exhaust brake compred to a Jake brake

[Bob & Tracey]

Does anyone have expierence with the exhaust brake that is installed in the exhaust system before the muffler compared to a Jake brake on a 2 cycle Detroit?

Thanks,
Bob

[prevost82]

Never heard of one on a 2 stroke ... I doubt if they would work all that well because they don't work as well on a 4 stroke compaired to a Jake.

[larryh]

Bob my company I worked for we put 5 Williams exhaust brakes on 5 over the road line trucks at first 10,000 mile service I installed Jake brakes on all five due to driver complaints and refusing to drive them any more this was on trucks running  Pacheco Pass and the GrapeVine and  the Tehachphi grades day in and day out,

LarryH

ps. one driver said he would have more brakeing standing on running board and dragging a foot.

[boogiethecat]

I've seen them on DD 2 stroke school busses.

My take, from personal experience, all with the same bus as it gained goodies over the years:


Scale 1-10, coming down 6% grades (the grapevine mostly):

No brakes other than service brakes: 0 (arsclencher for sure)

Exhaust brakes: 2 (still an arsclencher) 

Jake brakes: 6 (much easier on the ars muscles) 

Telma retarder: 10 (Don't even think about it anymore)     

[makemineatwostroke]

Some have had problems with breaking the compresson ring on 2 strokes equipped with exhaust brakes

[Jerry32]

exhaust brakes are a waste of time and money. The engine needs to be in high revs to work at all and then hard to tell of they are doing any good. Jerry

[Lin]

Having never driven with either, I am perfectly unqualified to comment.  I am not up to installing an aux brake yet, but will probably have to in the future.  Are the Telma brakes still made?  What is the downside to them?  I believe there are also some other retarder systems, maybe hydraulic, that are integrated into the transmission.  Aside from researching those, Jake brakes to seem to be the standard for the heavy transport industry.  You probably could not go wrong with one.

[boogiethecat]

Hi Lin,

I wouldn't waste my time with exhaust brakes either.  Lots of expense and very little help on a grade.  That said, an exhaust brake is better than nothing for sure, but not by much...

Telma is still made, you bet.  They are almost a requirement these days on all European trucks.. we here in America are "getting it" but slowly as always.


Jakes are good, many trucks and busses have them and they have an excellent safety and reliability history.  Highly recommended.

Telmas are better than anything if you can install one.  Telmas won't install on many busses though, due to lack of space or too short a driveshaft.  My front engine Bluebird was a cinch to add a telma to, but my Crown was much more difficult.  They make two types- one that  goes in the middle of the driveshaft (called "axial) and one (called "focal") that mounts on the rear end.  My Crown required a Focal style and now all I have left for a driveshaft is a 3" piece plus the slip spline joint.  Really short!!

The only thing I can see as a downside to a Telma besides the cost (new about 6 grand plus installation) is that when full on they eat 150 amps or so at 12 volts.  So you either have to have a battery bank that will power it for the full duration of the longest grade you'd ever encounter, or stick in a hefty alternator, or both.  Other than that, the Telma provides me ABSOLUTELY the safest way I've EVER come down a grade, period.

Hydraulic retarders aren't much good for grades because they dump the energy they eat in the form of heat into your automatic transmissions' oil.  Unless you have a whopper of an oil cooler (you won't) it won't last the grade before overheating the tranny.  The telma makes hot air out of the energy it absorbs and that just blows away under the bus. No big deal!!!

As time goes on I will wager that you'll see MANY more Telma's being spec'd in, and fewer Jakes.  They are basically much simpler (no wearing parts) quiet (absolutely soundless) and much more efficient at slowing a vehicle than Jakes ever were.

Here's a photo of the Telma I stuck into my Crown.  It's sitting on a "high pinion" rear end which raised it up enough that my ever-so-short driveshaft now has excellent angles.
It was quite a ride to stuff all that into the old girl!!!

[TomC]

Rest assured that an exhaust brake cannot be used on a 2 stroke engine.  Why-because all the back pressure created by the butterfly valve in the exhaust will be absorbed by the blower, since the blower on the Detroits are what is called a positive displacement pump.  Hence you'd burn up the blower in a very short period of time with an exhaust brake.  On 2 stroke Detroits, only a Jake or Pacbrake are available (same idea, different manufacturers).  You can use an exhaust brake on a 4 stroke, but it only produces about 150-250hp of braking, compared to around 400hp for a Jake brake, or up to 800 hp for the Telma electric retarder.  Good Luck, TomC

[larryh]

I thought the question was exhaust brakes compared to Jake brakes. Then everybody started asking and remarking about telma retarders not even connected to engine except via driveshaft which 95 per cent of our buses cannot use anyway no how. back to question exhaust brakes vrs Jacobs brake no comparision on 2 strokers.

LarryH

[boogiethecat]

Tom, I got my original exhaust brakes off of Crown school bus that had a pancake 2 stroke DD in it (6/71 I think), blower and all.  Evidently it worked well enough to be safe for the school system, and it was a factory install, not an aftermarket.  So they do happen although I won't argue if it's a wise thing to do to your engine or not...

Larry, sorry, I get carried away when people start talking about engine braking systems.  I know the question was addressing exhaust brakes vs Jakes, but it did also ask if anyone had experience with the two, which I do, firsthand.  When these discussions come up, I always like to give the whole story, because some of us just might be able to use a product that is superior to either of the others, and I think when safety is an issue one should know all the options.  I'm in a good position to actually talk about all three systems since I've installed and used all three on my bus, starting with nothing, then installing an exhaust brake and gradually moving through Jakes up to the Telma... and from that experience I feel that I can make quite informed comments on them, and should.  This is all about "insurance" as far as I see it, and everyone with a bus who drives the grades should know all the options...

Cheers
Gary

[Lin]

I actually appreciate it when the replies here, aside from covering the subject, include deeper information.  Sometimes the most useful tips are just dropped in.  Thanks all, Lin

[HB of CJ]

Way way back in 1970 or soooos, the 1963 Crown Super Coach 92-passenger 40-foot 3-axle 10-wheeler school bus I drove part time had a 220 hp 743 inch Cummins engine with a single stage Jake.  Did run the Ridge Route (the north half) both ways loaded with 50 to 60 high school kids.  The Jake absorbed more power than the Cummins put out!  Never had to touch the service brakes.

My current 1974 Crown 40-foot-3 axle 10-wheeler ex-schoolie maybe some day to become a motorcoach has the Williams exhaust brake.  The bus has a 250 hp non turbo 855 Cummins engine.  If memory serves correctly (quite suspect!) I would say the Jake worked at least twice as good and perhaps three times as good as the Williams exhaust brake.  Subjective.  Hope this helps. 

[DrivingMissLazy]

I thought the question was exhaust brakes compared to Jake brakes. Then everybody started asking and remarking about telma retarders not even connected to engine except via driveshaft which 95 per cent of our buses cannot use anyway no how. back to question exhaust brakes vrs Jacobs brake no comparision on 2 strokers.

LarryH

Larry, I have to agree with the others, the other information is valuable to some, maybe not to you, but there are 1600 other users on the board also. I suspect that many had never heard of the info about the Thelma alternative.

Richardd

[larryh]

Richard I will not answer any other questions on this board then. That is how a good infomation gets hijacked and never found again sorry to have bothered.

LarryH