You Do Need 4" Exhaust

[Ted Jannetty]

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.

 

[ToolManTimTaylor]

NIIICCCE R&D

Sweet R&D TED!!!! #ad
<BR>

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Truck Bio:

Y2K+1 3500 4X4 Quad Cab 4:10:1 LSD



Powerpack By Bank's (4 inch exhaust,High ram intake,wastgate mod to 38 psi,ottomind TLC +guages,K&N) ,DTT~93%TC~&~VB~TC Smart controller, Mag-Hytec's Double Deep Trans pan,DD injectors+Van Aken+Autometer Guages. ,Piers Modified PDR HX turbo,Enterprise Engine PerformancePusher pump setup Front End Leveling Kit from Jakit with 255/85R16 BFG http://www.bfgoodrichtires.com/ M/T's Custom Rhino Liner (see Tool Man's truck feature)DeeZee Black Diamond Plate Bed Rails And Tool Box , WAAG Side tubes with kick~outs Mopar Performance accessories-Sill plates-hitch cover-cargo aux lamp'n'Power, Hadley air systems 150 psi comp and air storage. DynaMat Sound deadening applied to entire cab and doors, Check out Tool's Stuff#ad


N. E. T. D. P

 

[Ted Jannetty]

Nice Pic.

Nice Picture!



I love the multicolored smoke, nice contrast of black and white.

 

[K_Arts]

Ted,



I have to disagree with you to an extent. Let me throw in another factor that changes the whole scenario.



High Altitude!



I put a Jardine 4" Pipe on my truck and I lost a ton of power, turbo lag was unbearable, EGT's went up about 150*, and over all is a bad idea in high altitude.



The only way I was even able to get some of my power back was by adding one of Piers hx-35 turbos on my truck (note that I said "Some" of the power, not the majority of what I lost). I do have to say that I will be going back to a 3" pipe as soon as I can locate one, and in a couple of days my truck will be over 350 hp. So we'll see how it performs.



Any ideas on how to get around the high altitude thing????



Kev

 

[RustyJC]

Kev,



Man, that's strange. We've added a BHAF, Edge EZ with boost elbow (31 PSIG vs 22 PSIG max boost) and Jardine 4" exhaust system - power is up substantially (what were tough 5th gear hills towing the 5ver are now taken in 6th gear and still accelerating) and maximum pre-turbo EGT's have dropped from 1250 degF to 1050 degF. Therefore, our experience very much bears out Ted's results. As you say, maybe it's just a high altitude thing, but from a design engineering perspective I can't understand why at first blush. Are you sure you didn't leave a shop rag in the new muffler?



Rusty

 

[Ted Jannetty]

That makes absoutley no sense at all.

I can't speek for the Jardine down pipe, haven't seen one.

But ours works.

The Turbocharger works on pressure drop.

Drive pressure vs. back pressure.

I think something else went arri when you installed the 4" pipes.

Did you make any other changes at the same time?

 

[K_Arts]

No other changes were made at that time. Just the Jardine 4" pipe with a straight through Magnaflow muffler.



I have been told by several muffler and diesel shops that it has to do with back pressure. Being in the altitudes that I am in, the turbo doesn't have enough pressure on it to help it spool up.



Also, one last thing that I forgot to add, is that with my stock 3" pipe minus the muffler and a set of DD2 injectors and an EZ box, my boost was around 32lbs. After the 4" pipe it went down to 25 lbs. Once I added Piers turbo the boost then went up to 27lbs.



So it all has to be related to alitude.



Kev

 

[wyosteve]

K Arts, not trying to start an argument, but I also would have to disagree with you. I also live and drive at high altitude. (Wyo. 6k to 11k commonly). Granted, I have an 01 ETH which may make a difference, but when I put my 4" Jardine on, I got quicker turbo spool up, EGT's about 100 lower and smoother running. This is both with and without towing. Can't really imagine why you ran into your problems, but I don't feel altitude was the cause.

 

[K_Arts]

Yeah... I dunno. . but I sure would like to know what caused this issue. If it wasn't for the quick spool up of Piers turbo... I'd probably be selling the truck. The performance loss was that bad.



I'm glad to see different opinions though. . maybe I can get to the bottom of this problem and figure out what the heck is goin on.



Thanks guys.



Kev

 

[Ted Jannetty]

K-Arts, I believe it is your muffler choice that is causing your problems.

Take it off and install a walker 22572 muffler.



You may also want to check the AFC boost line on the back of the injection pump

 

[RustyJC]

Originally posted by Ted Jannetty

K-Arts, I believe it is your muffler choice that is causing your problems.

Take it off and install a walker 22572 muffler.

Ted,



If that's the Magnaflow that comes standard with the 4" Jardine system, why would Kev have a problem when the rest of us don't?



Rusty

 

[Diesel Freak]

My opinion

This has always been a hot topic.



I agree that untill you are over 350 RWHP you probably do not need a complete 4" exhaust system (a straight piped 3" works VERY well), unless you just want the cool sound. Four inch ID pipe has a cross sectional area of 12. 56in^3, three inch ID pipe has an area of 7. 07in^3. As a gas expands, it cools, so if you do not have enough exhaust volume to fill a 4"pipe it could cool so much that just the action of moving the cooler more dense gas out of the pipe could raise backpressure to more than it would be if a 3" straight pipe were used. Keep the Gas hot and moving! Why do you think header wrap came into existance?



