CDD DB4 Pump Build

First off want to thank @Goose_ss4 for making this project possible, without guys like him who are willing to take some risks to help further development of performance idi parts I wouldn't be able to make half the parts I do. I would also like to thank Justin Anderson who has been very helpful in answering some of my own questions as we put this pump together.

So, db4/db2 hybrids have always been a real hush subject, with not a lot of info out there on what goes into some of these firebreathing rotary pumps, hopefully with this thread I can shed some light on some of the benefits of going with a 4 plunger pump, what it takes to build and calibrate a db4, how I plan to improve on this style pump and finally our results on the stand.

First off, lets talk about db2s and the drawbacks of these injection pumps. Our injection pumps only have two opposing .310" plungers, which is the largest plunger ever put into a db series pump. Fuel displacement is made by these opposing plungers taking the pump's transfer pressure and forcing it through passages in the head to each injection outlet. The amount of fuel delivered is mostly controlled by three things; transfer pressure, plunger stroke, and metering valve position. Transfer pressure is inlet fuel that is further pressurized by the transfer pump and fed to the plungers. This pressure is delivered in a curve based on rpm and is regulated by a bypass spring in the front of the injection pump. We can increase this pressure to increase fuelling, but only have a marginal amount of room for improvement since past 130-140 psi we start seeing the pump's housing flex and can seize the head in the pump. The metering valve is the "gate" for this transfer pressure, as the governor or throttle input commands more fuel this gate opens more to allow more fuel to flow to the plungers. At low rpm/low load situations the metering valve does all the control for fuel delivery since the plungers can only be limited to so much fuel, and transfer pressure can only be brought down so low without loosing the proper advance at idle. Lastly that leaves the plunger's stroke, which is controlled by the leaf spring and the profile of the cam ring.

Here you can see the shoe and roller removed to reveal one of the plungers:

And with the shoe and roller installed, you can see how the leaf spring (adjusted by the fuel screw) limits the travel of the plungers by contacting the edge of the shoe stopping the plunger from travelling its full stroke while the roller can still freely ride the profile of the cam ring:

There are multiple sizes of leaf springs that can be used in a rebuild, for my 90cc spec I use a stage three leaf spring and no leaf spring for anything higher.

Here you can see how the cam ring sits and how the driveshaft can spin inside the cam ring, with either roller riding the inside lobes of the cam ring. Each hump is an injection event, and valley is a fill point. below the cam ring is the advance piston and cam pin that can move the cam ring a few degrees back and forth to alter the timing that the injection event occurs. For the most part, at wot the cam ring is stationary.



There are hundreds of cam rings for various applications that these pumps are built for, obviously a cam ring with deeper valleys will allow for more displacement, but the 7.3 db2 cam rings have been best I have seen for performance. I am hoping to have my own cam ring developed later this year.

The biggest drawback with any of these rotary pumps is their inability to supply fuel at high rpms. You can see with this fuel curve of my latest 150cc db2 that despite our best efforts to limit fueling down low and increase fueling in higher rpms, the designs of these pumps really looses it's efficiency past 2500 rpms.




Compare that graph to a typical specification for a na 7.3 and you can see how much work has been put into trying to hold the fuel curve at higher rpms, with it following about the same curve as stock up to 3000 rpms, just with double the fuel and instead of the fuel dropping off at 3300 rpms, it keeps pulling hard to 4000 rpms where airflow and turbos can really use the fueling.

7.3 na calibration spec example: http://www.stanadyne.com/dealerportal/ssi/Navistar/04826.pdf

Im really happy with the results of that 150cc db2, but with anything we are always pushing the limits for more. Im pretty confident thats the limit that a db2 can safely make with still the original .310 plungers and stock cam ring. The next step of course going to a four plunger pump.

