Building a better db2

[Jimbanjer]

I know it would be hard tuning, but has anyone ever done a twin p-pump setup from two 2 - P7100 pumps from Cummins 4bt engines? I would think that if you could make them belt driven it would be doable. (This is just a random idea of mine so if I’m missing something, feel free to fill me in!)

 

[Goose_ss4]

Getting rid of the transfer pump should take some stress off some parts inside correct?

 

[Ironman03R]

Why not just use one of these? Lol

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[Jimbanjer]

I just know 4 cylinder p-pumps were mass produced for cummins and should be cheaper and easier to find than a 8 cylinder p pump

 

[Thewespaul]

Why not just use one of these? Lol

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You know you might need something like this for that

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[Josh Oldenburg]

That's ok. You can make them

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[Jimbanjer]

That's ok. You can make them

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[Thewespaul]

Two 4 cyl p pumps would be more expensive than one 8, and unlike a common rail you cant run the pumps with a belt because of they need to be timed perfectly, so it needs to be able work with our gear train. An inline conversion would likely be 7-10k and most people dont want to drop that kind of coin on an idi, especially since another 10k would be needed just to use the fuel.

@Goose_ss4 Having the transfer pressure externally controlled would help the pump live since you can control the pressures more closely, any spike in pressure can put it in the danger zone and sieze the head which turns it into an expensive anchor. Im working on a way to block off the advance piston lube orifice for your db4 so we can run it without the transfer pump, but the issue is anything in that bore on the advance piston side will limit how much we can push the cam ring over, limiting our fueling and advance.

 

[Jimbanjer]

http://www.trucktrend.com/cool-trucks/1206dp-twin-p-pump-cummins-race-engine/

Someone did on a Cummins 6bt. Sorry to change the direction of the thread, it was just something random that popped into my head!

 

[Thewespaul]

As usual you're an invaluable source of information and innovation. Thanks for sharing your work.

Thank you, its a pleasure to be able to do what I do and to share it with all yall!

 

[Thewespaul]

So! Finished the V3 of the 150cc db2 build this past week, getting lots of good data so far and wanted to share the progress. I built this one for the shop truck from a 5070 housing I had laying around, and a decent head and rotor that came from a junkyard core haul recently. Im pretty confident this is all you can get from two .31" plungers, I think more fuel can be had by going with larger plungers, but its debatable if that is cheaper than a four plunger conversion or not, I wont know till I try, but back to this pump.

This first run is just after setting up the idle setting and no leaf spring at all. 150 rpms denotes what cranking fuel the pump makes when heat soaked. You can see with nothing done to the governor setup, the governor is cutting back fuel very early, but at 1400 rpm where the governor isnt acting its making a decent 130cc.

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Still leaving the governor alone, I pulled the nose cone and transfer pump off to install my new custom delivery valve spring, which picked up fuel significantly everywhere, more than 30 cc more hot cranking fuel too.

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Now we modded the governor, installing the cut down guide stud, shimming the minimax interior spring and installing a 6.2 governor spring. You can see the bottom end stays about the same, but the governor now carries out fuel much better, this would feel like the engine can really "breathe" on the top end with having the fuel not cutting back so early.

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And for S&G heres with the gutting the return fitting. I saw 3* more advance across the curve, an instant drop in housing temp, and a good increase in peak fueling, remember 1cc completely burned will make 2.75 hp, so even a 10cc change is a significant seat of the pants difference.

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Pretty happy with how this pump has come out, very linear fuel delivery for a db2 after all the testing and mods. If you look at the first graph vs the last graph, you can see just how much more linear it becomes and for comparison, heres one of our 90cc pumps, which instead of being built for maximum delivery is built to have to flattest fuel curve around the 100-90cc range which is perfectly suited for stock turbo setups.

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Going to get this pump installed on the shop truck soon so I can get some miles and abuse on it, but I'm very happy with how it performs on the stand, and if testing goes as well this will be on the market soon!

 

[Thewespaul]

An error I just noticed on the graphs, I had the main fuel setting still in test stand rpms not engine rpms, 700 rpm point should be 1400 rpms, fuel is the same.

 

[Chemgrad]

Awesomesauce!!!

 

[Thewespaul]

Just an update, gotten a few of these sold and gotten some very good responses overall. They perform fantastic for the amount of money for those who don’t want to drop the coin on a db4. Not bad for a stock bore 2 plunger pump:

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Working on a couple big brothers to the 150, hoping to see 200cc with the plunger upgrade on one we are starting on now, I’m going to continue it in this thread for continuity. More to come.

 

[onetonjohn]

A little over my head. What is the target application of this type of pump? Are we talking tractor pulls, or daily driver? What type of mods would one need to support these higher fuel rates?