Stuttering at Spa?

[shane@mbtech]

Because it produces the correct 5 bar at normal rpm's.

It's not until I started pushing the car constantly ie on track that the oem fuel pump started showing its weakness.

Plus my regulator was new.

Any more questions?

Why would pump pressure drop just because revs increase?

The pump should pump constant pressure should it not, whether at 1000rpm or 8000rpm?

The regulator controls the pressure. I concur that a weak pump would lose pressure whether it was measured after the reg or not.

The reg regulates pressure, but if at say 7000rpm the pressure needs to remain constant, then the regulator will be trying to keep pressure at say 5bar, but the pump would have to work harder due to the amount of fuel being used, in order to maintain a constant pressure. A weak pump would mean a slight drop in fuel pressure.

I think a weak pump is only part of the issue, a poor designed tank setup is another.

I never had any issues in straightline driving, just out of sharp corners on 1/4 tank.

This to me says poor pickup design rather than faulty pump, in my case.

[cantfind1]

Hi,

Quote-

''The 10 psi drop is not measured at the pump but after the Fuel pressure regulator.''

Please explain, how do you know its the pump thats
faulty if its measured after the fuel pressure regulator ?


Regards,

The Gorilla,

Because it produces the correct 5 bar at normal rpm's.

It's not until I started pushing the car constantly ie on track that the oem fuel pump started showing its weakness.

Plus my regulator was new.

Any more questions?

[The Gorilla]

Hi,

Quote-

''The 10 psi drop is not measured at the pump but after the Fuel pressure regulator.''

Please explain, how do you know its the pump thats
faulty if its measured after the fuel pressure regulator ?


Regards,

The Gorilla,

[cantfind1]

The 10 psi drop is not measured at the pump but after the Fuel pressure regulator.

M3 pumps loosing pressure/flow over time is well documented now.

I have found this out the hard way.

If you are tracking your car at regular intervals or revving the engine hard constantly the fuel pump needs replacing as a matter of course.

Then adding some sort of fuel pick up or second pump is a must for sweeping right handers.

[The Gorilla]

Hi,

Cantfind1- the oem pump is up to the job.

The OEM fuel pump is pumping at over the 5 bar fuel pressure
required, its the fuel regulator that
determines the 5 bar fuel pressure delivery.

So a 10 psi drop in a OEM pump already pumping
at 6 bar +, which the OEM pump is, would not
make any difference.

''Tight'' and ''cheap'' do not enter into it.

Regards,

The Gorilla.

[cantfind1]

Hi,

The Standard E46 fuel Pump is fine for what were
talking about.

It pumps 5.5 bar at 350mm so no problems.

If changing the pump though, then a Bosch 044 would
be my choice.

Bosch 044 Pump 120.00
Adjustable Fuel Reg 100.00
Sytec Filtre Pre Pump 60.00
Rubber Hose & Fittings 25.00

About as good as any Road / Track car will ever need
and a long way shy of the CA fix.

But as I said the hose alone is a simple easy fix for
a Car that does some Track days.

Regards,

The Gorilla.

As I said if you want to be tight then yes you can do it this way, however the oem pump is definitely not up to the job, especially the old ones most of us have in our cars. They may pump that pressure when new, but they have been proven to be losing up to 10 psi at high rpm as they age.

Hey you are only risking engine damage that's all! So yeah go cheap.

I am not saying buy the CA kit, to be fair it's expensive however it is the best solution, but yes you can do this yourself with a bit of effort.

[Bealo]

Good thread and good read :thumbs:

[DuncanR]

dont start that one, i did that one on the kids last week and still trying to convince them they are the same.......driving me mad :bigcry:

What you need to find mate is a 6 foot tall fookin wood pigeon !!!:hahaha:

[DuncanR]

Sorry not convinced

Gonna try it with some straws and Stella tonight!

Be careful not to injure Stella Shim ...

[billy-m3cutters]

Very interstingn thread guys and very helpful indeed especially for those who do regular track days.

I would suggest this to be a sticky in a trackday section.


Well done cantfind1

[The Gorilla]

Hi,

The Standard E46 fuel Pump is fine for what were
talking about.

It pumps 5.5 bar at 350mm so no problems.

If changing the pump though, then a Bosch 044 would
be my choice.

Bosch 044 Pump 120.00
Adjustable Fuel Reg 100.00
Sytec Filtre Pre Pump 60.00
Rubber Hose & Fittings 25.00

About as good as any Road / Track car will ever need
and a long way shy of the CA fix.

But as I said the hose alone is a simple easy fix for
a Car that does some Track days.

Regards,

The Gorilla.

[cantfind1]

Hi,

I have found this thread fascinating.

To address any problem you need to undestand the
cause.

The standard E46 petrol Tank pick up operates
from one side of the tank.

ie] the fuel pump is having to 'suck' the fuel
as opposed to 'push' it from one side only.

Thus when the pipe that the fuel is sucked up
to the fuel pump is not below the fuel
level, then air enters the fuel pump, fuel
pressure drops and the spluttering on
heavy cornering on 1/4 tank can and does
occur.

As the standard fuel pump is rated for 5 bar then
its only issue is fuel supply and what its pick
up is, ie] what distance away from the pump
will it still suck up fuel.

So, if you had a short length of rubber fuel hose
fitted to the bottom of the existing fuel pick
up, then a 'T' fitting, and then another length of fuel hose
to the other side of the tank, which would be no more
that about 1.0 mtr in length, you would ensure that
the fuel pump was always able to suck up fuel,
which is the cause of the problem.

Although this is all internal to the tank, access via
the existing pump set up would be quite easy, and
you have to remove this to fit the CA solution
anyway..

The CA fix just creates another part that can go
wrong, adds more weight !!!!!! and the same
results can be acheived a lot simplier and a whole
lot cheaper.

Regards,

The Gorilla.

Yes well put, however the fundamental floor in your plan is that the crap oem pump is not strong enough to suck fuel through lengths of hose around the tank hence why you install a second pump in place of the sender unit on the left hand side to push fuel to the right hand pump.

Hardly any extra weight as you are replacing the other unit with the same thing any way, it just has a pump in it which weighs grams!

The oem pump degrades over time and does not produce enough flow anyway, hence why i am going with the walbro conversion for piece of mind.

If you want to be tight the just do the walbro conversion and let it suck fuel through pipes from the left and right side of the tank.

[shane@mbtech]

dont start that one, i did that one on the kids last week and still trying to convince them they are the same.......driving me mad :bigcry:

Ha.:hahaha:

[shimmy]

Fuck me your sharp you Shimmy.

Whats heavier? A ton of bricks or a ton of feathers?

dont start that one, i did that one on the kids last week and still trying to convince them they are the same.......driving me mad :bigcry:

[glendog74]

Fuck me your sharp you Shimmy.

Whats heavier? A ton of bricks or a ton of feathers?

W..w..w..what's h..heavier?

Shh..Shh...Shimmy in...O..Oc...October 2009 or Shh..Shh...Shimmy in..Oc..October 2010?