So we started putting parts together for this db4, theres many four plunger db series pumps out there, but very few were 8 cylinder and none were ever an on road pump. The head and rotor I chose to use was an extremely rare 6.5 detroit marine application pump. From what little I could gather on these they seemed to be rated at 370-450hp and they seem to be most common in northern europe. This brought many challenges to the table, one being that the pump number DB2831-5722 was a dead part number, talking to many grey beards at stanadyne we were able to find a part number for the head and rotor for that pump that had been superseded three times before we came up with a good part number. Next problem was getting one, theres no cores available from my sources so we got pricing on a new head and rotor, stanadyne said they had none in stock and that it was made to order that it would be coming from europe and would be up to a two week wait. For the h&r, plungers, leaf springs and shoes along with the parts to do a regular rebuild, we were looking at over 2 grand in parts before we could even spend time on the bench trying to make this work. I got the costs to @Goose_ss4 and he gave us the go ahead.

So, fast forward a few weeks and we've got the parts to put our db4 together. Detroit's rotate opposite from our idis, so we could either use the db4 cam ring and flip it so that it is setup for the correct rotation or we could use the 7.3 cam ring in its normal rotation. We compared db4 cam ring to our db2 7.3 cam ring and found that the 7.3 cam ring had much more lift than the db4 design, so weve opted to use that. With the rotation issue fixed we started inspecting our "new" head and rotor. We noticed the plungers were pretty stiff in their bores, and needed tapping from a brass punch to remove. I talked to justin about this and he confirmed the same thing with the db4 heads hes gotten. Seems stanadyne is selling old parts that have been on the shelfs for who knows how long and claiming they are brand new made to order, kinda a disappointment but at least we have what we need.

Looking at the spec for the marine 6.5 we found some interesting things. These use a smaller orfice plate test nozzle and are set to open at 3000 psi. Main fuel spec is only 120 cc of fuel, which is still much more than any db2 stock spec, but less than you would expect for that power level. Of course pressure is a measurement of restriction so testing with the 7.3 orfice plate and pop pressures we should expect to see a good increase in fueling.

We assembled the pump with leaf springs bottomed out but still installed, with the highest fuel calibration shoes in place, with the 7.3 cam ring and 7.3 cam pin. Went through our idle fuel and hot cranking fuel adjustments first and were able to get things within spec. Noticed right away this pump is very noisy, but with twice as many rollers as a 7.3 pump its to be expected. Brought the rpms up to test our main fuel and got 110cc, brought rpms up more to test 2000 rpms and had a pop and the room went silent, pulled the pump down and the cam pin had clean snapped, so the cam ring was rotating with the driveshaft making no fuel displacement. After talking with Justin he recommended using the db4 cam pin with the 7.3 cam ring, the db4 cam pin is much larger and would require machining the extremely hard cam ring but should be able to hold things together to make some big fuel. This next week were going to be reassembling the pump with the larger pin and spending another day on the test stand, Ive got some tricks I want to try to get more fuel out of the pump in the higher rpms and adding more adjustment to the pump to be made on the truck for driveability, as well as some things that will get added on after the pump is done to allow for transfer pressure to be externally monitored with the pump installed.

Just wanted to get this thread going early so I can answer any questions before we get the results in later this week, since once we're on the stand we dont have much time to answer questions as the numbers roll out

Wes

I'm curious how hard it would be to send one of those DB4 head and rotors off to a shop in China and have them duplicate it. Seems like they can make just about anything else(like injector nozzles) very cheaply and with decent tolerances, and that might be good for a "value" DB4 pump.

It’s a thought, I don’t know how willing they would be to do such small batches, there’s not a huge demand for stuff like this, if I sold ten a year it would be worth it for sure. I think going forward the inline pump conversion will be the best long term solution but that’s much further down the line. The stanadyne parts are getting to the point even the db2 rebuilds will be thousands of dollars, lots of pumps lately have been taking two to three cores just to make one good pump

Thewespaul said:

It’s a thought, I don’t know how willing they would be to do such small batches, there’s not a huge demand for stuff like this, if I sold ten a year it would be worth it for sure. I think going forward the inline pump conversion will be the best long term solution but that’s much further down the line. The stanadyne parts are getting to the point even the db2 rebuilds will be thousands of dollars, lots of pumps lately have been taking two to three cores just to make one good pump

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Might be worth asking about a DB2 head/rotor as well?
You might try asking somebody like starsdiesel.net - they have a large collection of (made in china) injector nozzles, heads and rotors etc.
Also this random post: http://chinahanjipump.sell.everychina.com/p-90444727-stanadyne-db2-head-rotor.html
They say they can make you just about any diesel pump part... Might be worth contacting them with part numbers or dimensions or something.

