Diesel LPG injection systems

[britemp]

Does anybody offer an LPG injection system for marine diesels?

I drove a friends LR Defender TDi recently to which he has fitted an LPG injection system and the increase in power and torque is huge.

For those not familiar I think the idea started with Australian road-trains needing huge power outputs to pull their several trailers. Injecting LPG at a controlled level into a turbo-diesel (as well as the diesel) engine greatly increases it's output, throttle response and reduces emmissions and smoke with no noticeable reduction in life. You can get kits for things like Land Rovers, but I would've thought they would be ideal for marine applications as boats have plenty of room for an LPG tank to supplement the diesel. Typically you could expect a 300hp diesel to increase to over 400 with lots more torque for virtually no increase in running cost as less diesel is used when LPG is injected. The diesels will still run perfectly on just diesel if LPG runs out.

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[studgies]

I think there is a place in southampton does cars and trucks etc, they had a huge american truck outside advertising it for a while. Not sure if they will do boats but I can not see why not.

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[Its_Only_Money]

I don't think it has caught on to date for several reasons:

Many diesel owners regard petrol as worrying enough never mind LPG onboard in huge quantities.

The performance increase is all torque, this tends to require further changes to the boat to maintain reliability such as higher cooling system thermal capacity (very difficult to achieve - remember you can't lose ANY of the available heat direct to air as you can with a truck, it all has to go to water), and perhaps even changing the drive leg to cope with the higher torque.

The boat will certainly need repropping to make use of the extra torque (conversely when you run out of LPG the boat will be terminally overpropped for the available torque, it may have trouble getting onto the plane depending on the torque difference). Unlike a truck or car you can't simply change down a gear when you have no LPG....

LPG availability - to make best use of the boat (esp with the overpropping problem when running only on LPG), you would be restricted to areas where LPG is available waterside - which places big limits on your cruising range.

<hr width=100% size=1>Rgds

Simon
Its Only Money
Fairline Sprint
Solent-based

 

[ari]

You got to wonder what extracting 400hp from an engine designed to develop 300hp is going to do to its longdetivity...

No thanks!

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[britemp]

The cooling system is not an issue as the injection and vapourisation of the LPG actually lowers combustion temperatures - 100ton RoadTrains crossing Australias vast deserts at
45 degrees C needed no upgrades and ran cool.

The prop issue you point out would however be a problem - isn't it about time boats caught up with the 21st century and got variable pitch props? /forums/images/icons/smile.gif

As for LPG safety when I had it fitted to one of my Land Rovers, I asked a friend who is a chief fire officer what he thought. 'I'd rather be in an LPG car crash with the leaking gas blowing away in the wind than in an ordinary car with a pool of petrol or diesel gathering right underneath me!' /forums/images/icons/wink.gif

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[britemp]

Most lorry engines (and thus boat engines) are available in different states of tune with no noticeable reduction in reliability.

The Australian lorries using this system have seen reliability and overall life increase with LPG injection due to lower combustion temperatures and the very healthy effect on the engines of the much cleaner burn that the system allows. If it's reliable over 500,000 miles at 45 degrees C on the Nullabor plain, I'm willing to trust it at 20 degrees on the Solent! /forums/images/icons/smile.gif


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[ari]

It might be cleaner burn etc, but to get extra power you basically need a bigger bang, and thats putting extra loading on parts not designed for it.

Leisure marine engines tend to be pretty highly stressed anyway as everyone wants least size/weight but maximum power. Engines like the Volvo KAD 300 started off life as a TAMD/AQAD 40 at 165hp, then became TAMD/AQAD 41 at 200hp, the KAD 42 - 230hp then KAD 44 - 260hp now KAD 300 - 285hp. Not far off double where it started.

Now no doubt they've upgraded parts to cope, but you're still talking about double the power for same sized engine and most marine engines are the same. They're catagorised as "light leisure" useage and pushed harder to satisfy a "performance" market where big power/light weight is the holy grail. No doubt Australian truckers have a different set of priorities. Their commercial truck engines are more compromised toward strength than max power for min size/weight.

Whack on a 30% increase to a "liesure" engine that was never designed for it and good luck!

