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Mack exhaust brake


Steve L
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I have a 454 Quantum with a jake brake and it also has an exhaust brake, I also have a CH 400 jake brake engine with no exhaust brake, also seen a CH E7 with exhaust brake. Why were the exhaust brakes fitted to some E7 engines, was it noise suppression or did it add to braking efficiency. If it helps braking could I fit exhaust brakes my CH and 2 R model 350 E6s. The 350s both have dynatards. 

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Well I'm think it was to help braking efficiency on the E7

I dont think Mack ever had the dynatard working like people wanted or expected 

I have a exhaust brake from a E7 to fit on my E6 when I get a chance 

They are a 5 inch pipe on a E7 and 4 inch on a E6 so I will make a adaptor

Blue Ox Exhaust brakes were the same type of thing

The butterfly type of exhaust brake just went straight on the back of the turbo with no mods 

The guillotine type need heavier exhaust valve springs so the valves didn't float when using the exhaust brake 

 

Paul 

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1 minute ago, mrsmackpaul said:

Well I'm think it was to help braking efficiency on the E7

I dont think Mack ever had the dynatard working like people wanted or expected 

I have a exhaust brake from a E7 to fit on my E6 when I get a chance 

They are a 5 inch pipe on a E7 and 4 inch on a E6 so I will make a adaptor

Blue Ox Exhaust brakes were the same type of thing

The butterfly type of exhaust brake just went straight on the back of the turbo with no mods 

The guillotine type need heavier exhaust valve springs so the valves didn't float when using the exhaust brake 

 

Paul 

Just a word on these ! when introduced these were marketed as Stealth brake it only happened for several years I believe! theses played havoc on turbo shaft seals creating real heavy Bloby on application on long steep grades  If you are planning on running this set up and have a lot of long steep grades you may want to think twice on it ! also when these were installed there was a valve spring up date done I don't remember the particulars  on it I only did one of these updates as they dropped the concept after a year or two! 

 

Just sayin!

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4 hours ago, fjh said:

Just a word on these ! when introduced these were marketed as Stealth brake it only happened for several years I believe! theses played havoc on turbo shaft seals creating real heavy Bloby on application on long steep grades  If you are planning on running this set up and have a lot of long steep grades you may want to think twice on it ! also when these were installed there was a valve spring up date done I don't remember the particulars  on it I only did one of these updates as they dropped the concept after a year or two! 

 

Just sayin!

 

 

Correct on the valve spring issue as I had already said, exhaust brakes are probably more common than a Jacob brake across the world, and mainly the butterfly type as they cant over pressurize as they just open a bit and allow pressure to escape

 

We dont have big long steep declines in Australia like I'm guessing they do in north America, however I have had some interesting moments 

So I guess the old saying about pilots rings true"Theres old bold pilots but no bold old pilots" common sense is still critical even with good engine braking 

But thanks for your thoughts

Nothing compares to a modern  Jacobs brake that feels like its gunna face plant you on the wind screen, well almost lol

I dont think anything comes close to a modern Jacods brake in a Cummins for engine braking 

 

 

Paul 

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Gotta remember Paul, Cummings have larger cubes than an E7 or E6, so in a sense “there’s no substitute for cubes” ,  we haven’t run the Quantum because it’s still being converted to a tipper so can’t compare yet, The CH E7 jake brake is much stronger than the dynatards on the 350s. Would the 350s brake better if the dynatard was removed and a jake fitted as it looks like exhaust brakes maybe problematic. I wanna be planted in the windscreen haha 

Edited by Steve L
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Paul I have a E7 exhaust brake setup ( butterfly type) from a CH if I want it and was thinking of doing exactly the same as you mentioned on my E6 350 4valve. The Quantum was a prime mover and I only drove it bobtail, it’s fitted with both ( jake and exhaust) and it really felt like it was going to face plant in the bitumen, it might be a different story with 40 plus ton sitting behind it, will be interesting to compare when it’s going. 

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Steve these questions have been asked on here many times about Jacobs versus Dynatard on a E6 and apparently if there is a difference it isnt enough to notice 

Apparently valve adjustment and keeping the gap very tight is the key on a E6 whether fitted with Jacobs or Dynatard

What very tight is I'm not sure, I  feel the butterfly exhaust brake will be fine because if to much pressure is built up it will just push the butterfly  open

Gotta remember plenty of people are running 30 plus pounds of boost on their turbo seals with out any dramas and I doubt the butterfly exhaust brake will ever get that high before pushing it open

Think about it like this, 120 psi pushing a air ram to hold a flap shut and that air ram is say a inch diameter

5 inch butterfly valve is a lot bigger, if we double the diameter of a circle we get four times the area

So it only needs to go to a two inch flap to get enough pressure at 30 psi in the exhaust to overcome the air ram and open it to let pressure out 

A guillotine type this will never happen 

I honestly think the butterfly type will be fine

And I also think we need to keep our expectations real, it is never gunna face plant you against the wind screen like a Jacobs in a Cummins but I feel good control can be achieved 

 

Paul 

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On 2/14/2022 at 9:04 AM, fjh said:

Just a word on these ! when introduced these were marketed as Stealth brake it only happened for several years I believe! theses played havoc on turbo shaft seals creating real heavy Bloby on application on long steep grades  If you are planning on running this set up and have a lot of long steep grades you may want to think twice on it ! also when these were installed there was a valve spring up date done I don't remember the particulars  on it I only did one of these updates as they dropped the concept after a year or two! 

 

Just sayin!


Correct me if I’m wrong, but wouldn’t this butterfly style exhaust brake possibly create enough back pressure to open the exhaust valve without a heavier valve spring? I guess that’s why you said there was a spring update….Also with this style is it also possible that it creates a strain on the shaft? Being your essentially creating a “compressor surge” on the turbine side? When the valve closes the exhaust gas flows back fighting against an already very fast spinning shaft in the other direction? End result in time possibly being a broken shaft especially with improper shutdown?

Edited by Onyx610
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