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High Performance Diesels
Testing the performance computer

Great news: We have leased a truck with an N-14 electronic Cummins engine to do the final testing of the performance computer. Our initial plans were to have the computer, which increases horsepower, ready for the Louisville truck show. However, not having a test truck slowed the process. That problem is behind us now and the performance computer is nearing production.

When you install a performance computer, here's some things you can expect. More fuel is injected into the combustion chamber, so the volume of exhaust also increases. Today's engine manufacturers are using very small wastegated turbine housings on the turbocharger, which are very restrictive. We will be testing the various N-14 engines with the increased horsepower to determine the back pressure in the exhaust manifold and we will be able to advise you as to which housing is the most efficient for your particular application.

Yes, the performance computer will enable you to develop horsepower and torque easier on the electronic engine than on the mechanical engine. However, the same principles apply. Plenty of fresh air must be available through the air cleaners. The exhaust system must be able to evacuate the burned hydrocarbons from the engine.

Next in line are the mufflers. Recommended are straight-through style, now available at your local Cummins distributor. Cummins has purchased Nelson exhaust systems and Nelson has an inexpensive muffler that can be converted to a straight-through flow style simply by forcing open a cone in the top of the muffler. That is what I have on my truck and they produce a deep sound. My primitive style of testing showed that the cheaper the muffler the least amount of backpressure. Now, that sounds great. It's cheap and it works. Expensive mufflers are very quiet. However, to make the quietness the backpressure greatly increases.

During my travels I am finding many NTC engines that are not using the dual fuel line system. I'm surprised that owners of trucks are not taking the time to install such a simple device. The engine will run smoother, gain 25 more horsepower without increasing fuel pressure and, as a result, fuel mileage will also increase. All of this for 75 bucks. How can you beat it?

How many of you are still using the No. 10 stratoflex suction line? Changing to a No. 12 line from the fuel tank to the injection pump greatly decreases fuel restriction. The end result is more horsepower without increasing fuel pressure. Don't forget to install the larger fuel filter and filter head designed for No. 12 fittings while installing the No. 12 line. 

If you would like our booklet on high performance Cummins diesels, give Aimee a call at 724-274-4080. The booklet is also available at Our e-mail addresses are, and

The above column is the opinion of the writer and does not necessarily reflect the opinion or beliefs of Land Line Magazine or Cummins Engine Co.