Why would larger delivery valves make any difference?

600 Megawatts

600 Megawatts

Many Irons in the Fire
Joined
May 6, 2008
Messages
80
Ok guys, bear with me here.. I am new to this P pump deal and learning as much as I can as fast as I can while I have my pump on the workbench here and gathering other parts to install it on my 24v....

I am really struggling trying to comprehend how larger delivery valves would make any more power....

Here is why I am lost:

The P pump plungers are positive displacement pumps, they will push a given amount of fuel per stroke and gvien position of the rack, which sets the position of the helix relative to the spill port, correct?

And the injector holes are by far the smallest flow area in the system by a mile, they are the control orifice if you will, correct? And the fuel is nearly incompressible.... So why does changing to larger delivery valves make any difference at all????

Or do the delivery valves also function as a sort of bypass relief internal to the pump, thus altering the pressure of the injection pulse??

The only way you could deliver more fuel through a given size injector is with a higher pressure or a longer injection duration... The injection duration is obviously set by the rack position... So are the 'larger' delivery valves everyone talk about, really just delivery valves with stronger springs, thus increasing the pressure of the pump shot ??????

Or do the delivery valves indeed have a restricted area close enough to that of the injector holes such that they do indeed represent a substantial restriction to high flows, so increasing the size of the delivery valve reduces the restriction increasing the pressure seen at the injector????
 
once you get a DV in your hand, you'll understand how it works.

the problem with monster DV's is the shot duration gets way to big and sloppy and smoke and heat go way up with very little power increase
 
600 Megawatts said:
The only way you could deliver more fuel through a given size injector is with a higher pressure or a longer injection duration... The injection duration is obviously set by the rack position...
Click to expand...
<= BINGO! And there's the possibilty that by cutting the DV shoulder down you decrease the resistance to flow around the DV thus increasing (maybe just slightly) injection pressure.(?)
 
Ok, so now taking this further, what is the lowdown on all the delivery valve sizes?? What is defined as 'monster'?? So far I have heard the following sizes of delivery valves:

181's
191's
022's
024's
"cut"
and "laser cut"

Whats the low down ??
 
Anything bigger than a 181 or 191 on a really built truck is a waste of money and time to much smoke and egt's thru the roof if you want usable power do the 4k GSK with a fuel plate to your liking then turbo and maybe injectors remember usable power is what you want!!
 
Why not go with the 4k Gov. Spring, a Set of Lazer Cut Dv's and NO FUEL PLATE or Aneroid Spring. While your at it, add some custom injectors, I don't know, say 5 x .018. Oh throw in about 22 degrees (or more if you really want it) of timing and were having a party! Now just use a nice S400 to compress all of this stuff! Wow, talking about power!!!
 
Well, what I did for now, is grind the plate flat and an amount such that with the plate full forward, it just limited the rack travel about .010" prior to the pin hitting the stop (I have a 2095 front plug and the rack doesnt hit it before the pin hits, the stock plug limited rack travel 2mm by the way...).

So in taking some measurements with this, total maximum rack travel is 18.5 mm. I then checked to make sure the AFC wont limit full rack travel, and it does not.

I then backed the plate up to mid position and its about 15mm of rack travel and I left it there for now. I set the AFC up on the bench to allow full rack travel at 10 Psi boost.

So, I'll try it out like this for now. In the fall I will be putting together twins for it, so then I move the plate forward more.

I already have a 4k GSK in it, and will be going with 17° timing for now.


I can always do the delivery valves later and while on the truck so thats no big deal.
 
Dreambreaker said:
Why not go with the 4k Gov. Spring, a Set of Lazer Cut Dv's and NO FUEL PLATE or Aneroid Spring. While your at it, add some custom injectors, I don't know, say 5 x .018. Oh throw in about 22 degrees (or more if you really want it) of timing and were having a party! Now just use a nice S400 to compress all of this stuff! Wow, talking about power!!!
Click to expand...

Because it will suck!

Jim
 
dangerous06 said:
Anything bigger than a 181 or 191 on a really built truck is a waste of money and time to much smoke and egt's thru the roof if you want usable power do the 4k GSK with a fuel plate to your liking then turbo and maybe injectors remember usable power is what you want!!
Click to expand...
This is not true. There is a way to make up for the sloppy, long duration of a full cut DV. There is also a step above the 191 that's not overly smoky or hot.
 
Forrest Nearing said:
may I suggest a couple more degrees of timing
Click to expand...

Yeah I'm thinking of bumping mine up to 22 now that I am studded and oringed, when I do the last retorque.. What is the best way to find true TDC now that my timing pin is useless "broke"? Is 22 to much?
 
joefarmer, what is the way around the sloppy, long duration of the FC's? I loved the way mine ran with them, but thier out untill i get a handle on temps. Thanks. Ryan

I fiqure nitrous is the answer??
 
Ok, well I tightened up the starwheel for about 15 Psi full rack travel. The reason I had it at 10, was when my setup was a 24v, once that tiny turbo made 10 psi, 1/2 sec later it was at 32 psi, so it goes quick. No prob, I'll start off with the 15 Psi for full rack travel now and can always tweak it easily after its all running.

Numerous discussions with a bunch of folks has been had already on the timing. I settled on 17° for now, since its a decent amount more than stock, but should keep me out of trouble with the head gasket for now. In the fall, I'll be pulling the head, doing springs, O-rining, studding and adding twins, so thats when I'll play with the 20° and 22° timing.

So back to the delivery valves, the 181's are just a bit more than stock, the 191's more yet, and the laser cut valves are way out there ?? Is this a fair statement ?
 
I would say that a correct statement. In my experence I think that 191's are the biggest that any one should run on the street. I have Lazer Cuts and they are just way too smokey and get very hot very quick. I dont have the need for them and wont lose any power stepping back down to the 191's. I run about 900-1000* unloaded going down the highway with my 71mm turbo running 10 psi so if that gives you any indication of how non-street friendly these are.
 
stock600 said:
joefarmer, what is the way around the sloppy, long duration of the FC's? I loved the way mine ran with them, but thier out untill i get a handle on temps. Thanks. Ryan

I fiqure nitrous is the answer??
Click to expand...
Nitrous can be used to clean up even the smokiest, nastiest full cuts. 022 are decent on the street and give a little more than 191's.
 
Well should I put some 181's in right now with the pump on the bench?? Its certainly convenient now. What would that be worth ?? Understanding of course that I really couldnt use all the fuel right now, but lets say after I have the street twins built ??
 
You must log in or register to reply here.
Top