lpg on diesel

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To get a diesel to run on lpg only is almost impossible as an added fuel with the ignition is caused by injecting a small amout of dieel or fitting spark plugs and lowering the compression ratio.
More successful is running on CNG (compressed Natural Gas) but still has to have lower compression ratio and spark plugs.
The big disadvantages is the size of the cylinder that is used as CNG is not liquefied and the gas is compressed to about 2000 psi where as LPG is a liquid form at about 170 psi.
The cost of converting a diesel is not worth it either way you go unless like some places that are running their bus fleets on it.
 
thanks...but we know this,talking here about using lpg as an additive..(like i do)
 
zen said:
thanks...but we know this,talking here about using lpg as an additive..(like i do)
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Do you find it worthwhile ?
I suppose you must and how many mpg do you get out of it?and also whats the power like and do you have to remap the injector timing for optimal performance?
 
yes i do..but non standard engine..nissan 6 pot turbo...makes it fell like a straight 8..can get up to 40mpg if keep her at 65-70..its quicker than the 3.9's i have owned!torque you know...(engine is running 2bar boost + cosworth intercooler,geared up to 33mph per 1000rpm..(it really likes pulling against something,rather than free revving))

mind you Mechanical fuel injection..i expect results on modern ecu controlled injection units would not be so good as injection sytem on them already more effeicent..
 
no...infact its cooler...i have egt gauge fitted,with lpg injection enabled egt's are down about 100c
 
Mctb said:
Because of the percentage of gas to LPG it's just not cost effective used a lot in Australia with there road trains.
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how you work that out???

costs £100 for kit if source 2nd hand bits..ie 40l tank,vaporiser,bit of piping (NEW) very crude injector (£5 new) micro switch,lpg solenoid and on/off switch..i just sold twin tank full lpg system for £50...

one tank lasts for ever unless you flat out all the time

gives you atleast 10% mpg increase or power increase (20% in my case as old mechanical injection)
 
youll burn through your piston if you use LPG as an ad on at tickover. and it doesent matter if its illegal to inject LPG into a diesel engine as it isnt injected, it works with a carb type ring introduced before the turbocharger and comes in with the air as an air/fuel mix.

i did an investigation of it for a uni assignment
 
discomikey said:
youll burn through your piston if you use LPG as an ad on at tickover. and it doesent matter if its illegal to inject LPG into a diesel engine as it isnt injected, it works with a carb type ring introduced before the turbocharger and comes in with the air as an air/fuel mix.

i did an investigation of it for a uni assignment
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bollocks to the burn hole in piston bit...did you pass cos you wrong..

mine has been adding lpg at tickover for 5 yrs..no hole.no burnt valves.etc..and why would there be ?egt of so little diesel and lpg is sod all..200c if that...no reading on gauge .gauge fitted pre turbo..remember..we aint talking much gas here..tiny amount,hardly uses any on full song..30l of gas lasts up to 2 full tanks of diesel if driven for mpg not power.

old pic..

005.jpg


have you tried it, or just talking?..oh reason for adding at tickover is otherwise when lpg is metered in it ups the rpm..so there was a noticable jump from tick over to not,made driving unpleasent,so add a little on tickover to raise the tickover rpm,then adjust down tickover by screw..job done.
 
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i may be wrong in your case. but, excessive amounts of LPG in the system will cause something called starfire. (i.e. burning through the piston). it happens when theres too much LPG as it burns at a hotter and faster rate than the diesel. back in the 70's a fair few cummins and perkins engines died of this as a result of running for extensive amounts of time on tickover as the mixture was too rich.

the mixture if got wrong will also increase chamber pressures by IIRC ~20%?? which on a tdi could be a problem, especially if running 18psi at the manifold as the engines dont like too much pressure.
it also causes pre ignition as the engine is running slower, in effect the lpg is burning more before the diesel. this doesent help.

i am talking 15-20% inputs here though not sure what you are using. i bet 10% would be ok in a land rover engine.

and yes i am talking more or less completely theoretical here from studies and journals, not necissarily from experience. i have seen it done on a blue disco 300tdi to quite good effect though.
 
discomikey said:
youll burn through your piston if you use LPG as an ad on at tickover. and it doesent matter if its illegal to inject LPG into a diesel engine as it isnt injected, it works with a carb type ring introduced before the turbocharger and comes in with the air as an air/fuel mix.

i did an investigation of it for a uni assignment
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Forgive my naievity, but wouldn't introducing LPG into the induction system before the Turbocharger be kinda dangerous, consider the heat and compression inside the Turbo casing?? Afterall it is driven off the exhaust, and also with the introduced heat from compression....

Also when passing through the intercooler, as the now air and gas mixture cools, it would seperate due to different specific denisties at different temperatures, you could end up with an intercooler under pressure filled with LPG....imho

If it was me, I would introduce the LPG downstream after the intercooler.....

But I am always open for suggestion.
 
Saint.V8 said:
Forgive my naievity, but wouldn't introducing LPG into the induction system before the Turbocharger be kinda dangerous, consider the heat and compression inside the Turbo casing?? Afterall it is driven off the exhaust, and also with the introduced heat from compression....

Also when passing through the intercooler, as the now air and gas mixture cools, it would seperate due to different specific denisties at different temperatures, you could end up with an intercooler under pressure filled with LPG....imho

If it was me, I would introduce the LPG downstream after the intercooler.....

But I am always open for suggestion.
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I work on gas fuelled generators, the gas is mixed with the air before the turbos, then both go through a cooler into manifold
 
Have a look at the LPG Discussion Forum website lots of genned up peeps on there I am sure someone will have the answer you seek.
 
lpg could be introduced post turbo, but the problem here is that you would have to overcome the pressure of the turbo, i.e. a n/a or pre turbo carburettor type thing will work on its own, using the vacuum effect. whereas post turbo, this couldnt happen because of the pressure created by the turbo, the air is being pushed rather than pulled. so it wont pull the LPG in with the air.
 
discomikey said:
and LPG is not compressin ignited. so the heat and turbo compression shouldnt make it ignite. it is ignited in the combustion chamber by the first signs of the diesel igniting.
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True, LPG is very high octane, so cannot be compression ignited. The diesel has to ignite first to start the LPG burn.
 
easy to inject post turbo....one just runs the "sense"..(i know what i mean,buts it late and cant remember proper name,)pipe from vaporiser to manifold, it then compensates for boost and rams up the lpg pressure accordingly.exactly the same as if its just watching the manifold vac..
 
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