Sigh... an EXHAUSTive topic.

Flea · **Posted:** Sun Oct 07, 2007 8:54 pm

Heh, yeah, went cheesy on the title...

Ok, greetings folks. Long-time lurker, only a couple posts, and owner of a 2006 CRD sport and 2007 Wrangler Sahara. I'm finally getting around to putting an exhaust on my CRD.

I'm going with Magnaflow for the muffler (GREAT history with them on my vehicles), but I'm torn as to SI/SO or SI/DO. I realize there would be a negligible difference between the two in price and (relatively) in installation... but are there any harmful side-effects of duals vs. single? I've heard over the years that some of the Cummins TD and PowerStroke guys actually gain less hp/torque by a wide margin with duals vs. a single pipe.

I'm mainly doing this to get rid of the factory garbage, and to gain a mildly aggressive tone. Power is a plus, but 2-3 hp difference isn't going to hurt my feelings...

-Flea

gmctd · **Posted:** Sun Oct 07, 2007 9:03 pm

In this case, just depends on the available real estate and whether you like the asymmetrical 1 or the symmetrical 2 look - if you're into racing, a single 4" turbo-back system will work

Good title, btw.......................

DarbyWalters · **Posted:** Sun Oct 07, 2007 11:50 pm

Splitting a 4 banger without an "H" pipe will probably sound very weird

Also you will be losing some of the scavenging by splitting the exhaust on a 4 banger into two steams...IMO

I think the CRD would easily handle a 3" freeflow exhaust...but you will have to make it :idea:

retmil46 · **Posted:** Mon Oct 08, 2007 9:42 am

I've heard the same from some of the big truck diesel crowd - that in some cases duals caused you to lose the scavenging effect and actually cost HP/torque. Although in this case, I think they were talking about a full dual exhaust system, not twin tail pipes out of a single muffler. In any case, good luck finding the room to run an extra tailpipe around that fuel tank and rear axle!

If memory serves, some on the list have already built a full 3" exhaust system and reported good results.

As far as the particular model of muffler, ANYTHING is better than that constricted stock muffler. Back when this was a hot topic two years ago, people were reporting good results with just about any brand and type of high flow muffler. Pretty much boils down to your personal preference for quality, looks, and how it sounds.

skywarn · **Posted:** Mon Oct 08, 2007 9:52 am

Go cheep, SI/SO and as straight as poss... the more free flowing the better, and as far as sound goes... you will not hear much diff. as the turbo kill most of the sound anyway. in fact, from what i hear on here if you can go without a muffler then do it.

Im running a manga flow myself and couldnt tell a diff in sound but MPGs got better and the "coasting" increased 100%

gmctd · **Posted:** Mon Oct 08, 2007 10:04 am

Just FYI - the 'H' pipe reduces drone in a two-bank system, such as the right 4cyl bank and the left 4cyl bank in a V8 system - drone results when two cylinders on the same bank fire successively - 1-8-4-3-6-5-7-2 - in this case, 8 then 4 on the even bank, and 5 then 7 on the odd bank.
You can look at a V8 engine as two 4-cyl engines connected at the crankshaft - same for any two-bank engine

No worries in a split-y pipe on a single-bank engine - real estate around the fuel tank is sometimes a problem - 3" single would be sufficient in this 2.8L system, as suggested - 4" for the 'mine's bigger'n yer's' crowd :roll:

boilermaker2 · **Posted:** Mon Oct 08, 2007 10:11 am

There are a couple of threads on this so you probably want to search.

Here is one http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=19397 (Thanks GMCTD)

There is another with a nice pic of a crd with dual cherry bombs on it.

Here is another thread with discussion of straight pipe:
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?p=227403&highlight=cherry#227403

DarbyWalters · **Posted:** Mon Oct 08, 2007 10:20 am

Borla used to make a dual out let setup for the 3.7L forking off the single at the muffler. I think the KISS method would be the best route to go here...

Flea · **Posted:** Mon Oct 08, 2007 7:54 pm

Thanks for the advice, guys

I think (know, rather) I'll probably do something and be unsatisfied, then do it over, then redo the whole thing turbo-back someday. However, being my first diesel, and my first turbo car, I'm kind of learning as I go. I think I'll probably go the single 3" catback route and get rid of that pathetic 2" neck down in front of the stock exhaust, so 2 1/2 in, 3 out si/so...

That is, until I get the mod bug again. I got it with my truck... I went through 4 different exhaust systems (5, if you count stock) from a mild cat-back to open headers before I found something I liked.

Def. going for a 2.5" Rockfather after the baby, then probably wheels/tires, only to install both on the same weekend (probably into spring/summer by then)... One can dream, though, can't one? :wink:

GregScuba · **Posted:** Thu Oct 11, 2007 1:01 am

About six months ago, I cut off the stock muffler and it's bottlenecked sections of pipe up just past the flange, as well as on the muffler outlet side. Then I put in a Dynomax cherry bomb. I needed just a little bit of extension pipe to get to the stock tail pipe from the cherry bomb outlet.

I love it, and am going to leave like this for quite a while. The cherry bomb is much smoother and tucks up out of the way much better than the stock muffler which would tend to get hung up on things off road and get banged up.

This project only took me a little under an hour, and cost way less than $100. Can't hardly beat that for bang for your buck (other than maybe the ORM which is free).

1....... 2.5" inlet/outlet cherry bomb
3........2.5" exhaust clamps
1........2.5" section of exhaust pipe
1........Can of black high-temp paint (for the clamps and the section of added pipe)

Or as they say, a picture is worth a thousand words:

DarbyWalters · **Posted:** Thu Oct 11, 2007 5:06 am

For offroad, putting the muffler as close to the rear axle as possible keeps it safer too...less likely to get hit.

Sigh... an EXHAUSTive topic.

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