nmb2
New Member
The last thing I read in this thread posted by him was about him using a DB4 head and rotor. Then I have seen claims of 160cc max fuel, 140cc, 110+cc over 3k. Being able to fuel out to 4500...
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Performance Tuning for the Tahoe
- Thread starter 6.2 turbo
- Start date
The last thing I read in this thread posted by him was about him using a DB4 head and rotor. Then I have seen claims of 160cc max fuel, 140cc, 110+cc over 3k. Being able to fuel out to 4500...
Cumminsfever
Been there, broke that.
The pump that was benched was a db2 with .31 plungers...
And that is currently what resides on the tahoe.
nmb2
New Member
Ok, so give the details. Stop making me beat around the bush.
What are the specs on the pump? Because as far as I have found...
A) You cannot get 160cc's max fuel from an xx31 2 plunger
B) Even if you could, there is no way you could hold it over 2,000 engine RPM, it would plunge greatly.
Cumminsfever
Been there, broke that.
What details? You've had these pumps apart. Where does it need work to get more flow?
littleboy
Can't quit now
Don't kid yourself on the ability of a small plunger pump. It will put 10mph on a 360 hp duramax in a quarter mile ....
buddy
Active Member
If you use some math, I know, I know, you guys cant stand numbers and math, but it really does work.
0.29" diameter plungers. Each have an area of about 42.5 square millimeters. There are two of them so ~85mm^2 area. To get to 140mm^3 (aka 140cc per 1000 strokes) output the displacement must be greater, so you need about 2mm cam ring lift (plunger stroke). I imagine the stock cam ring lift is only about half that though, never seen one, and I dont know how much tolerance there is to change that.
The DS4 uses 4 plungers obviously, and they are about 0.3" diameter, or about the same as the 0.29" DB2, and its cam ring lift is only about 0.7mm which is about 135mm^3 total displacement. The IP cannot use the entire range of the cam ring lift, because it has to spill before reaching the peak, but you get the general idea. The DS4 can probably do about 110mm^3 max with the stock cam ring, which is about 80% of its lift. If it can effectively use more of the stroke then the lift doesnt have to be quite as much. I dont know exactly what stroke percentage is useable.
A 0.31" plunger DB2 would need about 1.7mm cam lift to get 140cc output. And then the transfer pump pressure to feed it fast enough.
0.29" diameter plungers. Each have an area of about 42.5 square millimeters. There are two of them so ~85mm^2 area. To get to 140mm^3 (aka 140cc per 1000 strokes) output the displacement must be greater, so you need about 2mm cam ring lift (plunger stroke). I imagine the stock cam ring lift is only about half that though, never seen one, and I dont know how much tolerance there is to change that.
The DS4 uses 4 plungers obviously, and they are about 0.3" diameter, or about the same as the 0.29" DB2, and its cam ring lift is only about 0.7mm which is about 135mm^3 total displacement. The IP cannot use the entire range of the cam ring lift, because it has to spill before reaching the peak, but you get the general idea. The DS4 can probably do about 110mm^3 max with the stock cam ring, which is about 80% of its lift. If it can effectively use more of the stroke then the lift doesnt have to be quite as much. I dont know exactly what stroke percentage is useable.
A 0.31" plunger DB2 would need about 1.7mm cam lift to get 140cc output. And then the transfer pump pressure to feed it fast enough.
Cumminsfever
Been there, broke that.
Some math I can agree on Buddy! Nice 
So... make that 4mm of lift with a .29 plunger. What does that cc out to?
And... how bout a 14mm plunger with 4mm lift?
So... make that 4mm of lift with a .29 plunger. What does that cc out to?
