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Topic: D-Celerator Exhaust Brake (Read 2187 times) previous topic - next topic

D-Celerator Exhaust Brake

I was working on our exhaust brake this week (installing a new air cylinder), and thought I might take the opportunity to post a few photos and a little info.  It is a U. S. Gear Super Duty D-Celerator, Model EXB-4000M, air-activated, for 4" exhaust pipe.  This brake was installed on our coach when we bought it.  I knew nothing about these devices before we bought our coach, but I have of necessity learned a bit along the way.  I can't compare this exhaust brake to others on the market, because this is the only one I have ever used.  It does seem to provide a worthwhile braking force when traveling in the mountains, but of course it is nowhere near as effective as the Allison transmission retarder.  Still, for those members who, like us, do not have a retarder it is one possible means to improve braking performance on long down grades.

The principle of these brakes is pretty simple - you close a big full-bore valve inside the exhaust pipe (downstream of turbo), and the increased engine back pressure, transmitted through the transmission to the rear wheels, slows the vehicle.  Exhaust brakes work better at higher engine RPM, so you need to manage your gear selection to take maximum advantage.  If the torque converter in your transmission does not lock up in the higher gears, the effectiveness of the exhaust brake is severely reduced.  The back pressure produced by the brake must be controlled, because excessive back pressure can cause "valve float" and damage the engine.  All of the exhaust brakes currently on the market utilize some means of limiting the back pressure.

Our exhaust brake is designed to produce a maximum of 35 psi of back pressure, because our Cummins C8.3 has the standard exhaust valve springs.  If desired, I could install heavy duty "60 pound" valve springs in our engine, which would then allow us to increase the back pressure produced by our brake to 54 psi.  60 psi seems to be the generally accepted (by manufacturers) max allowed pressure for exhaust brakes.

I won't go into any detail about how different manufacturers control back pressure - they all have their own pet design.  The brake on our coach has a small spring loaded "bypass" valve that allows exhaust flow around the large closed main valve when maximum back pressure is achieved.  You can see this bypass port in one of the photos.  The idea is that when the brake is activated, back pressure will rise to the maximum value, then be held there.  This variable pressure design allows better performance at lower engine speeds, while at the same time protecting the valve train at high engine speeds.

By writing this little report, I'm not trying to promote this product.  I just want to add a few bits of info to the great collection of knowledge on this Forum, and perhaps enlighten those who, like me, have never seen the inside of a exhaust brake.  If anyone has any questions about this model, I'll be happy to try to answer.

More reading material here:

D-Celerator Diesel Exhaust Brake

Re: D-Celerator Exhaust Brake

Reply #1 –
Is U.S. Gear still in business?  ???  We had one of their overdrives that needed a part and were told "NA".

Re: D-Celerator Exhaust Brake

Reply #2 –
Quote from: mike leary –
Is U.S. Gear still in business?
Yes, kinda, sort of, but they were merged/absorbed/bought out or something by AP Products, which now markets the braking devices.  Don't know if they would have parts for other products.  The link below is where I purchased the new replacement air cylinder:

Exhaust Brake : AP Products, RV/Mobile Home Hardware

Re: D-Celerator Exhaust Brake

Reply #3 –
I had the heavy duty springs installed on my 93. 93 was when Cummins moved to the HD springs. Cummins can look up your engine. I was required to have the 60# springs for my PRXB Pac Brake. The Decelerator incorporates a unique design that is equal to the PRXB.

Re: D-Celerator Exhaust Brake

Reply #4 –
Quote from: Dave Head –
Cummins can look up your engine.
Hey Dave,

When we first acquired our coach, I read all your past posts concerning your PRXB exhaust brake with great interest, since you are one of the few members with pertinent experience.  In fact, I first became aware of the valve spring factor after reading your missives.

Since I am registered with Cummins QuickServe Online, I have access to all the build data for my specific engine.  It lists my valve springs as "Standard", part number 3906412.  That number checks as being the "weak" springs.  Our engine build date, according to the engine data plate (also viewable in QuickServe), was 15 JAN 1993.  Dang IT!  Just missed the good stuff!

The Super Duty D-Celerator is available with two different bypass springs - 35 psi and 54 psi.  The part number on the spring canister on my brake assembly checks as being the 35 psi spring, so they got that right when they installed the brake (one of the early POs).

We have crossed the Rockies a couple times with our 4000lb towd/tow dolly combo, and I found the exhaust brake was very effective, even at the lower back pressure setting.  In 4th gear at 2500 rpm, it will maintain about 45-50 mph on some REALLY steep descents, without my ever touching the service brakes.  If we were driving in the mountains all the time, I might install the heavier valve springs, but for now, I'm satisfied with the brake's performance.

For Cummins owners who are not signed up, highly recommended:  Cummins QuickServe Online

Re: D-Celerator Exhaust Brake

Reply #5 –
Good for you - another example where the D-celerator is better. Pac and Jake only offer 60 psi options on the C8.3...