Fuel system question! - Buying the right upgraded lift pump for my new external setup.

TLDR: What lift pump will work well with a Bosch 200 style external pump?

Hi guys, I'm running a Sr20 in my bmw e30, looking for about 300kw atw as a weekend driver. The engine was previously dynod at 400kw, so I'm looking to setup the fuel system to support 300 for now and maybe more later. Its an early 1983 so it runs a lift pump and an external pump.

Im not looking to run a surge tank or move too far from the standard setup as the car has a nice tidy interior. I have now recently purchased and installed a Bosch 200 style pump (044 replacement) and ran all new AN6 hard line - supply and return to the engine bay.

The car is running on a base tune at the moment before it see's a tuner, but it idles happily at 43psi. I cant log fuel pressures while I'm driving as i only have the mech gauge on the FPR at this time. The lift pump in the tank isn't original but it is the standard pump. Unfortunately the new 200 sounds very sad, I appreciate the '044' style pumps are notoriously noisy but it really sounds like its aerated and hurting haha. If i test the Fuel pump setup with the engine off you can hear the pump/s get noisy and quiet again several times almost like it gets a good head of pressure and looses it again (Tank 90% full). So it appears to me a upgraded lift pump is required.

Sorry for the long winded explanation but I figured as much info about what I'm trying to achieve from my project the better.

I have found the following graphs for the Bosch 200 pump and a possible in tank lift pump replacement which show the performance curves. (I picked this lift pump as it has to be small to fit in the tank - 38mm)

Unfortunately i find the graphs very difficult to interpret. Is there any way to determine from this data if the in tank pump will be sufficient for the job at hand? Or are my noisy pulsing pumps from a bigger issue which means I need a surge tank setup? At the moment the lift pump directly feeds the external pump. Have I gone over kill with the Bosch 200?

I know its just a $100 lift pump and I could fire the parts cannon at it and hope for the best but I'd prefer to understand why it will/wont work as that's in the spirit of how HP Academy has now taught me.

Ext Pump - https://www.efisolutions.com.au/bosch-200-fuel-pump-044-replacement

Lift Pump - https://www.efisolutions.com.au/pierburg-in-tank-fuel-pump-low-pressure-high-volum

Thanks if you have kept reading this far, looking forward to any advice. Cheers, Ryan.

I may be missing something - wouldn't be the first time - but I don't understand why you feel the need to run both the lift and pressure pumps if you aren't running a swirl tank/pot?

A lift pump would normally be used to ensure the swirl tank was kept full, and so be rated t a higher flow than the maximum expected to be drawn by the pressure pump - but this depends if the return to the main tank or the swirl tank.

In your position, I would just use a tank mounted pressure pump in the tank, as that's where the current pump is, or an external pressure pump that is designed for that application - probably a positive displacement with a suitable suction head, and some sort of priming ability for initial fuel flow.

I'm with Gordon on this, why are you running those two pumps in series? Depending on the location fo the 200, it may be able to draw directly from the tank, or fit a small (500 ~1000ml) surge pot fed by the Pierburg (and plumb the return line into the pot) and run the 200 from that.

My experience with those Pierburg pumps is that they are great for filling a surge tank, but they do not like being drawn through and do not like having a pressure differential across them.

I seem to remember that there can be issues with the AN adapters to the Bosch pumps. The threads on the pump inlet are short, and a normal sized adapter can "block" the flow, as it extends too far into the pump. The solution is either special AN adapters (which are both shorter and have a radius on the inside to smooth the flow, or use with a crush washer which helps space the threads farther out than an O-ring.

You can also cut the adapter to the length of the threads which works as well.

I always build a tall-narrow surge tank to feed the 044 pump.

External surge tank or a surge tank and feed pump hanger that drops into the main tank is probably a sensible thing to do. If not, a single in tank pump seems better than running them in series.

Thanks for all your helpful responses. I'll aim for a single in tank! cheers

Helpful tip.

Get some fuel gauges and upgraded pressure regulator if you havnt got already... It will make fault finding a whole lot easier in the far future