I have a cruddy dual fuel system fitted to my EF.

The mixer (where the lpg is feed into the intake piping) for my LPG system reduces the internal diameter of the intake piping to about 27mm right before the throttle body. This is serverly reducing the performance of my car on both petrol and LPG by restricting the airflow to the throttle body.

The mixer is fitted/glued into the rubber elbow in a standard EL intake pipe. It's a hollow donut like ring about 70mm OD and 27mm ID, with slots in the sides to let the gas out. (Square cross section)

I've turned off and disconnected the gas and fitted a standard EF intake from the trottle body to the airbox cos i can't stand how guttless the car is. But I'm missing the cost saving from running the LPG as its costing me about $ 120 per week to run the car on petrol.

I have a couple ideas on improving this mixer to avoid resticting the intake.

1. Running a perfirated tube 150mm long & about 15mm OD inside the intake tubing towards the airbox. It would have a wire frame to keep the tube sitting in the centre of the intake.

2. Running a perfirated copper tube about 10mm OD and 200mm long formed into a spiral. It would sits against the wall of the intake piping. The tube would only coil about 2 revolutions over the 200mm length so it didn't cause much restriction.

3. Build a new section of intake piping fabricated in metal. An externtal ring built on the exterior of the tube would have gas feed into it. This would cause no restriction to the intake as the gas is feed externally into the intake.

What do you guys think?

My father in law had a VN on gas and the gas ring in it (Vialle from memory) was as big as the intake pipe. If you could find something like this, then I'm sure your restriction would be eliminated.

It has to put a restriction in the air intake in order for it to work, its the venturi effect or something, basically the air getting through the restriction draws the lpg out, or something along those lines. The ID of the mixer ring will always be significantly smaller than your air intake piping.

hey did u find a solution to it? i have the same problem but dont want to touch anything just incase it f**k the gas up?

the gas system doesnt "need" the venturi effect because the gas is coming through the system under pressure into the intake piping with a vacuum in it when the engine is under load..

but in saying that, no venturi effect will result in a poor idle or possible stalling when letting go of the accelerator pedal after accelerating, hard to start, excessive backfiring and could also result in a poor distribution of gas, meaning some cylinders may run lean while others run rich.

you could try a pod in a box with a very large cold air intake and 3" piping all the way from the airbox and a bigger gas ring somewhere close to the throttle body? (you dont want a backfire with an intake pipe full of gas lol)