Reduce smell exhaust - Chevy and GMC Duramax Diesel Forum
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post #1 of 12 (permalink) Old 01-08-2020, 10:44 PM Thread Starter
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Reduce smell exhaust

2016 GMC 2500
5 inch flo pro exhaust
full delete kit.

How do I reduce the smell. People tell me just put a CAT on it and it’ll go away others say that won’t help. If the CAT does help can the stock one be put on ? or do i need an AFTERMARKET one put on ? thanks for helping guys my Mom can’t stand the smell. My buddy’s LBZ smells 10x less and it’s deleted and tuned
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post #2 of 12 (permalink) Old 01-08-2020, 11:09 PM
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I left the cat on mine and I dont have any issue with how it smells, even while warming up in the garage.

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post #3 of 12 (permalink) Old 01-09-2020, 07:28 AM
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What's wrong with the smell??? It's DELICIOUS! Diesel exhaust, Nitromethane exhaust, and cutting/grinding/welding steel... the three most wonderful smells known to man.
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post #4 of 12 (permalink) Old 01-09-2020, 10:30 AM Thread Starter
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My Mom hates how potent the smell is because it is very strong compared to my buddies LBZ. This truck idling stinks up the whole driveway garage, etc..
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post #5 of 12 (permalink) Old 01-09-2020, 10:49 AM
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Good luck. I've fought it to no end on my 2012. As far as I can tell, exhaust leaks under the hood cannot be eliminated. When I'm running A/C I can usually switch to recirc and cut down on the fumes a lot but if the A/C gets caught up to the set point the auto mode will just flip it back to fresh air anyway. So sometimes I go to manual mode. And when I'm running heat, I'm just screwed since it won't let me run recirc. I've learned to just run seat heat only with the air shut off down to maybe 35-40 degrees outside. I was running in a stiff wind this morning and got some pretty strong fumes inside at times even with the air shut off.
I've actually contemplated tearing into it to where the fresh air comes into the cab and seal it off. I haven't researched it yet so I don't know if I can go in through the cowl area or if I would have to tear into the dash somewhere.
With all the problems that I won't even begin to list, this exhaust fumes thing is enough on its own to make me want to trade trucks. I'll be watching this one to see if anyone else has any good ideas.

Edit: After re-reading your post it appears you're just looking for a fix for the smell coming from the tailpipe. I could care less about that. I'm just at wits end trying to stop it from coming in the cab while I'm going down the road. Same smell but nothing you do to the exhaust, including a CAT, will help the smell of exhaust fumes coming into the cab since any leaks under the hood are raw, untreated exhaust.

Last edited by blythkd1; 01-09-2020 at 10:54 AM.
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post #6 of 12 (permalink) Old 01-09-2020, 11:15 AM
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Quote:
Originally Posted by jpr10s View Post
My Mom hates how potent the smell is because it is very strong compared to my buddies LBZ. This truck idling stinks up the whole driveway garage, etc..
The cat will help with the smell from the exhaust, however if shes smelling the PVC that wont go away with a cat. Personally i find the smell from the breather worse then the exhaust.

A catalytic converter chemically alters the exhaust as it flows so the output gases are physically different then the input gases. Its not just a filter or something like that.

2015 Chevy Silverado 2500 HD 6.6L LML
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post #7 of 12 (permalink) Old 01-09-2020, 11:19 AM
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Quote:
Originally Posted by blythkd1 View Post
Good luck. I've fought it to no end on my 2012. As far as I can tell, exhaust leaks under the hood cannot be eliminated. When I'm running A/C I can usually switch to recirc and cut down on the fumes a lot but if the A/C gets caught up to the set point the auto mode will just flip it back to fresh air anyway. So sometimes I go to manual mode. And when I'm running heat, I'm just screwed since it won't let me run recirc. I've learned to just run seat heat only with the air shut off down to maybe 35-40 degrees outside. I was running in a stiff wind this morning and got some pretty strong fumes inside at times even with the air shut off.
I've actually contemplated tearing into it to where the fresh air comes into the cab and seal it off. I haven't researched it yet so I don't know if I can go in through the cowl area or if I would have to tear into the dash somewhere.
With all the problems that I won't even begin to list, this exhaust fumes thing is enough on its own to make me want to trade trucks. I'll be watching this one to see if anyone else has any good ideas.

