Bosch 044 Fuel Pumps, Filters & rubber lines heating up/getting hot

[dnegative]

Injectors + your going to need some capacity.

[DX20VT]

Injectors + your going to need some capacity.

Yes i'd agree with that.

[lexsmaz]

What sort of power are you aiming at, do you really need 2 pumps feeding the motor ... I would think a single pump should easily handle 350 plus RWKW ...

As has been said i'm sure its just running to much fuel through the pressure regulator etc & a lot of fuel being returned & recycled too & i'm sure quite quickly too ..

[oldcorollas]

couple of extra thoughts...

can you stage the pumps?

adn does your ECU have an extra input for fuel temp? should be able to easily make adjustment for fuel temps?

[allencr]

Like most of the above, 2 pumps = twice as much heat and when over capacity is just recycling it & adding to that whats already doubled.

Fuel Pump Sizing
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I have zero experience with that sizing site & maths and any other site , have only skimmed it briefly & know that there must be a dozen more sites with similar tech.

[stradlater]

Hi Guys,

Thanks all for your feedback. Interesting thoughts.

Here's the current scenario.

Facet 9psi lift pump between main tank and surge. Never had an issue flowing between the two.

Main tank is std RA23. They're upright, not under the car though they do hold circa 50litres.

Can't return to the main tank for 2 reasons. Firstly, the outlets are the wrong size and secondly this would work against the surge tank as at full noise the 044's may run the surge tank dry.

I haven't put a pressure gauge before the filters, hadn't thought of that.

ECU doesn't do staged fuel pump turn on as far as I'm aware. It MAY do a fuel temp input though.

It's a 40psi reg, metered off the manifold. Pressure always seems to sit at 40psi. The engine runs noticeably better at just above 35 to 38psi, ignoring AFR as I can control that. It seems that it atomises the fuel better.

Capacity wise, the thing is well over capacity, but this is deliberate because I'm going to run e85 in the future and will need the head room. Currently I'm targetting 300rwkw or so, but the plan is to significantly up that.

This issue is a fair recent issue, it's been fine for a number of years prior.

What's a Fuel cooler worth and how does it actually work?

[oldcorollas]

for the reg, is it vacuum referenced?
if so, it should be sitting 40-manifold psi, ie idle should be 40-X, and boost should be 40+X psi
40psi should be the differential between rail and manifold.

unless it is actually like 50-55 differential, and 40psi at idle... then getting up to 50-60 on throttle?

unless not vac referenced.
is it single reg? if it is keeping pressure down, then maybe no benefit to going to double reg..

pump staging can be issue if there can be back flow throughpump (i dunno).

[dnegative]

What's a Fuel cooler worth and how does it actually work?

Not a whole lot, looks just like an oil cooler (probably is)

[stradlater]

The reg is vacuum referenced - off the manifold.

The Fuel Pressure Sensor is on the fuel rail. Does that mean your 40-x / 40+x thing applies? I'm not 100% aware of how fuel pressure systems work.

It is a single reg. Currently the fuel pressure gauge shows 40psi at idle then as the manifold pressure changes the pressure on the gauge remains the same.

Does that help?

[oldcorollas]

yup. the fuel rail pressure should change with manifold vacuum.
the basic premise is that injectors are rated and function well around 40psi. some injectors like higher pressure, some lower, but most are around 40psi.
that is 40psi across injector, so as the manifold vacuum changes, the fuel rail pressure needs to change to maintain that 40psi. that may mean fuel rail pressure goes down to 30psi (10psi vac in manifold), or up to 60psi (20psi boost in manifold)

this might help? Fuel Rail Pressure vs Intake Manifold pressure - Here is the skinny

if you have say.. 7psi vacuum in the manifold at idle, and the fuel pressure differential across the injectors is 40psi (normal), then the fuel rail pressure and what you see on a gauge should be 33psi
ie, +33 on one side of injector and -7 on other side = 40 across it. but at idle, should be less than 40 in the rail.

easy way to check it is working, is to switch on fuel pumps with engine off.
fuel rail pressure should be 40psi.

