Anybody install an Exhaust brake?

Typrus

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Oh man...
This thread could legally drive now haha

I love all of the misconceptions with engine braking. I love them because I used to have them.
Just like several have stated- when you compress the air in the cylinder, it will want to return to an uncompressed state- it will push the piston back down. A true engine compression brake (Jake Brake colloquially) pops the exhaust valves open just after TDC to blow all of the compressed air, then snaps them shut so you actually have a partial vacuum by the time the cylinder hits BDC- that's where the braking comes from, from the partial vacuum and having to defeat friction to turn the engine.
In an exhaust brake, the braking doesn't come from "more compression", it comes from the 35-70psi of exhaust backpressure fighting the pistons as they attempt to evacuate, then being relieved as the intake opens and the charge moves back and forth to a point- it isn't as effective as a true engine brake though.
On an engine like the ALH, it is perfectly happy to fill over at 3500RPM while on a downgrade. It will contribute to your braking, but you will still need to feather the brakes at times. You won't hurt it doing this.
For years of living in the CO mountains, that's exactly what we did, with the 96 Passat, with Dads 11 Jetta and 14 Passat. No harm done. Also with their 99.5 F250 7.3L and 02 Excursion 7.3L. The Ex has over 250k miles, of which over 150k is towing and they downshift the auto of grades to help with speed all the time. No worse for wear, and no exhaust brake.

I get the appeal though and understand your concerns.
If you wanted to try to install a quality EB, get one with a spring bypass, not an orifice. You will also need an air compressor to actuate it. Also, you will need to make sure the pressure produced does not tend to float the exhaust valves. In addition, you will need to find a good place to mount it and to adapt it. For a quality brake kit and all the other good stuff, you may be in it for 2 grand.
Or, you could buy a lot of brakes for 2 grand.
 

[486]

Top Post Dawg
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MN
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02 golf ALH
A true engine compression brake (Jake Brake colloquially) pops the exhaust valves open just after TDC to blow all of the compressed air, then snaps them shut so you actually have a partial vacuum by the time the cylinder hits BDC- that's where the braking comes from, from the partial vacuum and having to defeat friction to turn the engine.
nope, the overwhelming portion of the braking from a compression release brake is the 300 psi of pressure compression makes being released before it can push the piston back down on the power stroke (though that seems like the name of the stroke could cause confusion, as there is no fuel being injected on overrun, nevertheless that's what it's called even when it is a net-neutral stroke)

the 14 psiA of air pushing up on the underside of the piston on what would have been the power stroke is nothing in comparison
 

Votblindub

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For a quality brake kit and all the other good stuff, you may be in it for 2 grand.
Or, you could buy a lot of brakes for 2 grand.
A lot of people forget about this part, but I get it. It's not always about money. I think a lot of people just want that big turbo whooshing-compressor-spooling whistle and the brapapapapapa when they let off, like on a big rig.
 

[486]

Top Post Dawg
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02 golf ALH
and the brapapapapapa when they let off, like on a big rig.
I know I put about 40 hours of machining into a compression release brake, got about 3/4 of the way through putting together a single cylinder one before I realized that it was more work than it was worth

just wanted the dakka
 

Votblindub

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I know I put about 40 hours of machining into a compression release brake, got about 3/4 of the way through putting together a single cylinder one before I realized that it was more work than it was worth

just wanted the dakka
Yeah, I don't imagine it's easy, fast or cheap to make it for a smaller passenger car diesel. Also, i don't think it would sound as impressive as a Peteterbuilt or something. It would probably sound like a kid blowing raspberries into a metal pipe instead of that deep rumble noise.
 

SilverGhost

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Yeah, I don't imagine it's easy, fast or cheap to make it for a smaller passenger car diesel. Also, i don't think it would sound as impressive as a Peteterbuilt or something. It would probably sound like a kid blowing raspberries into a metal pipe instead of that deep rumble noise.
I just about spit my coffee all over the monitor reading this one. :D:D:D:D

Made me remember the Swiss Army chain saw....

Jason

PS: I have thought about a way to adapt an engine brake for several of the long grades I have towed down.
 