Edit: After re-reading your post it appears you're just looking for a fix for the smell coming from the tailpipe. I could care less about that. I'm just at wits end trying to stop it from coming in the cab while I'm going down the road. Same smell but nothing you do to the exhaust, including a CAT, will help the smell of exhaust fumes coming into the cab since any leaks under the hood are raw, untreated exhaust.

but..... why do you have leaks under the hood? are you sure its not the PCV sitting under your drivers seat venting fumes into the cab? Everything up to the end of the down pipe should be well sealed since the system is pressurized up to the turbo. There should be no leaks on a properly installed kit.

2015 Chevy Silverado 2500 HD 6.6L LML
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post #8 of 12 (permalink) Old 01-09-2020, 11:29 AM
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but..... why do you have leaks under the hood? are you sure its not the PCV sitting under your drivers seat venting fumes into the cab? Everything up to the end of the down pipe should be well sealed since the system is pressurized up to the turbo. There should be no leaks on a properly installed kit.
The smell coming in my vents is the same as the smell coming from the tailpipe. When I had the motor out last summer I inspected all the exhaust joints and didn't see any evidence of leaks. I cleaned them all up carefully and reinstalled to correct torque. I hammered the downpipe into the turbo with a deadblow and torqued the band clamp, repeatedly until the band clamp quit moving.

I know the downpipe/header pipe joint leaks but it doesn't seem like it leaks much, just at the 3 joints in the band clamp. I can see soot tracks coming out the 3 spots between the sections of V-band clamp but don't know what to do about it. I'm assuming that's the leak that finds its way up to the cab fresh air inlet. I have no hard evidence but I don't know what else it could be.

First time I've heard the PCV theory thrown out. I haven't rerouted my PCV. Doesn't it get sucked back into the intake? Where could any fumes be getting out? I'm just questioning because I don't understand, not trying to seem like a doubter.

I'm like Barry Corbin in War Games at this point - "I'd piss on a spark plug if I thought it would do any good!"

2012 3500 4X4 CCLB
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post #9 of 12 (permalink) Old 01-09-2020, 11:33 AM
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Originally Posted by blythkd1 View Post
The smell coming in my vents is the same as the smell coming from the tailpipe. When I had the motor out last summer I inspected all the exhaust joints and didn't see any evidence of leaks. I cleaned them all up carefully and reinstalled to correct torque. I hammered the downpipe into the turbo with a deadblow and torqued the band clamp, repeatedly until the band clamp quit moving.

I know the downpipe/header pipe joint leaks but it doesn't seem like it leaks much, just at the 3 joints in the band clamp. I can see soot tracks coming out the 3 spots between the sections of V-band clamp but don't know what to do about it. I'm assuming that's the leak that finds its way up to the cab fresh air inlet. I have no hard evidence but I don't know what else it could be.

First time I've heard the PCV theory thrown out. I haven't rerouted my PCV. Doesn't it get sucked back into the intake? Where could any fumes be getting out? I'm just questioning because I don't understand, not trying to seem like a doubter.

I'm like Barry Corbin in War Games at this point - "I'd piss on a spark plug if I thought it would do any good!"
oh i figured with the full delete you had done a PVC reroute since its generally included with the kit. If you have not done that then that is not your issue (will make it worse by the way if you do). We do have different down pipes and exhaust flanges on our trucks but i think at the turbo they are the same. I have a whirli down pipe and do not have leaks around it as far as i can tell. What delete kit do you have installed? is it a full Y bridge or just blocker plates?

the weird thing is on your truck im 99% sure the recirculate system is 100% recirculated unlike the newer trucks that always draw in some outside air regardless of the setting.

2015 Chevy Silverado 2500 HD 6.6L LML
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post #10 of 12 (permalink) Old 01-09-2020, 11:41 AM
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Blocker plates. I may have used the term "full delete" a little too loosely.

It seems pretty good on recirc if I could just get recirc selected. It's only selectable in certain conditions. Seems the engineers want to be sure we're getting plenty of fresh air. I'd rather be able to make that call myself.

2012 3500 4X4 CCLB
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