You Do Need 4" Exhaust

[Vaughn MacKenzie]

I donno DF, I don't think this thread is in the wrong place. Ted seems to be talking about 4" exhaust in general, I didn't see him mention his own system. I think the Products forum is where you'd discuss Band X specifically instead of a product in general, especially when you are talking about the performance aspects of it vs. the product itself. I would say this forum is appropriate to discuss 4" exhaust systems in general and how they affect engine performance. But, that is just MVHO



Vaughn

 

[work2muchplay2little]

Thanks Ted, that kind of testing takes time and effort. Makes me wonder what the "upper limit" of a 4" system is. If you use the big rigs as a bench mark, engines in excess of 450-500 HP seem to use a 5" system. Anyone done any testing in this regard?

 

[BigYellowIron]

I still have 3". I make 371 hp and have no egt problems.





Adam

 

[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.

 

[Mopar-muscle]

oh sure drag me into it , i'll dig out my slips and see what happened ... if it wasn't for my HX40 i would go back to the 3" system before the dyno in 2 weeks , scott does have a kwikspool at the shop , and i have most of the pieces ready to go for a revist of a freeflowing 3 " ...



as far as the comment , they are just going on the my pipe is bigger than your pipe scenerio ( its a guy thing ), i doubt they would see any decrease in performance with a smaller set o stacks ...

 

[BigMo]

First, thanks Ted for posting this information here. I search 24V engine threads often and it is where I expect to find this type of valuable information.



Second, I STILL haven't modified my truck, but it's not for a lack of desire; just redirected cashflow (other needs have been greater!). However, recently I have been looking into doing a homemade exhaust. Our local NAPA Truck Parts store will sell me everything I need. If a pipe or connector doesn't fit, I can bring it back for exchange or refund (prior to welding, of course!). For the price, it seems like a 5" would be better than a 4"; there's just not that much difference in price. I would be going from 3" out of the turbo, to 4" connector, then to 5" connector on out to the end of the system (with muffler).



Any comments anyone?

 

[Ted Jannetty]

Stephan, 4" is too big for my cubic inches!



You could be right IF, IF is a big word here, IF you didn't have a turbocharger.



The Turbocharger could and does effectively double or triple the cubic inches of your engine depending on boost.



No one in the exhaust or header industry sizes pipe on cubic inches alone, they take into consideration Horsepower, and whether or not naturally aspirated or turbo or supercharged.



Horsepower being the biggest factor.



Pick up a Flowmaster catolog and look in the tech section.

there is a Horsepower to pipe size chart.



3" pipe can only support 200-250 horsepower.



Non of the information I have suggested is new, it has been around for longer than you.



FACTS are FACTS.



I do the testing to back up the facts and present it here for all to read, I don't make this stuff up.



If your really making 500 hp with a 3" pipe and you change it out for a 4" pipe you can expect to pick up a hell of alot more power than a stock truck does when changing from 3" to 4"

You won't see it on a Dynojet either, that is like testing down hill.



I come on this board to offer information to the members, I bring 25 years experience in performance.

I am not pushing anyones product, I am only stating facts.



How long have you been doing this?

Be honest!

 

[PRout]

Originally posted by BigYellowIron

I still have 3". I make 371 hp and have no egt problems. Adam

Sounds like a 4" exhaust would improve the egt's significantly here. Theres been lots of reports on this site from people w/ less HP than this claiming 100+ degs improvement. Not only Ted.



Anyways, Wide open testing is great for a dragracer, or competition pulling, but not for an average driver.



You can test for WOT all day long, and not be improving drivability at all.



I want:



1. quicker spoolup when grabbing the next gear.



2. Less smoke before spoolup. So you dont have to wait to roll on the gas.



3. Better mileage.



4. Ability to use more throttle, longer, while pulling heavy up a long grade, on a hot day in the desert.



WOT testing mostly reflects on #4, but doesnt say much for 1-3.



Saying your HP on the dyno is this, or my quarter time is that, so i dont need a 4" is fine, but it doesnt mean a whole lot for daily driving.



You might smoke like a train till you get rolling from stoplights, or have to baby it to keep from smoking, or whatever.



From what Ive heard, a 4" system does help all 4. But we need to consider (like we did) other factors than merely WOT testing.



I can say that my K&N re-0880 may not have helped WOT much, but it sure did make the motor snappier to spool up, w/ just a slight bit of throttle. So my opinion is that less restriction does help the motor before it gets force fed by the turbo.



