Engine/Transmission (1998.5 - 2002) Exhaust Restrictions

[TJMIV]

Just trying to figure out how much good the 4" exhaust does when it appears that there is a restictions in the down pipe from the turbo. I just re-read Joe Donnelly's article in issue 41 about air+fuel=power and it appears that you would have to change out the exhaust housing to a 16 sq. cm. and larger down pipe to get the most bennefit. Sorry for such a long post guys, but I am intersted in the 4" system & the downpipe seems to defeat the purpose. Am I better off changing out the housing & the downpipe & if so where can you buy these parts & pieces or who is the best person to point me in the right direction!

 

[HeavyHauler]

I've read that the turbo downpipe is actually the primary restriction regarding power that you can have from a stock motor. I really don't see any point in upgrading the exhaust if you're not going to add a "high-flow" downpipe too. It seems to me that you're not really going to benefit much if you don't have the downpipe too. I think Piers makes a pretty good one. I've been thinking about getting one myself but keeping my stock exhaust.



http://www.piersdiesel.com



I think most all aftermarket part manufacturer's make one but this is probably the one that I would buy.

 

[Mark Craig]

Exhaust Options

TJMIV,



Ncostello is correct as are the others here, to get max benefit you need to have a true 4 inch outlet etc. For most folks it's a difference that is pretty minor though. The difference for a typical member with say an EZ or maybe Super Chips tuner and an exhaust and air intake is way sufficient to lower the EGT's to a safe level and increase flow get the additional HP etc.



Now if youre going to really BOMB it with injectors and COMP box or maybe even more and you're going for all the HP available a true 4 inch outlet housing would be the best way to go.



What I'm attempting to say is you will get large EGT drop with a stock housing and a good flowing 4 inch system, you'll get some hp and torque, the turbo will spool up sooner etc etc all with a stock housing. For most folks thats all they need, if you're going for broke HP wise then a change is wanted and in some cases necessary as well. Call us if you need any more info.



Mark @ DPPI

 

[RustyJC]

I'm running the stock HX35-W/12 turbo with turbo-mounted Jacobs exhaust brake, so I'm pretty well stuck with a 3. 5 inch outlet to the downpipe. During one weekend, I installed the Edge EZ (with its boost elbow) and a Jardine 4" exhaust system. These two mods lowered maximum EGT's when towing our 13,500 lb 5th wheel from 1300 degF to 1100 degF.



Unfortunately, most of this temperature reduction came from the increase in boost from 22 PSIG stock to 30 PSIG with the EZ and boost elbow. I'm sure the 4" exhaust system, even with the initial restriction at the turbo/exhaust brake and the downpipe inlet, made some lesser contribution to this EGT drop, but since both mods were done simultaneously, I can't quantify how much.



With the recently added DD2 injectors, exhaust mass flow will increase enough to help justify the 4" exhaust system, although at around 330-340 rear wheel HP, I'm still not at the 4" required power level. Running stock or with a mild box alone, however, I'm not sure the 4" exhaust will really stand up to a stringent cost/value analysis in comparison to a stock system with the muffler removed. It's like most things on our trucks, I guess - most of us buy a 4" exhaust system because we want it.



Rusty

 

[Boondocker]

exhaust

So Rusty, how do you like the SOUND of the 4" exhaust compared to stock? Surely BOMBing isn't all about power and performance?



I'm hoping that a reasonable EGT decrease, 100-200 degrees, as motor protection, would be enough to justify the cost. The truth is, I want a bigger exhaust for the sound. At least from outside the truck, bigger pipes sound better to me, I've never heard it from inside though.



I have a new exhaust brake on my stock HX35 turbo that I don't want to mess with, so the whole downpipe issue is mute.



Cheers,

Neil

 

[RustyJC]

Overall, I like the sound of the Jardine system - compared to a stock system with the muffler removed, it's certainly quieter, but with more of a bass sound. You don't get as much turbo whistle at the exhaust tip as with the stock demufflered system. In other words, a little louder and quite a bit deeper sound than stock, but it doesn't set off car alarms or rattle the neighbors' windows.



The bad news is that the system has a drone in the 2100-2400 RPM range. When towing our 5th wheel (the primary use of our truck), 70 MPH = 2350 RPM. The drone can be pretty tiring after hours on the interstate. I guess I'm disappointed since I e-mailed Jardine asking if a resonator was available to cut the drone, and I never received a response.



Rusty

 

[TJMIV]

Thanks HeavyHauler,RustyJC,&MarkCraig for your experience & knowledge in this matter. By the way Mark, I see that you responded to both post that I had on this issue thanks. Basically I did`nt know what to ask to get the answers I needed, that`s the reason for 2 post` on the same subject. Mark, I just looked at the products on your web-site last night and will be in touch when I do whatever it is that I`m going to do!

 

[OTRPU]

I was running high EGTs, changed two things so don't know which was the cause for sure, but after installing the 4 inch exhaust and cleaning the aFe filter element my EGT's dropped from 1,500+ to 1,250. Everything else pretty much stayed the same. They added a new fan clutch and o-ring seal in the vacuum pump at the same time, but I attribute the change to the air going in better and getting out better.



Cheers,

Steve J.