|
|
Post by Graham on Apr 6, 2006 1:56:14 GMT 11
Hi all,
A few times, someone's mentioned the existance, or non-existance, of an exhaust brake on the MU and I'm confused as to the actual consensus.
About half way down the length of my MU is a 'contraption' in the exhaust which appears to have a butterfly to close the exhaust. This device seems to be controlled via a hydraulic line, or it could be a boost/vacuum line.
Can someone tell me exactly what it is and how it operates?
If needed, I'll grab a photo of it on the weekend.
Cheers, Graham.
P.S. I tried to find a similar thread, or even a good exhaust thread and search didn't want to return many results, so I created this thread.
|
|
|
|
Post by James W on Apr 6, 2006 7:44:03 GMT 11
It's a popular misconception that it is an exhaust brake.... It is not, it is part of the quick warm up system. You must have the quick warm up switch on the dash activated and the outside air temperature about 5 deg C or less. It is controlled by a vacume line and restricts the exhaust to place a small load on the engine. If you drive with it on it will seem to be slugish on the accelerator then all of a sudden it will switch off and come back to life.
|
|
|
|
Post by geeves on Apr 6, 2006 8:25:46 GMT 11
Ive always wondererd if this can be converted into a real exhaust brake or if it is even needed
|
|
|
|
Post by dani4JB1T on Apr 6, 2006 9:40:35 GMT 11
Ive always wondererd if this can be converted into a real exhaust brake or if it is even needed Mee too...I have been thinking installing a pneumatic cylinder or even more easy doing manually from the dash with a steel cable to the butterfly... My doubts are about the temps the engine will raise with this device working on, maybe it should be necessary a bigger radiator to keep all cool. Is great now there are more interested people in these thing... cheers |
|
|
|
Post by geeves on Apr 6, 2006 11:02:13 GMT 11
You would only use it while slowing so I doubt it would affect tempreture much
|
|
|
|
Post by dani4JB1T on Apr 6, 2006 13:45:17 GMT 11
yess...only a pair of seconds throtle out. So... what should be the RPM limits??...I think no more than 2000 revs/min so so.
thanks.
|
|
|
|
Post by James W on Apr 6, 2006 14:54:16 GMT 11
If you wanted to go the way of making it an exhaust brake, i've always thought it would be simple to do.
Follow the vacume line and find the solenoid driving the vacume line. It would be a smiple matter of adding another wire to it for brake control. i would be inclined to use two diodes so you don't back feed into the ECU or whatever and blow it up. Secondly i would employ the throttle switch on the accelerator pedal, it is activated (or deactivated?) at anything other than idle... just what you want, add a relay to again add isolation and bingo. Exhaust brake
|
|
|
|
Post by mulover on Apr 6, 2006 18:40:39 GMT 11
Only one problem with that there james, you don't want it working when you are actually sitting idel, which it would if you just hooked it up to the accelarator switch. All of the light trucks i have driven have some sort of a timer on them so that they only stay on for a short amount of time, or could be to do with rev's?? i'm not sure, but i'm sure there has got to be a way to make it work??!!
|
|
|
|
Post by James W on Apr 7, 2006 7:11:10 GMT 11
"Only one problem with that there james, you don't want it working when you are actually sitting idel"
Arh yes, obvious now you point it out... hmmm the idea just needs a little refinement then. Some way to detect engine braking is required? Throttle at idle yet revs over a certain amount?
|
|
|
|
Post by Graham on Apr 8, 2006 0:53:18 GMT 11
How about a manual button - on the steering wheel for example like the F1 speed limiter when in pit lane  |
|
Garth
Isuzu Senior
1989 Bighorn Irmsher R LWB
Posts: 164
|
Post by Garth on Apr 11, 2006 13:53:40 GMT 11
Most trucks with an exhaust brake have a switch on both the accelerator and clutch that switches it off when you change gear or accelerate, this way you can sit at the lights with your foot on the clutch and no worries. Some also have a switch on the gearbox for when you are in neutral so you can leave the truck idling without having to turn the exhaust brake switch off, would be easy to do on an auto. hope this helps
|
|
|
|
Post by roscoe46956 on Apr 21, 2006 18:09:55 GMT 11
On trucks that are fitted with exhaust brakes, they have a micro switch connected to the throttle and clutch so the brake cannot activate unless both pedals are right up.