[486]

Top Post Dawg
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Yeah, I don't imagine it's easy, fast or cheap to make it for a smaller passenger car diesel. Also, i don't think it would sound as impressive as a Peteterbuilt or something. It would probably sound like a kid blowing raspberries into a metal pipe instead of that deep rumble noise.
getting at the bucket tappets past the camshaft while avoiding the lobe was the hardest part of it

if it were a pushrod motor it'd be so much easier
 

Votblindub

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getting at the bucket tappets past the camshaft while avoiding the lobe was the hardest part of it
if it were a pushrod motor it'd be so much easier
See, you're to a point where it's more for just proof of concept, rather than making it practical, economical, reliable, easily accessible and anything a daily car would have. It's still awesome and I wish I could hang out with engineers and machinists and see this custom stuff get made. Maybe even learn a thing or two.
 

Jaden

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Location
Gresham, Oregon
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1998 Jetta
I did

I installed an exhaust brake. I have a push pull cable going next to the shifter so I can close it whenever I want. Mine does not have any wires involved at all. I think it does make a small noticeable effect in the engine braking, and it makes a major difference in power in I try to drive with it closed. The problem is I keep getting the engine code p0101 mass or volume air flow circuit range/performance
 

Andyinchville1

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Virginia
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2003 Jetta TDI wagon, 5 sp, 226K miles
I did

I installed an exhaust brake. I have a push pull cable going next to the shifter so I can close it whenever I want. Mine does not have any wires involved at all. I think it does make a small noticeable effect in the engine braking, and it makes a major difference in power in I try to drive with it closed. The problem is I keep getting the engine code p0101 mass or volume air flow circuit range/performance
HI,

Where did you get the exhaust brake ? if it doesn't help much maybe the hole to keep the brake from generating too much back pressure is too big (maybe it was designed for a bigger engine)?.

I know on the cummins diesel exhaust brakes (if installing a good one ... i.e. max engine braking) on an otherwise stock engine you have to upgrade the exhaust springs to 60 lns / inch vs the factory 30 lb units.

I'm thinking of trying to make an exhaust brake from a remote exhaust cutout dead ending to a plate with a small hole in it (for ease of making rather than the complex system used by the pac brake top if the line model) .... the thing that has to be worked out is the size of the hole and max RPM the engine is allowed to run to keep back pressure below the level of floating the valves (of course you could get stiffer exhaust valve springs but that's more to do but would offer better performance.

Andrew
 

Jaden

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Location
Gresham, Oregon
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1998 Jetta
I put a 3 inch exhaust cutout in my car the link below is what I installed. I recommend using a 2 inch because I had a very hard time stepping up from the 2 inch in my car to the 3 inch in the exhaust brake then back to 2 inch. There is no hole in this one but I think there are some leaks where I connected it so there is no need for a hole. The smallest leak will make a big difference. Also I took off the motor first thing and used a push pull cable instead that I had laying around, I don’t know where you can get a cable. The only problem this has caused to the engine so far is the check engine light comes on and sometimes it goes into limp mode. Also I have a manual transmission so I don’t know what this would do to an automatic. As for the engine rpm I never downshift when it’s already above 2400 rpm even then it revs up to 4000 rpm after downshifting. Hope this helps.
https://www.ebay.com/itm/3-75mm-Ele...-Valve-Motor-Remote-Control-Kit/233296895775?
 

Jaden

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Gresham, Oregon
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1998 Jetta
I blocked off the egr and now instead of getting a check engine code for mass air flow I get a code for egr system. Blocking off the egr did make the exhaust brake a lot more effective though.
 

Andyinchville1

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2003 Jetta TDI wagon, 5 sp, 226K miles
I put a 3 inch exhaust cutout in my car the link below is what I installed. I recommend using a 2 inch because I had a very hard time stepping up from the 2 inch in my car to the 3 inch in the exhaust brake then back to 2 inch. There is no hole in this one but I think there are some leaks where I connected it so there is no need for a hole. The smallest leak will make a big difference. Also I took off the motor first thing and used a push pull cable instead that I had laying around, I don’t know where you can get a cable. The only problem this has caused to the engine so far is the check engine light comes on and sometimes it goes into limp mode. Also I have a manual transmission so I don’t know what this would do to an automatic. As for the engine rpm I never downshift when it’s already above 2400 rpm even then it revs up to 4000 rpm after downshifting. Hope this helps.
https://www.ebay.com/itm/3-75mm-Ele...-Valve-Motor-Remote-Control-Kit/233296895775?
Hi

I just revisited this thread and looked at the link you provided .. THAT could be the beginning of a really good cheap exhaust brake if it can hold back pressure .