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[britemp]

I understand that many marine engines are in a higher state of tune than truck engines but they are run in a lower stress way - constant throttle, no gearchanges, far less shock loadings etc. Certainly something like a KAD300 which is at the top end of what can be squeezed out might not be ideal, but more modern engines like the D6 in a relatively low state of tune (around 56hp per litre) should handle it easily.

The TDi engine I gave as an example puts out more hp per litre than most boat engines, had done 135,000 miles when the kit was fitted and now has 206,000 miles on it with no problems, just lots more poke and no smoke.

I'm not saying it will be the ideal solution for everyone, I'm just surprised it hasn't apparently been investigated a bit further in a marine environment ever hungry for more power from less weight.

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[Marsupial]

in the late 1960's I was involved turbo charging truck diesels, "they" wanted to get even more power out of the old 1927 block! On the dyno, the engines didnt last half as long and many literally fell in half, the block cracked through the main thrust bearing. Much beefing up of crankcase bearing flanges and cylinder supports followed untill we had an engine that looked the same as the original but weighed about half as much again. There is no gain in HP and torque without considerable pain.

Does anyone know of any experiments water injecting diesels? The RAF managed to get a huge power increase from the merlin employing this technology.

Cheers





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[BrendanS]

Re: water injection

commercially available kits available
eg here
<A target="_blank" HREF=http://www.racetep.com/wik.html>http://www.racetep.com/wik.html</A>

<hr width=100% size=1>Me transmitte sursum, caledoni

 

[Dave_Snelson]

It all sounds good but two things conspire against this (and I'm an LPG user).

One is availability. With the recent closure of LPG at Essex Marina, there are now only 7 marina filling stations in the UK. Its simply not enough, and if you change the design of the engine and then run out of LPG, you're stuck. You will restrict yourself to cruising in your own waters, as I do - only I can run on petrol with no loss of performance as well.

The other is heat dissipation. Its untrue to say that marine engines are under less stress, as they run under far more stress and generate much more combustion heat that has to be cooled away. It stands to reason that when a boat burns 10-20 gallons an hour at 25kts, it must be working a gazzillion times harder than a road engine that does no work at all at this speed and burns 2-3 gallons an hour. The calorific mathematics speak for themselves. If two identical engines are running for one hour, and one engine burns 20 gallons and the other burns 3, then which one has the greater cooling requirement, and which one is working hardest?

One final note on reliability...a marine engine has a simple but effective formula for longevity and reliability (assuming correct service intervals and reasonable ownership). A marine engine should produce, as a maximum, an amount of horse-power equivalent to its swept volume in cubic inches.

So for my engines at 262 cubic inches, they could produce 262 horsepower as a maximum. They actually produce 205HP, so they are OK (I hope!!). Just for your info there are 16.39 cc's in a cubic inch.

Cheers
Dave

<hr width=100% size=1>Madoc Yacht Club
<A target="_blank" HREF=http://www.madocyachtclub.co.uk>http://www.madocyachtclub.co.uk</A>

 

[britemp]

The lack of LPG availability is certainly a problem.

Not so sure I agree with you about combustion temp though. The 100 ton roadtrains I refered to use 1-2 mpg at 60mph, that's 30 - 60 gallons per hour. The ambient air temp is 45 degrees C. Compare that with your example boat using half as much fuel and using a cooling medium much, much cooler than 45 degrees C. In either case, introducing something which reduces combustion temperatures and increases efficiency must be a good thing. Consider the thermal generation of your example boat at 25kts and near full throttle - now consider the higher output of the LPG-injected engine which is achieving the same 25kts but now at only 2/3 throttle and 2/3 revs - how much less heat is generated?