And... how bout a 14mm plunger with 4mm lift?
buddy
Active Member
Thats why you need to know geometry 
volume is area times height, so 85mm^2 x 4mm = 340mm^3 and maybe expect 270mm^3 output. I dont know the if the physical limits will alow that, or transfer pump pressure will be able to fill it fast enough, especially as RPMs increase and there is less and less time.
for a 14mm plunger which is 75% larger than a 0.31" plunger........pi x radius^2 = (14mm/2)^2 x pi = area of circular plunger = 154mm^2. If there are two of them, that is 308 square millimeters of area times 4mm height (which is the lift) equals 1232 cubuc millimeters, or expect almost 1000mm^3 output. That is 1000cc per 1000 strokes, or 1cc per stroke, which would take some serious transfer pressure to fill that volume in 1.5 milliseconds at 4000rpm. What engine uses an IP like that?
volume is area times height, so 85mm^2 x 4mm = 340mm^3 and maybe expect 270mm^3 output. I dont know the if the physical limits will alow that, or transfer pump pressure will be able to fill it fast enough, especially as RPMs increase and there is less and less time.
for a 14mm plunger which is 75% larger than a 0.31" plunger........pi x radius^2 = (14mm/2)^2 x pi = area of circular plunger = 154mm^2. If there are two of them, that is 308 square millimeters of area times 4mm height (which is the lift) equals 1232 cubuc millimeters, or expect almost 1000mm^3 output. That is 1000cc per 1000 strokes, or 1cc per stroke, which would take some serious transfer pressure to fill that volume in 1.5 milliseconds at 4000rpm. What engine uses an IP like that?
crash2win64
Member
Hey y'all are wasting your time arguing with this nmb2 guy. He's an "expert" and demands credible proof without showing his own credibility. Blowhards... 
Cumminsfever
Been there, broke that.
Thats why you need to know geometry
volume is area times height, so 85mm^2 x 4mm = 340mm^3 and maybe expect 270mm^3 output. I dont know the if the physical limits will alow that, or transfer pump pressure will be able to fill it fast enough, especially as RPMs increase and there is less and less time.
for a 14mm plunger which is 75% larger than a 0.31" plunger........pi x radius^2 = (14mm/2)^2 x pi = area of circular plunger = 154mm^2. If there are two of them, that is 308 square millimeters of area times 4mm height (which is the lift) equals 1232 cubuc millimeters, or expect almost 1000mm^3 output. That is 1000cc per 1000 strokes, or 1cc per stroke, which would take some serious transfer pressure to fill that volume in 1.5 milliseconds at 4000rpm. What engine uses an IP like that?
Just asking for information sake
nmb2
New Member
Buddy spelled it out perfectly while I was gone. The pumping mechanism/cam ring just isn't big enough to support it. A stock maxed out xx29 will do 72-75cc's.
The more stroke you add, the more unreliable the pump gets, you either want to go to a 4 rotor, or larger plungers. However, this will introduce the next problem, and the biggest issue:
Feeding the plungers. Turning up the transfer pump pressure is not the answer.... if you were turn the pressure up enough, to actually be able to fill the chambers at higher RPM's you would float the metering valve and be stuck in WOT. The only way to feed the plungers, and keep the pump streetable is to have the rotor EDM'd for more spill ports.
The recipe for a streetable, higher output rotary pump is:
4 plunger head and rotor
EDM'd rotor
Stock cam ring
EDM'd advance piston and cam ring
modded DB4 cam pin
My first 2 DB4's were just DB4 head and rotors, with a stock cam ring and stock turbo spec plunger to plunger. This gave 128cc's @ 1400rpm and would full fuel to 2300rpms where it started tapering off and basically fell off around 2550rpms. This is because of the reason above, the pumping mechanism cannot be filled fast enough with stock spill ports.
With my current DB4 we got the runout to .001", and increased the plunger to plunger slightly to get 142cc's. We wont know till we run it on the stand but we suspect that it should full fuel from 1400rpm-3000rpm, and drop off around 3200-3300.
The only weak link I have run into, building these pumps so far is using a DB2 cam pin. They are not strong enough to take the abuse of a higher output pump 120+cc's, and especially 4 plungers. I had my advance piston and cam ring EDM'd to fit a DM4 cam pin.
The more stroke you add, the more unreliable the pump gets, you either want to go to a 4 rotor, or larger plungers. However, this will introduce the next problem, and the biggest issue:
Feeding the plungers. Turning up the transfer pump pressure is not the answer.... if you were turn the pressure up enough, to actually be able to fill the chambers at higher RPM's you would float the metering valve and be stuck in WOT. The only way to feed the plungers, and keep the pump streetable is to have the rotor EDM'd for more spill ports.
