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.



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.

 

[Rammin On]

Ted ...



You are ABSOLUTELY CORRECT!! Get the exhaust out of there! The backpressure is at the turbo. After that ... the exhaust needs a free run out of the pipe ... as free as you can get (of course - individual preferences in noise levels will be a factor). Once the gasses expand through the turbine wheel they need a place to evacuate quickly and freely = faster spool up! And the more fuel you pack in there ... the more reason you need to get a larger free flowing hole.



Sure would like to compare back-pressure readings you saw on the exhaust after the turbine - stock vs 4" that would be interesting.



Max back pressure for our engines measured after the turbine wheel



with Cat 6 in hg to 5 in hg



without 4. 5 in hg to 4 in hg



best is less than 3 in hg



Hope I expressed this right ...



Thanks for all the hard work you do and esp getting the word out to everyone! You run a top-notch operation ...



Keith

 

[Ted Jannetty]

Back pressure

I didn't personally measure it, but I hear from two different very relialble sources that 5-6 inches hg. is correct for stock exhaust.



The 4" exhaust actually showed a negative pressure, or vacuum.

 

[RHARVEY]

Ted,



Did you test the difference from the factory 3" with muffler and then test a 3" straight piped. I did add Scott's filter system with the RE-0880 filter.

I would like to know what the difference would be between the straight pipe and a mufflered 4".





Rick

 

[Jeff Burke]

Ted,



On the 4" system that you installed, what components were in the system? Straight, or muffler? What K&N system did you use?



Thanks

 

[Cooker]

Jeff,

Ted mentioned the K+N was in the stock air box. Also I'm sure he installed the Janetty 4" kit. The kit includes a Walker 4" muffler.



Thanks for the info Ted. As always, I really appreciate it when vendors/manufactures take the time to comment here on this site.



-Ryan

 

[Joseph Donnelly]

I dyno tested a Ram at 380 hp with 3" exhaust and the Walker 21468 muffler. Then put on 4" with no muffler. Spoolup hp curve was the same, peak hp went up to 387 hp. Was the 7 hp from losing the muffler, going to 4" or both? Probably more from going to 4" in that case. Based on these findings, I feel that up to 350 hp will be OK with 3" with low restriction muffler. Going to 4" and a good muffler at the same time will lead to the conclusion that the 4" was beneficial when most of the improvement was probably the muffler. I too saw a "vacuum" in the elbow with a 4" exhaust after the HX35, but believe this is due to a change in the swirl effect as the gases expand into the bigger pipe. It does not necessarily reflect backpressure of the entire system, nor point to a mandatory hp gain. There is nothing on the tailpipe sucking out the exhaust so another explanation for the vacuum reading is needed.



Each to his own opinion and interpretation of data. For example, I have trouble believing that a 12 cm2 exhaust housing, equal to 1. 53" cross sectional area, is ideal for higher hp (over 300) Rams. Even the 18. 5 cm2 is only 1. 91", about what you get with a 2" OD exhaust pipe. With a turbo, we do need a fairly small housing to help spoolup, and the HX35/21cm2 is doggy. I have seen Rams make 400 hp with a 12cm2 housing that has a 2. 5" outlet, so I don't deny it can be done. Would they make more power with a bigger turbo--I think so. With that kind of restriction at the turbo, I think tackling that problem would be at least as important as increasing pipe size.



Yes I believe my Ram, Sickly, does need 4" exhaust, but dyno testing also shows that it needs a bigger exhaust housing too, to work with 600 hp. Somewhere around 17-19 cm2 seems to work well with a large exhaust pinwheel and turbo outlet.



Lastly, Ted's test Ram was an overvalved cousin, not a perfectly valved, ideal Ram wih the correct number of valves This is the forum for proper valving ya know, two big ones



Different opinions make this site what it is Or, maybe we got different air out here near the left coast

 

[Jeff Burke]

Cooker, my point was that when you read something like this, it's nice to have all the info. There have been many times when info has been posted, and you have to guess at part info or numbers. If the information is really going to be useful, it's nice to have the full part name and number so if someone new out there reads this and wants to try something similar on their rig, all the info is there.

 

[Diesel Freak]

Ted why are you saying that we all "need" a 4"? not everyone needs one. The posts from the Diesel Freak are in the Products and accessory forum where this thread should be !