then turn engine on, and let idle, and the fuel rail pressure should go down.
if it doesn't, then the vac referencing is not working.
you could get a syringe and pull a vacuum (or create pressure) on the reg, to see if it does change fuel rail pressure. you can do this with engine off, and fuel pumps on.
if it doesn't change, then the fuel pressure reg may not be working properly.

if fuel rail pressure does change when you manipulate pressure to the vac reference port, then need to look at whats happening in the vac ref line from manifold to the reg.


try the above first.
it is possible that the reg could be maxed out, and 40psi is what it flows maxed out?
in that case,it is possible that when at full noise, fuel flow goes down so the reg can then maintain pressure control, but with no manifold vacuum the rail pressure will stay at the 40psi , as no vac, and differential pressure is still 40...

that make sense?


edit: if reg is maxed, then pulling vacuum on the reg with engine off should not lower pressure belowe 40 (cos it can't lower any more),
but pumping pressure into vac ref with syringe will make fuel pressure go higher (cos it makes more restriction to increase the pressure
that could help to differentiate what's going on.
if reg is maxed, then could be generating a lot of heat right there.

[dnegative]

What do you mean by across the injector?

[oldcorollas]

across injector means:
fuel pressure before injector, minus air pressure after injector.

so basically, fuel rail pressure minus manifold pressure.

this is still the case if the manifold has boost.


examples.
manifold pressure : fuel rail pressure
-10psi : +30psi
-3psi : +37psi
+6psi : +46psi
25psi : +65psi


forgot to add that the regs work hardest at idle, as they need to open widest and flow th emost fuel they ever will.
full noise/rpm, the regs are doing much less work. if you have reg flow issues, they will show up at idle.

Bosch motorsport injectors have operating pressure that vary from 2bar to 8bar (30psi to heaps)
http://www.bosch.com.au/content/lang...linjectors.pdf
but they are flow rated at 3bar (44psi).
the higher operating pressure (more than 3bar) measn they can be used with boost.

[oldcorollas]

also, page 8 and page 10 here
http://www.autoshop101.com/forms/h22.pdf

[stradlater]

That's very interesting stuff and something that I didn't already know so thanks Stew - appreciate it!

However... This conundrum of noisy pumps and warming fuel lines, etc... happens at idle. EG - ran the setup for a couple minutes in the garage last weekend, the reved it a little bit, but it was in park the entire time - and it still happened.

So whilst I'm interested in checking the pressure setup as you suggest, the fact that it happened at idle would suggest that it isn't the problem?

Or am I getting it wrong.

I would have thought too - 40 psi rail pressure, out of 2x044's shouldn't be hard work for them at idle should it?

[oldcorollas]

yah, wrong way around
highest fuel flow through regs is at idle, because that'when least fuel is used by injectors, so the fuel pump output (which will always be as much as it can at that pressure and pump voltage) has to be relieved by the regulator.
so if heat is being generated by a restriction in the return system, it is most likely to happen at idle. what i mean by return system is fuel reg and return line to tank.

if heat is generated by pumps or delivery system (pump, filters, lines to engine bay, and fuel rails), then it will generate more heat at higher throttle, cos the system pressure will be higher with higher manifold pressure. ie, less heat generated at idle.

if heat is from exhaust/engine bay etc, less likely to happen at idle? or maybe not, depending on engine bay airflow.

nope, 40psi is not hard work for 044's, see http://i39.tinypic.com/j5i1kw.jpg
they should do it verrrrry easily!
but the heat may be being generated elsewhere, and the noise could be due to pumping hot fuel... perhaps..


regardless of all that, the fuel pressur enot changing is an issue that needs to be sorted.
even if you just check presure with pumps going and engine off, (should be at static reg pressure, around 40psi)
then with engine running at idle, (should be maybe 5 or so psi lower)
then with vac ref disconnected, (should go back to same reading as when engine off, since in both cases, the "reference" is atmospheric pressure)

that will tell you if the reg is functioning properly or not.
if the reg is a restriction preventing pressure from reducing, it is likely that the orificies in it are too small, and generating heat as the fuel is forced through at higher velocity than usual.

if reg is working properly/big enough, the fuel flow is same, but maybe less fuel velocity and less friction heating in the fuel?

i dunno, see how it goes may not be anything to do with the reg at all