Anybody install an Exhaust brake?

This doesn't usually make sense on a small diesel car, but I am curious if somebody actually tried to install an Exhaust brake and how the brake ware changed.

2FastDre.

curious why you feel one is needed? I drove a TDI and the engine braking was good as any. You just need to keep the rpms up.

I consider the TDI to have near zero engine braking. I am amazed at how well it coasts in gear, for such a high compression engine.

My Land Cruiser with 4:88 gears and a small block with 10:1, that was engine braking!!

Tim

Here we go, again...

Diesels provide virtually no engine braking. Period.

Use the brakes. They give you a lot more control over the vehicle.

Right. A diesel of the same displacment has more engine braking than a gasoline engine. The higher compression results in higher compression temperature increase. The loss in temperature in the compression charge results in a braking effect which is higher due to the higher compression temperature.

The VW TDIs seem to have poor engine braking because the gearing is very high compared to other vehicles with similar sized engines.

Engine braking doesn't really come from pumping -- it comes from friction.

TDIs have poor engine braking because they have tall gearing, for all intents and purposes.

How a Jacob's Engine Retarder works from the horse's mouth and not from a conspirator.

Now that y'all have some small idea of the working of a 'jake' brake, do you really want to put one on our beautifully engineered and integrated VW TDI? Why do you think we have huge disk brakes and the wheels to put them in.

Use the brakes Luke, use the brakes. Or you will go over (to) the dark side.

The conspiracy of ignorance masquerades as common sense.

Stirling Moss (World Champion driver long ago) insisted that engines and transmissions were made to make the car go, brakes were made to stop the car. I've been using his system for a lot of years and it works quite well.
Rodg

Originally posted by John B.:
A diesel of the same displacment has more engine braking than a gasoline engine.

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<font size="2" face="Verdana, Helvetica, sans-serif">Not correct. Some basic understanding of thermodynamics and in particular what's going on during the compression and expansion strokes are in order.

It's true that work is consumed to compress the air in the cylinder. However, what happens to all that energy gained from applying all that work? Does it disappear? NO, according to the First Law of Thermodynamics!

The compression and expansion processes occur roughly without any heat being transferred between the air and its surroundings (adiabatic), and the work previously done to compress and heat the air returns back to the crankshaft, minus of course any mass lost (i.e. blow-by), heat-transfer, and of course, friction and an esoteric thermodynamic term called "irreversibility".

Anybody who has driven an old Merc knows what engine braking is all about. My '79 240D would slow down pretty quickly once I let up on the "go" pedal. My g/f's '81 300D does the same thing. I always thought it would be nice to get some of that resistance back. How cool would it be to have that "jake brake" sound? If it's not too expensive, I would consider it just for that. Only if it actually works, because you don't want to be a poser.

Yeah, I had a 1983 240D. Lots of engine braking.

- 25% larger engine

- insanely low gearing (55 mph = 2750 rpm in top gear)
compare to TDI 55 mph = 1900 rpm in top. Even the VW 4h is taller than the M-B fourth.

Try changing down to 3rd at 60 mph --> loads of braking!

Originally posted by Rodg Petersen:
Stirling Moss (World Champion driver long ago) insisted that engines and transmissions were made to make the car go, brakes were made to stop the car.

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<font size="2" face="Verdana, Helvetica, sans-serif">On the race track, this is a less subjective subject than it is on the street, where sponsors aren't buying 1) our fuel, and 2) our brake pads.

Engine braking (when not combined with improper downshift braking) is a fine and dandy thing on the street. It keeps coolant flow up, oil pressure up, and fuel flow down.

It should also be noted that a JakeBrake is a much different thing than an exhaust brake.

[ February 28, 2003, 04:41: Message edited by: Variant TDI ]

i'll second that a exhaust brake is very much differnet from a engine brake or "jake brake" although the "Jake brake" company does also manufacture exhaust brakes. a engine brake uses a mecahincal divise to manipulate the engines valves. a exhaust brake basically is a valve in the exhaust that restricts the exhaust size down to use backpressure to slow the vehicle down...exhaust brakes make a hissing noise and engine brakes make the loud common" jake brake" noise . A freind and i are experimenting with a exhaust brake on a vw turbo diesel either on his ti or my older td engine..its for fun.
as for diesels having low engien braking my experience has been with older vw diesels which have the same or very similar trannsmission ratios as the older gasoline engines and the diesel does have muchbetter engine braking..case in point my td rabbit pickup has a 2.0L gas engine 10.5 to one compression and a fn coe tall box tranny ..i swapped that engine out for a 1.6L TD engine and kept the same tall box fn tranny an the 1.6L Td ha much more engine braking...now as for my wifes 2001 golf gl tdi ..it feels good to me and i don't have a gasser version to compare it too etc...and my cummins has a auto that doesn't lock up so it has zero engine braking ha maybe if it was a manual tranny it would...
later
Deo
\x/ hillfolk!

