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Exhaust brakes ???
by
jpedro
on 28 May, 2010 23:22
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Hey People, I know this is gunna sound rediculous, but do any of you or have you heard of exhaust brakes for a 1.6L td i know everyone will be like why do you want one, but it was just an idea tonight that was in my head and thought id ask, i know ive got one in my truck and its an IDI as well but a little bit larger and works like a hot damn, or do i have to be a first and try something out and report back?
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#1
by
truckinwagen
on 28 May, 2010 23:25
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I had thought about an exhaust brake many a time, but never actually got to it.
I see no reason not to...
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#2
by
Patrick
on 29 May, 2010 03:36
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Only exhaust brake I ever had was a Jacobs engine brake on an 855 cummins. Ran valves at the wrong time to make the engine brake like a gasser. DOn't think you could build a setup like that for a volkswagen overhead cam engine, the cummins had rockers with the cam in the block. Never had anything to do with the other kind........
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#3
by
Rabbit on Roids
on 29 May, 2010 06:42
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i think the only thing you would really be able to integrate onto a VW would be a exhaust butterfly. or take a VNT, and make an actuator for the nozzles that closes them down when you are decelerating. thats how the new banks speedbrakes work. they lock up the trans and close the turbo. the exhaust brake on my dads duramax will skid the rear tires if you have it set on high and theres nothing in or behind the truck.
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#4
by
truckinwagen
on 29 May, 2010 14:53
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the Jacob's engine brake does hold the exhaust valve closed longer, adding an additional "compression" stroke, and such a system would not work on a VW motor, but many many trucks(pickups and the like) use a butterfly in the exhaust to accomplish the same thing(sorta)
I am sure that an exhaust brake butterfly could be incorporated into the VW exhaust with ease.
-Owen
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#5
by
dh13
on 30 May, 2010 08:59
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Yes it could be done. The only thing that you need to worry about is the back pressure holding the valves open, which creates a problem with vw diesels due to the interference between the pistons and valves. This can be solved by using your choice of performance valve springs.
This is the same concept that the 12 valve Cummins uses in Dodges. They have to run 60lbs valve springs when using exhaust brakes due to the "floating" of valves when the brake is engaged.
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#6
by
rabbitman
on 30 May, 2010 12:49
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Yes it could be done. The only thing that you need to worry about is the back pressure holding the valves open, which creates a problem with vw diesels due to the interference between the pistons and valves. This can be solved by using your choice of performance valve springs.
This is the same concept that the 12 valve Cummins uses in Dodges. They have to run 60lbs valve springs when using exhaust brakes due to the "floating" of valves when the brake is engaged.
Cummins valve springs aren't built to return the valve at 5500rpm so they might be on the weak side.
On the vdub I don't know how you'd ever know if the valves were close to hanging open, but a less restrictive butterfly valve would keep it from happening but would result in less braking affect.
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#7
by
dh13
on 31 May, 2010 14:18
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Yes it could be done. The only thing that you need to worry about is the back pressure holding the valves open, which creates a problem with vw diesels due to the interference between the pistons and valves. This can be solved by using your choice of performance valve springs.
This is the same concept that the 12 valve Cummins uses in Dodges. They have to run 60lbs valve springs when using exhaust brakes due to the "floating" of valves when the brake is engaged.
Cummins valve springs aren't built to return the valve at 5500rpm so they might be on the weak side.
On the vdub I don't know how you'd ever know if the valves were close to hanging open, but a less restrictive butterfly valve would keep it from happening but would result in less braking affect.
That is true. But the problem does not lie within the rpm that the Cummins is running at. The use of heavier valve springs guarantees the valves will not hang when the exhaust brake is applied. Also I bout you would want to apply the exhaust brake when the rpm's were at 5500.
I am not saying that this has to be done, in my mind it is more of a precautionary measure. I would rather spend extra money for valve spring to ensure that there is not fighting of space inside my engine between the pistons and valves. But that is just me.
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#8
by
rabbitman
on 01 Jun, 2010 14:38
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Maybe use a wastegate actuator linked to open the butterfly if exhaust pressure got too high and keep from blowing the mani off the head and you'd have a variable exhaust brake
.
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#9
by
Rabbit on Roids
on 02 Jun, 2010 09:18
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we blow headgaskets from too much back pressure, theres no way in hell im going to fit a device to my engine to add THAT MUCH MORE back pressure. i bet head gaskets would suffer...
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#10
by
truckinwagen
on 02 Jun, 2010 10:55
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I am not sure they would.
the back pressure itself is not going to blow head gaskets out, as the peak cylinder pressures are much higher than backpressure will ever be.
the issue is the heat involved in high backpressure, and the way that the extra pressure makes it absorb into the motor(and headgasket)
with the exhaust brake, it will only be used during engine braking(when you are off the throttle) and so there will be little, if any, fuel being injected and burned. so EGT will be low, and the headgasket should be OK.
that is, if the exhaust brake is never used under throttle.
-Owen
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#11
by
rabbitman
on 03 Jun, 2010 15:20
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I am not sure they would.
the back pressure itself is not going to blow head gaskets out, as the peak cylinder pressures are much higher than backpressure will ever be.
the issue is the heat involved in high backpressure, and the way that the extra pressure makes it absorb into the motor(and headgasket)
with the exhaust brake, it will only be used during engine braking(when you are off the throttle) and so there will be little, if any, fuel being injected and burned. so EGT will be low, and the headgasket should be OK.
that is, if the exhaust brake is never used under throttle.
-Owen
X2
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#12
by
Pat Dolan
on 05 Jun, 2010 08:01
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Just a couple of notes: The Jacobs brake is a compression brake, not an exhaust brake.
There are exhaust brakes and engine combinations that won't work well (due to limited valve spring seating pressure) and for those engines, one buys an exhaust brake with a pressure limiting pop-off valve. I have a 7.3 with one for exactly that reason, and it works reasonably well. It is also controlled by throttle and brake electronic signal. Not cheap, though.
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#13
by
OM617
on 06 Jun, 2010 06:04
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Another note: Jake brakes don't hold the exhaust valve closed, they hold it open.
The injector lobe pushes a master hydraulic cylinder and the slave pushes the exhaust valve bridge down to open the exhaust valves. That releases all the energy consumed in compressing the air as well as creating a strong vacuum on the down (would be power) stroke.
Not even remotely like an exhaust brake.
An exhaust brake makes the engine compress the exhaust instead of just pushing it out and there is no possible way it can blow the headgasket, even if you're running extreme pressures. The turbocharger creates the exact same backpressure force when you make boost and combustion pressures are several orders of magnitude higher and hotter.
A butterfly valve is one way, as is closing the vanes on a VNT turbo.
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#14
by
dankcorey22
on 06 Jan, 2011 13:14
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