6.7L Cummins Forum

I have a 2007 6.7l dodge. I am thinking about putting a dpf exhaust back on it. I am wondering if I will gain lower exhaust temp by putting 5" instead of 4" from the particulate filter back. And will I also gain more horsepower using 5" instead of 4". Any and all input is appreciated.

People say there are no gains from replacing the pipe after the DPF.

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2007.5 Dodge Ram 3500 HD,QC, 6.7L Cummins, 6speed Auto, 4X4, Bighorn Edition.
Click for installs: Carr Steps PML Diff Cover Edge Juice with Attitude Volant Intake Hankook ATM RF10

I had no gain.

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2008 Dodge 2500HD 6.7L 4X4 Laramie
Edge insight, Amp tailgate step, 4" Boss Bars, rear air bags with compressor, spray in bed liner

Controversy. If you lower the EGT on a unit that runs a DPF wouldn't that be detrimental to the way the system is designed to operate? If the EGT is lower by the means of removing restriction (larger dia. pipe work) wouldn't the ECM tell the system that it needed to add more heat to the DPF to keep it from clogging, sort of forcing the re-gen? I could understand if the DPF was removed and the sensors were tricked not to see it in the system there may possibly be a gain by lowering the EGTs. Just asking, curious minds want to know, because lowering the EGTs in this system would possibly cause you to use more fuel to keep the temps up.

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07.5 3500 Quad, SRW, 4X4, Laramie, Leathered, Dark Metallic Gray, 6.7, 68RFE, 20K Reese, Ride Rite's, 2 Viair air compressors, Bully steps, Kleinn Locomotive air horns (5 in all), Billet polished locking fuel door, 'A' pillar mount Auto Meter Pryo, PML X-deep trans pan
06 Durango 285 RL 5'er Lifted by KZ

We sure have learned a lot when it comes to the DPF and EGT's. Heat is your friend!

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2007.5 Dodge Ram 3500 HD,QC, 6.7L Cummins, 6speed Auto, 4X4, Bighorn Edition.
Click for installs: Carr Steps PML Diff Cover Edge Juice with Attitude Volant Intake Hankook ATM RF10

So I gather from you all are saying that it would basically be a waste of money to put 5" exhaust back from the dpf and will not lower my egt's and maybe cause me some problems with the dpf and regen. Thanks for all your info. My goal was to be able to possibly lower my egt's somehow and remain legal here in cali. I pull a 20,000 fifth wheel trailer occasionally and have always thought it was best to keep egt's low as possible. But I am knew to dodge cummins and the dpf thing. I have been using an older ford 7.3l powerstroke with no emmissions crap on it to this point. But bought this dodge truck cause I really needed a 1 ton dually to pull my trailer.

You don't really want to have low EGT all the time. The heat (from like towing or hard driving) is what burns up the particulates in the DPF and you would have less Regen. That is what Regen does; raise's the EGT.
I would not say the 5" pipe has lowered my EGT, it has stayed the same; but is does sound better. I would say the the 5" pipe alone has had little effect but with the new air cleaner I would say I have noticed a difference.

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2008 Dodge 2500HD 6.7L 4X4 Laramie
Edge insight, Amp tailgate step, 4" Boss Bars, rear air bags with compressor, spray in bed liner