ericg25 (Offline)
#1
6/18/24 10:56 AM
Hey all, wondering if there's anyone out there who can help me figure out what i need to do to get my fuel system working properly. I'll list some info below, if anyone has any pump curves for a DSR "0" pump that would be great, it's been really tough to get any good info on this since Darryl passed away.
Pump part number: DSR p/n 0-30069 (card says CCR rotation, 1.66 GPM @ 1800 RPM @ 50 PSI)
Engine: Iron block & Head SBC w/ Willy's 4412 carb. I have dyno sheets that show fuel usage in #/hr vs. rpms
Problem: Engine stumbles a lot on lower rpms, especially starts and restarts. It behaves like a rich stumble. I think the pump provides too much fuel to the carb for it to work properly so i'm looking for help on sizing a bypass system that will take the excess flow away from the carb to help it work more effectively. Waterman won't offer any technical help, only rebuild parts, as they don't have any performance data on the DSR pumps.
Any help or suggestions on who to talk to on getting this sized and sorted out would be greatly appreciated. Thanks!
Frank Reiner (Offline)
#2
6/18/24 11:49 AM
What is the fuel pressure at the carb inlet under full load?
Hustlin-Hoosier (Offline)
#3
6/18/24 2:39 PM
Does your fuel system have a Pill Holder that returns fuel to your fuel tank ?
ericg25 (Offline)
#4
6/18/24 6:44 PM
@ Frank Reiner: I don't have a fuel pressure gauge installed. It's a Willy's Super Bowl carb, which I've heard multiple sources (incl. Willy's themselves) say that their arrangement can cause pressure spikes in the inlet line up to 100psi when suddenly dropping the throttle under full load. Obviously this complicates things.
@ Hustlin Hoosier: No it doesn't but I'm considering adding one to cut down on the flow going to the carb. I'm thinking it just doesn't need this much fuel but I'm struggling to figure out how to size that. Have heard from one friend that a Kinsler 3112 w/ a .100 pill is a good start, no idea where to start with quantifying that though.
Frank Reiner (Offline)
#7
6/18/24 9:20 PM
A very interesting system indeed. Typical floatless carburetors have a standpipe in the bowl to establish the fuel level, with the exit of the standpipe connected to a scavenge pump. The question here is: what in the valving of the Willy's system acts to create a low (below atmospheric) pressure condition at the scavenge connection?
For the immediate problem that you are facing: closing throttle at high rpm, a barrel valve that both closes to an idle flow rate to the bowl, and, diverts excess fuel to the return line (like a high-speed bypass in an injection system) would be required. The key to your problem would seem to be in the connections between supply and return. What guidance does Willy's offer?
Frank Reiner (Offline)
#9
6/19/24 2:59 PM
Is your fuel pump camshaft driven or belt driven? If it is belt driven it could be run at a lower ratio (less than 1/2 speed), so as to reduce the overall flow rates.
The comments about vertical orientation of the return lines do tend to emphasize the desirability of a return scavenge pump. Would class rules permit that?
Could the combined return connections in the Willy's plumbing be separated into two returns, one for the overflow, and a separate one for the supply side to dump the pump output when the barrel valve is closed at high RPM?