Duramax LM2 3.0l Independent Exhaust Brake Actuation

[jdrockin]

Hi Everyone, 

 

  Long-time lurker, first-time poster. I have searched this topic high and low across the net and can't find an answer so I'm either terrible with Google (very likely) or no one has yet asked the question.

 

I recently sold my business and was able to finally transition from my HD trucks down to a nice 2021 Sierra 1500 with the Duramax diesel. I absolutely am loving it, except for the fact that I cannot actuate the exhaust brake independently of using Tow/Haul mode. I know the brake doesn't do a ton but I can certainly feel the difference, even when empty, when it comes to stopping and I had gotten used to having that exhaust brake feature on all of my late-model diesels for the business. 

 

I have searched this topic high and low across the net and can't find an answer so I'm either terrible with Google (very likely) or no one has yet asked the question.

 

Question is, has anyone been able to isolate that circuit such that a bypass can be made to a switch enabling/disabling the exhaust brake independently of using Tow/Haul mode? If not, is it something that someone would be willing to look into?

 

Thank you,

Rockin

[jdrockin]

As a follow-up it would be pretty amazing to be able to program the commanded VVT position to increase or decrease the braking you feel at varying loads. Just one more thing to think about.

[boomerjml]

I own a truck with the LM2. FYI there is no EXHAUST brake on the LM2. They utilize an ENGINE brake only via the transmission. During normal use the transmission will downshift up to 3K rpm once you start braking down a hill. In Tow/Haul mode it will general downshift 1 more time to ~4K rpm in which you will feel a noticeable difference. Hope this helps.

[jdrockin]

37 minutes ago, boomerjml said:

I own a truck with the LM2. FYI there is no EXHAUST brake on the LM2. They utilize an ENGINE brake only via the transmission. During normal use the transmission will downshift up to 3K rpm once you start braking down a hill. In Tow/Haul mode it will general downshift 1 more time to ~4K rpm in which you will feel a noticeable difference. Hope this helps.

Well, that’s partially correct. It also used the VVT to create back pressure against the engine to aid in the slowdown. Still widely considered an exhaust brake. The VVT actuation is what I want to toggle on and off at my discretion. 

[poppy510]

On 10/1/2022 at 9:59 AM, jdrockin said:

Well, that’s partially correct. It also used the VVT to create back pressure against the engine to aid in the slowdown. Still widely considered an exhaust brake. The VVT actuation is what I want to toggle on and off at my discretion. 

This would be good. The auto exhaust brake on tow mode is worthless. As far as I can tell it just redlines the engine even when light braking would be adequate. I often turn tow mode off downhill to avoid the excessive downshifting. 

[silveradosid]

vgt turbo is what is used not vvt. there is aftermarket exhaust brakes you can buy, but it is not cheap