORD 6.0L TURBO diesel.

You’ve added a new topic each time you responded. Now you want to talk density. Density is the weight of air in a given volume measured in pounds per cubic feet. The more a cubic foot of air weighs, the more oxygen molecules are in the air. More Oxygen better cylinder combustion (more complete) lower EGT DON'T NEED BIG EXHAUST.

Been fun, TAKE CARE!

 

I have a 04 6.0l diesel and just put on a mbrp 4" pro series exhaust, what most people dont understand is that it doesn't matter what size pipe you have 4",5",6",8" , you are only going to have 4" pipe restriction out of the turbo, that's your size of exhuast that you are going to be running, if you notice that on all ford applications the down tube is only 4", you can't put a 5" or a 6" tube coming out of the turbo, also the size doesn't change until after the down tube which is only 4". DON"T get me wrong I love the look of a 5" or a 6" tail pipe coming out of the rear of a truck but what a waste of money to only have the same restriction of 4" that I have on my system.

 

You funny. You are partially correct in calling me a "gas dude" in that I have a street stock gas engine that makes just shy of 600 HP and a purpose built pulling truck that makes just under 1,000 HP. I also have 3 Diesels (2 7.3's and a 6.0) in the driveway. Each one of them is worked at least slightly. All of the things I mentioned in posts above ARE standard hot-rod things (gas or diesel), and some of the best running diesels today HAVE went so far as to gasket/port match the heads, polish the ex ports, redesign camshafts, and of course you ALWAYS have to worry about how you finish a valve job.

These are the things that will seperate a backyard builder from the best of the best.

A diesel may throttle by fuel, but it still has to get the air to burn it. The better the airflow in and out, the more fuel that can be burnt.

Back to your density comment, if your exhaust were restricted....how could your turbo force air into the chamber? If restricted exhaust is no big deal, why are the truck puller diesels running a 90 degree elbow thru the hood for exhaust? Why are the intake 6-8" pipe?

Heck, based on what your saying use the stock air filter and put 2" exhaust on it....its ok...the turbo is going to fix everything.....Like I said, I dont like to sound challanging, and I hope I am not. I take no offense to what you replied, but I still think you have a flawed way of thinking about this particular matter. I live my life around engines, from stock to pro-stock, gasoline to jet fuel. There are certain rules that apply to all of them....and your are suggesting that the rules I am talking about.....are false. In that, I find the fatal flaw.

 

BassCat,

Here let me help you out with some info, a typical diesel engine will use 8-10 times the amount of air per combustion cycle as a same size gas engine. The typical diesel will respond and get 100 extra HP thru fueling mods and a typical gas engine will get maybe 25 HP, usually 15-20 on a good average using the same fueling process. If you increase fuel you need to increase air in and out to try to get the air fuel ratio somewhere close to the 14.7 to 1 in a gas and of course you know the diesel ratio is all over the place based on load and pressures. If you run the same amount of air thru a warmed up diesel the EGT's rise like a rocket, the combustion efficiency goes way down and the BTU use of the fuel is very poor rsulting in less HP and potential MPG. So if you increase the air into the engine you have to increase the ability to get air out as I said in the previous post. You are correct adding and exhaust only will not really help with air in, (it actually does as the suction effect on the exhaust will actually pull thru more intake air if the intake tract will allow it to happen that is). But adding exhaust alone will drop EGT (up to 200 degrees) and it wil aloow the turbo to spool up faster.sooner because the back presseure that hinders the turbo is now gone. Quicker spool up gets you more HP at a lighter throttle setting and that is free HP, plus potential MPG, if you can pedal the go foot easy anyway.

So as you can see intatke and exhaust upgrades are like salt and pepper, they go together and work in harmony to create a more efficient engine. Hope this helps you understand my post.

Mark @ DPPI

 

Just removing the cat in my 4" system I see a 100-200 drop in overall EGT. With the 4" system vs. stock I saw a 250-300 drop.

Less heat out + more fuel in = more HP

 

Wow...in the end...I guess this old fashioned drag racing, truck pulling, Top-Fueler/Pro-Stocker aint as dumb as some of ya'all are wanting to claim.....and engine is an engine...I dont care what kind of fuel your burning.....unless its nuclear, it needs air. Thanks for backing up my story Mark....I knew it was only a matter of time before I got some back up....

 

fordtrkpuller, I was supporting your comments not BASSCAT.

 

Mark, adding a large exhaust will NOT increase air-flow through a diesel engine as I stated. The only way your theory works is to turn the engine faster. Which is a whole different topic. EGT? Exhaust gas temperatures are controlled by cylinder combustion. Air will not burn alone / fuel will not burn alone which we know.
For diesel fuel to burn efficiently (completely) in the cylinders combustion chamber it needs "air" more specifically oxygen. What is the difference in air and oxygen? Like I already said It's density. Density is the weight of air in a given volume measured in pounds per cubic feet. The more a cubic foot of air weighs, the more oxygen molecules are in the air. More Oxygen means better cylinder combustion. You are into volume of air in a diesel I’m into density quality. I will make more HP than you will.

How do I get the best air-density in my engine? Remove as much heat as possible from the charged air with a decent CAC (Charge-Air-Cooler). I designed and built my own air-filter-box and CAC for my truck. Tuners / Chips SMOKE like a train because the engine is over-fueled with nothing done to add more quality air (oxygen) to the engine. In-complete cylinder combustion is what causes EGT temperatures to soar. They make a bunch of HP / SMOKE right out the exhaust instead of to the rear wheels.

I have spent the last 30 years in machinery-turbo-engineering working with large compressors and turbine drivers. I know a little bit about how a turbo / charged engine works. I'm not trying to show you or truckpuller up you guys have my respect I assure you. There has been NO personal attacks here and we certainly have our right to disagree. This post went from a simple exhaust thread to a major tech / discussion.

I run a stock exhaust with a Magnum / Flow muffler, my own CAC and Air-Filter-box with the stock air-filter. I use a 80HP Predator / Dr. Performance module which you do not care for. My truck runs from a dead stop / through the power / band to the rev-limiter with NO SMOKE. My EGT run 930-950 degrees.

Take Care

 

Would you consider showing us pics of your CAC, I am kinda curious.

OTH I know guys with a 80HP predator and they don't smoke either. What is the Dr. Performance module?

 

2nd that. My questions have been answered, but this has turned into a very interesting topic. Also my truck only smoke in the highest setting, in the low and medium setting, there is none. I have a SCMT btw.