Most however dont have any means to de-activate the brake when idling so you need to manualy switch it off yourself.
On the truck Im driving at the moment, I leave it switched off unless I am working down through the gearbox or on a twisty road etc.
I fitted one to a diesel Toyota Landcruiser I used to own and instead of fitting the micro switches, I replaced the gear knob with one that had a range change switch on from a truck and used that to activate the brake. I found that was a very conveniant place to have the switch.
The engine was also used in a light truck which had an exhaust brake as standard so there were no durability issues.
An exhaust brake will put more stress on the valves, especialy on the stem, just below the head of the valve. The main thing is to never shut the exhaust pipe of completely, only up to 80% max.
The higher the RPM, the more efective the braking effort will be.
A word of warning though, exhaust brakes can be very effective and can cause the rear wheels to break traction descending a hill on a shingle road or wet tar seal so that is something to remember.
Note: An exhaust brake will be even more effective if the fuel supply to the engine is shut off at the same time and this also eliminates the usual blast of black smoke out the exhaust when you dis-engage it.
Cheers
Roscoe
|
|
|
|
Post by dani4JB1T on Apr 23, 2006 13:54:06 GMT 11
What i think is drive the butterfly through an electric knob on the dashboard. A solenoid valve will receive the knob signal to move a neumatic valve and then an air cylinder. That`s all. No pedal switches. It would be great to shut off the fuel injection at same time, but I cannot figure it how can be done yet.
cheers.
|
|
|
|
Post by dani4JB1T on Apr 23, 2006 13:58:37 GMT 11
OOOHH yes...the above I wrote is assuming an OBA system installed. Forget to mention it.
|
|
|
|
Post by roscoe46956 on Apr 23, 2006 19:33:22 GMT 11
Gday dani, Go to a truck wrecker and get the whole unit off a small Isuzu truck that has the same pipe diam as yours, may be a simpler option mate.
Cheers
Roscoe
|
|
|
|
Post by roscoe46956 on Apr 23, 2006 19:42:41 GMT 11
Oops, I meant to add, I presume on the 4JB1, the fuel shut off is via a solenoid on the pump, if it is, then redirect the cable to it via your ex brake switch(which may need to be a Double pole/double throw switch) so that the engine will only run if the brake switch is in the Off position.
(Also gives added security if you leave the brake on while you are out of the vehicle and some low life tries to bypass your key switch one day)
Cheers
Roscoe
|
|
|
|
Post by lndrvamad on Apr 28, 2006 19:29:15 GMT 11
On the Scania I drive for work, it activates the exhaust brack from a micro switch on the brake (its an auto), the exhaust brake comes on but not the actual foot brakes, it also deactivates and low revs but I dont know how you could control that simply.
|
|
|
|
Post by roscoe46956 on Apr 30, 2006 17:55:17 GMT 11
Gday Indrvamad, Not hard to do if its an electronic tacho, the engines management poota will simply dis-engage the brake below a certain RPM level.
What model Scania is it? When you say auto, do you mean the "Opticruise" system they have? Or do you mean the cruise control brings the brake on automaticly when speed over-run is detected?
The latest 580HP with Donaldson Free Flow mufflers would have to be one of the Horniest V8 sounds around.
Cheers mate
Roscoe
|
|
|
|
Post by lndrvamad on Apr 30, 2006 18:30:48 GMT 11
Its series 4 fire truck, with a ellison auto. As soon as you take your foot right off the gas, the gearbox selects a lower gear to aim for and changes down till it gets there exhaust brake dosen't come on until you touch the brake.
|
|