I was just thinking that installing an Exhaust Brake on my TDI would prolong the Brake Rotor / Brake Pad life and safe me money in the long run. Exhaust brake makes more sense if I am towing 14000 lbs with a Dodge Ram down a 20 mile 6 percent grade, but...

VWs and Audis usually don't machine/polish the old rotors when the time comes for new pads (they just replace old rotors). And we all know that this is NOT cheap. This and the timing belt are most costly maintenance items.

I understand that downshifting will slow me down, I just wonder if an exhaust brake is better for the overall health of my vehicle in the long run.

Here is what Mr. Banks from BanksPower tuner has to say about Exhaust Brakes:
"To provide some supplemental braking, typically drivers downshift to a lower gear, allowing the engine to exert some braking force as the engine attempts to intake air against a closed throttle. Of course, this only works for gasoline engine-powered vehicles that have air throttles. Drivers with diesel engines, which have unrestricted air intake, face a different problem. Diesels provide little engine braking unless they are fitted with either an internal or an external device that uses the pumping action of the engine to do work. In either case, such devices on diesel engines are intended to create a pumping resistance that results in engine braking.

The internal mechanism built into some large diesel engines is called a Jake Brake®, so named after Jacobs Vehicle Systems® that originated it. This mechanism opens the exhaust valve of each cylinder at the top of each compression stroke. Thus, the engine has to work to compress the air, which is then released into the exhaust system. Unfortunately, the operation of Jake Brakes is fairly noisy, making a loud burbling sound as the vehicle decelerates. This is a fairly complex and expensive system that is usually found only on large trucks or some large motorhomes. It is also something that cannot be retrofitted to a 'non-Jake Brake diesel' since it is incorporated into the engine’s original design."

I got this from:
http://www.bankspower.com/why_add_exhaust_brake.cfm

The signs in residential areas that say "NO ENGINE BRAKING" are talking to the Jake Brakes. The valve that closes the exhaust can be virtually silent (not louder than engine, wind, or tire noise).

I too have considered an exhaust brake as I do extensive mountain driving. I really do not like having my car sitting up in the 3k-3500 RPM range just to get keep from accelerating with the 2.0 in the mountains, it's just not pleasant. Increases wear on the engine and I don't want to have to turn the radio up just to go down a mountain without burning up my brakes. But I also don't want to pay someone to design it since there really aren't any options out there.

hallwd94 said:

I too have considered an exhaust brake as I do extensive mountain driving. I really do not like having my car sitting up in the 3k-3500 RPM range just to get keep from accelerating with the 2.0 in the mountains, it's just not pleasant. Increases wear on the engine and I don't want to have to turn the radio up just to go down a mountain without burning up my brakes. But I also don't want to pay someone to design it since there really aren't any options out there.

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Resurrecting a 16 year old thread? To what avail?

MichaelB said:

Resurrecting a 16 year old thread? To what avail?

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Looking to put useless junk on a car maybe. I have a brake on my TRUCK.

hallwd94 said:

I too have considered an exhaust brake as I do extensive mountain driving. I really do not like having my car sitting up in the 3k-3500 RPM range just to get keep from accelerating with the 2.0 in the mountains, it's just not pleasant. Increases wear on the engine and I don't want to have to turn the radio up just to go down a mountain without burning up my brakes. But I also don't want to pay someone to design it since there really aren't any options out there.

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You'd be better off getting better brake pads. Get ceramic pads at minimum, or race pads if you're really using the brakes a lot. They'll be noisy when cold, make more dirt, and wear faster, but they won't fade.

The difference between race and stock pads on a VW is night and day. If I used stock pads on the track they would be faded to nothing in less than two laps. With race pads there would be no noticeable fade.

