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Old 13-01-2015, 15:42   #16
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Re: LPG mixed with diesel engine

" LPG is not a practical propulsion fuel for boats. "

I think that statement is a little too broad. LPG is a great fuel for small outboards.
I had a lot of fun just two days ago on my LPG powered boat.

I think you're going to be seeing more and larger LPG fueled marine engines in the future.

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Old 13-01-2015, 15:43   #17
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Re: LPG mixed with diesel engine

Hi, you should also concider that LPG is not just propane. Ithink in Qld it is mostly propane but in Vic it is about 80% butane and 20% propane and this may not suit the jets in your stove.

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Old 13-01-2015, 15:51   #18
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Re: LPG mixed with diesel engine

Originally Posted by a64pilot View Post
Wow, I hadn't thought about the massive propane leak you could get inside of the boat too, heck with the motor, you could blow the whole darn boat up.
On the bright side, you'd be going very fast for a very short period.
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Old 13-01-2015, 20:46   #19
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Re: LPG mixed with diesel engine

The first place to go to reduce the cost of diesel fuel on your boat in Australia is to apply for an off road fuel excise exemption.

Dual fuel systems are not uncommon in other parts of the world but the only one I am aware of in Australia is the Carnarvon power house in WA.

For the benefit of our US friends. With the exchange rate as it is at the moment 1US gal of diesel costs about US$7 at the moment.
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Old 13-01-2015, 21:09   #20
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Re: LPG mixed with diesel engine

Originally Posted by phalo View Post
I have gone through half the threads but can't find if anyone has tried LPG mixed with their diesel like some vehicles do. It must go in with the air intake like in some petrol/LPG engines.
It's supposed to give an extra 20% power I read somewhere or maybe brings it up to turbo performance and cleans up the combustion some.
Thought it might be handy to fit a big LPG tank on board, fill up at bowser LPG prices (when you can find them and it is about 1/4 cost of bottle gas in Australia) to run the cooking stove and just stop using gas for the engine when the LPG tank gets low, so you can still do the cooking.
But is it an economic excercise with the 20% and claimed engine life improvement.
I believe the process is diesel fumigation, designed to increase both horsepower and torque.
It also redeces particulants.
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Old 14-01-2015, 03:48   #21
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Re: LPG mixed with diesel engine

Well DougR and Socaldmax are on the money for what I had in mnd and seems there may be some application for lpg or natural gas injection for mono and multi (which I had in mind) diesel engines but possibly more for the former cost wise if there is just the one engine to modify. But none seems to have done it to a cruising boat on the forum
I have had a couple of petrol work vans converted in the past to also use lpg and was impressed with how clean the sump oil kept but did not keep them long enough to assess engine longevity . The first van back in the 1980 s had an extra tap on the line from the gas cylinder to connect a the BBQ which worked ok from what I remember but rules and regs probably prevent that on vehicles these days...but should be ok on boats and be no more dangerous than gas bottles on board now.
As to extra weight of a larger gas cylinder it would depend on how many gas cylinders you carry now and maybe the spun glass may even out the weight. Plus the saving of 20% less diesel weight needed for each trip.

What I had hoped to be the main benefit was engine longevity and improved combustion and HP of the diesel as claimed by one Austalian site I just searched relating to motor vehicles:
The system operates by simultaneously burning diesel with a small quantity of gas resulting in a more efficient burn rate of 95%-98% (most diesel engines achieve around 75-85%). This increase in the burn rate results in less diesel being used to create the same outcome....And this is effected by.........High-pressure liquid petroleum gas (LPG) is converted to a low-pressure (just above atmospheric) useable gas. The gas passes through a solenoid...... system’s computerised processor measuring precisely the quantity of gas required. This metered amount of vapour travels through a hose into the vehicle air intake system and subsequently into the inlet manifold as a mixture of air and gas.....................The computer module (processor) controls the flow of gas optimising performance and ensuring safety. Manifold pressure (via a MAP sensor) or throttle position (via a throttle position sensor) and engine speed are monitored. The module then adjusts the gas flow depending on engine load and driver demand. The amount of gas injected (or the ‘gas map’) is completely (and only) programmable by a laptop computer. ..........Documented evidence indicates net fuel cost savings of 10-20% are achievable running on either bio-diesel or normal diesel. A 4x4 vehicle will use approximately one litre of LPG for every 25-30 kilometres traveled under normal driving conditions.

Can we believe this?
By the way diesel in NE Australia (Qld) is about AUD1.40/L which at 3.8 to a US gal would make it around USD4.50/USgal on my calculations which may still explain the definite non starters on the idea
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Old 14-01-2015, 04:32   #22
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Re: LPG mixed with diesel engine

I've had petrol conversions since the late 80's in Australia. We used diesel conversions in mining industry when doing my trade. Busses are commonly converted to diesel/gas for public transport in New Zealand.

Certainly with petrol conversions I've never seen a HP increase but always about a 5% loss in power. But the main benefit is in cheaper fuel. An added advantage is cleaner emissions and cleaner engine, less maintenance problems.

I've never known of a power increase with diesel conversions either. It's usually done for no other reason than for fuel economy.

Another issue is cost of installation. For the past 25 years there was a great inventive to convert. Our federal government paid half the conversion cost with the remainder soon made up on fuel savings. But that no loner apples and the government is taxing LP with it increasing each year. Quite frankly it won't be worth economically doing a conversion at all. Busses convert for no other reason than fuel economy and they claim environmental conscienceness.

On a boat? I can't see any benefit at all.

Very expensive to convert diesel with duel fuel. It's more than half the cost of a new engine.
Very difficult to fill. It's illegal to fill up from a fuel bowser, at least in Australia.
Dangerous. The lpg we use for cooking/heating is risky enough as it is.
It's impractical for reasons stated. Theres a hell of a lot of weight in a full 80 ltr tank
Hull speed determines your max speed not HP, so what would be the gain.

Anyway that's my take on it.

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