With all this talk about pressure boxes and rail pressures and such, I decided to try and get some straight info from Cummins. I went by the Cummins Northwest facility today and got a little info, but they recommended I call the big office in Seattle and the parts guy gave me an inside Tech Line to call.

The Cummins Northwest engine techs didn’t have too much to say. They said they had heard rumors of this happening and that happening, but admitted that these engines are still too new and they don’t get many of them in at all that are having issues. They did say that raising fuel rail pressures will have an adverse effect in the long run but couldn’t elaborate due to lack of testing (my call to the Seattle office went into more detail). They looked up the specs and said that the fuel rail pressure is at 3200 (yes hundred, not thousand) psi at idle. At wide open throttle, based on the amount of air available, it will steadily increase rail pressure to a limit of 23,300 psi, according to the manual we were looking at. Oh, and this is for the 03/04, not 04.5. They didn’t even have the new manuals for the 600 yet. He said to be careful with anything involving “pressure”, as there are many components in the fuel system that are only designed to operate at the stock tuning parameters. That was about all they could tell me, but as I’m headed out the door he said to come see him when I’m ready for bigger injectors.

Then I call the Seattle office. This tech person said that pressure is the worst method you can use to gain performance, but if you have the money to replace parts when they go, then it is not that bad because it shouldn’t cause anything catastrophic. Fuel injectors, he said, was the issue (as some of you have suspected). He said that the fuel system was designed to have a certain amount of acceptable wear on the parts. He said the injectors have an average expected life span of 150,000 miles. When I told him I would have thought this was longer, he said yeah, but again that is average. Good fuel and proper maintenance (filters) will get you over 400,000, but the average person does not take good care of their stuff. He said particles (dirt) in the fuel are what kills them. He said everything has to work harder with increased pressure. He said the problem is that with increased pressure, the holes in the injectors get bigger faster and the springs inside the injectors get looser than they would under normal use. He said this would lead to leaky injectors and a poor running engine because the injectors are essentially “honed” at an uneven rate from all the dirt being forced through at higher than standard pressures. He then said in a worse case scenario, small metallic pieces of the fuel system (from inside cast parts) can break off under the increased pressure and clog the injector, which will ruin that injector, or pass through and usually get blown out the exhaust. All in all, he said increased pressure is not a big deal. Sure, it will ruin your injectors, but you just replace them. That is where the “but if you have the money to replace parts when they go” comes into play.

I then asked him about the timing and duration boxes. He said that advancing timing and increasing duration would not hurt the engine until the parameters are put into a position that causes the engine to run bad. He said it is a matter of smooth operation. He said a smooth running engine is being as gentle as possible to parts like bearings and such. He said put the engine into a position where it looses its smoothness and you are putting uneven stress on internal parts, which will take its toll rather quickly.

On a good note, he said the engine is capable of way more than what the sticker on the engine says. He said the biggest limitations are heat and DC specifications. He said put ungodly huge injectors in it and a turbo to match, accompanied by a free flowing intake and exhaust, and you would have a combination that can’t be beat.

I hope that helps some of you. I know it sure helped me. I’m thinking a pressure box to get me by until summer when reliable timing/duration boxes come out may not be a bad idea, but no long-term use from me. Just putting in bigger injectors seems the safest way to go. I guess judging by what the Cummins folks have said, someone needs to make a box that increases pressure slightly, advances timing slightly, and increases duration slightly. Too much in any one area is where we get into trouble. So, who makes that box?

 

Thanks for sharing ak. That answered some questions I've been pondering.

Kris

 

Banks. 105 HP and 258 ft. lbs with 24,500 psi max fuel pressure (stock is 23,000). 30-40 HP from timing alone, 60-70 HP from pressure and the associated natural consequences of timing and duration.

great work AK!

I've found sometimes there is a gap between what the Cummins reps say and the engine on our trucks. sometimes they know a lot about our (DC) engines and sometimes they don't! Those psi numbers are higher than I've seen printed, but who's gonna argue with the source iif they were talking about the 305 HP DC engine. . All the press I've seen (coming out of the TDR) says 23,000.

