Thread: 300Tdi exhaust brake - possible

A lot of Japanese trucks employ this simple type of exhaust brake, so it should work.

I've always wondered if the stalled exhaust gas would fatigue or break the turbine impellers, but keep thinking about the Japanese truck example.

I'm also waiting with baited breath for the first person to try this

I would be very simple really to fit one,as far as overpressure you could just make the flap about 1/3 smaller than the exhaust so it can't choke off the pipe.I would go to a truck wrecker and look at some of the small trucks or buses,vans as you could just swap it over.You could also fit real brakes on the van axles and make it stop itself,that is what I did with my shooting buggy trailer and that is a better choice IMHO. Pat

the flap valve works, and if you set it up right and drive it smart you wont encounter valve float.

set the flap valve up to choke it off and then drill 2 1/2 inch holes in it....

depending on how you set it up you may want to drill them on opposite sides of the flap or both on the side that helps close it which will make it open up faster when your turn it off...

Its embarrasing when you install it the wrong way around and when you turn it on it wont turn off till you kill the donk.

When you say drive it smart do you mean keep the RPM low?

BBS

Originally Posted by PAT303

You could also fit real brakes on the van axles and make it stop itself,that is what I did with my shooting buggy trailer and that is a better choice IMHO. Pat

Hi Pat,

Well, the 'van has 4 x 10" Alko electric brakes that are well adjusted and do their share of the stopping. But after a long downhill run, they and the Disco's discs are going to be seriously hot, even using the gears to help as much as practical. What did you have in mind?

Ian

PS: I never 'ride' the brakes all the way down a hill. If the rpm get up to nearly 3500 in whatever gear I'm in, I usually brake firmly 'til the revs are down to the lower 2000s, then let the brakes off to cool a bit until the revs climb too high again. Is this good practice or is there a better way?

and lets face it, a Tdi's engine braking is pretty poor.

I've contemplated an exhaust brake quite a few times.
When you're in low low pointed straight down a hill and continually having to ride and try and modulate the brakes over a loose surface to keep the speed sane, you really wish the engine had more friction.
It's the same when towing, even SWMBO comments on the lack of engine braking in the 'fender compared to her TD42T Patrol engine.

Originally Posted by Leo109

Hi All,

Has anyone actually fitted an exhaust brake to a 300Tdi? (Did a search but didn't find anything specific.) Been thinking about this recently and would like to explore the possibilities.

Our caravan has an ATM of 2300 kg and weighs in at not much under this. With two people and a fair bit of gear semi-permanently in the back of the Disco, our GCM is at least 4.5 T. This takes a bit of holding back on long down hill runs - something which Tasmania (our present location) has plenty of.

I do of course change back to 3rd and even 2nd at times to reduce the strain on the vehicle and 'van brakes but often some extra retardation would be helpful. I could use 1st or even low range (and have done so on a very steep gravel road decent) but this starts to get dangerous on busier roads. Other drivers expect to encounter semis and B-doubles crawling down mountain roads at walking pace (well, some idiots don't), but seldom caravans. Being shunted down the hill by an unsuspecting unladen truck is not a nice thought...

A bit of reading in an old Bosch Automotive Handbook suggests the main limitation and danger in using a simple exhaust flap valve is developing excessive exhaust manifold pressure at high rpm. This apparently can cause the exhaust valves to stay open, with nasty consequences next time the piston comes up! To counter this a pressure reduction valve to bypass the flap seems to be a good idea.

So, Gurus of such matters (like those with truck engine experience), is there an exhaust brake unit around (preferably one with an over-pressure bypass) of a size and shape that might suit a 300Tdi? Even better, has anyone fitted one and is it worthwhile?

Ian

PS: The thread title should have read "- possible??"

Hi Ian

Approx six years ago I responded to an exhaust brake kit ad I saw in a 4WD mag and recieved a pamphlet that discribed it in detail. The kit was fitted to a patrol but the supplier advised it would be ok on my Disco 200 TDI. I don't know if I still have the pamphlet. I will check around and advise.
The kit manufacturer was in the Cairns - Atherton Tablelands area.
Regards
Graham