tobyw

Hello DTR! After a several year hiatus, I am back in the diesel truck game, this time with a 2012 Megacab Laramie. When I picked it up a couple months ago, it was bone stock with ~59k miles. It rolled over 61k last week, and I went ahead and installed a Sinister EGR and throttle valve delete, as well as a Flo-Pro downpipe and DPF/cat delete pipe going into the stock muffler. I'm using an H&S Mini-Maxx for now.

My issue is that I've now got a very audible hiss from the tailpipe, and the exhaust smell is atrocious. It reminds me of the old John Deere we had on the ranch growing up, and while I can appreciate the fond memories it induces, the smell is NOT what I was after getting back into a diesel pickup... Are either of these things common with an EGR/DPF deleted Cummins? When installing the Mini Maxx for the first time, it specifically asked if the DPF was still present, but there was no mention of disabling the EGR functionality? Is that normal? I don't have any error codes or anything and it seems to run fine, but the hiss and smell are making me seriously consider going back to stock???? I appreciate in advance any input or ideas on what to check.

Busboy

The "hiss" from the tail pipe is normal with the exhaust brake on, the mini max commands the brake to a more closed position than stock. The exhaust smell is not normal and I suspect it will be the inboard nut on the rear blocker plate that is thread bound. Take the nut off and add a washer or 2 under the nut then tighten it back down. Don't even think about going back to stock.

tobyw

AWESOME tip on the threadbound nut, THANK YOU!! I will check that out and get back to you on the results!!!!!

Interesting note on the exhaust brake, that is exactly what the noise emulates. So the H&S programming "drags" the exhaust brake at idle all the time, even when fully warmed up? Any idea what the theory is behind that?

6.7L MegaCab

When you enable the exhaust brake, if the engine coolant temp is below 160*F (or close to that temp), the VGT will be commanded to a semi-closed position when the truck is in park. This is to enable quicker warm-ups. The will happen with or without a tuner. With the tuner it is closed slightly more as Busboy indicated.

With cruise control, you can set a high idle while in park. Just turn it on and set it as you normally would. With the engine brake on and high idle, it will sound like a jet engine...at least that's what I think. It can be quite loud.

Congrats on the new to you truck!

tobyw

Thanks for the info, wasn't aware of the cruise control high idle feature?! Pretty cool, I'll have to check that out once it cools off around here!

Just to be clear though for the sake of discussion, my exhaust does hiss without the exhaust brake engaged, and at full operating temp.

6.7L MegaCab

My truck has a slight hiss to it as well. I think it's just because of the exhaust flowing freely and the turbo is a VGT...never researched though, just my own assumptions.

I also removed the baffle in the factory intake, which I think plays into that as well.