A Banks box and DD II injectors would be awesome. but the beauty of electronics is that in 30 minutes or less you can be stock again. I'm not talking about fooling the dealer, I'm talking about troubleshooting. you always have the stock platform to return to to if you need it.

I've started a box summary matrix which I'll try and post soon.

 

Excellent information. Even for us "unbombaholics* Thanks

*unbombaholics. noun. Someone who doesn't intend to modify their truck.

 

*unbombaholics. noun. Someone who doesn't intend to modify their truck.


I think INTEND is the operative word. Peer pressure is a terrible thing.

 

pass me a smoke will ya????

 

CORRECTION!!!!!!!!!!!! I made a typo. THE MAX PSI AT WOT IS 23,300!!!!!!!!! Not 26,300.

Slip of the fingers...sorry!

 

AK RAM,

Did Cummins NW happen to mention which injectors that they would be willing to install? Watching all of the posts on fuel boxes, injectors is the only BomB I have any faith in. I'm an old school hot rodder and chopper builder and I still believe in mechanical parts over electronics any day! (unless Cummins offers a program uprate someday )

 

They just made an offer to install whatever I decided to go with. They can only sell factory parts, so their injectors are limited to like the 370 marine injectors and such, which work great in the earlier trucks for a nice kick in the pants. We briefly talked about the DD injectors and the various EDM injectors out there. They didn't seem to have a preference on either one but the Seattle tech hinted the EDM process will provide better results. Nothing definitive though. They just stressed that I would have to do something with the heat if I go that route, whether it is intake and exhaust or a bigger turbo if I was to get an outrageous set. Bigger injectors mean more fuel = more heat. He used the 5.9 ltr they put in boats as an example. Said they are the exact same engines we have, but they are pushing over 1,000 in torque from the factory. They get away with that because they are constantly drawing in fresh cool water to take care of the extra heat generated with that much power. If I could only convert the bed into a fish pond.

 

LOL, we'll do anything in the name of HP.

Thanks for the quick reply...

 

Good info, man, although Bosch rates their system (including injectors) at 30,000 PSI continuous. I do not know what the MTBF is at 30,000 and am unaware of Bosch giving away this info anywhere. I've been trying to find that out, as Cummins doesn't appear to know either.

As far as the best way to turn things up, injectors only isn't the answer either. The secret to a properly tuned truck is one that does everything in the correct proportion. Too much fuel without enough timing equals bad juju, same as too much fuel pressure or too much timing without enough fuel.

Rod

 

Anytime we push the limit, we erode design margin. It all depends on which design margins we are willing to erode and by how much. The Cummins comments really make sense to me -- go by how the truck sounds. smooth is good, and if you yank any one parameter too far, you'll notice a change in sound.

If you want a mild pressure increase, consider Banks and Volumizer. I'm reading in between the lines on the Volumizer but suggest that if this box makes only 100 HP with both timing and pressure, it may be in the same pressure category as Banks. this is not confirmed however.

Staying away from pressure has the advantage that this is one system where zero design margin has been eroded.

It makes sense that a collection of parameters, not just one or two, need to change in our quest for more power. to me, that means squirt rate (how much), squirt timing (when), and squirt duration (how long). squirt rate can be addressed with pressure or injectors, timing and duration with a box. Just my opinion, but I'd suggest the safest approach would be injectors, timing, and duration. By the time you max out all the potential there, you're approaching the limits of #2 fuel, not to mention the HPCR system itself. And at those power levels, a pressure increase erodes no more design margin than you've already eroded in the drivetrain and long term durability isn't as high of a priority

 

Just as a quick side note that ties into this thread, we had a customer yesterday with a PMCR, DD2s, and KSB1B pull a 450 HP run on level 5x5. The truck is a real sweetheart, with smooth power all over, although his temps are definitely on the high side.

As time drags on, we'll be able to take alot of this conjecture and turn it into reality. What works, what doesn't, and what will wreck things .

Rod

 

Off topic I know, but has anyone received any new information on TST's progress with the PMCR? Still code issues?

I know..I could get off my butt and call'm.

 

On my 1.5 saw spikes of temps at 1700, Nowel(bless his soul) didnt worry about 1500 and over egts.