 

[illflem]

Ted, your data looks good to me but you have done something every researcher I know dreads, repeated someone else's research. Nothing wrong with that though. Banks published results comparing a 3" stock system with their 4" system with free flow muffler about seven years ago. No other mods. If I remember right the 4" was good for 15 more HP besides paving the way for future HP gains that wouldn't be possible without the increased exhaust size.



I agree with Banks and your conclusions completely, no need to get complicated about it.

 

[Ted Jannetty]

Repeating research is what puts this country ahead of every other country in the world!



So I don't think this is a bad thing.



Banks did not even offer a 4" system for the Dodge till 2 or so years ago.

They only offered a 3. 5 inch muffler and tail pipe for the 12 valves with cat converter.



Joe, Your findings on a Dynojet Dyno are completely invalid and you know it.



The Dyonjet dyno can only simulate a 5,000 lb load, Most Dodge Diesel pickups weight 6500 lbs or more, they have more load on them driving on flat ground, never mind driving up a 9% grade or towing a trailer.



Use a REAL Dyno Then post your findings.



We used a Dynojet Dyno, and I will not post the numbers because they don't represent anything accept driving down hill.



The EGT would not even rise above 900 degrees pre turbo and the boost would not go past 28 lbs. where normally we see 1450 and 35 psi respectively driving on flat ground.



If you want to test your truck running down hill that is your choice but don't rain on my parade.



I do real world testing out on the big hills, with trailers and at the race track all of which we can collect real data.



Yes it takes longer but I have never been one to be impatient or lazy.



I have been modifying vehicles and testing performance parts for 25 years.

This stuff isn't new to me in the last 5 years like most people doing it.



Don't Get me wrong I respect the information you collect from TST Piers, and Diesel Dynamics a bring it to the board.

I also respect your writing skills, you should have been a Journalist.



Tell us what you do for a living, Chemical Engineer????



Oh Yeah! I am from the Right coast.

 

[Reddog1]

I am new at this, and I live in the other state (Calif. ). I own a 49 State Ram, w/cat and no EGR. If Ted Jannetty is correct, it would be a bad idea for those of us in the other state to increase our HP. Internal modifications are difficult to detect, and require more than a visual inspection. The 4” exhaust would serve as a flag to the smog cops.



I agree we must take care of the support systems first then add power. That’s one of the reasons I will spend approximately $3300 on a trans. However, based on Ted’s conclusions, I am having second thoughts on the other $1000 to $2000 I was going to spend. I was going for 300 to 350 HP.



Ted’s conclusions could have a substantial dollars and cents impact on the performance industry. . Smog flag prerequisite before serious HP?



Perhaps Joseph Donnelly conclusion on the air is correct. If so, I might be ok due to having the correct number of valves and being on the left coast.



Please post more data in support of either Ted’s or Joseph’s position.





Wayne

 

[Joseph Donnelly]

Ted, I guess we will have to agree to disagree. I have lived on the right coast and I like it way better out here in the proper part of the country nearer to the left coast So long as I don't have to go politically left, its OK, really, trust me.



Dynos:

This argument has gone on and will continue to do so. Lawrence has the high slug dyno and has a new line of dynos with Dynojet that will be higher yet. The data are real, and include spoolup data at the lower rpm end of the curve. Dynojet determines the number of slugs for the wheel in a rigorous manner and then the dyno operates in a foolproof manner. Unfortunately these data don't always support the conclusions someone wants to get. And, my properly fueled, properly valved Ram has no trouble getting "enough" egt on the Dynojet. The other Rams I tested did likewise. My testing has been on two Dynojets of the high slug design.



TST, the guys who started you on torque plates and their design, as Mark did for me too, have a Mustang [your idea of a real dyno, I suppose] and they detected no hp gain at all from going to 4", with one of those excessively valved Rams like you tested in your post on this correctly valved forum In fact, Mark told me the egt went up slightly with 4" and he took it back off and put on the 3", even for the PowerMax3 level of power. Yep, he got plenty of load and time under load-mor load than your hills give--see below



Hills: You better go to Colorado and other parts of the mountaious west before saying you have real hills there! I checked the Connecticut map and your highest point is closer to sea level than many of us BEGIN at before climbing our REAL MOUNTAINS. Even if you have 8% grades, you have real air on them. Try 8% at 8000 ft where the air is thin

 

[Joe G.]

