Converting DDEC I to DDEC III or IV

[Hard Headed Ken]

There is a discussion on the Prevost Community board about a DDEC I to III or IV upgrade. I'm reasonable sure it can be done. Has anyone here done it or know about it?

Thanks
Ken

[Don Fairchild]

Ken, howdy how you doing. If you are going to change from DDEC I, I would go all the way to DDEC IV even Detroit goes from II to IV.

I believe you will change or make a new wiring harness front to back to eliminate the double computers and add several sensors, a new timing wheel and new srs and sts pickups.

If this is for Bills bus I have a call into a Detroit Dealer to see if I can get him a new E-prom  That is probably his problem. can you burn one if I found a blank one or do you have any blanks you can burn.

Don

[Don Fairchild]

Ken, I forgot but you also have to change camshafts and injectors. he would be better off to go back to mechanical. pull the blower install a Gov. racks, link rods, injectors and run an air throttle.

Don

[Hard Headed Ken]

Don,
I talked to my long time friend from Covington Detroit Diesel today. He says he did one a few years ago where he went from DDEC 1 to 3 and it required an ECM, engine harness, a different boost sensor, an intake air temp sensor and like you say maybe a new chassis harness. Maybe it's been long enough he forgot about changing the cams. I'll call him back tomorrow.

It is Bill's Bus

I don't have anything to program DDEC I. I do have extra DDEC I control modules, one for a 6V92 and one for an 8V92. I told Bill if I can figure out which one is which he's welcome try it.

Ken

[luvrbus]

They do need different cams they changed about the middle run of the DDEC II that was a costly lesson for me  The firing order is totally different in the way the DDEC I vs the DDEC II and up read, the DDEC I is a standard mechanical engine timing it seems like one could program the IV to do 1L,3R,3L,4R,4L,2R,2L and 1R so the cams would not need to be changed ? 

[Hard Headed Ken]

looks like Don's advice to go back to mechanical would be best in this situation.

Firing order - I know I must be overlooking something but instead of changing cams or reprogramming could you just rearrange the pins in the injector harness? like rearranging the wires on a distributor cap? The ECM sends out a signal ever 45 degrees on a 2 stroke for an injector to fire (is that right??) rearrange the pins so that signal is going to the injector that is coming up on TDC.  Make me feel stupid, what I missing, gotta be something or I think Detroit would have done it.

Ken

[Hard Headed Ken]

Don,
I think we talked about switching around the injector wires to change the firing order maybe a year or two ago. I can't remember if we reached a conclusion. What do you think? I must be overlooking something simple. I know you would get the wrong cylinder cutout on the diagnostic side but that's about I can think of.

Ken

[luvrbus]

I could never understand the reasoning why Detroit and Motorola did that ? if a automatic 700 series with the ATEC is that going to be a problem with the IV or is it going to need changing to WTEC

good luck

[bevans6]

Here is my dumb question for the day - I seem to recall that the bank angle of the V-series DD two-strokes is not 90 degrees, it's 75 degrees or something like that.  I also seem to think that the cranks shaft is the typical shared-pin crank with the throws at 90 degrees like any V-8 crank shaft.  Would that not make the actual firing timing uneven, so it would not fire at 45 degrees?

Brian

[Hard Headed Ken]

I think it's not ever 45 degrees. Wasn't thinking about two cylinders on the same crank pin. So the V configuration will affect the rotational distance between power strokes (I think).

Ken

Found this explanation http://www.caranddriver.com/features/the-physics-of-engine-cylinder-bank-angles-feature

[TomC]

I would by all means go back to mechanical injectors. My first truck had the 8V-92TA at 435hp at 1275lb/ft torque with 9A90 injectors (now 9G90). While I did change the injectors once, in 880,000mi (one inframe overhaul), I never lost an injector. Go for reliability, rather then fuel economy. Granted you can get better fuel mileage with electronic fuel injection-but have one failure because of the electronics, and all the savings go down the drain. Good Luck, TomC

[Don Fairchild]

The DDEC I used J32 mechanical cams and the others used cams made for the DDEC engines. ( easy change back to mechanical) The DDEC II J39 DDEC III-J41 and DDEC IV- J42 cams, timing, valve lift and lobe centers are all different on each of these cams. The DDE I only ran the engine, and had very little diagnostic's to it and if you wanted Jakes and or cruse control it had to be wired separately. DDEC-II you still wired the Jake with one wire out side of the ecm and DDEC-III everything went thru the ecm, That's why the early ecm used a black box to control the V-Tec and or A-Tec transmissions.
They had a lot of difficulty getting the HD transmissions to talk to the DDEC II ecm that's why for the most part you don't see them until DDEC-III. You have to have DDEC-IV or better to run the auto shift trans like you have

The new 5th gen j1939 backbone communications will run every thing from the trans not the engine. There are several other changes to the new systems.

Don

[Hard Headed Ken]

Don,
Thanks for taking time to post the correct information. I think converting back to mechanical is good advice.

Ken

[luvrbus]

I am going to put him in touch with a guy that has a couple of of the Proms for the DDEC I me I think they have been installing the wrong boost sensor over the years

[Mex-Busnut]

I have always wondered why folks with ancient buses want the latest electronics on their engines. Perhaps they will get 20 miles per gallon that way, instead of 7? Or is it necessary when you use an automatic tranny?

Anyway, the PO of our bus told us that when he installed the 6V92TA in it, it came with DDEC (No idea which version.) His mechanic removed all the electronics from it, stating as the main reason:

"Here in Mexico in the mountains or the deserts you may easily find yourself 10 or 15 hours away from the nearest mechanic who can fix an electronic-controlled engine, whereas you can usually get a mechanical engine running again without a specialist."

Might that be right?