As fate would have it, I recently upgraded to a 3" exhaust so that piece should fit on with minimal issue.

Since you've already done it , How much retarding force do you think the exhaust brake provides?

About the only thing that would concern me about doing it is floating the exhause valves potentially.

My EGR is still connected and I saw where you said That probably makes a difference also. ..

I know a lot of folks will say just use the brakes but I think it would just be cool NOT to have to use them on long steep downgrades which I sometimes have to go down.

Are there any mathematical gurus out here that could calculate The size of the hole that should be cut into the butterfly and the maximum RPMs That the engine could be allowed to run in exhaust braking mode without floating the exhaust valves?

I'm sure it could be back for figured mathematically , but how many braking horsepower do you think the above setup could be engineered to provide without floating the stock exhaust valves?

I know on the Cummins engine somebody figured that out and if you want more breaking from the exhaust brake you'd have to install stiffer exhaust Springs... But I prefer to have Maximum braking Force without floating valves using the stock exhaust springs on the TDI Just to save the trouble and expense..

On the other hand where would one get the stiffer exhaust valve Springs for the tdi?

Thanks
Andrew
 

SilverGhost

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I blocked off the egr and now instead of getting a check engine code for mass air flow I get a code for egr system. Blocking off the egr did make the exhaust brake a lot more effective though.
Just a thought - maybe have a solenoid that blocks EGR function ONLY when the engine brake is active. With the motor on instead of a cable it would be simple to wire them both to the same switch.

Jason
 

[486]

Top Post Dawg
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Stupid question - how exactly is restricting the exhaust requiring stiffer valve springs?
think of how a valve normally holds pressure and how it opens
now imagine trying to hold pressure on the other side of it
 

SilverGhost

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think of how a valve normally holds pressure and how it opens
now imagine trying to hold pressure on the other side of it
Oh, ok. I know there is a lot more physics and engineering than that simply there is pressure on wrong side, but I do understand how that would be an issue.

So biggest point is your engine "Red Line" is effectively been dropped at higher back pressure levels, contradictory to how you would operate with engine with that forced back pressure. Seems a RPM switch to go along with the EGR switch would be in order. And some sort of common sense while operating in this mode.

Jason
 

[486]

Top Post Dawg
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02 golf ALH
nothing to do with RPM, just increased backpressure holding the valves open and letting the hydraulic lifters pump up

like when you've got really bad vane control maps and you run into that issue where you take off real hard and immediately get a stall and no-start with a fast crank from the lack of compression

ETA: oh and the EGR thing in #46
it only works because the EGR is physically blocked off
the backpressure can blow that valve open just the same
 
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SilverGhost

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nothing to do with RPM, just increased backpressure holding the valves open and letting the hydraulic lifters pump up

like when you've got really bad vane control maps and you run into that issue where you take off real hard and immediately get a stall and no-start with a fast crank from the lack of compression

ETA: oh and the EGR thing in #46
it only works because the EGR is physically blocked off
the backpressure can blow that valve open just the same
Heh? Pressure in the exhaust manifold (before turbo) won't be higher than peak cylinder pressure. So regardless of absolute pressure it should be no more than equal on both sides of the valve, all the valve spring has to pull against is its own inertia. What is looses is the extra help closing from the pressure gradient between cylinder pressure and what should be lower manifold pressure along with the outward flow from the exhaust gases. That of course assumes the point at which cylinder pressure is still higher is at a point when cam lob has returned to base circle.

Maybe I looked at EGR valve too quick. I though pressure would blow it shut, not open. My mistake. If that's the case then switching from vacuum to pressure would push the valve back shut?

Jason
 
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