Joe,



I know what you mean about altitude. Here at sealevel mine only smokes if I stand on it. In eastern UT I have to be careful at 9K or 10K. The way it smokes I've afraid that I might get a load of borate dropped on me.

 

[Diesel Freak]

Originally posted by Joseph Donnelly



excessively valved Rams

hehe, gotta love it





I like Cabbage hill on I-84 and the hill eastbound out of Laramie on I-80.

 

[Diesel Freak]

Originally posted by Ted Jannetty



The Dyonjet dyno can only simulate a 5,000 lb load, Most Dodge Diesel pickups weight 6500 lbs or more, they have more load on them driving on flat ground, never mind driving up a 9% grade or towing a trailer.

an empty truck running down the road at 60 MPH on a level grade needs about 30 HP a 4x2 wil need less, and a lifted 4x4 will meed more.

 

[Don M]

For what its worth I did some before and after dyno runs with the 4" exhaust system from Ted Jannetty Racing. It has the Walker muffler.



I did a set of dyno runs before and after the JRE exhaust.

My conclusions are below.



At the time of before and after testing I had a TST #11 torque plate, stock 215 injectors, HX-35 turbo with 16cm housing and made 326HP on a dyno jet dyno in the Dallas area with the stock exhaust system. Ted, you said earlier it was a fact that 3" exhaust can only support 200-250HP. I have proven that incorrect in the July heat of 100 plus degrees. Your facts must be wrong or you are posting disingenuous information.



After the JRE exhaust system was installed I noticed no difference in performance or seat of the pants feel and the dyno numbers were 324hp. Down by two HP. Maybe the air was warmer or maybe the combination was wrong, yet the HP was lower.



I did get a slower rise in EGT on full throttle runs though. Normal cruising speeds netted about 25 degrees cooler.



I do feel the 4" system did pave the way to more HP later after making more mods. I still cant help but think the 4" is not always worth the money in terms of a return in HP for guys that are below 350 and dont plan on going any higher.



I myself have lived on the right coast and the mole hills are not anywhere close to the mountains we have in Idaho or the Western states. The good air value is much higher in the East, even in the mole hills, compared to the Western Valleys, I am at 4500ft ASL when Im at my place in Idaho.



Using the dyno to compare exhaust systems did not have the desired effect I was hoping for. This data was from a dynojet. Could it be Ted, that you dont want to use the dynojet data because they dont support your claims of gains in HP?

It seems you may be raining on your own parade.

25 years of experience does not have the same meaning for everyone either.



Don~

 

[Garry Verheyden]

My 2 cents

My friend Dan was up here last spring and we put in a 4" down and 5" back exhaust system that we built ourselves that weekend. His truck is a 97 5sp , 4x4,#10 plate,370s,governor kit etc.

He had stock exhaust with cat but no muffler. On a long relatively flat stretch of road we did two-three full out from a stand still excelleration tests. In every case, we had the pyrometer pegged at 1500 degrees by 50-55 mph.

That same day on the same stretch of road, we did the tests after installing our exhaust sytem ( 4" down to transmission bracket 5" back with 5" straight through muffler) . We did not peg the pyro. to 1500 until we were at 75-78 mph. This was obviously a huge reduction in egt. s, more than we expected.

So a larger exhaust is very benefical for higher HP engines.

By the way he is making 413 rwhp. with his set up.

Garry.

 

[rhoads]

4" exh

Only "if you have the cash to burn

 

[Stefan Kondolay]

I had my truck around the 500hp range with no problems. When I changed my exhaust to a 3' performance muffler and eliminated the resonator my egt's drop by approx. 150 degrees. I have talked with several people with 4' exhausts and they lost about the same. I will go for 600hp with the 3' as I feel that the 4' is to big for my cubic inches and that it will be a waste of my money. We had a conversation with Mopar Muscle about the spool up times with the 4' system on his truck and he said that the 4' made a difference in spool up, but when we pointed out his time slips from the race track had said otherwise. Maybe the seat of the pants might feel a little different than whats actually going on. He also went from a factory 3' to your 4', so what would have happened if he had a performance 3' system? I know that I don't have any spool up problems other than I can't keep traction.