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Exhaust brake

Phil Hancock

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nope not seen one. as far as know the ones on the coaches i drive are just a butterfly in the zorst that closes the pipe off. your choice how you operate it.

cant really see much point apart from the odd noise, even on coaches with them i hardly bother to use them as they make so little difference.

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As per Andy's explanation, the Jacobs/Cummins exhaust brake that I have on the 5.9 L CTD in my pick up is a butterfly valve (operated by vacuum pump in my case) that activates about 2 seconds after defueling. Below is a link that provides more detailed info on the brake:

Jacobs/Cummins Ebrake for CTD 600

Unlike Andy, I think they are brilliant. I use mine all the time and find that it makes an enormous difference. It's great for modulating cruise control on the highway and is the dogs balls when towing. In fact, it will slow the truck to an almost complete stop downshifting to second gear. That's about 6,300 lbs of truck + about 4000 lbs of trailer and Land Rover.

Having said that, exhaust brakes are a function of available horsepower. At 2800 rpm, the Jacobs exhaust brake on my CTD is delivering about 140 braking horsepower. Given that engine hp at 2800 rpm should be round about 300hp. At 1500 rpm, it delivers 40 braking horsepower, so the relationship is not an entirely linear one between engine horsepower and braking horsepower/rpm. Thus, when you take say a 2.25 diesel which delivers an alleged 63hp at 4000 rpm and imagine a similar relationship to that described for the CTD/Jacobs set up, then at say 1500 rpm, you might be getting somewhere in the range of 7 - 8 braking horsepower? Where I am trying, perhaps rather ineptly, to get to is that I think an exhaust brake may really only be useful on relatively powerful engines. 40 braking horsepower at 1500 rpm on my pick up equals 13hp/ton (US) vs 4.6hp/ton (US) for a typical Series III 88". This of course assumes that the exhaust braking on the 2.25 would have similar characteristics to those on a turbo charged 5.9 L straight six delivering in excess of 325hp and 600 lbs/ft torque which may very well be very wrong....

Having said all that I thought I had seen contemporaneous butterfly type exhaust brakes available for the 2.25 diesel ? I may be confusing this with the diesel vacuum pumps designed for the 2.25 ?

In any event, it may well be a clever piece of kit (although they are expensive) for a Land Rover - at least for the more powerful TDI and TD5 engines. This won't help the TDI and TD5 crowd much, but I wonder if there isn't an aftermarket brake already available for the Ford Duratorque?

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i also drive and maintain various coaches, volvo b10ms mainly, as well as a couple of dafs, and are all fitted with brake exhausts, and i also find them very useful, generally for steep downhill gradients, but you obviously need to be in a low gear to get the rpm up, then select the ex brake, very effective, dont know what effect they would have in a 2.25 landy, i know my defender comes slows down considerably, just by letting of the throttle.

i wouldnt think it would take to much effort to graft one onto a landy..best bet is to ask at your local coach depot, and have a good look at them.


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