by RCCUMMINS89 » Wed Jul 01, 2015 2:22 pm
The pump that you used back in the day had a 1" plunger. The "High Volume Pump" that I use, has a 1.25" plunger. We have replaced a number of those particular Cummins pumps..........it is quite common for 400hp trucks (and even under) to be pulling the Cummins pump down to zero psi. Generally that 0 turns into 8ish on average with our 15 psi pump.
The lowest psi that I have had reported back from using our pump that we use is 6-7 psi. Which is what I have pulled mine down to.
Would I suggest our pump on YOUR set up? No....your injectors are ginormous. Not to start a debate in a different direction, but I still feel that your set up could make the same power with smaller injectors though as well. And don't let me take away from the fact that your setup has made more power than any other 12mm ve.......this is a mere matter of my personal opinion from setting up as many trucks as I have helped with.
Like you mentioned on Facebook.......about sucking the bottom out of a piston pump has a tremendous amount of truth to it. A piston pump is rpm driven, and therefore proper tuning is the key. Large injectors has the flushing the toilet affect that can inhibit the pump to ever catch back up.
On my truck, I can change sustained inlet psi by 3-4 psi just by changing fuel pin profiles. Now..........as we all know, the slower the fueling comes on ( in a hot ve ) the more benefits across the entire rpm range.
Now, this all comes back up to the debate of how much inlet pressure is needed to gain maximum cc.......... according to the test benching I've done.....not much. Just like BC has shown, the highest 12mm ve on record (his) did that with only 12 psi of inlet pressure. I gained no power upping my wot psi, as long as my case pressure was maintaining......
89 RC on shortened 92 diesel frame - NV4500 w/dual disc/4.10s on 37s. - Self built pump, "hot screw", lots of timing, True high volume low pressure lift pump, 62fmw/68/.7gated, 77lpm SAC Inj., Studs/O-rings,- 423/1220 Mustang - 11/16/2013
http://www.TheHungryDiesel.com full line dealer, if you don't see it please ask.