Thread: isuzu & LPG

Originally Posted by DeeJay

Originally posted by Bush65 "quote"
You haven't shown any engine manufacturer that use diesel injection with a small amount of LPG added to the air as in what is often called diesel fumigation, which was what I was talking about.
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I'm sorry to see you totally missed my point.
I never intended to show any engine manufacturer as they have moved on to LNG.
Get it??

I never missed your point.

The dual fuel systems that you are referring to are a completely different kettle of fish. They are nothing like the diesel fumigation systems that are being added on to vehicles, like this thread was about.

The dual fuel systems have been researched and used for many, many years, for some years they have used LPG, propane, natural gas, etc. as fuel.

Natural gas has characteristics and cost advantages that have made it prominent with dual fuel engines. I recall hearing that the buses where I am were to use it.

Natural gas is mostly (~90%) methane (CH4). Methane has good anti-detonation properties, unlike long chain hydrocarbons like propane or LPG. Natural gas is abundant and relatively cheap compared to diesel

The common types of combustion systems used in dual fuel engines are:

1. Conventional dual fuel.
2. Low NOx (also called lean burn).
3. Gas injection direct into the combustion chamber (similar to how diesel is injected). The best know user of this system is Wartsila Diesel of Finland (ship engines, etc.), also MAN (joint development with Mitsui).
4. General Electric 'H-process' - a hybrid of 1 and 3, widely used in locomotives in North America

None of these can be compared with diesel fumigation.

Dual fuel systems use only a small quantity of diesel for ignition - typically 5 to 8% of what would be used if running full load on diesel alone.

Diesel fumigation systems use only a small quantity of propane/LPG.

Edit:
A diesel engine requires extensive modification to use any the dual fuel systems.

Only the direct gas injection systems offer similar power to diesel - all others produce considerably less. On the positive side they emit much less NOx compared to diesel.

In the case of the Wartsila and MAN gas injection engine they were made to take advantage of gas produced at the oil well (where the engines are located) or given off the crude oil in the tankers transporting the crude from oil well to shore. Essentially using what would otherwise be wasted.

I was talking $$$ & you guys are talking techo stuff.

first 300 klm, 19ltrs LPG and 18 ltrs diesel

no melted pistons.

oh it was in the hills as well

will have some more numbers when i top off the tanks again

Originally Posted by bee utey

OK so you are right, as soon as all the diesels on gas in oz realise this they will all go bang at once. Cheers!

cant argue with that aye

Please tell me you're running an egt gauge.

Originally Posted by clean32

first 300 klm, 19ltrs LPG and 18 ltrs diesel

no melted pistons.

oh it was in the hills as well

will have some more numbers when i top off the tanks again

As Dougal said and Gerry reiterated, please fit an EGT asap. DaveS and I almost killed an NA 4BD1 with retarded ignition. An EGT would have helped a great deal.

Originally Posted by isuzurover

As Dougal said and Gerry reiterated, please fit an EGT asap. DaveS and I almost killed an NA 4BD1 with retarded ignition. An EGT would have helped a great deal.

Why? As i posted before. EGT although a measure of gas temperature it is also an indicator of pressure pre turbo. Or in other words back pressures created buy the turbo. i don’t have a turbo as well as the fact the exorst gas temperatures would be of little value or really no value. I am interested in CC and head temps. all which are well with in spec so far.

Oh and my pistons haven’t melted either.

Originally Posted by Dougal

The temp drop across a turbo is the energy being extracted from it. Turbos feed on both heat and pressure. It's got nothing to do with putting in more fuel and not monitoring exhaust temps.
.

Actually that’s not correct. Energy being extracted is a very misleading way of trying to explain it just as saying a turbo uses waste energy,

The turbo uses the pressure differential between pre turbine and post turbine. this pressure differential ( you read 2.5 times inlet pressure for a turbo to work is a measure of the differential and not a measure against ambient) is generated buy the induced back pressure of the turbo its self. in inlet tract of the turbo being shaped like a nozzle to increase the gas velocity as it flows from the high pressure side to the low pressure side.

the difference in temperature is a simple calculation of the same amount of energy ( heat in this case) occupying a smaller volume ( pre turbo) and a larger volume ( post turbo), admittedly there is some energy in the form of head being extracted by soak though the casting of the turbo its self but this is neglable in the over all scheme of things.

If you doubled the volume from preturbo temp of 750 deg you would get about 500deg