LOST JEEPS :: View topic - To muffler or not to muffler, that is the question.

In the early years mostly on gasoline engines, back pressure was taken advantage of to reduce the stress on the connecting rod cap bolts during the exhaust stroke. To allow the engine to run better, carburetor jets were sized to compensate for the flow through the engine. Change the exhaust, the carburetor had to be modified from stock to allow the engine to run properly.
Early naturally aspirated Diesels used the same trick to help reduce the stress on the connecting rod cap bolts during the exhaust stroke.
Add a turbocharger, you have the internal back pressure that drives the turbocharger. As far as the connecting rod cap bolts are concerned, they don't get yanked on when the piston goes up on the exhaust stroke. In fact some engineers have gone through the stress calculations and found that if you could remove the connecting rod cap bolts with the engine running, there would be enough pressure on the upper journal to allow the engine to keep running.
Conclusion: With a turbocharger, you don't need exhaust system back pressure to hold the engine together, the turbo provides enough. Get rid of the back pressure which is USELESS with a turbo diesel, your turbo boost will clime faster and you will move more air through the engine and lower the EGT. Many of us have found out that opening the exhaust up to 2 1/2" CAT back provides optimum performance. Whe I ran a gauge between the turbo and cat, I would get as much as 5PSI when towing. After I opened up the Exhaust to 2 1/2" the back pressure dropped to 0.0PSI.
Conclusion: Opening up the exhaust and getting rid of the BEAN COUNTER ENGINEERING stock muffler is the CHEAPEST way to get quicker boost with out shelling out for a more aggressive turbo.
True, someone can always come up with a turbo (turbo manufactures love to sell them) that will give more boost and remap the ECM (tuners love to give you that magic fairy dust flash), but when you can do something in between the crappy doggy stock muffler and hanging on a turbo kit that will also provide thrust out the tail pipe like a jet engine, opening up the exhaust has more bang for the fewest bucks performance upgrade.
Besides, if you go with the turbo kit that also provide Jet Engine thrust, you better have an engineered exhaust system bigger than 2 1/2" and have the discharge of the exhaust in the middle so it does not effect handling, you don't want to swerve into oncoming traffic. :ROTFL:

Author:	andytom [ Tue Jul 13, 2010 5:41 pm ]
Post subject:	To muffler or not to muffler, that is the question.
Hello all, I'm looking to change the stock muffler but do not know quite what I want. Does anyone have any links to sound clips or general comments on good mufflers or using a straight pipe? I have seen posts about this but am looking more for specifics. Thanks.

Author:	stoutdog [ Tue Jul 13, 2010 5:56 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
Well, I run the Magnaflow #12226. I can say that it sounds a little more throaty at idle, but is otherwise very close to the stock sound. Some have a straight pipe and love it; some have a straight pipe and say that the noise/rattle is too much for them. Another factor to consider is that many states require a muffler to be there for your visual emissions test... check with your DOT. Some links/clips: http://liberty.eurekaboy.com/magnaflow.htm http://liberty.eurekaboy.com/magnaflow2.htm http://liberty.eurekaboy.com/tailpipe.htm

Author:	Joe Romas [ Tue Jul 13, 2010 6:47 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
The first thing you want to do to your exhaust is to relieve the restriction of the joint where the cat and muffler bolt together

Author:	racertracer [ Tue Jul 13, 2010 7:41 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
Unload that restrictive stock Muffler ASAP and repalce it with a 2 1/2" diameter one. You wont believe the performance increase and how quiet the engine becomes.

Author:	LibertyCRD [ Tue Jul 13, 2010 8:02 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
I heard a lot of stuff about the "restrictive" joint at the OEM muffler. Personally, I don't see how on Earth that joint could be restrictive enough to make a difference. Therefore, I left my OEM flange joint IN PLACE so that in the future, any upgrades to other cat-back systems would be a 10 minute job. The OEM flange joint = convenience and flexibility....and I like that. The straight pipe is "ricey" sounding...generally does NOT sound good at the tailpipe...however it is not very loud. I don't notice it much at all in the cabin. It did open up my ability to coast to redlights more. I have seen zero increase in fuel economy from it. I have seen a little increase in power...but once the ECU "learned" that it was straight piped that increase became less noticeable. All in all, for $35 the straight pipe is the best option for the KJ.

