LetsGetThisDone

iTrader: (1)

Most know that fluid pumps flow less as pressure increases. The crap about keeping resistance in the wiring to maintain fuel pressure is his typical word vomit bull****.

Biggiesacks

you really don't want any resistance in your power transmission wires. Usually the way it goes is engineers have to work around less then favorable conditions, cost/weight of the wire, so its possible they took into account the resistance of the stock wiring and the stock pumps characteristics when selecting the R value of the low voltage resistor. That is a whole lot different then saying they designed it to be that way though.

I mean technically you could say everything on the car is designed to be the way it is. Somebody had to design it right. So really its just saying nothing at all. End of the day it doesn't matter how something was designed, it matters if it can do the job your asking it to or not.

Raceghost

iTrader: (4)

From my years in the small circuit analysis and design, this has been true in some cases. However, in this case, I am not sure, and lean towards less resistance, being better. However, if resistance is constant, not elevated, or depreciated, in a circuit, that is based off of a certain level of resistance, as to not over power a circuit, then consistency is correct.

You don't want resistance to change or get out of spec, if your trying to hold an end result. So his statement is somewhat true on a technical schematic.

If power and all out flow, for racing are what your after, then the least resistance possible holds true.

More resistance drop, lessens current, unless voltage increases.

Ohms law. I = v/r. We are discussing two different outcomes in this debate of topic.

If your trying to maintain a level of current or voltage, then staying within spec is true.
If your trying to get all you can out of performance, then least drop is true.

It just depends on which side of the coin your looking at.

I agree with you.

LetsGetThisDone

iTrader: (1)

His statement is alludes/leads back to obsession with fuel pressure, and his thought proces that the stock FPR can't handle anything other than the OEM fuel pump, which is wrong. That is why I said his statement is wrong.

I understand that circuits generally have a specification for resistance. Though in the case of the fuel pump wiring, I don't think Mitsubishi designed resistance into it (other than the resistor pack itself) in order to control fuel pressure.

mrfred

iTrader: (50)

Yeah, the resistor pack for the low voltage circuit sets the pump voltage (along with the battery voltage). No one designs wiring to have a resistance to control something like motor voltage. With that said, higher flow pumps will have lower inherent resistance, and because of this, when the fuel system is in low voltage mode, they will run at a lower voltage than a stock pump. That's not necessarily a problem though as the pump may run fine at the lower voltage. Its a case-by-case basis.

RightSaid fred

GM built many thousands of cars with resistance wire to the coil.
You can even google it.
It's because when you want a very small value of resistance as a ballast, that's the best way to do it.

Raceghost

iTrader: (4)

Should be the case. HOwever, I will say this. I found almost a full volt, being dropped over the 4 connections from the passengers kick panel to the pump in the white wire that comes from the fuel relay low voltage, and high voltage side. The harness at the kick panel is dual sided harness that can be unplugged from both sides, the pins in the center unit are tiny, and the plugs themselves are very restrictive in nature. Then there is the harness connection at the back door, in front of the tank inside the car. It is the same setup.

All I am saying here, is that the size of the wire is coming into play with having a specific resistance when you use multiple plugs and harnesses to get to the end result.

As for me, I just bypassed these with a 12G. I left the factory harness connected, and just offered a secondary path with heavier gauge.

Did mitsubishi design it this way, don't know, I think in all the years on this forum, know one has been able to get any sort of answers from any Mitsubishi Engineer.

My thoughts is they created all these sub harnesses in the racing world as to maintenance after a rally race or in damage, it was easy just to grab a sub harness where damage was, and replace it that easy. I'm sure some engineer was like, um, that is gonna lessen electrical flow, and some other engineer said, yah, but we can account for that in tuning, but we need speed, and need to get the race car back up as fast as possible, so speed beat robust in this case. Just saying.

mrfred

iTrader: (50)

There was no intent by Mitsu to create a voltage drop with the wiring and connectors. All Mitsu did was use wiring that was sufficient for the factory fuel pump and fuel flow requirements. Its the same thing happening with the factory intake, exhaust, fuel lines, etc. Its all about making something that accomplishes the objective for the least amount of money. We just happen to be lucky that Mitsu did make several aspects of the Evo much better than needed such as the 4G63 block.

I guess I'm not sure where this conversation is supposed to be going. Is there a need to use monster size wiring to achieve maximum possible flow when operating in full voltage mode? - Not necessarily. Only enough voltage is needed to meet the fuel flow requirements. If you want to know the answer for a particular setup, monitoring of fuel pressure is needed to determine if the fuel flow requirements are being met. Most people don't know how to or want to bother with trying to determine the minimum required voltage. Its much easier to simply make the wiring and connectors as good as possible, and then make sure the fuel system itself is up for the job of dealing with the any potential excess flow. This still isn't an easy task for most people because the Evo fuel system and fuel flow requirements across the operating range are still not very well understood by most people.