With regard to your reliability formula - you'd better send it to Volvo coz most of their popular engines exceed it by some margin like the KAD300, D6 and TAMD63! /forums/images/icons/smile.gif

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[Its_Only_Money]

britemp, you are confusing combustion temps with the thermal flow required, there are now short cuts in physics. In order to creat your hypothetical extra 100Hp on a 300Hp engine you >must< increase the thermal intake energy of the engine (confined in the intake air, diesel fuel and LPG fuel), this is released as increases in both the useful energy at the crankshaft and an increased requirement to dissipate the waste heat - you appear (correct me if I'm wrong) to be arguing that only the useful energy output of such an engine increases, not the waste heat. If this is true and you've found a way to do this then Ford will be your newest best friend

The extra heat then has to be got rid of via the cooling system. The success of this will revolve entirely around the capacity of the cooling system being used before the LPG system is added. Now I'll bet that a Volvo D6-130 has the same cooling system as a D6-160, so the D6-130 could be upgraded with an extra 30hp without an issue BUT why not just have the D6-160 in the first place and avoid all the issues about fuel availability and propping???? As you have said it will become more difficult to consider whenh you look at the engines at the top of the particular engine tree - such as the D6-160 for instance....and its not as if adding the LPG fuel will offset the cost of the additional diesel required by the higher-spec engine as (for the next couple of years anyway) that incentive doesn't exist with marine diesel in the UK.

"at 2/3 throttle and 2/3 revs" - have you been on a boat? They generally only have one gear. at 2/3 revs I get more or less 2/3 speed. Also heat generated is proportional to power generated, not any particular combination of torque or speed.

So take a small (but strong) diesel block, add a larger than expected cooling system, add a two-speed outdrive leg and be willing to limit your cruising range to LPG-supported areas and it would work but I can't see it becoming as widespread (relatively) as with road vehicles.

Regards the reliability formula I think you'd better take a look at the duty cycles the manufacturers specify in the small print, their higher-output "leisure-rated" engines usually have much lower service life expectancies than the lower, commercially-aimed units based on the same engine family. No free lunch.



<hr width=100% size=1>Rgds

Simon
Its Only Money
Fairline Sprint
Solent-based

 

[britemp]

'there are now short cuts in physics.'

Are there? When were they introduced? /forums/images/icons/wink.gif
I'm not arguing that only extra useful energy and not extra heat is generated per se, but at the same boat speed as opposed to engine speed, the extra power will allow that same speed to be attained at lower load and lower revs thus generating less or no more heat than previously when flat out, subject to getting round prop issues already mentioned.

I think you mean D3, not D6. The simple answer is I wouldn't specify a 130 when I could have a 160. What I am talking about is an alternative to the huge cost of replacing an engine when you want more power but want to keep your boat. An LPG injection system will be a fraction of the cost of a re-engine. When red diesel for boats disappears it will make a huge difference in the running costs:

<A target="_blank" HREF=http://www.agpl.co.uk/diesel-fuel.htm>http://www.agpl.co.uk/diesel-fuel.htm</A>

I can't see it becoming widespread either with the problems already identified, until red diesel goes that is. Then the supply of LPG will greatly increase and LPG injection will be the only answer for the thousands of diesel boat owners who will need to reduce costs, but not be able to replace their diesels with petrol units to be able to run solely on LPG. As the above website shows, if the savings are viable on a 2.5 litre Transit, they would be golden with a couple of 12 litre MAN's!

The duty cycles of the engines are irrelevant - Dave Snelson pointed out that the power output of a marine engine should never exceed the capacity in CI - I merely pointed out that many already do. No free lunch expected or received! /forums/images/icons/smile.gif


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[Its_Only_Money]

'there are now short cuts in physics.'

Don't you watch Star Trek? Well spotted on my typo's.

With a boat you can't have "that same speed to be attained at lower load and lower revs", the boat speed defines the load on the engine in terms of power required. Revs are defined by the gearing in the gearbox or leg and the prop fitted.

You could end up with a boat that is capable of higher speeds due to more power and suitable gearing BUT the load at 25kts will still be the same, any marginal efficiencies in running the engine at a lower speed will be similar to driving your car in 5th rather than 4th at 50mph, you may show a saving but it isn't going to be earth-shattering and nothing like enough to go towards offsetting marine diesel increasing in price to petrol levels.

From the site you link to: "It is therefore important that the maximum torque of the standard engine is not increased, however the torque curve is widened to give considerable performance increase."