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To muffler or not to muffler, that is the question. http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=54241	Page 1 of 2

Author:	CRD Joe [ Tue Jul 13, 2010 9:29 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
At first I just did a 2.5" cat back with no muffler. I noticed a drop in torque because of a loss of back pressure. After a while I added a small muffler.

Author:	GreenDieselEngineering [ Tue Jul 13, 2010 10:18 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
Exhaust backpressure is calibrated into the KJ CRD. When the backpressure after the turbo is lowered with a straight pipe or less restrictive muffler it will cause changes in how the turbo governs boost pressure. The turbo governing system has an open loop control with a closed loop PID governor working on top of the open loop. Let's say you are cruising at 70mph: The open loop will have the vanes set at a 55% duty cycle, which sets the vanes at about half open. The open loop typically never provides the exact boost pressure the system is requesting so the PIDs go into action and adjust the vanes more closed or more open until the set point boost is reached. With less backpressure the I-part (integral) will load up more than normal and have the vanes more open due to the greater pressure differential before and after turbo. In cruising this is not an issue, but if an accel is necessary it will take more time for the vanes to close and build more boost due to the loaded governors. This may give the feeling of less torque for a bit, but it should recover. Ideally, if the backpressure is loaded the turbo open loop should be remapped to compensate. In general terms, more open vanes reduce backpressure making the exhaust flow out easier and a slight increase in fuel economy. In reality, tuning the combustion process to be more efficient is a much more effective way of gaining fuel efficiency.

Author:	warp2diesel [ Wed Jul 14, 2010 12:11 am ]
Post subject:	Re: To muffler or not to muffler, that is the question.
In the early years mostly on gasoline engines, back pressure was taken advantage of to reduce the stress on the connecting rod cap bolts during the exhaust stroke. To allow the engine to run better, carburetor jets were sized to compensate for the flow through the engine. Change the exhaust, the carburetor had to be modified from stock to allow the engine to run properly. Early naturally aspirated Diesels used the same trick to help reduce the stress on the connecting rod cap bolts during the exhaust stroke. Add a turbocharger, you have the internal back pressure that drives the turbocharger. As far as the connecting rod cap bolts are concerned, they don't get yanked on when the piston goes up on the exhaust stroke. In fact some engineers have gone through the stress calculations and found that if you could remove the connecting rod cap bolts with the engine running, there would be enough pressure on the upper journal to allow the engine to keep running. Conclusion: With a turbocharger, you don't need exhaust system back pressure to hold the engine together, the turbo provides enough. Get rid of the back pressure which is USELESS with a turbo diesel, your turbo boost will clime faster and you will move more air through the engine and lower the EGT. Many of us have found out that opening the exhaust up to 2 1/2" CAT back provides optimum performance. Whe I ran a gauge between the turbo and cat, I would get as much as 5PSI when towing. After I opened up the Exhaust to 2 1/2" the back pressure dropped to 0.0PSI. Conclusion: Opening up the exhaust and getting rid of the BEAN COUNTER ENGINEERING stock muffler is the CHEAPEST way to get quicker boost with out shelling out for a more aggressive turbo. True, someone can always come up with a turbo (turbo manufactures love to sell them) that will give more boost and remap the ECM (tuners love to give you that magic fairy dust flash), but when you can do something in between the crappy doggy stock muffler and hanging on a turbo kit that will also provide thrust out the tail pipe like a jet engine, opening up the exhaust has more bang for the fewest bucks performance upgrade. Besides, if you go with the turbo kit that also provide Jet Engine thrust, you better have an engineered exhaust system bigger than 2 1/2" and have the discharge of the exhaust in the middle so it does not effect handling, you don't want to swerve into oncoming traffic.