Thanks Rob, I’ll admit I’m a bit hesitant going with Chinese manufacturered parts but it’s a real tradeoff because the alternative is these 20-30 year old parts with unknown histories. I know there’s a good amount of the 12 and 13mm ve pumps that are Chinese manufacturered and seem to perform well, just seem to have issues handling rpm well. Definitely worth looking into though, at least for the sake of getting some numbers.

I'm looking at it thinking that as long as they can hold the tolerances on just a couple of spots, the thing will work. It may be off just enough that it won't produce as much as an original, but hey - If we could replace the head and rotor for, say, $250(which seems reasonable considering Chinese pricing), you could have a ~140CC DB4-hybrid pump(@3K RPM) that could be sold for $1K or so, versus an OEM build at ~150-160CC(@ 3K) and $3K+.
And if I could get my hands on a DB4 head/rotor myself, chinese or not I'd definitely be seeing if I could make it work. Even if it took, say, a high cranking speed or "booster" lift pump to make it start hot.

Thewespaul said:

Just wanted to get this thread going early so I can answer any questions before we get the results in later this week, since once we're on the stand we dont have much time to answer questions as the numbers roll out

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I've got a question for you Wes. Does your head ever hurt from all of the information that you shove inside there? Seriously, this looks to be another very good write up that has details that are WAY above my level of understanding. I can usually get the overall point, but all of the small details are past my level of understanding. Maybe they are just past my level of caring? At least there are people like you who understand this stuff and let the rest of us know.

Macrobb said:

I'm looking at it thinking that as long as they can hold the tolerances on just a couple of spots, the thing will work. It may be off just enough that it won't produce as much as an original, but hey - If we could replace the head and rotor for, say, $250(which seems reasonable considering Chinese pricing), you could have a ~140CC DB4-hybrid pump(@3K RPM) that could be sold for $1K or so, versus an OEM build at ~150-160CC(@ 3K) and $3K+.
And if I could get my hands on a DB4 head/rotor myself, chinese or not I'd definitely be seeing if I could make it work. Even if it took, say, a high cranking speed or "booster" lift pump to make it start hot.

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Well if it were possible to make one at that cost it would make sense, but I don’t think it could be made for $250. It makes sense using chinesium parts as an individual, but when you’re a business selling a product you have to look at things differently, I’d rather my parts be more expensive and never leave a customer on the side of the road, I don’t want to sell a product that could potentially lead to unhappy customers, regardless of the price. I’ll look into costs for the db4 head and I’ll report back.

IDIBRONCO said:

I've got a question for you Wes. Does your head ever hurt from all of the information that you shove inside there? Seriously, this looks to be another very good write up that has details that are WAY above my level of understanding. I can usually get the overall point, but all of the small details are past my level of understanding. Maybe they are just past my level of caring? At least there are people like you who understand this stuff and let the rest of us know.

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Just lots of pots of coffee! Thanks Jeremy, I’ve got a lot to learn still, always learning more every day

I agree with Wes about staying away from china. The work involved with changing out a head and rotor and then having it calibrated again that cheap Chinese part is starting to look real expensive.

In relative terms the price for a db4 hybrid is not that bad for almost doubling your fuel output. Not all of us have access to the means to fab a new front cover for p pump. The pump and cover will make the cost of a db4 look real appealing. Plus lines and turbo kit that will fit everything. I'll stick with db4 Wes is building me. It simple works with stock configuration.

