Exhaust brake temps

[DNewell]

Alright guys, I've been with TDR now for a year, and just renewed because of all the helpful advice I've gotten. Now I've got some more questions that I'm looking for advice on.

I was talking with my brother the other day about the fact that when I get my tax return, I'm going to get an exhaust brake for my truck. With a 13k# 5er, and hilly terrain, I think that it's in my best interest to do so. I've already decided on a Pacbrake model, and won't really contemplate anything else at this time.

here's my quandry: When using an exhaust brake, what kind of exhaust temps can I expect to see and does anyone know what can potentially happen to the motor while using the exhaust brake? I hadn't ever thought of it this way, but it takes engine power to create exhaust which ultimately is backed up to create pressure on the pistons. when doing this, it is generating energy, which must be distributed in the form of heat. Basically the same principle as energy to move the truck forward, it takes energy to hold it back.

I guess that with all the trucks out there with exhaust brakes that don't have problems, I suspect that I won't have a single problem. However, I'm just really curious as to see what some of you are seeing on EGTs and if anyone knows if I'll see an increase potentially in engine temps.

 

[RustyJC]

The exhaust brake doesn't engage until you are off the throttle, so all you're pumping against the exhaust brake during braking operation is compressed air. This is what creates the retarding horsepower - the e-brake turns the engine into an air compressor, and it takes horsepower to drive it.



Therefore, EGT (other than whatever restriction is offered by the open e-brake valve during normal operation) isn't a factor. In fact, Cummins recommends use of the e-brake during sustained idling to bring EGTs up enough to prevent varnish formation on the valve stems, which causes stuck valves and bent push tubes (pushrods).



When towing, mine shows about 200 degF (pre-turbo) when coasting downhill without the e-brake and 500 degF (pre-turbo) when the e-brake is engaged.



Rusty

 

[brista]

DNewell you will not see an increase in EGT's because of the EB. I tow heavy with mine and it makes no difference in how high EGT's get because it does not activate until you are off the throttle. What you will see is a much slower cooling of EGT's while the brake is activated due to the exhaust restriction. This is perhaps a good thing as it takes away the wild temperature fluctuatuations you get when cresting a hill while towing heavy then beginning the descent. Without EB the EGT's will drop like a stone, with EB on the EGT's will fall but much slower.

 

[DNewell]

Alright, this is the information I'm looking for. Thank you both for getting back to me with this information. I would have checked sooner, but been crazy busy at work and all. When tax return cometh, Pacific Clutch and Diesel getteth slightly richer. Thanks!

 

[wcjp]

Friend with a 99' 5spd sees about 600deg preturbo with EB engaged.

 

[cojhl2]

This is perhaps a good thing as it takes away the wild temperature fluctuatuations you get when cresting a hill while towing heavy then beginning the descent. Without EB the EGT's will drop like a stone, with EB on the EGT's will fall but much slower.

Years ago when exhaust brakes were new in the big trucks, (At least to me they were as I had not seen one before 1957 or so) the old timers told me they were designed to eliminate that big temp change brista talks about.



It was not only the quick cooldown, but here in the West where we have long down grades the combustion chambers would cool way down, then when at the bottom a big fire would be built. . Very hard on engines.



In fact we were taught to not remove the accel pedal all the way just to keep some burn in the cylinders.



I always thought the retardation came as an added bonus,, not as a result of a requirement.



The real "Jake Brake" came later and works not by closing off the exhaust but by opening the exhaust valves at near Power TDC. .

 

[McLaughlin]

I'm at about 6500 ft elevation and idling with the Pac Brake off my EGTs are about 400 with the Pac Brake on the EGTs run about 600. Costing down hill empty and not polling, I've seen temps on the order of 400 or 500 with the Pac Brake on and less than 300 with the Pac Brake off. My daughter pulled a loaded 30ft horse trailer over Wolf Creek Pass (10800ft) and on the downhill side (5000 ft drop) only had to touch the truck brakes twice in about 20 mi so there is a definite benefit from using the Pack Brake.