The truck has, for lack of a better description, an underwater sound at about 30-35 mph and 1500 rpms. Seems to be sluggish when I press on the gas as well. It's a little better if I turn off the overdrive, but still a problem. Could this be because of the MDS as some have suggested? It is a HEMI as well. Also how about the octane? I tried some booster with little or no change. Any ideas?
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2007 Dodge Ram 1500
Question: Truck sounds/runs worse after install of Magnaflow aftermarket exhaust.
DO U HAVE ANY ENG CODES?
ReplyZimmy58, July 27, 2012, 15:10Rookie
No engine codes. Talked with a maganflow rep and let him listen and he denied hearing/feeling anything different. Forgot to mention that it gets better if I turn off the OD, not 100%, but still better.
Answer #2Chevy Power July 27, 2012, 07:09Journeyman
It sounds like the noise you are describing is a drone type noise. Dynomax just came out with a muffler that has an internal valve to prevent this droning noise. The lack of power could be due to lack of back pressure. Too little back pressure is just as bad as too much. Call Magnaflow and see if they have any suggestions or they may warranty the system for you. Good luck.
ReplyZimmy58, July 27, 2012, 15:12Rookie
The "no back pressure" seems about right. Especially when you step up the RPMs and it runs and sounds better.
Answer #3ziptie12 July 29, 2012, 22:16Master
Sounds like the exhaust change just made an existing problem more obvious. What other aftermarket items (perf. or other) do you have on it? Is the trans going into lock-up to soon? May be worth paying someone to test drive with you and watch live data trans & engine, to see what's happening.
ReplyZimmy58, August 02, 2012, 15:11Rookie
Just a K&N High Flow air filter. As for the trans going into lockup too soon part. I claim ignorance on that part. My experience with vehicles tells me no, but then again Im not 100% certain. Im waiting on a reply from Magnaflow to see what thier take is. If they claim ignorance as well, I know they know that something is going on or there wouldnt be as many posts claiming the same problemas tere is, then I guess I might have to go back to the original exhaust system.
After further contact with Magnaflow here is the answer to my question about the sound and feel of the exhaust on my truck.
"The fuel economy mode which makes a 8cyl engine switch to 4 cyl is what is causing the drone you are experiencing. We don't have a "fix" for it as it is sound cause by what the engine is doing. What we have suggested before is to add a resonator or switch to a larger muffler to help absorb that sound. Some people have gone back to stock exhaust and customers with other manufacturers have turned that fuel saving mode off.
To explain in more specific detail is with the 8 cyl engine the sound waves from the engine detonations are close together. When it switches to that MDS or 4cyl those sound waves are doubling in distance apart. This wave pattern is what is causing the resonance you are hearing at certain RPM's. Dodge manufactured their exhaust to be restrictive to counter act this drone, which impacts performance. When you install an exhaust kit or a muffler that allows for better airflow, your performance will increase, but so will that sound that was dampened by the stock exhaust."
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Replyziptie12, August 04, 2012, 17:34Master
Sounds sensible to me. If dodges MDS is anything like Hondas' VCM-variable cylinder managment , then that would also explain why I thougt it was going into early lock-up , from your original description. Think you got your fix.
Answer #4kyjoe January 10, 2013, 09:31Rookie
If it a hemi its cause the mds is coming on early, and when the over drive is on the mds is turn off and it runs on all 8 not four
ReplyZimmy58, January 10, 2013, 20:32Rookie
kyjoe-Ya, I pretty much run the truck with the overdrive off, which defeats the purpose of going to a highflow muffler, and a high airflow K&N filter for the supposed increase in the MPG's. Thinking about getting a Diablo Predator tuner to just turn off the MDS and then be able to leave the overdrive on, thus my MPG's should rise...so it's believed. However Im on a very restricted budget right at the moment so getting one of these tuners is out of the question at the moment. But it is what it is. Thanks for the reply though..Happy New Year.