Found some dirt cheap venturi mixers online. Opinions?

Propane, Butane, LPG, GPL, C3H8, C4H10
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evranch
Posts: 53
Joined: Thu Dec 13, 2018 11:11 am
Location: Saskatchewan, Canada

Found some dirt cheap venturi mixers online. Opinions?

Post by evranch »

A friend was building a forge and came across these, so he sent me the link since he knew I would be interested: https://www.aliexpress.com/item/33048996547.html

Let's be honest, these are cheap as free, available in a variety of sizes, and not sensitive to orientation like a diaphragm gas valve. I'm pretty tempted to at least buy one and give it a try on an old truck or stationary engine since there isn't much to lose here.

The biggest problem I see is there appears to be no way to adjust the mixture aside from putting a flow restriction in the vapour line. The other issue is what the intended supply pressure is - I'm assuming you would run these with a negative pressure supply like an Impco Type J or similar since, of course, the manufacturer supplies zero documentation. That looks like what's going on here, and the middle device looks like an adjustable flow restrictor to me?

Image


Of course for the truly brave there is a $400 8 cylinder multiport injection system that won't pass any sort of inspection https://www.aliexpress.com/item/32854459731.html

storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Found some dirt cheap venturi mixers online. Opinions?

Post by storm »

This is a spud, it is a "dumb" mixer and does nothing itself. To use it you need a "smart" regulator which is where you set the idle mixture. A regulator like a Vialle is what you need to run these thing. Ford Australia used similar mixers on their 4 litre 6 cylinder eGas engines for many years.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

evranch
Posts: 53
Joined: Thu Dec 13, 2018 11:11 am
Location: Saskatchewan, Canada

Re: Found some dirt cheap venturi mixers online. Opinions?

Post by evranch »

That explains why they are so cheap. I've never come across this style of mixer in the junkyards of Canada. I took a look around AliExpress for the regulator in the picture and it appears to be this one: https://www.aliexpress.com/item/32854407982.html

It has the idle and max power adjustments on the regulator as you describe. I assume the venturi does still suck in more fuel as airflow increases, but it doesn't produce enough suction at idle and some propane must be fed in through the adjustable idle orifice? Is this the purpose of the solenoid beside the idle adjustment, to only supply this idle flow when the ignition is on, or would this be part of a truly smart system designed to work with a MAF and oxygen sensor?

storm
Posts: 796
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Found some dirt cheap venturi mixers online. Opinions?

Post by storm »

On Australia Fords the Vialle has 2 solenoids. The 1st is simply a lockoff, the 2nd is an idle solenoid. There is a metering valve that the idle solenoid sits above and blocks when the engine is not running but lifts out of when the engine is running. The valve is sized according to emissions requirements rather than good idle and or performance. They require cleaning every 10-15 thousand kms.

Full power is supplied like a normal regulator with the external inline power valve (restrictor) in the fuel hose between the regulator and the spud.

When I did the LPG course in 2007 I fitted a similar system to an Australian Mitsubishi Magna 3.5 litre V6. I grew to hate them very quickly.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

C3H8
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Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: Found some dirt cheap venturi mixers online. Opinions?

Post by C3H8 »

Storms correct. A Vialle reg or similar europen or Italian reg would probably work good with these. I think the size is misrepresented though. The mixer may fit a 52MM opening but the venturii's appear much smaller. They are probably only good for 4 cylinder engines.

The regulator you show would not work. It has an output rating of 120 KPA or about 17 PSI according to a conversion chart. It is more suitable for a fuel injection system. I can't be sure of what the idle screw is on that reg for as the reg. outlet pressure exceeds any mixer system requirement. Also any regulator used in Canada has to be approved to a CSA standards or Europe's EN67. I don't see any markings on that reg that it meets these standards.

evranch
Posts: 53
Joined: Thu Dec 13, 2018 11:11 am
Location: Saskatchewan, Canada

Re: Found some dirt cheap venturi mixers online. Opinions?

Post by evranch »

Storm that makes sense as I assumed there would be an external lockoff solenoid rather than it being built into the reg.

For sure, I'm not planning to install this uncertified equipment (and if I was going to play with one of these on an old motor, I would almost certainly go for the cheap multiport system just to see how it runs)

I find from a farmer and tinkerer's perspective the biggest issue with buying Chinese junk like this is the complete lack of documentation, and what is supplied is is often wrong. On this item I suspect the reg I linked is likely to work with the spud, due to the appearance, idle screw, and the claim of "LPG Vaporizer for normal suction/traditional aspirated system, suitable to EFI vehicle as well as carburetor engine".

That would mean the pressure rating is in fact the wrong number which doesn't surprise me at all. I'm clearly not going to order this thing since... who knows what you are getting. But I will look to see if I can source a proper regulator for this style of system because I'm interested in the simplicity of installing this style of mixer.

There are some really small spuds available and they would be great for items like auger motors that often have odd old carbs and linkages. I've adapted carb conversions to a couple, before but it's a lot of work making adapter plates and getting the governor to work right - simply putting a venturi mixer onto the intake would be much easier. Something like this little motorcycle mixer would be interesting for small engines.

On days like today I would love to get all my motors on propane, no luck getting the gasoline snowblower to even fire, not enough ether in the can, but the old LPG tractor will be happy to clean up after the blizzard.

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