After seeing how the newer vane turbo trucks use the vanes as an exhaust brake, I did some similar programming on my car, where when you're at 0 fuel and above 1000 rpm it will request full vane actuation. I don't remember but I might have also backed off the vane stop screw slightly as well.

it did make a very noticeable difference, however I'd rather severely damaged my vanes through unrelated shenanigans, so they'd sometimes get stuck full closed which was annoying, so I returned it to normal and it did a little better on not sticking them full closed any more. Certainly would wear out the vanes quicker, flapping all the way back and forth near constantly.

MichaelB said:

Resurrecting a 16 year old thread? To what avail?

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there are some fresh opinions available

The first engine braking question I would as is does the vehicle in question shut fuel completely off during drop throttle coast down? It it doesn't, engine braking will be extremely minimal. Even with zero fuel delivery, that high compression ratio for diesels does NOT give effective engine braking - because what energy you stored to heat and pressure during the compression stroke is recovered (less lost heat) on the non-firing "power" stroke coming behind.

Compression brakes ("Jake" brakes) are extremely effective (you can hear to turbo spool a fair bit when the Jake is barking) but you need to be able to radically alter cam timing to do so. Not a VW option.

Exhaust brakes are minimally effective, but better than nothing. What you need to consider if building one is you can't simply block off all of the exhaust, or the backpressure will lift the exhaust valve off its seat - crashing it into the pistons. Premium diesel truck exhaust brakes have a constant pressure blowoff valve, whereas the cheap crap ones use a throttling plate with fixed orifice. The latter works well at redline and effectiveness decreases exponentially as flow drops off, whereas the former is linear.

Just buy better pads and rotors for your MkIV!!!!

Don't be afraid to use the brakes. Pads and rotors are pretty cheap. The people behind won't laugh at you when they see the brake lights.

Turn on the A/C compressor, that will provide a lot of "braking."

Nevada_TDI said:

Turn on the A/C compressor, that will provide a lot of "braking."

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not near so much as even the stock turbo with the vanes snapped shut at 4k rpm

On TDI's so equipped, perhaps in a spirit similar to [486]'s experimentation with the VNT mechanism, the ecu could be programmed to close the anti-shudder valve butterfly when all of a user-defined set of criteria are met. Example scenario: for ASV closure to be commanded, the following criteria must all be satisfied: crankshaft speed greater than xxxx rpm AND throttle pedal less than xx% AND MAP less than xxx mbar And vehicle speed greater than xx mph/kph. When any of the criteria are no longer met, the ecu would command the ASV to reopen.

I think that a setup in a similar spirit could provide us with an engine braking result that is in some ways similar to closing the throttle plate on a gasoline engine.

kidflyr said:

On TDI's so equipped, perhaps in a spirit similar to [486]'s experimentation with the VNT mechanism, the ecu could be programmed to close the anti-shudder valve butterfly when all of a user-defined set of criteria are met. Example scenario: for ASV closure to be commanded, the following criteria must all be satisfied: crankshaft speed greater than xxxx rpm AND throttle pedal less than xx% AND MAP less than xxx mbar And vehicle speed greater than xx mph/kph. When any of the criteria are no longer met, the ecu would command the ASV to reopen.

I think that a setup in a similar spirit could provide us with an engine braking result that is in some ways similar to closing the throttle plate on a gasoline engine.

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The guy with the vanagon... AndyBees tried it out and the ASV has the butterfly shaft is offset just slightly on the valve, so once it gets a vacuum in the intake manifold it does not reopen until the vacuum in the intake manifold comes down. You could adapt a conventional throttle body to be used as an ASV, but then you're still just up to the amount of engine braking you'd get with a gasoline engine (up to 14 or so PSI differential across the engine) where with an exhaust brake you can go up around 40 PSI before you start blowing exhaust valves open with stock springs.

Also, you'd lose a lot of mass flow, making the exhaust brake ineffective

2fastdre said:

I was just thinking that installing an Exhaust Brake on my TDI would prolong the Brake Rotor / Brake Pad life and safe me money in the long run.

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You'd probably spend several thousand to save like $235 worth of brakes over the course of a few years per set?

Just rig up a T fitting and solenoid to the ASV and use an intake brake. Would be much simpler and have the same effect as an exhaust brake. I personally think brakes are a much cheaper wear item.

jayb79 said:

Just rig up a T fitting and solenoid to the ASV and use an intake brake. Would be much simpler and have the same effect as an exhaust brake.

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*cough* post #25 itt *cough*

Ah should read more

Just use the OEM jA/Ce brake.