Why can't we use an external fuel pump?

[magindat]

External meaning not in-tank.

I can't see a reason why we can't use an external fuel pump. I have no agenda or project. At this point, it's an academic discussion.

[FordNut]

You can. BUT...
All of the external pumps I know of are high flow at a constant rate. The returnless fuel system in our cars needs a variable rate pump. Using the external pumps would require conversion to a return-type fuel system. I believe Marty has such a setup.

[magindat]

So, do I understand then that it's the PWM motor inside the pump that makes it such that we want an in-tank pump to be controlled by the ECU?

To take it further, the external pump would then have to be PWM or the system would have to be return type and the ECM would control the amount of return instead of the PWM signal. Is this the right idea?

[Pat]

I'm thinking it has to do with ECU programming and sensing. There seems to be nothing that car can do that it is not monitored by the computer directly or indirectly.

Boost a pump seems to be the perferred method when needing extra fuel or an in-tank larger pump, these seem to satisfy the ECU's ever watchful "eye".

If you could bring in the ECU to "talk" to an external pump it might work.

Looking at my Parameter test booklet from Diablo Sport there are about 150 items concerning Fuel that the ECU monitors.

[Zack]

Returnless pumps are internally different and have a specific design for constant off and on.

[FordNut]

So, do I understand then that it's the PWM motor inside the pump that makes it such that we want an in-tank pump to be controlled by the ECU?

To take it further, the external pump would then have to be PWM or the system would have to be return type and the ECM would control the amount of return instead of the PWM signal. Is this the right idea?

Yes. The PCM (ECM) can be programmed for a return style system which allows it to not try and control the fuel pressure with the PWM signal. I believe the return-style system is always on and the fuel pressure is controlled by a device on the return side. Not sure how it works, whether it is electronically controlled by the PCM or simply a hardware device which maintains constant pressure referenced to a vacuum/boost line.

[magindat]

I think I got the picture.

A PWM signal is constantly on-off-on-off. It does take a certain design motor to 'handle' this kind of signal.

I have no desire to convert to return style system. Nor to convert the ECU to learn such a system. I was more curious to upgrade pumps without the hassle of going into the tank.

I am at the point of diminishing return. A few HP will cost big$ at this point and begin taking me to the 'danger of blowing engine' zone.

I'm happy with my power for now and was just curious to learn why things are as they are.

thanx

[MM_BKK]

I was more curious to upgrade pumps without the hassle of going into the tank.

If you want to boost your pump's output inexpensively and without the hassle of going into the tank, install a fuel pump voltage booster module or the Kenne Bell BAP.

[MarauderTJA]

You can. BUT...
All of the external pumps I know of are high flow at a constant rate. The returnless fuel system in our cars needs a variable rate pump. Using the external pumps would require conversion to a return-type fuel system. I believe Marty has such a setup.

What Brian said^^^^^^. I have twin Bosch high flow external fuel pumps with my custom fuel system, which is a return system.

[martyo]

You can. BUT...
All of the external pumps I know of are high flow at a constant rate. The returnless fuel system in our cars needs a variable rate pump. Using the external pumps would require conversion to a return-type fuel system. I believe Marty has such a setup.

Correct.
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