This may have been covered but I couldn’t think of how to search for it effectively.

I’m sick and tired of being told I can have my cake and eat it too when it comes to getting the best out of my petrol and gas set up on my EL XR6. We all know the pro's and cons of having duel fuel however I want to free up the restriction in the top end of the rev range whist on petrol. My aim is to keep gas as an everyday economy town driving tool and if I want to give it a boot full and abuse it I simply flick it to petrol with the best performance expected.

My idea is having 1 pipe from the air box which then splits into 2. 1 Pipe goes via the gas and the other simply goes right to the T/B. Now I had an image in my head of a 2 into 1 collector as found on a set of extractors except in reverse picture this......Y.

To make this work I was thinking about a gate that’s attached to an electronic motor inside the collector which diverts the air flow down the desired path (either the LPG or straight to the TB) I want to try and design this with both N/A and boosted applications in mind.

I want to know if this has been done or if it’s been tried and failed or that it’s simply just a $hit idea.

Ill post this up on a few forums just so I can get broad coverage on the topic.

Cheers

Hi Vegabass

I have been giving this exact idea a fair bit of brain time, and discussion with some knowledgable fellas, and have decided that, not only is it NOT a s**t idea, it is achievable.

There are a few things to consider.

The Valve. There can be no lag in it shutting off the airflow when switching from Petrol to LPG. ANY vacuum/air leak will cause the engine to stall. So the valve needs to SHUT - BAM! not wind shut etc. You only need to block the pipe bypassing the LPG mixer, as when it is on Petrol, air can flow through both the bypass and the mixer.

As part of my progress to make this work, my first step is to convert to a BBM inlet manifold. I don't believe there is enough room for this to work using a log, and retain the factory airbox.

If you use an exhaust cutoff valve, it could be actuated by a hand cable. This would allow you to shut the valve fully before switching back to LPG. Other wise you will need to find an electronic method, of which I have a couple of ideas, to close it quickly.

BenJ

Yes, I see so I dont need to block off the LPG side when its not in use? That would make it heaps easier.

My vision is to have the electonic gate/ valve attached to the LPG/Petrol Switch so its all done at once.

As I said I want to make it strong enough so it can handle boost as I the supercharger will be going on shortly, and want the best of both worlds.

Yes, it does. You just need to close the Petrol side when on LPG.



Me too.



Hmmmm, boost. That will make the set up design more interesting. The valve will need to be strong to stay shut while under boost, and on LPG.

BenJ

Mate, seriously run a GRA or similar throttle body and boost the engine and you will notice no difference between it and the standard throttle body (might be a difference on the dyno - but drivability and pants in the seat I cannot tell the difference at all).
For all the effort of stuffing around making your variable intake it's a lot of effort for nothing.

Even if your not running boost a far easier option would be to just move to a more efficient throttle body and mixer set up (e.g. the GRA set up verses the common ring in the air intake) - sure the potential gain on an NA car isn't as great, but it's a s**t easier and still going to achieve part of the result.

At the end of the day with your system you would be adding weight to the car (sure not much, but weight doesn't help the performance), making the system more complicated (more to go wrong/fail on you), and with the car being NA the change in air intake setup effects the power curve. You'll also need the flap to completely seal off the petrol side when it's on LPG, any leak and it'll probably run bad - when you move to a boosted setup this'll be a bigger issue as the seal will need to be even tighter. Not sure how you'd achieve a seal that strong for something that is moving...

I can see your point and yes that is why I thought I would throw it out there because between all of us smart people Im sure we could make somthing work. However Can you post up some pics of your set up? I havent seen many different gas systems.

Cheers

there would be a way of doing im sure. how mechanically minded are you and how good ane you with electronics?

benj ide love to hear more about you ideas on what your thinking of doing. not to copy or use just to see how it would work

I have had a responce from my installer that moves the diaphram in the mixer to eliminate the restriction whilst on petrol. He also said it was suitable for boosted applications.

However I have been looking in the jaycar cataloge and there are plenty of things there to make it work.