Exhaust without a tune

[Jakezed22]

now i know what your thinking, "this guy must be on crack!" but hear me out.

Has anyone tried to install an after market exhaust without a tune?

I’ve heard of this being done without setting codes.

I tried last night to unbolt the exhaust just in front of the dpf and went for a drive.

Ran fine with no codes. still running fine with no codes or lights.

Next I’ll try running it with the sensors out of the exhaust bit still plugged in and see how that goes.

If all good there’s no reason why the truck shouldn’t run fine with a straight exhaust.

at this point its looking like we can run them with the dpf off but still have the sensors plugged in. which sounds crazy but im literally doing it so prove me wrong.

 

[hondarider552]

LOL don't try to reinvent the wheel please.

 

[clrussell]

It won’t work. Period. The computer is smarter than than you.

 

[Jacy_dzlguy]

:violin::didimiss:::happy:

 

[Dirtymaxx03]

i did this to my lb7 a decade ago

 

[Jakezed22]

okay yes its pretty easy to say it wont work, but i dont think you read my post, im literally driving around right now with the dpf disconnected.

an lb7 would be fine it doesnt have dpf or scr

i want this to be a technical discussion not an argument.

reasons so far i think itll work.

-as long as the differential pressure sensor doesnt detect a plugged dpf itll never regen, it will just think the exhaust is clean.

the nox sensors for the scr system just measure nox in the exhaust, so if they are just sitting in open air they will detect no nox and the scr will inject def fluid accordingly.
-or keep them in the exhaust and let it inject def fluid into open exhaust/ or possibly run the injector to the def tank so it just puts it there - problems with this will be if the computer has a code that will set for scr efficiency, but if it does it should be set right now with half my exhaust off.

the three egt sensor just measure temp, if it never goes into regen they never need to see a huge change in temps.

this isnt reinventing the wheel, emissions systems arent that complicated, it just a few sensors and metal pipe.

 

[Jakezed22]

id also like to state that i do agree, theres no way this should work.

 

[clrussell]

IM literally saying it won’t work. I read your post and it doesn’t mean shit because the dpf is unbolted.

Spend your money and put exhaust on it without a tune. You’re wasting yours and our time.
It’ll have to be tuned or returned to stock period.

If it would work everyone would be doing it.

Have fun, I’m done here.

 

[Jakezed22]

nobodys doing it because everytime someone tries your here to shut them down.

you give zero reason to why it wont work

how can you possibly sit there and tell me it wont work to unbolt the dpf when the dpf is unbolted and working.

 

[zakkb787]

It’ll run fine till it figures out the reading are screwy then you’ll be locked in limp mode. Be prepared.

 

[JoshH]

If you look at the data, it will have a parameter for miles since last regen. If it gets to a certain point without doing a regen, it will know something is wrong. There may be other things that it looks at as well, but I know they look at that.

 

[Jakezed22]

i would expect it to, ill run it for at least a week and see. when the light comes on ill update this.

 

[Jakezed22]

If you look at the data, it will have a parameter for miles since last regen. If it gets to a certain point without doing a regen, it will know something is wrong. There may be other things that it looks at as well, but I know they look at that.

This is the kind of info im looking for, do you know what dtc's are related to this?

 

[Jakezed22]

Scrolling through the dtc index i dont see a code for regen interval.

i do however see a few for scr efficiency which over time should show up and start a count down.

 

[2004LB7]

The computer doesn't just look for back pressure to start a regen. It also goes by miles. Don't remember what it is but I think it was in the neighborhood of 700 or so.

When it does go in to regen that is when it will detect it is way off and set your CEL and send it into limp mode

Others have tried it before you. Exhaust tunes would be non existent if you where right

 

[Jakezed22]

Thats unfortunate, do you know which dtc is for that interval?

agreed

yes i was talking with a few guys that have done it, they reported all is good. i will ask one of them how many miles hes put on like that.

 

[Chevy1925]

How many miles and key cycles do you have on the truck thus far? how much city and highway driving?

 

[IdahoRob]

Thats unfortunate, do you know which dtc is for that interval?

agreed

yes i was talking with a few guys that have done it, they reported all is good. i will ask one of them how many miles hes put on like that.

There isn't a DTC for this that efi live or HP tuners can see. What year truck do you have?

The LML will hit 700 miles and try a regen, it doesn't matter the soot grams. I have tested this. If the regen isn't successful (reducing soot grams) which happens if the dpf is unbolted, then it will throw codes.

I have unbolted the DPF at the drag strip for testing and found the same, no codes for short durations.

I often thought of doing a "y" pipe and let the exhaust go through both the dpf and the open exhaust side. I never tried it to see if something like that would work to satisfy the ecm, just was a thought.

 

[Jakezed22]

not much, 8 key cylces, maybe 50 miles

 

[Jakezed22]

There isn't a DTC for this that efi live or HP tuners can see. What year truck do you have?

The LML will hit 700 miles and try a regen, it doesn't matter the soot grams. I have tested this. If the regen isn't successful (reducing soot grams) which happens if the dpf is unbolted, then it will throw codes.

I have unbolted the DPF at the drag strip for testing and found the same, no codes for short durations.

I often thought of doing a "y" pipe and let the exhaust go through both the dpf and the open exhaust side. I never tried it to see if something like that would work to satisfy the ecm, just was a thought.

not using hp or efi live, im just going by the dtc index as listed on prodemand.

2018 l5p

i was also thinking along those lines, using an exhaust cut out or something like that.