View Full Version : how restrictive is the stock muffler?
10-05-2005, 06:57 AM
I have an 05 and was considering upgrading the intake to something like a BHAF or similar. Would I be wasting my time if I left the muffler stock?
10-05-2005, 08:59 AM
The stock Dodge, or Ford and GM mufflers for that matter are very restrictive, we have one of each laying around that we cut open years ago, it's amazing to me that the trucks run as well as they do stock! They have louvers in them as small as 1/8th of an inch, three chambers that are blocked off with only 1 2-2.5 inch pass thru etc etc. The best part is if you get a good muffler to replace it with the sound level still stays nears stock on a diesel! Do a search here on replacement mufflers you'll get a ton of info. If you have any questions just call us up, we'll be glad to help!
Mark @ DPPI
Actually, I disagree....I replaced the stock muffler with an aftermarket unit and the only result was a noisy roar....after 3 weeks I replaced the stock muffler and the truck ran better...more low end torque that was lost with the aftermarket unit...
I have been told that this is because I have no other mods....
10-05-2005, 09:36 AM
The stock muffler on the 05 from the cat back flows 320cfms. Increase that and you can gain a little.
10-05-2005, 01:09 PM
EKUGrad. By putting on a better airbox or even just replacing the stock air filter with something better will only help. It will allow the motor to get more air which should lower your EGT's down a little. But granted, replacing the stock muffler will make the intake upgrade that much better as now it has a place to go.
Gauges should be the first purchase as then you can get a good baseline of what the stock truck can do.
10-05-2005, 05:51 PM
Thanks everyone for the responses. I really don't want to do any big mods, was just thinking about the fact that I get a good deal of black smoke when I romp on it on exit ramps and was wondering if this could be corrected (some) by getting more air flow.
10-05-2005, 09:32 PM
will reducing backpressure on a diesel cause a loss of low-end tq like on a gasser? The line between too much and not enough is a fine line isnt it??
10-06-2005, 03:14 AM
On my 03 installing the AFE stage1 setup did nothing for MPG.When I replaced the exhasust with the full 4 inch from Banks including the turbo down pipe it was a INSTANT increase in MPG.About 1.5 or 2.Rest overhead and on first test drive with new exhaust I got better mpg the I ever saw previous.
10-06-2005, 03:41 AM
Diesels don't need backpressure like a gas engine.
10-06-2005, 03:47 AM
May not need back pressure but too LARGE of a exhaust reduces power with out the h.p. to back it up.This has been hashed and discussed many times on several forums with dino results showing the same findings.
10-06-2005, 08:07 AM
You're correct, you have to add intake air if you free up the exhaust air. Doing one without considering doing both is a mistake overall for MPG and EGT drop. If all you do is add something like our MBRP replacement muffler that sets you up with the stock 4 inch pipes to create a pretty good 4 inch system and don't get more air in the intake side you sort of creating a suction that can't be satisfied. I haven't ever heard until today of anyone losing power or bottom end by just replacing the muffler. We have sold hundreds of the MBRP replacement mufflers for the 3rd gens and have had nothing but reports of EGT drop, spool up times decreased and nicer exhaust tone etc.
Mark @ DPPI
Actually, the biggest reason I removed the aftermarket muffler was the noticeable decrease in low end power...I added the muffler as the ONLY modification, with no intake air box change (may have been a problem).
I noticed that the power seemed to increase at 70 mph but off the line is was a real dog.
After I put the stock muffler back on, my low end torque came back.
10-06-2005, 05:28 PM
Well if memory serves me correct the STOCK exhaust(maybe just the muffler)flows 300 and some CFM. The muffler I use was advertised to flo 900+ cfm. lots of straight piped trucks out there.Never heard of any mention of loos of low end/low speed power with a muffler delete or a more free flowing one.
10-08-2005, 12:54 AM
now correct me if I'm wrong, but a turbo diesel is an entirely different animal than a naturally aspirated gasser. With the turbo in the loop the backpressure is a mute point because you are compressing air into the engine mechanically. The only thing you have to keep in mind is the velosity of the air moving through the turbo. So with that said if you open up one end you have to open up the other to get the full benefit. I suspect the loss of low end power is a result of the turbo having to suck through a smaller straw with less force on the turbine because of less pressure on the exhaust side causing a slower spool up. Just my way of looking at it. Hope it gets you thinking.
10-08-2005, 06:39 AM
I suspect the loss of low end power is a result of the turbo having to suck through a smaller straw with less force on the turbine because of less pressure on the exhaust side causing a slower spool up.
a turbo on a diesel will spool best with 0 restriction on the exit of the turbine. the greater the pressure differential across the turbine housing, and the more heat you feed the turbine, the quicker it will spool. i don't believe the loss in spool has anything to do with the restriction it self, but could very much be due to the temprature decrease when having a non restrictive exhaust. having a insulating blaknet around the turbine housing and on the exhaust manifold will make the charger spool [a little] better
10-13-2005, 08:36 AM
Im in the same boat as the gentleman who started this thread.
Iv installed a Airraid JR kit on mine shortly after I got it.
I would like to change the muffler or straightpipe but dont want to increase the noise level inside the cab.
How much of a noise level increase would there be with an aftermarket :confused:
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