Dynotard/Jakebraking a td5

On the money with a jake brake... Just to clarify

A jacobs brake, or jake brake is typically aftermarket fitted to an engine/head and works on the same basic principal of a dynotard

A dynotard uses a modified exhaust cam with a second lump that decompresses the engine at the end of the compression stroke. This gives one retardation per cylnder every 2 turns of the crank.

The really strong ones have a modded inlet valve and exhaust valve and produce one retardation per turn per cylnder. Tho Ive never seen one apparently they're popular over in europe where they have real hills they need to slow down on.

Essentialy both the Jake brake and the dynotard turn your engine into a big aircompressor. Injection is turned off and only intake air is vented to the exhaust there is no need to mod or re-enforce the manifolds as all compression takes place where it should, in the combustion chamber.

An exhaust brake is essentially the same as sticking a potatoe in the exhaust pipe... Which means all of your manifold/head gaskets need to be up to scratch. As there must be some exhaust flow the valve does not completely close off the exhuast...

With a turbo engine you can use the boost air from the manifold to charge an air tank with a one way valve that will get you your actuation pressure.

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Originally Posted by Blknight.aus

As Big Red does lots of towing and I was already thinking of fitting an exhaust brake to her then someone asked about fitting common rail injection to a tdi300 for some reason my head jumped to the mack Dynotard brake... and the phrase "why not" lingered around in there somewhere...


So given that Dynotards and Jakebrakes are essentially modification to the exhaust valves does anyone know of

a, is there a reason it cannot be done
b, anyone or a local (australian) company that mods diesels that would be willing to have a look at it
c, how well the TD5 brakes with just an normal exhaust brake.

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Dave, what sort of effect is an "Exhaust Brake" (Valve blocking exhaust flow) going to have on the Engine ECU, maybe you should check out the electronic retarders as mentioned elsewhere in this post, Jake Brakes turn your engine into a compressor by modifying through electric and hydraulic action your valves which reverses the engine from producing horsepower and uses the compressed air produced to retard forward motion, as also explained elsewhere in this post, Regards Frank

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Originally Posted by Blknight.aus

Because of the govenor on 99.9% of diesels if you get em spinning fast enough they all cut injection. When you stomp the loud pedal or yank the hand throttle your not directly influencing the rack, or spill ports your having a "tug-of-war" with the govenors fly weights.

When engine speed and therefore govenor speed is low the loud pedal wins and the engine gets more fuel conversely when the engine overspeeds the flyweights win and cut back the fuel.

The only "direct" control you have is the fuel cut off which manually forces the rack to the zero fuel position bypassing all the other gumpfh in the injector pump... Td5's just do it electronically.

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the Td5 cuts injection in overrun....at any revs above idle......
its nowhere near the redline....they do this to assist with engine braking.....

As Defenderzook said the TD5 cuts all injection if the engine overspeeds, most mechanically injected engines only retard as far as the idle setting but they can be adjusted so that they cut all fuel if over the speed requested by the throttle. However as the mechanicals are comparitively slower to react than the near on instant speed of a computer controled injector they will hunt worse than Elmer Fudd.

There is generally a pretty direct relationship as to how much the injection is cut and the amount the engine is overspeeding. IE the faster the engine is going and the less pressure you have on the loud pedal the greater is the reduction in fuel supplied. (I think i got that right....)

In theory

As I would be wiring the exhaust brake to come on on command or with the brake lights The only time the exhaust brake should be able to come on is when Im off the noise.


The ECU would see engine overspeed and cut injection, and theres half the battle won. The exhaust brake would come on and restrict flow in the exhuast and provide the rise in pressure required to retard the pistons upstroke on exhaust

Most exhaust brakes only provide about a 90% restriction to exhaust flow so that there is still enough flow to support Idle speed settings.

Here is the major advantage of the Jake/dyno type brakes, as they use only the combustion chamber to provide the retardation as the exhaust valve opens the flow out the exhaust is fast enough to keep the turbo on the go where as a poorly adjusted exhaust valve brake will slow the turbo to the point where its off boost, if you need the power in a hurry again you have to wait for the turbo to come back up.

All this is awesome stuff and I can't contribute on the tehnical side, but I do recall seeing someone was selling an exhaust brake setup for passenger 4wd's about 10 years ago. If someone has a big pile of 4wd mags (can't recall which one) I think I read about it in about 1996. Or maybe they're still selling. I think the article I read had a Toyo 70 series as the demo rig. Thought at the time it was a very sensible idea but didn't have an application for it in my Suzuki...

Steve

all that was was a butterfly which closed off the exhaust.......
should be ok for mechanical injection engines.........

not too sure what would happen if you did that to one with all the electronics.....
probably throw some type of faults on the ecu maybe......

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Originally Posted by DEFENDERZOOK

all that was was a butterfly which closed off the exhaust.......
should be ok for mechanical injection engines.........

not too sure what would happen if you did that to one with all the electronics.....
probably throw some type of faults on the ecu maybe......

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The fuel does need to be cut off whilst the exhaust brake is activated and then turned back on so you can keep driving. M-Benz 1418, 1922, 1923's etc. actally had a button the floor which activated the ex. brake and was also the stopper, no cable on the dash.

My wife tows her extended 2 horse float with her auto D2 TD5. All up the float can weigh up to 2.5t. Pick the correct gear for the situation, and she has good quality electric brakes on the float, with an Australian made controller in cab. Stops on a dime if you dial it up and costs way cheaper than where this thread is leading. If required I could fit brakes to the trailing axle as well????. It would snap your neck if required.

Worth a thought.

Regards Justin

Dranged thats true however that doesnt stop the underlying pair of problems Im trying to eliminate.

My trialer is braked but Im not always towing my trialer :(

and even if you have brakes on the trailer, if the days hot enough, the loads heavy enough and the descents long enough your going to get brake fade... Engine brakes dont have that problem and if for some reason you loose the engine brake you still have a full compliment of vehicle/trailer brakes to pull you up till you can fix it.

Someone mentioned electric retarders. Ive had em in cranes and they are worth their weight in gold (should that be diesel now?). But to fit one to the deefer is going to cost buckets more than the exhaust brake, they dont like getting wet/muddy/oily and they weigh substantially.

If I ever get to redesign the Deefer you'll all get an exhaust brake, a retarder in place of the hand brake, engine driven air compressors and an air off spring applied park brake/emergancy brake. And on that day Satan will drive to work in a snow plow...

If I ever get to redesign the Deefer you'll all get an exhaust brake, a retarder in place of the hand brake, engine driven air compressors and an air off spring applied park brake/emergancy brake. And on that day Satan will drive to work in a snow plow...[/QUOTE]

That really would be a design exercise, finding somewhere to put spring brake chambers on a passenger car, particularly a 4wd. Put 'em under the axle and they get ripped off. Put 'em above? Where? Make room by putting bulges in the floor? Room in a cab/chassis with dropside body maybe, but a wagon? Agree with the exhaust brake and compressor, but feel the retarder would be too heavy, too expensive, and too complicated .We already have a bush car that is suffering from over-complication and excessive points of maintenance and possible failure. The KISS principle appears to have been by-passed at LR drawing office.