You Do Need 4" Exhaust

[Turbo Thom]

I must say in reading these good natured barbs, it seems to me trucks equipped the same do not perform the same left to right coast. What say you Steve Stl?

. . Preston. .

 

[Reddog1]

Does this mean I can avoid the Smog flag prerequisite before serious HP?



Perhaps the left coast air is correct (more smog, including un-burnt fuel?).



From the post I have read, both Ted Jannetty and Joseph Donnelly are well respected on the TDR , even if Ted has only been testing performance parts for 25 years and Joe is only a Chemical Engineer that should have been a Journalist.





Hopefully Joe is right. If he is not, I question just about all of the venders performance advertising I have read. I may have overlooked Jannetty Racing Enterprises stating their performance parts for HP over 200 to 250 must first have a 4” exhaust.





Wayne

 

[TxDieselKid]

andI thought I got them stired up...

Hotdog guys...

I thought I stired up the pot on the cam thread, but you all got me beat by a mile.



AJB

 

[Reddog1]

AJB,



Is that a Texas mile, East Coast mile or a Left Coast mile? Additionally, how do we (not you) know?



Some wise guy once said, “The only thing that is true, is what you and I agree on”.



These guys are doing great.



Wayne

 

[Ted Jannetty]

Diesel Freak, QUOTE; 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.



Boy did you take that one out of context.



Oh Yeah, it would take even less power to turn the Dynojet drum at the same speed.



We test at full throttle on the track and on the hills just like on a dyno.



Don M, I don't want to use the Dynojet because for these trucks it is like testing running DOWN HILL!!!



I am in the process of purchasing a real dyno, that can test these trucks properly.



The Mustang dyno is a good one with the right options.

The Superflow offers one with Eddy current and waterbrake combo for extended testing at steady state, drag race simulation, road race simulation, towing simulation, the possibilities are endless.



But I will still always back up my findings out on the road.



Stephan, see my post in the 24 valve section.



Don M.

Explanation 326 hp vs. 324 hp.

Again; you used a Dynojet, Not enough load, not a real test.



The 4" exhaust will lean the mixture some becuase the turbo works that much better and boost will increase and exhaust efficiency will increase as well which lowers EGT near stock levels.



The idea behind installing the proper size pipe is to support the intended hp.



Keep EGT down and protect our investment.



Fact; you add fuel EGT goes up

Fact; you increase exhaust pipe size EGT goes down.



We want to maintain Air Fuel ratios and make more power at the same time, so increase air flow then add fuel, simple common sense.

 

[Reddog1]

Ted,



All joking aside, I live in the other state (Calif. ). I own a 49 State Ram, w/cat and no EGR.



If HP greater than 200 to 250 requires 4” exhaust, 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 am having second thoughts on spending $1000 to $2000 for BOMBing. I was going for 300 to 350 HP, 200 to 250 is of questionable value.



Ted, do you stand by this statement, “Fact! a 3" pipe can only support 200-250 HP”. Please clarify.





Wayne

 

[Boldt's Wagon]

Does Walker or other manufacturer make a "flow through" 4" x 3" muffler to replace the stock muffler? Or do you have to use 4" or 3" mufflers and a 4x3 adapter?

 

[Cooker]

Boldt's Wagon,

I would get a 4" muffler and an adapter to connect it to your 3" tailpipe. This way if you ever decide to go with a bigger exhaust, you already have the muffler.



I don't know of any performance aftermarket muffler like the 4" in/3" out of the factory.



-Ryan

 

[Brandon]

humor me... if we have no pipe off the turbo then we have no egt...





hmmm now this might go somewhere... .

 

[Joseph Donnelly]

Yeh, I like that.

Lets continue: if 3" pipe is good for 220 hp and 4" is for 300 hp, I guess Sickly needs an 8" pipe. Poor thing just can't run with only 4" exhaust, no wonder it struggles to make 600 hp with such small exhaust.

 

[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.

 

[Power Wagon]

Stefan, that's not necessarily true.



As the exhaust travels back toward through the system, it cools, which means it contracts, which means there's really less of it, and it'll flow through a smaller area with the same restriction.



Having a somewhat restrictive muffler is not as bad as say, having a restrictive downpipe like the early PSD's had.



I know, it's all theoretical, but then so was going to the moon until they did it

 

[Ted Jannetty]

All Kidding aside, 4" will support up to 450 hp.

5" will support 650 hp.

 

[EOliver]

I know the exhaust contracts as it cools, but as it cools it also creates more resistance. Cooler air is much harder to push through a pipe than warm air because of the molecule velocity. This is why the tailpipe should be at least the same size if not the largest part of the exhaust system.



Correct me is I am wrong guys, it has been a while since gas flow lessons... .

 

[chrgr446]

EOliver you are correct sir, the cooled gases are harder to move than the hot ones. Which is why wrapped pipes are popular.



Ted your stuff works Nuf said. (No he didn't pay me to say that) Just a stisfied 8900# drivin' customer, who by the way has had a dyno unable to properly load my engine.



I have a thought on the vaccum created at the elbow. May be the speed and the spinning of the exhaust gases as they come out of the turbos relatively small outlet into the 4" pipe is creating a venturi effect thus a vaccum, which should help to scavange the gases (Like the proper cam in a nomaly aspirated motor) may be this helps to keep turbo rpms up at the shift points, because the turbo is not "fighting" back pressure rather "seeing" a vaccum? (could this explain the boost increase testing has shown?)With any luck the 4" pipe, as the gases cool keeps them from backing up and causing backpressure, at any rate I don't think that it can hurt to have a 4" pipe. I know it has one mean sound!

BTW This thread is one of the reasons I like TDR so much, open debate, and ideas.