Also have to remember where your going with your build. For me my limit was connecting rods limits (400hp) and clutch sb again 400 hp. So at 160 cc with room to grow I'll be able to hit all of that and then some if so wanted. That was my line I wasn't gonna cross. Hate to say it but funds to fun ratio goes out the window above that level, and I'm going to be just happy with my lil db4.

Just want to say it has been extremely helpful working with wes. I think he regrets giving me his number because I never leave him alone know. Asking about the pump what we are running for transfer pump monitoring and mods. BTW the adapter showed up to monitor transfer pressure

Thanks man, good to hear the adapter showed up, if you got any running IDIs around it’s really interesting to be able to watch transfer pressure even from just the engine bay, I use some -4 an line to a liquid filled 150 psi gauge.

Very good point on the fun to funds ratio, I have to say the shop truck is a great example of this, cheap junkyard idit with about a grand of studs and gaskets, set of injectors and an intercooler and you gotta a lot of fun for the money, add in the nitrous and you’re keeping up with modified 6.7s and whooping 7.3s and 6.0s. The 300-400 hp range in an idi doesn’t feel like the same power in other diesels, especially in smaller cubic inch 5.9s with comparable power you would think a 300hp idi has over 500 when compared to a 300hp 12 valve. I think 300-400 is a real sweet spot in terms of a fun street truck for our engines, plenty of reliability at that power with the right parts, fairly accessible money wise and tons of fun for shenanigans, not to mention owning something completely unique from what you normally see on the street

Thewespaul said:

The 300-400 hp range in an idi doesn’t feel like the same power in other diesels, especially in smaller cubic inch 5.9s with comparable power you would think a 300hp idi has over 500 when compared to a 300hp 12 valve.

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Say what you will about the 5.9, Cummins fan boys, but stock for stock, a 7.3 will run circles around a 12v 5.9. Those things can't even get out of their own way.

Hey Wes I like what your doing, keep it up. I only read stuff on here now and then, but I had some pump models you might find useful for tuning the DB4. You may have this info already. I see you've been in the Stanadyne dealer portal, where I found this info. I got these specs some years ago just punching in model numbers because I couldn't access any menu. The spec sheets have all the part numbers and calibrations, that may be of help. In our trucks the DB2 only comes with .290 or .310 plungers, but the DB series pumps as a whole have plungers from .250 to .390 and one with .450. The big pumps are mainly for old 60's era engines in 6 cyl or less and lower rpm, but it shows the capacity of the pump, which may or may not be useful to us. The DC pump (AC example) is sort of the predecessor to the DB4. The JD DB4 .290 plunger puts out almost 200cc, but it's a 6 cyl. I built a DB2837 pump (.370 plunger) for my truck that's been sitting for a few years, until I can calibrate it. I enlarged the plunger bore of a DB2831 on a rod hone and installed plungers from a JD 5020 (DBGFC637-91AL). I don't know if I honed past the heat treatment or not, but I have $150 in it for the two cores to test my idea. For your reading pleasure, Josh.

Peninsular diesel 310hp 6.5l marine DB4831-6380 79cc (Look up code in dealer portal) 06380
Peninsular diesel 6.5l marine DB2833-6413 89cc 06413

John Deere 6068HF Fire Pump DB4629-5709 192cc 05709
Allis Chalmers TL745 DCGFC629-7AJ 138cc 02270
IH D-817 Truck Engine DBGFCC639-1CP 149cc code 01002
IH DT-817 Hough H-120c DBGFCC645-6FM 205cc 01560

Thanks Josh, I thought the larger plungers weren’t the same length as our head and rotor needed, and that the .31 was the largest for that style plunger, I actually have a set of 45s on order I’m waiting to show up to try and to fit into an 831 head. I could try calibrating that pump for you if you don’t have access to a stand, I’d like to see what it could do for sure. Those last four pumps I have not heard of, gonna have to do some reading, thanks again!