Author:	Cowpie1 [ Thu Jul 15, 2010 11:38 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
Gotta side with warp2diesel on this one, on just about every one of his comments. Pittsburgh Power has done a lot of research on backpressure in modern diesels. Increased backpressure causes a slowing of exhaust gasses such that it increases EGT's at the turbo. Not good The idea with diesels is to get that exhaust out as quickly as you can to gain maximum performance and fuel economy. Many owners of larger diesels in semis, including me, have "opened" up the exhaust and have experienced faster turbo spool ups, lower EGT's, better performance, and decidedly better fuel economy. For instance, my Cummins 435ST in my big truck now will pull loads up the hill right along with higher horsepower engines with stock exhaust systems. My Cummins is rated at 435 HP / 1650 lb torque, but will walk up a hill right along with 450's and 475's, with all of us pulling roughly the same payload weights. Meanwhile, while experiencing 100-200F lower EGT's than before opening up the exhaust. Also, my overall fuel economy on the semi has gone up roughly 13%. I do have to watch out where I engage the Jake brake though... it is not a good idea to be along side my stacks when the jake comes on. Straight piped Harley's have nothing on me. This led me to cut off the cat on my CRD, put a 2.5" pipe in place of it, go with a 2.5" dynomax flow thru and 2.5" tailpipe. Results are better than stock and only cost a total of $180 in parts. I do not have to experience such things as emissions inspections in Iowa. For those that do have to deal with this, just gut out the cat to get the same effect. Even if one decides to shell out the cash for performance upgrades like ECM tunes and Turbos, opening up the exhaust would be needed to really get the full benefit of any other upgrades. And it offers just about the best bang for the buck as far as modifications go and is a good place to start. warp2diesel wrote: In the early years mostly on gasoline engines, back pressure was taken advantage of to reduce the stress on the connecting rod cap bolts during the exhaust stroke. To allow the engine to run better, carburetor jets were sized to compensate for the flow through the engine. Change the exhaust, the carburetor had to be modified from stock to allow the engine to run properly. Early naturally aspirated Diesels used the same trick to help reduce the stress on the connecting rod cap bolts during the exhaust stroke. Add a turbocharger, you have the internal back pressure that drives the turbocharger. As far as the connecting rod cap bolts are concerned, they don't get yanked on when the piston goes up on the exhaust stroke. In fact some engineers have gone through the stress calculations and found that if you could remove the connecting rod cap bolts with the engine running, there would be enough pressure on the upper journal to allow the engine to keep running. Conclusion: With a turbocharger, you don't need exhaust system back pressure to hold the engine together, the turbo provides enough. Get rid of the back pressure which is USELESS with a turbo diesel, your turbo boost will clime faster and you will move more air through the engine and lower the EGT. Many of us have found out that opening the exhaust up to 2 1/2" CAT back provides optimum performance. Whe I ran a gauge between the turbo and cat, I would get as much as 5PSI when towing. After I opened up the Exhaust to 2 1/2" the back pressure dropped to 0.0PSI. Conclusion: Opening up the exhaust and getting rid of the BEAN COUNTER ENGINEERING stock muffler is the CHEAPEST way to get quicker boost with out shelling out for a more aggressive turbo. True, someone can always come up with a turbo (turbo manufactures love to sell them) that will give more boost and remap the ECM (tuners love to give you that magic fairy dust flash), but when you can do something in between the crappy doggy stock muffler and hanging on a turbo kit that will also provide thrust out the tail pipe like a jet engine, opening up the exhaust has more bang for the fewest bucks performance upgrade. Besides, if you go with the turbo kit that also provide Jet Engine thrust, you better have an engineered exhaust system bigger than 2 1/2" and have the discharge of the exhaust in the middle so it does not effect handling, you don't want to swerve into oncoming traffic.

