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School Bus Emissions For 2014

The first diesel engine manufacturer I think of for emission changes in 2014 is Navistar who never went to an SCR system likes it’s counterpart at Cummins. The Navistar design just used the EGR to control the recirculated exhaust gases internally and in doing so had to pay for credits to the EPA to keep their system on the road.

But now they have switched over to the Cummins ISB which in my mind will be the stand alone diesel engine for medium applications. Cummins has developed the SCR (selective catalytic reduction) along with the DPF (diesel particulate filter) to keep up with demands from the environmental protection agency which uses California emission standards as their template for the rest of the country.

Canada has to follow these guidelines as well since all of the equipment and drive trains are manufactured in the USA. In our case Navistar buses are built in Memphis Tennessee while Thomas buses are manufactured in Highpoint North Carolina.

Since I started with the school district the emission changes have changed drastically. Not that I am against this move going forward but it’s advancing faster than it should before proper testing. This has been proven with the Mercedes medium engines we have in our fleet right now. We have logged hundreds of hours troubleshooting these engines.

From day one in 2007 there were many problems with these engines right out of the gate with raw diesel exhaust leaks and engine codes that were developing non stop. It’s still happening to this day and we still have 6 or 7 years left with these models. The cost to repair these engine codes with replacement EGRs and sensors alike is continuously occurring and with warmer weather the DPF codes start to accelerate like clockwork.

I’m extremely happy with the Cummins ISB and their tried and tested SCR / DPF system which will give us more reliability and best of all less break downs. Running a fleet is a busy proposition especially with preventive maintenance which we carry out diligently to prevent unexpected break downs.

The only extra service step we need to keep our eye on with the 2014 Cummins engines is the DEF (diesel exhaust fluid) that has to monitored and checked during services. It’s part of the SCR technology which works as long as you support it with care and attention. If you would like to ask a question or comment please do so or ask a question on the mechanicshub.com forum.