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At certain point it gets easier to just do a regulator, lines etc.
That being said, 1650's tune out completely fine with a walbro 450 or 525 on hi/lo voltage wiring, stock regulator, and stock siphon drilled to 9/64", with no issues getting fuel from the other side of the tank. (Source- my car and idk how many others I've done)
Larger injectors idle better at 55-60psi base pressure anyways, it seems to smooth out the non-linear short pulse width region. Every 2000/2150 car we do with a real fuel system, we set base pressure to 58psi. This also allows the 2000cc injectors to support over 1000hp if we have enough pump. I end up doing the same base pressure with 1650's, they tune out better.
totally agree, but going down that path isn't without compromise either. 1650's are too big for a walbro 450 pump (1650's at 60psi base pressure are way too big) but you need them because the fuel pressure is falling off at high IDC which also means your AFR at max power is controlled by the fuel pump flow performance not the ECU. that seems ok...until it isn't and I already have a melted piston on the 'shelf of doom' from doing that. the only real benefit of drilling out the siphon and running larger return lines and FPR is so that you can pump ~400lph of fuel from your tank through the fuel rail and back to the tank and I just don't see much value in that, certainly not enough value to justify the >$1k it costs to replace it all.
You shouldn't have a melted piston. That points to a per cylinder issue, not a global (all 4 cylinders) issue like fuel pressure.
The raised "base" pressure from overrun isn't actually increased base pressure, pressure normalizes once the engine is consuming enough fuel So that the stock regulator isn't being overrun.
My car ran out right 600whp with a walbro 450 and 1650's (AFR went from an 11.2-3 at 575whp, to a 12.5 at 600). Right about where they're supposed/expected to without the fuel map getting weirs. Swapped in a 525 and now it has head room, also didn't require any base map changes. Just tailoring of the open loop fuel table
I just got the controller working with the walbro 255 pump and it is pretty neat. I can vary the pump voltage from 0v to full voltage as a function of injector duty cycle and boost.
and just for reference this is the post from mrfred that i'm trying to prove out. I have no idea if this PWM controller will be able to tame the 295 pump on the stock regulator/return lines/siphon but if it does I think it would be pretty cool to help move the community forward a tiny bit.
and just for reference this is the post from mrfred that i'm trying to prove out. I have no idea if this PWM controller will be able to tame the 295 pump on the stock regulator/return lines/siphon but if it does I think it would be pretty cool to help move the community forward a tiny bit.
My plan to prevent 074 overrun is stock wiring limiting voltage . But I'll be running a pressure gauge to monitor.
Here is how I did my fuel pump wiring setup with the Emtron.
OEM high power fuel pump resistor, using a Solid State Relay (SSR) to increase fuel pump voltage as I need it with PWM.
Not all the current goes through the SSR, as I was having relay overheating problems (80ºC).
The Emtron uses fuel temp and pressure to work out fuel mass. So even if there is pressure drops or spikes, the ECU does all the compensation work for me.
RE: fuel pump control
I deleted most of the relay/resistor stuff under the hood and have just the main relay on the firewall send 12v. But that's more as a signal for another relay for a dedicated 12v from the (trunk mounted) battery. Power from that relay is split to a 3phase DC controller for my surge tank and the in tank lift pump is a wally 525 controlled with a Hella SSR. Pwm signal for both comes from tapping the deleted EVAP purge solenoid's ground line which is pin 35 on usdm Evo 9 ecu pinout. That's about as simple as I could make my fuel pump wiring and it works well.
You can bypass all that factory relay/resistor/hi low stuff.
For me i had 2 bosch 044's in parallel coming out the surge tank controlled on a relay much like RSMikes drawing. Then i had an additional wire coming off one of the relays which fed power to the in tank pump(walbro) supplying it 12v constantly. you could probably even give it its own relay in hindsight. plumbing wise the walbro fed the surge tank in a loop which returned any excess back to the main fuel tank. the 044's drew out the bottom of the surge tank and then the fuel rail return circulated back into the surge tank also. This ensures the surge tank is always full or almost full.
I have it running via the PDM now so the PDM controls each fuel pump individually. but the hose layout etc is still the same for the surge tank.
Also strange some of you run such high fuel pressure. Your base fuel pressure is dictated by the injector manufacturer as the CC rating is calculated at a set fuel pressure. I have 2433cc siemens injectors which only ask for 43.5psi of fuel pressure.
Speaking of surge tanks, this was my winter project/experiment... to try and turn this thing into a surge tank. I'm using strong magnets and non-magnetic materials. I have these materials submerged in e85 for over a month to test. Not tested with gasoline yet. Anyway as expected, when i fill this bowl it takes over a minute until it stops draining out. i'm not sure yet how the DR side syphon thing works at aroud 1/4 tank but i'm open to pumping fuel from the drain plug to the return hose, to ensure this bowl is filled.
. But I'll be running a pressure gauge to monitor. 
