Thread: isuzu & LPG

Originally Posted by bee utey

People hold opinions, are loath to consider another one, therefore everyone else is wrong...
As far as economy goes, results posted on this forum and elsewhere show that direct replacement of x litres/100km of diesel with x litres /100km LPG (up to 20%) is totally realistic. As LPG has a lower heat value than diesel then something is obviously happening that but by saying this I am risking 100 snarly replies denying this. And if LPG is 1/2 the price of diesel then there's a possible 10% saving in running cost as a minimum.

And yes many people have benefitted from the insulation program, a few have died which is sad. Would they have been headline news if there hadn't been political mileage in reporting these deaths? Dunno.

true true...

I question the economics from the angle of would the average driver be willing to shell out the full retail cost of an LPG fumigation system if there was no rebate? It's a fair expense and would take a long time to recoup (of course varyable depending on how many Km you drive a year), thus I don't many of us would even take a second look at buying something that might take years to recoup in fuel savings alone.

Forgive me, but I don't understand the concept of the "extra power" thing - energy is energy, it isn't created by the gas, its just cheaper per joule in this format, thus if you substituted extra diesel for extra gas, the net effect would be the same wouldn't it??? the beauty of the 4BD1 mechanical injection pump is that anyone can change this fuelling equation at home... add an EGT, intercooler, big/better/best turbo and you can play around with the fueling to achieve your goals (whatever they are)...

I guess its horses for courses - do you want the extra HP from diesel or gas energy sources? if you want it from diesel, I hope you own a 4BD1, otherwise newer injection technologies and electronics start to make it a LOT more difficult for the home mechanic.

Originally Posted by Bush65

Direct measurement of temperature in the combustion chamber is appealling, but easier said than done. I considered using thermocouples in place of the glow plugs, but it soon becomes apparent that a thermocouple would not be practical.

I don't have data for how combustion chamber temperature changes, but expect it to be somewhat related to the heat released during combustion and expansion as the piston travels down the cylinder. The 1st pic below shows the normalised heat release rate per degree of crankshaft rotation for a typical, normally aspirated diesel engine - the heat release rate was normalised by dividing by the product of total mass of fuel injected and the heating value of the fuel. The negative dip is due to fuel vapourisation and endothermic pre-flame reactions. When autoignition occurs, the heat release rate rises rapidly - the large spike is much smaller or non-existant with highly turbocharged engines.

One crankshaft revolution takes 0.03 seconds (30 msec) at 2000 rpm. To my way of thinking, to be meaningful we would need to measure the temperature at intervals less than 30 degrees, which is 2.5 msec at 2000 rpm.

Thermocouples use an effect know as Seebeck effect (after its discoverer Thomas Seebeck) whereby the junction between two metals generates a voltage which is a function of temperature. For example, the K type thermocouple, which uses Chromel (Nickel-Chromium) and Alumel (Nickel-Aluminium) as the 2 metals produces 12.2 mV at 300C.

When a step change to the temperature being measured occurs, there is a response time for the voltage to change. This response is specified as a time constant, defined as the time required for the voltage to reach 63.2% of the voltage corresponding to the new temperature being measured. The thermocouple requires five time constants for the voltage to approach 100% of that corresponding to the new temperature.

The conductivity and motion of what is being measured has a very large bearing on the response - air is a poor conductor compared to water, so the time constant in air is much greater. How/where the thermocouple is mounted also affects the response e.g. a thermocouple mounted to a manifold will take longer to respond to a change in temperature of gas because of the thermal properties of the manifold.

An exposed junction thermocouple provides fastest response. Smaller wire provides faster response, but the maximum temperature may be lower (accuracy/reliability is affected by diffusion of atmospheric particles and other impurities into the wire at high temperatures). When the thermocouple is protected by a sheath, the smaller the sheath diameter, the faster the response. Sheathed probes of the grounded junction type (thermocouple juction grounded to the sheath) provide better response. See 2nd pic below.

The 3rd and 4th pics below compare time constant to diameter of wire or sheath, for exposed junction and grounded junction type thermocouples, calculated for air at room temperature and atmospheric pressure moving with a velocity of 65 feet per second. For beaded-type and ungrounded junctions, multiply the time constant by 1.5.

then you would want to use the glass tipped fiber optic probe with the remote processor

Originally Posted by clean32

then you would want to use the glass tipped fiber optic probe with the remote processor

No, if you are really serious you use this method:

Flame Temperature Measurement in Diesel Engine on Two Color Method utilizing CMOS Camera-Evaluation of Measurement Accuracy for Detailed Flame Analysis-
Accession number;05A0916851
Title;Flame Temperature Measurement in Diesel Engine on Two Color Method utilizing CMOS Camera-Evaluation of Measurement Accuracy for Detailed Flame Analysis-
Author;TAJIMA HIROSHI(Kyushu Univ., JPN) NARUSE YUICHI(Kyushu Univ., Graduate School, JPN) KINO****A EIJI(Kagoshima Univ., JPN) ANDO RYOJI(Kyushu Univ., Graduate School, JPN)
Journal Title;Journal of the Visualization Society of Japan
Journal Code:S0973B
ISSN:0916-4731
VOL.25;NO.Suppl.2;PAGE.97-98(2005)
Figure&Table&Reference;FIG.3, TBL.1, REF.1
Pub. Country;Japan
Language;Japanese
Abstract;Flame temperature is an effective indicator to estimate the amount of NOx formation. The Two-Color Method (TCM) is widely used to measure flame temperature of diesel combustion because the TCM can calculate temperature from color information of flame images. Taking flame images using the CMOS camera and analyzing those on TCM, however, have some problems such as the limitation calibrated range or measurement accuracy, by having digitalized all processes of the analysis. The purpose of this study is to evaluate the measurement accuracy of TCM analysis using CMOS camera. (author abst.)