....widening the torque curve may not apply so much in a marine diesel, these are designed in mind with the fact that they only effectively have a single gear, so consequently they normally have a relatively broad torque curve already, trading peak torque in necessary.

The fuel savings quoted come from reducing the diesel input and replacing it with the cheaper LPG. Return on the cost of installation takes a while even with a petrol conversion where nearly 100% of fuel used is at the cheaper rate, taking the lowest mpg rate and assuming 100hrs/year the saving on the site you use comes in at approx £350/yr.

Duty cycles are relevant, they indicate the service life of the unit, add 100Hp and any manufacturer would lower the duty cycle - which would impact the resale value of the engine(s). Dave's quoted rule is a good guideline for >reliability< of non-turbo engines, most/all modern leisure engines are turbo/compressed where you can up the output on the same block by increasing the pressures, but do so and the manufacturer would drop the duty cycle and lifespan expectations. So add 100Hp and you can expect to be replacing the engine much sooner than without. Note that an engine can wear out without breaking down during its life, lifespan and reliability aren't the same thing.

<hr width=100% size=1>Rgds

Simon
Its Only Money
Fairline Sprint
Solent-based

 

[britemp]

The savings may not fully compensate for the increase in diesel price, but buying 25% of your fuel at 28ppl instead of 100% at 90ppl will nonetheless be a worthwhile benefit to many diesel boat owners who can't afford a re-engine and who will also benefit from greatly reduced emmissions and smoke.

The engine in the example from the webpage is for a commercial diesel engine so it's torque curve will actually be flatter than your average marine diesel as it is likely to be in a lower state of tune - most modern marine diesels are highly tuned and actually quite 'peaky' compared to lorry diesels producing far less HP per litre than a boat engine. Thus the widening of the torque curve is actually a large benefit to the leisure marine diesel, more so than to the lorry engine. The potential cost savings will also increase in proportion to this benefit.

Everything you say about duty cycles is correct, but nonetheless irrelevant to my point! Dave said a marine engine output should not exceed it's swept volume on CI - I pointed out that many popular engines already do. /forums/images/icons/smile.gif

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[Dave_Snelson]

Yep - I agree with you there on the new Volvos. I hope the build quality is mighty robust. Truth is, we won't know until 5 years or so have elapsed. If I'm wrong, then I would be happy to bin the old rule for a new one.

Cheers
Dave.

<hr width=100% size=1>Madoc Yacht Club
<A target="_blank" HREF=http://www.madocyachtclub.co.uk>http://www.madocyachtclub.co.uk</A>

 

[Its_Only_Money]

Yes, but the more you exceed it the greater the danger of overstepping the strength of the engine and its wear characteristics. I am pointing out that in your original post you wanted to add 100Hp to a 300Hp engine, this will make it more likely to catastrophic failure and it >will< wear out quicker.

Whether "many do" is truly irrelevant, simply moving up the Hp/litre curve will make the engine more prone to failure etc etc, irrespective of where on the curve a particular engine sits.

I note that you have however stopped talking about power increase and the site you refer us to specifically DOESN'T want the peak torque increased.......?

<hr width=100% size=1>Rgds

Simon
Its Only Money
Fairline Sprint
Solent-based

 

[britemp]

Yep - I'm certainly not disagreeing with your maxim, just pointing out that the boaters need for more and more power has already lead companies to exceed it.

Judging by how fragile some of the engines seem to be on this forum it probably good advice! /forums/images/icons/wink.gif


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[britemp]

Thats simply because the example webpage i gave is biased towards installing these systems for economy rather than power as is the case with the roadtrains I gave. They have still used it to greatly increase power/torque output and found longevity unaffected and in many cases improved.

Simply taking a low tune lorry engine and tuning it to put out lots more power by conventional means also makes it less reliable, but people still buy KAD300's by the lorry load. Personally I think a D6 (turbo, but no supercharger) with LPG injection to increase and broaden the power and torque curves will be more reliable in the long term than a standard KAD300 (turbo with supercharger to fill in the torque hole) with far fewer moving parts and a lower compression ratio and much more efficient burn, but I guess we'll have to wait and see if fuel prices force the market that way.

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