Reply to thread

Message: [QUOTE="Black_Lightning91, post: 447432, member: 2972"] So since no one has even attempted to explain whats going on I will. I use the Scientific method for all my problem solving because it works. So first lets cover what we know about the situation. First a regulated return will maintain set pressure from its location in the return back to the pump because it creates a restriction. We know there are probably 5-10psi worth of pressure drop across filters, lines, rails before it gets to the regulated return so pressure at the pump must be greater than what the regulator see's. Now we got people lowering supply set pressure and seeing gains in throttle responce smoke output and lower egt's. A pressure difference of 5-15 psi (45 min to 60 max) is meaningless because that pressure is increased to tens of thousands of psi inside the injector. So long as it has enough psi to quickly fill the injector with fuel it should have no other effect. So how is lowering this pressure causing an effect. Well anytime you create pressure you create HEAT (no one mentioned this). So lets look at heat in the fuel system. Pump generating flow against a restiction creates pressure and heat. this heat moves through the fuel system gaining more heat from injectors rails ect till it goes back to tank. Now if a regulated return is set to 60 psi it will remain closed much more than if @ 45 psi meaning more of the heat the fuel picked up stays in the system and continues to build and less is allowed to return with the fuel to the tank to be dissipated. The injectors however heat the fuel much more when creating injection pressure so how could heat cause this. Well heat before the injector has a large effect on fuel DENSITY. The density of the fuel before the injector actually changes how much fuel the injector can produce per stroke. Another thing think of air flow, density and temp in a forced induction system. If the compressor is forced out of its map or happy place by the pressure(increases density) it must produce it starts to generate more heat(lowers density) than actual flow which actually causes a density loss despite what pressure its at. Okay few more pieces we know, after an orifice (fixed or varible) there is a pressure drop. When there is pressure drop there is a cooling effect (principle that AC systems work on) and heat is lessoned. The factory setup had the regulator pre-rails, it returned lots of fuel(and heat) to tank and created a pressure drop before rails also lessening heat in the fuel to the injectors. Seems to me they knew an importance of heat in the fuel pre-rails causing lowered density. Now lets add all this together to give my hypothesis, In a regulated return fuel system the heat built up in the fuel from generating pressure and other outside heat sources causes a change in the specific density of the fuel. This is further compounded in higher psi systems because the orifice is closed more meaning less hot fuel return to tank which in turn carries this latent heat with it. Lowing the desired pressure allows for more return flow removing more heat and increasing the density of the fuel in the supply rails. This would explain the results we are seeing. Now to test this. Measureing fuel temp and psi at (pump, Pre-rails(close as possible for accuracy) and after the regulator) we can varify a difference in temp in the system from lowering and raising the regulator set psi. Now with this data looking at the tempurature difference at the rails we can mathmatically figure the density of the fuel with regulator at x and y psi. This data can be used to guess an amount of hp increase or decrease based on density and this can be verified on a dyno by setting x psi measure and y psi measure then compare to your math. Well hopefully that sums up what I think is going on here and gives a rational way for someone to test this. Since I don't even got a diesel powered anything atm that is left up to you guys. Another thing to further test this one could add a fuel cooler pre supply rails and further cool the fuel and see what effect that has. I believe it was said best above that the system must be designed to work in harmony throughout. Judging by no one even saying anything about temps and latent heat ect I'm assuming this is the over looked part and the key to this problem. A regulated return is a great thing for making sure the injectors see the right amount of fuel and dont starve but I think over looking heat & density and an abilty to cool fuel pre rails like the factory set-up does through multiple ways is the down fall to current RR set-ups. If someone wanted to measure psi and temp pre supply rails on a completely stock well maintained setup it would be great to compare with out RR measurements from pre rails to see the diffence in what IH Pressure/heat to our RR pressure and heat. Good day and sorry if its long winded but I just woke up lol [/QUOTE]