Author:	FastSRT8GC [ Fri Jul 16, 2010 6:00 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
Sound clip http://www.youtube.com/watch?v=8VYhC8tfVvc

Author:	flash7210 [ Fri Jul 16, 2010 10:14 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
No muffler on mine and I think its great! I unbolted the cat-back and bolted in a short pipe that dumps out the side in front of the RR tire.

Author:	NJCRD [ Sat Jul 17, 2010 2:35 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
I side with warped. Cheapest bang for the buck. Try it straight and if you don't like it you can always put a performance muffler on. I'm straight piped for years and love it.

Author:	theirishman [ Mon Jul 19, 2010 1:02 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
Howdy. Has anyone tried a verticle pipe, as on a duece and a half? Pictures please.

Author:	salden77 [ Mon Jul 19, 2010 4:21 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
im straight piping mine this week if i have time, i disconnected it after the cat. for now for the extra power, i dont mind the sound at all, the louder the better, that is why i bought a diesel

Author:	evolDiesel [ Tue Sep 21, 2010 6:38 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
Mine sounded like a Johnson (boat engine) and WOT can only be compared to the scene in Team America where Gary pukes his brains out. Seriously. I was waiting to hear nuts and bolts fly out the tail pipe Speaking of Johnson if you're having a bad day at work this will cheer you up: http://www.youtube.com/watch?v=fxVH5sKUlPg

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Author:	evolDiesel [ Tue Sep 21, 2010 4:44 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
I ran straight pipe (stock CAT & Muffler delete) for 6 months. The first couple days were obnoxious. But then I got used to it. Had some fun with it. Then I did a couple LONG interstate trips. That sucked. The drone was brutal on the long trips and to be honest the sound, while menacing and head turning, really didn't have a… uhhh… “inspiring tone”. So I put a Magnaflow PN 12226 in it last night (no CAT). It basically sounds stock until you get on it, and even then it's nowhere near the apocalypse that was the straight pipe at WOT

Author:	salden77 [ Tue Sep 21, 2010 6:08 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
if you do not care about how loud your diesel is like me then straight pipe it, it is loud but it sounds sweet, i cut my cat off too, the turbo is way louder now too, i love the sound, people come up to me and say wow sweet jeep i cant believe its boosted, can we video tape you doing a run and loading the engine so i can hear the turbo, or omg i have never seen a jeep turbo diesel thats so sick!

Author:	SpaghettiCRD [ Tue Sep 21, 2010 10:20 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
I straight-piped my `06 and I LOVE it. The sound isn't too loud. My muffler guy thought it was going to be unbearable, but he was amazed how mild it was. Definitely the best mod for the price ($50.) I highly recommend it. It feels like it has more pep. It's been straight now for... 10,000 miles or so. NO complaints. DO IT!

Author:	evolDiesel [ Fri Oct 15, 2010 12:57 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
Troy from SWAG Offroad just showed me this... cake and eat it too ? ? http://www.pertronix.com/prod/new/details.aspx?ID=137

Author:	warp2diesel [ Fri Oct 15, 2010 4:06 pm ]
Post subject:	Re: To muffler or not to muffler, that is the question.
As covered before in previous posts. I put a pressure gauge in my head pipe between the turbo and cat and tested under various driving conditions including towing a 6,000# trailer load. It does make a difference in back pressure under all of the conditions I tested. Just another Pesky Law of Physics, may Sir Isac Newton Rest in Peace. Unlike CARB, I run my tests to determine the truth, report what I find weather I like it or not, and would even testify before Congress with the test results. That is if they would even care about a the restriction of a Bean Counter Engineered 2 1/8" ID flange and crap muffler between two 2 1/2" pipes. If they did care, there would be a Political Commercial on TV Challenging my test findings and how this would effect the outcome of their political agenda. When you Vote with your wallet, vote for the configuration that provides you the most freedom. Since the Stock Muffler is the most restrictive with the 2 1/8" choke flange on the cat, it offers the least freedom and exhaust system Liberty. Some locations do not offer the freedom of the straight pipe, so putting on a full flow muffler is the next best thing to do.