Foretravel Owners' Forum For owners and Fans of Foretravel Motorcoaches September 11, 2025 ...

Well that just takes all of the fun out of life.  Do you think the early adoption was a last gasp attempt to meet emmission standards?

The 92 series was introduced in 1974 and the electronic controls aka DDEC was introduced as an option in 1985. It was the first heavy duty diesel to feature the electronic controls. It continued to be used for highway use until the end of 1994 when Detroit introduced the 60 series. The 60 series was the first HD diesel to have electronic controls from the engine's beginning.

When Mercedes (Daimler AG/MTU) took over control of Detroit, they took the famous 60 series engine and made changes to it and it's now sold as the DD13, DD15 and DD16.

To smog 92 series 2 cycle, a lot of major changes would have had to be engineered. As you probably know, the 92 series has no injection pump but rather has unit injectors with each cylinder having it's own injection pump/ injector.

The big advantage for a motorhome is the very low failure rate.
Pierce
https://www.youtube.com/watch?v=XaKhIjYazrk

So please tell me this:  What changes were made to the fuel injection system with the advent of the DDEC system?
My being raised in New England, during the last ice age, the idea of a diesel engine whose injectors are on whoopee until oil pressure is raised revolve around "God!  That engine is tough!"
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DDEC II (that all U300s have) is what determines when and how much the unit injectors inject. Instead of a rack (steel rod) that twists to controls all the injectors in unison, there are wires that go to the injectors. There is a pressure relief valve on both  systems (like most diesels) that keeps diesel from draining back to the tank so the engine starts quickly. The camshaft on both systems has a pushrod that goes up to the injector and creates about 3000 psi.

With the mechanical system, the rod has to control all the injectors evenly so they are working at the exact same time. The amount of fuel is mostly controlled by the size of the injector nozzle. The DDEC beats that all to hell as the signal from the ECU triggers the injector to spray and even better, how long it sprays. To get more horsepower, the DDEC ECU can be modified (by Detroit) to increase length of time the injectors spray. The longer they spray, the more horsepower the engine makes.

So, instead of having to have a lot of mechanical ability, the DDEC only needs an inexpensive reader with a LCD display to see how the injectors are working and it even cuts a cylinder and checks the RPM drop and how much more fuel the other injectors have to add to keep the RPM stable at either the 600 RPM idle or at 1000 RPM. It does almost 50 other functions that would take days for a shop to do.

The down side: the mechanical injectors are dirt cheap at about $50/each. One electronic injector costs the same as replacing all six mechanical types.

The only other down side it that now, the engine has to have electricity to make the ECU work. The mechanical versions don't need any juice to run, not even for a fuel solenoid. Nothing.

Replacing a mechanical injector is a little tricky as they have to be at just the right height plus the rack may need to be adjusted so the engine runs smoothly.

Here is a guy "running the rack" on a mechanical Detroit.  As you can see, it's not difficult, just time consuming.

https://www.youtube.com/watch?v=YZ-31etm0a8

Replacing a mechanical injector. Note that all four valves are exhaust valves. Intake is through ports in the cylinders.
https://www.youtube.com/watch?v=MSk3bTCxZ0U

Thank you very much.  I never thought that the Detroit Diesels made it into the modern age before being superseded for emission control purposes.  Also many thanks for telling me how they accomplished the fact.
I've always had a soft spot in my soul for 2-stroke diesel engines for their potential thermodynamic efficiency, the cold end stays cold and the hot end stays hot.

That's the trouble with 95% of the DIY bus conversions. Poor vision, DIY skills, etc. But the high end buses would fit in where a mobile brothel was needed.

This Greyhound conversion is the best I have ever seen for any motorhome here or in Europe. Wish I had the talent to do something like this:

I have the software on my laptop. I have Detroit software and can and am writing , changing, modifying ecm programs But have just done DDEC3 and IV. DDEC II has a different harness and I have not gotten it yet. The software allows you to upload a copy of the calibration in the ecm. You then save it on computer. You then open cal in the software and make your changes then save as another cal.  Then you can download the new cal in the ecm snd try it outm you still have a copy of the original cal saved on computer if you want to go back stock. Its pretty cool i have been playing with my semi ECM trying different tunes etc. The calibration has to be opened using the correct meta file I have all ddec 3 and 4 but only 1 ddec2 so far. The DDEC3 and 4 are so superior to the ddec2 . When i figure out the ddec2 cals I'll clue you in to what  can be done.

Maybe my HP tuner Pro package can trim these.
It does 99 % of post 96 vehicles.  Spent enough it should.
It has to have the OBD data port.