As for turbo spool up and back pressure... ... Turbines abhore backpressure!



All turbines whether they are in a Turbo, Gas Turbine, Steam Turbine, and even a Hydroelectric Power Plant require a differential pressure to work, and in some instances a temperature difference (condensing turbines).



Lets do an analysis on the gas flow through the exhaust side of the turbo.

As we add fuel to the engine, it speeds up and exhaust temperature gets hotter ... Higher mass flow rate and kinetic energy (flow work)



the effective nozzle area of the turbo housing is conatant 9, 12, 14, 16 (these numbers are completely arbitrary for this analysis) as we all know them.



As the mass flow rate out of the engine rises exhaust manifold pressure rises(potential energy) and consequently so does the mass flow rate into the turbine.

The velocity of the gas rises through the nozzle due to a differential pressure. The high velocity gas impinges on the turbine blades and the kinetic energy of the gas decreases and the rotational energy of the turbine increases (it accelerates)



If the differential pressure across the turbine nozzle is raised the gas velocity at the nozzle outlet will be faster therefore the turbine wheel will accelerate faster.



How can the differential pressure be raised?

Add more fuel to raise manifold pressure or change compressor wheels to raise boost and lower intake charge temperature and consequently raise mass flow rate through the engine which raises exhaust manifold pressure.



The easiest thing to do to raise the dP across the turbine is to put a low restriction exhaust on the engine... the closer you can get to atmospheric pressure at the turbine outlet the better!

Be careful with this (see my first paragraph)



The temperature drop across the turbine is mainly due to the drop in pressure across the turbine nozzle. As a gas expands it cools.



The reason that some people have had trouble with larger exhaust systems at high altitudes is due more to the efficiency of the compressor wheel and the air density at the intake manifold than due to exhaust modifications.



The key to optimum engine performance is air density at the intake manifold and the ability of the engine to breathe. Raise the volumeteric efficiency of the engine and turbo as a whole will make the engine run like it should.



Lower the back pressure on the turbine as much as possible, put a "properly" modified turbo on the engine to match the power output, and rpm range you want.





Ted, When I straight piped my truck I had comparable changes in performance, EGT and turbo responce, I do have a 4" system now for two reasons... it sounds sweeeet, and the 3" straight pipe was getting on my nerves. I would like to add that I saw no increase in performance or drop in EGT when going from a straight 3" system to a 4" system with a Dynomax 4" welded race muffler. I just don't have enough exhaust volume to fill a 4" pipe (yet)

 

[pwr2tow]

K_Arts - Kevin,

I don't know squat about high altitude but with my truck and stock air filter,stock exhaust, and DD stage I injectors i can make 28PSI of boost. I have just a boost elbow and no boost module. Just trying to give information. If it's not altitude I would say there is something else wrong with your truck.

Ron

 

[Barry]

Something is wrong! Every year we take our truck ( pulling a 5th wheel of some sort) to Colo. and it runs up the mountains like a bandit! Most of the passes I go up in 6th and come down in 5th! So... ... ... ... ... ... ... ..... altitude is not the problem. Get your truck to someone that can solve the problem.

 

[Diesel Freak]

One more thing... . We are comparing three completely different exhaust systems



Stock (very restrictive)



3" straight pipe (keeps the exhaust gas velocity high, but lowers the backpressure on the turbo drasticly. )



4" muffeled (basicly a straight pipe)



of the 4" systems I have seen, they all expand from 3 to 4 inches in about the same distance. It looks almost like too drastic of a change. If the pipe expands too fast then turbulence and flow irregulaities can cause a high pressure area at the begining of the pipe expansion.



how hard would it be to make a downpipe that flared from 3 to 4 inches in lets say 26 inches

 

[DennyDay]

4" exhaust

I don't understand the excessive turbo lag with the 4". After Ted removed my 3" and installed my 4" there is a very noticable improvement. I've run from above 10k feet (Leadville, CO) where there was slight turbo lag, but nothing like it was with the 3" to below sea level (New Orleans, LA) with no adverse effects.

Denny

 

[TxDieselKid]

I kind of agree with Diesel Freak...

Ted, please try this test again, only before the 4", try a stright 3", no muffler, no resanator.



Andrew

 

[Ted Jannetty]

Ok dieselfreak, here are some more facts.



Test subject 97 3500 Cummins turbo Diesel 5 spd 3. 54 axle, JRE #3 camplate, 300 hp injectors, 3" straight pipe exhaust K&N air filter.

Had more power than I could use because everytime I floored it the EGT would go to 1500 degrees in 3rd 4th or 5th.



Boost was max 36 psi.



Pulled the 3" exhaust system and installed the 4" with muffler.



I picked up 6 mph on our test hill

EGT would only climb to 1250

I picked up 3 psi boost

Throttle response was greatly improved

Average boost was higher at all throttle positions.

 

[Diesel Freak]

What was the rear wheel horsepower on that truck? I am guessing over 350

 

[C Schomer]

The bigger stuff helped mine especially in the lag area. About 1-2mph(towing) on a familiar test hill. I thinks it's even more important to have the better flow with the atmospheric pressure handicap we have. I had a K&N(3 yrs. ago) and it had moderate restriction - 11"wc. It sucked the filter minder down a little. Then I put the original BFAF on, and it dropped to 2"wc. Craig