Engine/Transmission (1994 - 1998) I don't get it...????

[EMD-Run8]

Hello all. Just re-upped my subscription. Hope I haven't missed much. I'm thinking I might like a good used '98 QC 12v. You know trying to go debt free, building a house on fresh bought property, blah, blah, blah. I can't argue with the deal I got on my truck (48 months same as cash) but------I digress. What I don't get is---why do so many guys advance the timing on these trucks when they mod them? I mean I've followed Bruce Mallinson's "Horsepower & Torque" articles for a good while and his mantra is "RETARD THE TIMING" when increasing fuel and boost. Surely he is no novice when it comes to diesels. Educate me please. Oh and besides the KDP and a loose transmission (a 5-spd will be hard to find so I'll probably settle for an auto), what else should I look out for? Thanks to all!

 

[Vaughn MacKenzie]

EMD, glad you're back on here.



So you're thinking to do what I did. . . drop down to a 12-valve from a 3rd Gen truck. I did it and for the most part don't regret it. I do miss some of the comfort features and handling of the '03, but not having a payment more than makes up for it it seems.



The 12-valve is quite a bit different by nature and has its shortcomings like all other iterations of the Cummins TD. I've had some issues with a miss and sluggish power curve down low which may require pulling the pump and having it gone through. But it's running pretty good now and overall I'm happy with my old ride. Besides not having as much stress when things go wrong (because of no payments) it's nice to be able to rack up the miles with nil effect on the value. Mine had 351k when I got it, rolled 372,000 this afternoon.



To the timing, the reason it is advanced is larger injectors take a few microseconds longer to light off so the timing helps offset this. Where did you hear about retarding it? I have never heard of that. Even guys running mega boost advance it. Evidently you're reading about a setup running nitrous and/or propane, retarding it makes sense here I guess.



There's lots to read, I learned a lot from this forum, NW Bombers and just jumping in and doing it. Give it a try, I think you'll find 12-valvedom to your liking



Vaughn

 

[HBrunton]

www.pittsburghpower.com

 

[EMD-Run8]

Hey Vaughn..... Good to hear from you. Diesel Injection of Pittsburgh CEO Bruce Mallinson has a very long running series of articles called Horsepower & Torque that he has produced for years. "Where the Strong Ones come from" is the caption they're known for--------I LIKE it!! Anyway, over the years he has built MANY high horsepower & robust Cummins engines for big trucks and his big thing is retarding the timing NOT advancing it when going for higher fuel/boost. I'll have to review his stuff to see exactly what his reasoning is. The guy's no armchair mechanic! Anyway, it would be nice to hear what folks are doing with their motors. I'm curious to know what shops like Schied & Piers do with the motors they tune and build. So anyhow----like your route I'm thinking hard about no truck payment. Also, as smooth and flexible and refined as the 3Gens are----frankly the electronics make me a little nervous. From some of the threads I've seen, man! When they quit they QUIT!!!! I'm familiar with the 12v, just not with a p-pump. My dad had a '92 D250 and the first test drive I ever took in a CTD was an '89 with that tight 727 Torqueflite and the 3. 07 rear----remember those? I was 21 then and I really think that was the most impressive CTD I've driven yet! I don't know why I just remember that with that tight transmission those trucks had it was like 1st-2nd-3rd in rapid succession and HEY we're doing 60! I know I'll have to do some work on a 47RE but ahh, I'm just thinking right now.

 

[EMD-Run8]

No takers I guess. I read through Mallinson's articles again to make sure of what he said-------and there it is. "Do not advance timing in a Cummins engine" when increasing fuel/boost. I'm stumped. This guy's shop has built and tuned more than a few Cummins engines. Is he wrong or is it a fair warning?

 

[BLujan]

I am curious to the timing issues too, seeing that I have not set mine yet. I've heard that a little advance will give you better MPG, but I have heard everything from stock to infinity to give you more power. From my underdstanding the further advanced you go, the more top end power you gain. The closer you are to TDC the more bottom end power you will gain. I asked Piers in person what I should set mine at and he told me 15. 5*. I also understand that the advancing makes for higher cylinder pressure, so what is the right amount to time it at?

 

[tp0d]

Hmm. . I had my timing advanced by Diesel Injection, and noone said anything to me about it. I took mine from around 12-13 to 16, and the guys there didnt make any comments. . BLujan, you are right about the higher pressures. . here is a quote from their page:



To control the pressure we lower the compression ratio and retard the timing. If you compare the compression ratio and timing of an NTC 290 versus an NTC 400 you will see the difference. Where do you think we have to be on the timing to produce 700 horsepower from an NTC?



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I didnt find any info on the b59, but then again I didnt look too long. Makes sense what he's saying, but my engine runs smoother after the advance, and once I get my azz in gear to mod my plate, the timing advance will really show in lower egts. .



hmm...



-j

 

[ABorchard]

I've read Mallinson's articles before and have come to the conclusion he's talking about the engines in OTR trucks that don't have to meet the emissions standards a pickup does. Our trucks have been detuned to meet emissions and to help the drivetrain make it though warranty. Advancing the timing on a Dodge (to a point) is in reality just putting it back up to what it was designed to be.



I've seen our same B engines in tractors with 17° on the data plate and marine engines listing 23°.

 

[EMD-Run8]

That may be right on the OTR trucks. However, I think they have certain emission standards to meet now also. Perhaps he means don't advance it outside of its specific designed parameters say between 15-23 degrees. I dunno.