Blow-By & Boost

Did you ever wonder why the Acert Caterpillar engine has a lot of blow-by? Did you ever stop to think why they have so much turbo boost with only moderate horsepower for the amount of turbo boost being produced? Think about this: a good-running single-turbo 3406-E or C-15 single-turbo engine producing 550 hp requires 32 psi of turbo boost and the Acert 475 produces 38 psi of boost, while the 625 Acert is as high as 60 psi of boost. The single-turbo engine produces about 17 to 18 horsepower per pound of boost and the Acert twin-turbo is only between 11 and 12 horsepower per pound of turbo boost.

Now, think about those numbers. Why does the Acert twin-turbo engine rank so low on horsepower per pound of boost? Well, what makes turbo boost? Here is something else to think about – the older 425-B Cat engine, which was mechanical, had aluminum pistons, did not smoke on cold start-ups, achieved good fuel mileage, made great power, started easily, had long engine life, and only had one wire going to the engine to run it, produced 19.3 horsepower per pound of turbo boost! That is 60% more power per pound of turbo boost than the 2004-2007 Acert twin-turbo engines. And how about efficiency? Well, that old 425-B has it ALL over the Acert!

The 1998 through 2002 Signature 600 ISX Cummins produces 18.75 horsepower per pound of turbo boost, which is 50% more power per pound of boost than the Acert. When I evaluate an engine, the first figure I look at is the horsepower per pound of turbo boost ratio. That number will start the equation as to how efficient an engine is on fuel mileage. This is just the start of the equation on our quest to obtain 9 mpg from a truck, but it is a very important number.

So, here we are with the C-15 Acert BXS, MXS, NXS and the SDP with a DPF muffler producing only 11 to 12 horsepower per pound of boost. As you can see, the cure for the Acert is to lower the turbo boost and raise the horsepower, thus eliminating the excessive blow-by. Once that operation is performed, the engine will gain 1 mpg, pull like a bear from 1,200 RPM up to 2,000 RPM, and be your all-time favorite diesel engine to drive – it will also gain 50% more power per pound of boost over the stock Acert.

The efficiency of a diesel engine is greatly determined by how much power it can produce per pound of boost. The all-time highest producer of horsepower per pound of turbo boost was the Cummins KTA-600 (see photo), a mechanical engine that was released in 1976 for on-highway use that produced 23 horsepower per pound of turbo boost. So, why do our newer EGR engines have to produce so much boost for only moderate horsepower, run with higher internal pressure, burn more turbos and exhaust manifolds, leave soot along the side of your trailer, and have more failures than we did in the 2002 and older engines? I guess that question is a rhetorical one – just some things to think about. There are cures for these engines, but they are NOT plug-and-play solutions and they cannot be sold in a kit.

Pete Sharp, our Vice-President, and I had the opportunity to recently meet with Craig and Lyle of MicroBlue Bearings, Inc. If you listen to Kevin Rutherford’s radio show (The Trucking Business and Beyond), then you may have heard of MicroBlue, a revolutionary new coating that reduces friction between moving parts by changing the way lubricants work and interact with the metal surfaces. We asked, “What is MicroBlue and how does it work?” Craig answered by saying, “It’s commonly thought that blow-by is caused by leakage between the piston ring faces and the liner bore surface. Although possible, the leakage in fact happens when the gases go around the back of the ring, roll underneath it, and lift it off the bottom of the ring groove. The primary reason for this is the design of the piston rings used in diesel engines, where the primary goal is to limit carbon build-up. However, that effectiveness comes at the expense of ring seal. So, how do we improve on this design? That’s where MicroBlue enters the equation. The makeup of this coating has an active interaction with lubricants on the atomic level. In the case of ring and ring grooves, this interaction results in considerably greater oil retention. In effect, what this creates is like two pieces of glass with oil between them – you CANNOT pull them apart. The same thing happens with the rings and ring grooves. If you cannot lift the ring, it simply cannot leak.”

I will tell you, we at Pittsburgh Power are never the first to jump on the bandwagon and endorse a product or process that we are not sure of or have not tried ourselves. I have spoken with three owner operators who are running 12.7L DD4 Detroits with MicroBlue-coated cylinders, rods and main bearings, and they are seeing increases in their miles per gallon. Starting on November 5, we will be rebuilding a 460 hp N-14 Cummins and will be using the MicroBlue process on all of the parts that come in contact with oil. I will inform you as to how this engine performs later this winter. This truck currently has a MicroBlue-coated 10-speed transmission which has gained half a mile per gallon and 7 mph on the hills of southwestern Colorado. It’s an interesting process and we are looking forward to implementing it into our rebuilds if it works. If you have any comments or questions, I can be reached at Pittsburgh Power in Saxonburg, PA at (724) 360-4080 or via e-mail at bruce@pittsburghpower.com.