I think what you are doing is great. The stock FPR is actually pretty capable in my experience, although its definitely not immune to causing overrun if too much fuel is thrown at it. Just make sure you have the low/full voltage crossover well-tuned to avoid overrun as best as possible. If you want more voltage under full voltage mode, I suggest moving up from 12 ga wire to at least 10 or 8 ga wire. Also use high quality automotive relays. I have tried several different brands/models, and my current favorite is the Tyco F4 relay version 13801.

A key problem with utilizing the W450 though is the factory fuel filter inside the pump carrier housing. From my own experience, it appears to be rather restrictive when reaching E85 flow rates above 500 whp. It needs to be bypassed in combination with utilizing a high flow aftermarket fuel filter.

Raceghost

iTrader: (4)

Thanks bud, and notated for when I start to play with E85.

I was merely trying to add insight to conversation. Most likely, I will probably go to a double pumper hanger down the road.

My rewire which is a combination of yours, and others, is doing fine so far.
Did you ever get good solid state relays?

Thanks in advance

mrfred

iTrader: (50)

Double pumper is definitely one solution, and I've considered using one myself. However for up to 600 whp DJ on E85, a W450HP can get the job done fine. 650 whp DJ on E85 might even be within safe range of the W450HP if eliminating the factory fuel filter and using a -6 AN supply line. The factory fuel pump carrier can be modified for the W450 to bypass the factory fuel filter similar to how its done for a double pumper.

Turns out that solid state relays are not viable. As much as I'd like to use them, they pull too much voltage. Best option is to replace automotive relays yearly.

2winscroll

Well that's actually a false statement too. The Best way would be to use a IC current regulator that would adjust output voltage to maintain a steady state current. Another option would be to use a wire wound resistor placed on a heat sink, kinda like Mitsubishi did with their fuel pumps. Third and worst/cheapest thing you could do is use a chunk of wire as a resistor. The reason being it gets hot. They don't do it like that anymore because it caused a lot of vehicles to catch fire. Very cheap is the only reason for doing that. Definitely not the best way too skin that cat.

Biggiesacks

I have been wanting to make something like this for a while, just outside my skill level still. Like a DIY boost-a-pump with some kind of feedback mechanism to allow for a lookup table for duty cycle.

Something kind of like what this guy made, but with a MC.

https://www.camaroz28.com/forums/f-b...t-pump-810985/

RightSaid fred

Steady state current?

No, you don't want that.

Not when a 450 pump draws over 20A at full load and less than 8A at low load.



But if you want to increase the voltage to say 21V, a stock pump will deliver about 450 litres/hr at zero pressure (13A) and 400l/h at over 60 PSI with a stock FPR (16A).

A walbro 255 pump at 22 ish V will give about 420 l/h from 10A at zero pressure and 400 l/h at over 80PSI (stock FPR, with over run) and 14A.

That's comparing to about 5.5A for a stock pump running through the resistor (7V across pump) to give 3 bar pressure.

Biggiesacks

im sure he meant a constant current power supply. You dial in the current you want and the voltage does what ever it needs to deliver that current. Think about how the oem controls the fuel pump. They use resistors, what do resistors do, they limit current. You would obviously need to adjust / stage the current as demand on the pump increased. It wouldnt work if you just left it at a single current value.


What i would probably do is a boost stage to bring the voltage up to say 18-24 volts then pwm that signal and have the duty cycle of the pwm determined by that lookup table / feedback mechanism. So i guess technically you wouldnt call that CC or CV but CP (constant pressure)? Main issue for me is automotive electrical systems are noisy as all hell and it takes a ton of knowledge and engineering to get switching converters to live happy in this environment.

2winscroll

Correct Biggie,
I was speaking in terms of a direct replacement for the resistor. CC amplifier will maintain a constant voltage across the pump regardless of battery voltage, and even poor connections to a point. It's much better than using a resistor voltage divider. Using a wire like Fred said is about the cheapest and worst way to do it. But once again he has tried to totally BS his way around his false statements.

All those numbers fredthemeathead is throwing out there are totally useless. Why do you care what a pump flows at zero pressure? Unless I see pictures of the test equipment I'm calling total BS.

Lol a 255 pump delivers 400 liters an hour @ 80psi, NFW! You could put 40 volts on that beatch and it wouldn't do tha kinda flow @ 80psi.

This guy is needs to be banned for blatant lies!