It may be noticed more if you have a stick shift since youre getting under the turbo more.

 

[Stefan Kondolay]

Ted,



I have always been told by experts in the exhaust field that your air flow is only as good as it's smallest restriction. Is the 3' exhaust the smallest restriction? I have never claimed to be an exhaust expert but I feel that we don't need 4' exhaust, some may want them, but they don't need them. I have been told of some test to do with my exhaust system that will tell me for a fact wether I would benefit from one or not. I will perform these test this week and post my findings. Who knows I may end up with a 4' exhaust.



We do sell 4' exhaust systems, only 2 in the last year and a half, but we do sell them. We don't recommend them but half our customers have them. They want them for the sound and egt's. I personally run the rhino 911 muffler but we don't sell them because you can get them at your local midas shop. I don't dislike 4' exhaust I just don't feel that they a neccessary upgrade for most.

 

[Ted Jannetty]

ttt, I thought this would be fun for the newbies.

 

[TxDieselKid]

Originally posted by Stefan Kondolay

I will perform these test this week and post my findings. Who knows I may end up with a 4' exhaust.

Ted, nice to see you post again over here.



Stefan, what did you ever find out?



Andrew

 

[GiesJ]

elevation?

I’m a bit nervous post here cause everyone has way more of a clue than I do, but here goes…



I’m at 7200+ feet in elevation, how does a larger exhaust help/hurt me at this altitude. I notice that as I drop in elevation I see less smoke (I only have the EZ) but that smoke reduction may just be in my head. Any comments on how larger exhaust will work at high elevation? For that matter how do bigger injectors play into the elevation game?

I have heard other people in the Rocky Mountain Region comment that larger exhaust hurt their spool up but just plain don’t understand the physics involved in how higher elevations can affect turbo diesels.



People say it all the time, but the TDR is amazing. You guys are very generous with your knowledge and time invested to share that! I appreciate it.

J

 

[Cobra]

4 inch exhaust

I read in the latest TDR magazine that the 03 RAMs will have 4 inch exhaust from the factory. With or without the preformance, I like the sounds of mine.

 

[Okie-Go]

I also like the sound. With some of the money spent on mods for some of us I personally will not complain about the money part for my 4" exhaust. I feel like it helped my egt's. This is pulling the same trailer up the same hill.

 

[Riflesmith]

Turbochargers thrive on low backpressure.

It is an absolute fact that any turbine becomes more efficient as backpressure decreases. The higher the differential pressure between the turbine inlet and outlet, the more work you will get out of the turbine.



Steam turbines used in power generation exhaust the steam driving them into a near perfect vacuum(as high as 28" mercury).



If it wasn't efficient, trust me, power companies wouldn't do it.



I have read claims to the contrary. "Turbos need some backpressure" is claimed by some. This simply is not true because it violates thermodynamic laws.



I have witnessed the benefit of a 4" exhaust system and am very satisfied with it.



I live at 5100 feet.

 

[tntway]

i'm with cobra

i have one of ted's 4" systems and i love the sound... . 'nuff said. Oo. Oo. Oo.

 

[Jetson]

I have always intended to get a larger exhaust, but it's still stock. I run 40 psi boost with the stock turbo and stock exhaust. Unloaded, egt's are not a problem. I'm running 275's, a VA box, an Edge Hot 3 box and BHAF. I don't see 40 psi for long because I have to feather it to save the clutch(still stock too). I guess I can't keep waiting for the perfect clutch to be invented. The clutch doesn't seem to slip until I go over 34 psi boost. The exhaust system kept getting put on the back burner because I got so much more bang out of the other mods and didn't see a temp problem.

 

[Maximus]

I have heard that the first 2 feet after the turbo is the most important and should be left with the 3" pipe (not changing the down pipe).



My question is: Is it better to leave it with the 3" down pipe or change to a 4" down pipe?

 

[Royk]

OK, I convinced now I NEED a bigger exhaust. I just put some 12" culvert under my driveway last week and have some left over. I figure I'll put in a 12" exhaust and lower my EGTs to where I have to scrape the frost from my turbo!:-laf :-laf



-Roy

 

[Archive]

Royk... U'll look like "Sparky" going down the road... (I just saw the video clip of KwikKurt pulling the sled. . they got the name right. . )



but that could be the setup for a 12in lift too. . (bigger tires, more shocks, trailing arms, different gears. . it just never ends. . lol...

Bryan