Thread: Exhaust jacks and diesel engines - yes, no, or maybe?

you know that diesels come with exhaust brakes right?

Nope, I am a diesel noob.

But thanks to your tip and the wonders of Wikipedia I do now!

[ame="http://en.wikipedia.org/wiki/Exhaust_brake"]Exhaust brake - Wikipedia, the free encyclopedia[/ame]

So is my read right: the increased exhaust pressure slows the fuel intake to the engine, but not be enough to stop the engine? Google tells me some diesel exhaust brakes operate in the 50-60psi range, so given my exhaust jack reckons 10psi is the max operating pressure that's nowhere near enough to stall the engine / do damage.

gets the big tick from me.... however the diesel doesnt restrict the fuel, a petrol with enough back pressure will drop the fuel off as the MAF says less air in the computer demands less fuel in to maintain the correct AF ratio ( a carby does it as well). A diesel, having no direct control over air in, meters the fuel directly. A modern diesel will use a MAF (td5+) to do about the same as a petrol (for emission reasons) whereas a mechanical one will up the injection as the RPMS drop off to try and maintain stable idle. As the AF ratio of an idling diesel is about one wet fart to a roomful of air its not going to cause you a problem.

when it can cause problems is (and this is really only on modern diesels) if you have a damaged EGR valve If its in the wrong spot and not working correctly the EGR mechanism can be damaged by the additional back pressure from the restriction. Yes, technically thats damaging the engine but its just damaging a bit thats already not working correctly so is due for replacement it'll just need renewing sooner.

you can also get problems IF you happen to hook it up while your DPF is trying to do a burn but thats not likely to damage the engine it would more likely destroy the bag from the additional heat being generated by the DPF burn off. You get a really obvious indication if your DPF is trying to do a static burn of, namely automatically varying engine RPMS and a warning light on the dash.

oh and ignore what that wiki had to say about jake and pac brakes (it also didnt mention dynotard) what its got right is the bit about blocking the exhaust path for the exhaust brake (which is what I was referring to with my comment)

Thanks for the clarification. Accelerating the demise of already failing parts does not count as "breaking" in my books either.

PS: I also needed a follow-on lesson about DPF burn off - yes I was off to wikipedia again!

let me know if you need a hand on how that does its magic and link me to the wiki you use.