The recipe for a streetable, higher output rotary pump is:
4 plunger head and rotor
EDM'd rotor
Stock cam ring
EDM'd advance piston and cam ring
modded DB4 cam pin
My first 2 DB4's were just DB4 head and rotors, with a stock cam ring and stock turbo spec plunger to plunger. This gave 128cc's @ 1400rpm and would full fuel to 2300rpms where it started tapering off and basically fell off around 2550rpms. This is because of the reason above, the pumping mechanism cannot be filled fast enough with stock spill ports.
With my current DB4 we got the runout to .001", and increased the plunger to plunger slightly to get 142cc's. We wont know till we run it on the stand but we suspect that it should full fuel from 1400rpm-3000rpm, and drop off around 3200-3300.
The only weak link I have run into, building these pumps so far is using a DB2 cam pin. They are not strong enough to take the abuse of a higher output pump 120+cc's, and especially 4 plungers. I had my advance piston and cam ring EDM'd to fit a DM4 cam pin.
nmb2
New Member
Hey y'all are wasting your time arguing with this nmb2 guy. He's an "expert" and demands credible proof without showing his own credibility. Blowhards...
You're just the only one that missed the boat I guess. Since you want my credible proof... you can sift through my 200k+ views, and 2600+ reply build thread:
http://powerstrokenation.com/forums/showthread.php?t=108058
I'm a blowhard? I was actually trying to keep my stuff out of this thread, since it's someone else' thread... but if you insist, and for the sake of my credibility in here, nobody minds... you have the link above and here are a few pics of my work:
This is with the first pump... remember... 128cc's and defueling @ 2300
Here are some pics of my new pump parts I've been working on. I will have the pump done next week.
Added spill ports. Now has 8 instead of the stock 4. Also, its hard to change the size of the spill ports because they are around, and the charge ports in the head are rectangular. If you were to just increase diameter you will mess up the port duration, so I had mine elongated as you can see.
This is a DB2 cam pin next to a DM4 cam pin before mods
After mods
And the machined cam ring/advance piston to accept the larger cam pin:
nmb2
New Member
It will be very interesting to see what my engine does with another 14cc's of fuel, but what I'm really excited to see is what it can do with max fuel over 2300rpm. I'm expecting the results to be pretty significant.
Cumminsfever
Been there, broke that.
That's ALL you modded in the pump?
nmb2
New Member
it starts life as an xx31 turbo pump. Gets a brand new DB4 head and rotor. Rotor gets EDM'd. Get a DM4 cam pin, EDM the advance piston and cam ring. Stick the cam pin on my lathe and machine a relief groove into it. Then pass it off to my pump guy who calibrates it to the specs we have come up with. The calibration is the most important thing.
nmb2
New Member
There isn't really a ton you can do. If you didn't care about reliability and you just wanted as much fuel as you could possibly get out of it for a tractor puller or something...
You could build the pump the same way I did, except with larger plungers, and remove the vane pump inside of the case and feed it with a powersteering pump.... regulate to 250psi WOT or something. You'd just have to cut power to the pump at the end of your pull to shut it down. Input shaft wouldn't last long.... but making a new one is pretty easy.
For all that work, lack of drive ability, and reliability... you'd be better off dropping the coin and converting to an inline pump. That's what I'm doing to Brandon's drag IDI.
You could build the pump the same way I did, except with larger plungers, and remove the vane pump inside of the case and feed it with a powersteering pump.... regulate to 250psi WOT or something. You'd just have to cut power to the pump at the end of your pull to shut it down. Input shaft wouldn't last long.... but making a new one is pretty easy.
For all that work, lack of drive ability, and reliability... you'd be better off dropping the coin and converting to an inline pump. That's what I'm doing to Brandon's drag IDI.
Cumminsfever
Been there, broke that.
I would hate to think what that pump could do if it spent a day in my hands.
crash2win64
Member
Oooooo but you wouldn't be credible cumminsfever.......
Cumminsfever
Been there, broke that.
I know. That's why I don't talk much about what I do.
littleboy
Can't quit now
Nmb2, according to buddies math, cumminsfevers pump far surpasses yours in cc's.