This DIY jet pump (aka siphon or venturi) worked so well I decided to re-post it in the performance area.

The jet I used is from a Honda lawnmower engine. Any small engine shop should have a junk carb kicking around to get the jet from. I'm not sure what size hole it is. Very small. Maybe .010".

I used an 1/8 NPT tap on the 1/8" brass T so the hose barb fittings would thread in deeper.

The two smaller hose fittings are 1/4" barbs to 1/8" NPT. The straight one was tapped 7mm x 0.75 for the jet. The 90 is unmodified and screwed into the side of the T and will be the suction line. The larger hose fitting is 5/16" barb to 1/8" NPT. A small section of brake line was cut and pressed into the 5/16" barb. The outside lip of the flare had to be ground slightly to fit into the T.

Sorry I don't have a more scientific method for testing this but I'm quite pleased with the results. Volumes (in the Solo cups) were after 1 minute of flow. With just the jet spraying into a cup, almost one Solo cup was filled after 1 minute of running. With the suction line connected, almost 3 cups were filled. It's drawing in more liquid then is being provided to the venturi.

 

Jet in operation and pic of finished assembly.

 

I'm sorry, I don't understand.
What is it you are trying to improve or fix or solve?
Honestly

 

I'm attempting to improve on the OEM jetpump for higher reliability when fuel pump upgrades are used. Also aiming for low cost, ease of plumbing, versatility, compatibility with fuel return setups, and adjustable flow rate.

 

This is to solve the fuel problem when turning. A jet pump upgrade could allow more fuel to be taken from the passenger side tank and keep the pump cup full. But... without a comparison to the stock jet pump we won't know if this is an upgrade. When I was interested in this problem I found some info on BMW saddle tanks which advocated a second pump instead of a jet pump upgrade because the jet pump could only do so much to fix the problem.

I think rerouting the pressure regulator to the fuel pump cup along with a jet pump upgrade might work. Or you could use a pump controller to do away with the regulator.

 

I'll be eliminating the regulator and filter from the factory assembly and converting to a fuel system using a return line. My filter and regulator will be external.

When I get the assembly out of the tank I'll test the OEM jet pump and see how much fuel is being used to feed the jet pump and how much is being transferred from the other half of the tank. If I can match it, I'll at least have a more reliable jet pump. I'm sure I can increase the suction rate by increasing the ID of the nozzle but doing so reduces available fuel volume for the engine.

In the mean time, it's interesting to see it work, and cheap enough to experiment with.

 

60 second results...
1mm orifice / 52psi

Jet pump consumes: 1150ml
Jet pump transfers: 1740ml

Total at jet pump outlet: 2890ml
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1 hour results...
1mm orifice / 52psi

Jet pump consumes: 69L per hour.
Jet pump transfers: 104.4L per hour.

Total at jet pump outlet: 173.4L per hour.

 

Why not just run one pump from each side?

 

Because the passenger side tank will eventually run dry and overheat the pump.

 

Ahhh ok thanks

 

where are the tests of the OE system to prove if you did anything beneficial, or not ...?

 

"Upgrade" is a relative term. It won't blow apart under pressure and is easy to plumb.

Send me an OEM jet pump and I'll flow test it if volume is the only concern.

 

I'm just pointing out that you did something and posted it up without any verification that it's a positive change. For all you know it could flow less over from the other saddle than the OE siphon.