Originally Posted by isuzurover

No, if you are really serious you use this method:

lol do you have any idea what i used?

Originally Posted by EchiDna

true true...

I question the economics from the angle of would the average driver be willing to shell out the full retail cost of an LPG fumigation system if there was no rebate? It's a fair expense and would take a long time to recoup (of course varyable depending on how many Km you drive a year), thus I don't many of us would even take a second look at buying something that might take years to recoup in fuel savings alone.

Forgive me, but I don't understand the concept of the "extra power" thing - energy is energy, it isn't created by the gas, its just cheaper per joule in this format, thus if you substituted extra diesel for extra gas, the net effect would be the same wouldn't it??? the beauty of the 4BD1 mechanical injection pump is that anyone can change this fuelling equation at home... add an EGT, intercooler, big/better/best turbo and you can play around with the fueling to achieve your goals (whatever they are)...

I guess its horses for courses - do you want the extra HP from diesel or gas energy sources? if you want it from diesel, I hope you own a 4BD1, otherwise newer injection technologies and electronics start to make it a LOT more difficult for the home mechanic.

Well I've had mine dynoed and it got ''extra power'',the torque was the biggest increase not hp. Pat

Originally Posted by clean32

interesting
Firstly it answers the question of if fumigation is done in other countries, in this case Thailand. no surprise as I have posted before that fumigation is common in Thailand, mainly in larger trucks.
2 other points of interest regarding this report firstly it states that biogas is used and not LPG. Biogas being basically methane and hydrogen with a bit of CO2 chucked in for good measure.
Secondly you are unable to get unblended diesel in Thailand, it is at best 25% bio diesel or at worse 60% coconut oil mixed with aviation kero. In some places its just pot luck as what you get.

Pom tamnarn be sarm dos sa dor, ubonratchatani, logistics, kou burn weapons karp

As I said in the other thread, there are HEAPS of papers on Natural gas (and biogas) duel fuelling as it is most correctly called. However there are relatively few on Propane or LPG dual fuelling, and fewer still on engines running propane at levels as low as these systems use.

Pump Diesel in Australia can now contain up to 10% biodiesel without any labelling. This coincided with the sulphur limit being reduced from 50 ppm to 10 ppm.

Originally Posted by PAT303

Well I've had mine dynoed and it got ''extra power'',the torque was the biggest increase not hp. Pat

Hey Pat, sorry I think you misunderstand - I didn't mean that diesel gas is a false technology like (for example) hiclones, I meant that the gas doesn't give you any more or any different changes than what an equivalent amount of energy in the form of more diesel would also give...

what I do think is a furphy is the semi-common thinking that the increased power/torque etc is something that is akin to a free lunch - it isn't, it costs you fuel and capital expense up front (even when the government pays for the bulk of it). I still think that an equivalent amount of extra diesel (which I agree costs more per "bang" than gas) would give you the same increases with appropriate tuning.

Originally Posted by EchiDna

true true...

I question the economics from the angle of would the average driver be willing to shell out the full retail cost of an LPG fumigation system if there was no rebate? It's a fair expense and would take a long time to recoup (of course varyable depending on how many Km you drive a year), thus I don't many of us would even take a second look at buying something that might take years to recoup in fuel savings alone.

Forgive me, but I don't understand the concept of the "extra power" thing - energy is energy, it isn't created by the gas, its just cheaper per joule in this format, thus if you substituted extra diesel for extra gas, the net effect would be the same wouldn't it??? the beauty of the 4BD1 mechanical injection pump is that anyone can change this fuelling equation at home... add an EGT, intercooler, big/better/best turbo and you can play around with the fueling to achieve your goals (whatever they are)...

I guess its horses for courses - do you want the extra HP from diesel or gas energy sources? if you want it from diesel, I hope you own a 4BD1, otherwise newer injection technologies and electronics start to make it a LOT more difficult for the home mechanic.

The simpler d-gas systems (including the one I fit) add LPG therefore some extra power is available. The same result can probably be achieved by diesel alone it is true. The economy gain is simply a matter of backing off the accelerator when applying LPG. Tuning an engine to run less diesel and adding LPG is also a way to reduced running cost.

I don't precisely understand what happens in a cylinder during combustion so I can't answer techy questions on molecular behaviour etc. However as I said before if I get repeated results where there is replacement of an amount of diesel with the same amount (litres) of LPG, then I am inclined to believe the effect of adding LPG is greater than a simple sum of the two fuel's energies. Websites touting d-gas systems make claims I can't verify about catalyst action, cleaner burning or suchlike, but I can detect diesel smoke and I can add up.

Mostly only high mileage travellers and well off people fitted d-gas systems before the rebate, just lucky then that the rebate makes it affordable for ordinary plebs.

Modern diesels are subject to stringent emission laws so the simple enhancement systems are not automatically approved. Full electronic control of LPG using sensor inputs from the engine ECU allow the new systems now to pass stringent emission tests. Yes they cost more, equivalent to petrol cars having gas injection, but people do their sums and get it done anyway.