Exhaust break

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crinklystarfish
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Re: Exhaust break

Postby crinklystarfish » Wed May 30, 2018 2:00 pm

Yes, they seem to have crude micro switches or ECU interfaces to ensure the brake can only actuate whilst the throttle is closed - all logical stuff.

When I had a look around when this thread was concerned with cutting fuel I didn't find one that did. Not to say they're not out there - I just didn't find one.

It's usually about this time in this kind of discussion that electromagnetic retarders start to look attractive...

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ClivePhoto
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Re: Exhaust break

Postby ClivePhoto » Wed May 30, 2018 10:32 pm

One of the things I was initially quite keen on was fitting some kind of retarder as overheated brakes on a long downhill in a DAF was a bit of a nightmare scenario which appeared to be very possible.

However, after touring around Wales, the peak district and the lakes I've found that steep downhills are best negotiated with low-ratio selected. The vehicle is perfectly able to achieve a reasonable speed in top, around 30 ish, and there's a useful amount of engine braking (and so far no breaking, thankfully) plus those steep downhills are often interspersed with equally steep and windy uphills so low ratio is a very good place to be.

On faster roads where low-ratio would be impractical I've found that keeping on top of speed build up with gentle and frequent braking works well. Once you let the speed get up past 40 though things can get very scary very quickly.

I might change my mind if I find myself in places with very long steep descents but so far I've put the engine brake to the bottom of the list of mods I'd like to make.

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Re: Exhaust break

Postby crinklystarfish » Thu May 31, 2018 7:30 am

More or less my sentiments exactly, low ratio box and the occasional dab to stop the engine over-revving works just fine - especially as ours is @7.5t. Not sure if I'd have the same view if we were hovering at the 10t mark.

No one would drag the brakes all the way down a mountain in too-high a gear, would they? :o :lol:

Not denying that if exhaust brakes were a standard T244 fit I'd use it all the time and trumpet it as a real asset. I think they're a genuinely useful thing.

On the flip side I've never yet had any indication of brake fade even on genuine mountain descents. Ventoux springs to mind, that was about 13 miles of unbroken descent and it just wasn't an issue.

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ClivePhoto
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Re: Exhaust break

Postby ClivePhoto » Fri Jun 01, 2018 1:06 pm

crinklystarfish wrote:...
On the flip side I've never yet had any indication of brake fade even on genuine mountain descents. Ventoux springs to mind, that was about 13 miles of unbroken descent and it just wasn't an issue.


That's interesting and useful to know. My feeling is keep the speed down and the brakes don't need to work too hard so they're not going to overhead and fade. Let the speed build up and I get the feeling it would be very easy to get into serious trouble very quickly.

Not strictly analogous but a very graphic example of what happens to a brake which is perfectly adequate when things are under proper control but when it all gets too much... (love the cry of despair at the very end!)

https://www.youtube.com/watch?v=lLLBhIJbVFs

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NeilandPat
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Re: Exhaust break

Postby NeilandPat » Fri Jun 08, 2018 10:39 pm

There's a retarder on many trucks here in South America.

I dont know how it works but the noise it generates is beyond belief.

It sounds like a huge digger with a concrete breaker atttachment. You can litterally hear the trucks from miles away when they put it on

Neil

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bromleyxphil
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Re: Exhaust break

Postby bromleyxphil » Sat Jun 09, 2018 5:25 am

NeilandPat wrote:There's a retarder on many trucks here in South America.

I dont know how it works but the noise it generates is beyond belief.

It sounds like a huge digger with a concrete breaker atttachment. You can litterally hear the trucks from miles away when they put it on

Neil

I think that's what they call a Jake Brake and they are now banned in most places due to the noise. It has an extra opening of the exhaust valve.

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bromleyxphil
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Re: Exhaust break

Postby bromleyxphil » Wed Jul 11, 2018 2:38 pm

Well guys this runs on and on, I have been to MAN again today to pick up the correct set of parts for my engine. I hope to crack on with this job before Stratford and there proudly show off my working exhaust break.
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Re: Exhaust break

Postby bromleyxphil » Wed Jul 11, 2018 2:49 pm

For those who are still interested, and I know the length of time this has rumbled on for some have fallen by the wayside. The butterfly doesn’t completely close, I set up a torch behind to show the small gap on the edges but there are also four small gaps one each corner of the hinge.
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Brian-reynolds
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Re: Exhaust break

Postby Brian-reynolds » Wed Jul 11, 2018 4:01 pm

I got all excited that you had it fitted and working! Once again you let your public down!

Can anything be this difficult! Obviously yes!

Keep cracking on with it, I am very interested it the things.

B.

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Re: Exhaust break

Postby crinklystarfish » Tue Aug 07, 2018 8:18 am

Did we ever find out from BK (or anywhere else) whether fuel is required to be cut when the butterfly is operated?

I still suspect it doesn't but am very curious to know the ins-and-outs of the factory-fitted systems on your average 20-40 yr old truck.

It occured to me that as a result of a rather embarrasing self-inflicted moment that manual non common rail systems might even suffer airlocks if fuel is cut


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