If anyone of you guys with line pressure gauges - can someone post a reading or three from whilst using the stock filter with its integrated pressure regulator.


Is it simply a 3bar (44.1psi)?


Been searching posts but havent found the elusive data yet....

 

I have two, one at the pump and one at the rail. Before adding the SL55 pump and adj regulator, with the stock pump, I would see 56 psi at the rail.

 

Ditto here.

 

Thanks guys.
This weekend I managed to put some time into injectors and pumps - I finally confirmed our stock pump versus the Walbro and the SL55. I've been looking for reliable curves for months...and today I finally got undermy car and confirmed my stock pump details.


I have an engine model I've developed over the past 3 years - I still think its a little heavy on the air and subsequently the fuel requirements, but is getting closer to the mark.


See the chart.....


I am suprised the Walbro doesnt perform as well as I would have thought.
I'd be aprehensive in installing one, given it has little margin unless you put in the larger 550cc injectors so you can continue to run a 3.8bar rail. It doesnt look like it would cut the mustard if you put in a higher rail pressure. Like I said, my calcs may be a little heavy on the air (=fuel) and I believe some have installed it with some success to 20psi simply with the Bosch 0280156304's.


I think to be safe I will be going with the SL55 option + a 4.5-4.7bar fixed rail pressure and Bosch 0280156304's.
You could make the stock ones work, at 5.5bar, but I'd be concerned about the bottom end tune then.
The excess fuel from the SL55 pump back to the tank (recycle line) will be required to spill back twice as much fuel but this shouldnt be too much of a problem.


I'd like to simply use a suitable 400L/hr line filter with a 400L/hr 4.5bar pressure regulator downtream. and hook the spill back line back into the existing line back to the tank. + Plug the stocl vent line up.
--------------------------------------------------------------


I've also added a couple of tables to adjust the injector capacity for the boost.
I looked at the Bosch 0280156072, Bosch 0280156304 and the DeutschWerks 550's sold by Needswings.
Of course they are normally rated at 3bar (for sale purposes) - however with a 3.8 bar rail pressure hitting a 1.36bar (20psi) manifold pressure - they will only be operating at a dP of 2.44bar not 3bar....so their capacity needs to be reduced accordingly by "the rule of squares".
.............eg: New cc's = rated 3bar cc's X SQRT(2.44bar) / SQRT(3bar)............to work out lb's divide by 10.5 seems to be standard number but there have been comments around different fuel densities etc....I didnt go there.


----------------------------------------------------------------
Now I need someone to correct me - I'm thinking if I simply go with this setup, the duty cycle will look after the rest....but I still havent gotten my head around LTFT's, STFT's and their effect on open loop WOT where the damage can be done.


Appreciate any comments.


I hope someone appreciates the pump curves.

 

What's the internal diameter of our fuel lines.....roughly...??? 3/8th inch?......9mm?
I mean the main lengthy one from back to front...

 

just looking at some photos I took the other day when I was under there and it's looking like more 1/4" outside diameter than 3/8th.....

 

working on 6mm internal ID ~1/4 inch....velocity at 200Lphr is 2m/s and total loss is about 8psi if I use 3m of fuel line.
For the stock case.....160Lphr total loss is about 5psi
...3psi is not savage - but enough to be factored in to the 35-40psi dP across the injector.


L8tr...changed original 4.4m/s to 2

 

With the throttle <20% open we see vacuum in our manifold....see attached chart.
So our injectors are seeing anywhere from -10psi all the way to +16psi (Code365mm).


With a set fuel pressure of 56psi the stock 440cc (@44psi) inectors therefore have anywhere from
.....(56-16)=40psig ....less than 440 at WOT
.....(56+10)=66psig....more than 440 at <20% Throttle
across them.


I'm guessing the ECU fuel map takes care of that spread with some help from the O2 probes and STFT....can someone help me understand this a bit better?

 

the fuel filters with internal regulators are 54-56psi at idle, they fall off as rpm increases with the stock fuel pump.

 

Needswings - yes - note - we're talking 17+ psi case - not everyone.
In ref to the stock pump - as per Post#4 ....technically very likely - especially with a blocked fuel filter or aging pump.
Your years of experience helps confirm this.


Takeaway from this - When adding even a 65mm pulley - at least change your fuel filter!


Unfortunately as per Post#4 - the 255 Walbro will only satisfy at stock 56psi pressure - if you up the pressure to 5bar - it too doesnt have the legs for higher than stock boost. I was very suprised at this. But again your wealth of experience may add some light to this finding.


I'm currently looking at the SL55 pump which is "HUGE" in comparison - pulls heaps of amps and wastes alot of the enrgy back in the recycle.
One option there would be to possibly trim the pump input voltage to 11.5-12V instead of my stock 13.5V. I understand the SL55 does this with a unit dynamically on the go (GG may still have one) - but I'll just settle for a set volts reduction. My calcs indicate 11.2V should do it, but I'd probably go 11.5-12V. Could be another add on to purchase!

 

I can confirm the Walbro will support 409 rwhp with 550 cc/min injectors, upgraded fuel rail, lines, regulator, 65 psi fixed fuel pressure, and 21 psi of boost.


Hi everybody I'm back on the forum.

 

What sort of minimum AFR's are you seeing....?


and...."65psi fixed"....nice where did you get the reg?

 

Mid to low 11s afr. I am trying to teach myself to think in lambda though so .75 to .80 lambda low to high.

The fpr is an aeromotive, I have dual 6an lines going into the reg, single 6an back to the tank, I think you could go larger if needed. I have 8an on the supply side to the rail. I bought all the fuel system parts at Jegs. We have a local Jegs retail store, which is awesome.