By Scott Dalgleish
While I was up having the PRXB and air bags installed in my 1998 Turbo Diesel this past winter, I was treated to a look and test ride of the all new P-67 engine brake for the Cummins 6.7.
How does it work? Unlike an exhaust brake which is the typical “potato up the tail pipe” device, the P-67 engine brake holds an exhaust valve open to take advantage of the engine’s compression stroke to build retarding pressure as opposed to just using the exhaust stroke. The results are amazing!
The brake is a system of electronic and hydraulic components housed in an aluminum body, which replaces the “spacer” on the top of the head, below the valve cover. Within the new spacer a solenoid actuates a valve that uses oil pressure to hold the exhaust valve open, thereby taking advantage of the engine’s compression stroke.
The brake is controlled via a programmed module that automatically engages and disengages under varying conditions, making the use of the brake as simple as turning on a switch. The test vehicle I rode in had a 20,000 lb. load and was equipped with the cab and chassis version automatic transmission. We descended six and seven percent grades using service brakes, the VGT exhaust brake, both the P-67 and VGT brakes and just the P-67 engine brake. In a word, the brake’s performance is impressive!
During our test-drive we descended grades that required hard service brake application. Then we repeated the same descent using the VGT brake and service brakes…better, but still required a significant use of brake pressure to control the service truck’s speed. Next we used both VGT and the P-67, and not only did we not need to apply the service brakes, our speed actually SLOWED during the descent.
The sound of the P-67 meets the global requirements for noise, but has a definite big rig tonal quality, the kind Turbo Diesel owners will love. Will every Turbo Diesel owner NEED one? If you are using your Turbo Diesel to haul heavy, then I would put it on my list of GOTTAHAVITTS… but then you be the judge.