Thread: isuzu & LPG

Originally Posted by PAT303

If gas is increasing the tune why don't I get EGT's as high as tuned Tdi's?.My engine has an 18% inprovement in power for an increase of 30 degree's in EGT's.Thats more power with less heat compared to a pump wind up. Pat

Because it advances the burn speed. The gas in the cylinder ignites early and causes the injected diesel to burn faster with no ignition delay. Because the burning happens sooner you get more conducted into the head, cylinder walls and pistons and not as much in the exhaust.

Advancing the timing on straight diesel has the same effect. More power and cooler EGT's with no change in fuelling.
Retarding the timing has the opposite effect. Less power and higher EGT's with no change in fuelling.

Originally Posted by PAT303

If gas is increasing the tune why don't I get EGT's as high as tuned Tdi's?.My engine has an 18% inprovement in power for an increase of 30 degree's in EGT's.Thats more power with less heat compared to a pump wind up. Pat

sorry Pat, this is going in circles, but if you haven't tried adding an equivalent amount of energy in diesel in your particular motor then none of us really know what the increased EGT and/or power would be.

I can imagine that the rapidly expanding gas on the air intake might have some form of cooling effect to lower EGT's but given that it is going bang a very very short time after expanding, then this effect should be minimal - a guess on my part, happy to be corrected.

As Isuzurover currectly assumed on my part, I think that adding extra energy into your motor in any form, gas, diesel, petrol, alcohol is in effect overfuelling it and then this requires retuning to cater for the extra fuel. hence you are in fact 'fiddling' with the fuelling of the motor, just not via the diesel pump....

Regarding the environmental side - Bio-diesel is renewable, gas and dino diesel are not. leaving gas/oil/petrol/diesel in the ground or under the sea is far better for the environment than burning it. Growing new diesel/ethanol is even better for the environment as the "pollution" remains sequestered - if you keep your vehicle well tuned, the pollution from bio-diesel is minimised and the waste byproducts from bio are similar to those of LPG anyway (apart from particulates) both have low CO and low SOx compared to petrol... sure the jury is out on high pressure injection systems and bio-diesel, but that is yet another beauty of the 4BD1, its mechanical, low pressure diesel pump runs perfectly fine on bio...

If I had an electronic motor and doing long miles, gas injection certainly becomes more attractive financially as the energy is cheaper on a per joule basis... but thats it, there is no magic secret energy in gas, its just fuel to turn over the motor... inherent variable power losses due to friction, tyre pressures, aerodynamics, variable intake air density, moisture levels etc muddy the waters a lot too...

So in summary, If I had to pay $1000+ for a new fuel delivery device, and I was using the vehicle as a tourer and occassional offroad driver rather than a daily driver, I would spend it on an I/C, EGT gauge and a new spanner to adjust the fuelling

Originally Posted by isuzurover

I think that is Echidna's point - by adding the gas you are effectively "winding up the tune".

and that’s a fair question

Originally Posted by isuzurover

As Bee_utey states, the claims of some other installers/systems that the gas has a catalyst effect or allows the diesel to burn more completely are BS. .

why are they BS?

Originally Posted by isuzurover

Emissions are not necessarily reduced, .

true you can over fuel lpg fumigated systems and up the Emissions just like any other fueled vehicle, but I think the claim is that there are less emissions when producing the same amount of power mainly

Originally Posted by isuzurover

as the review paper I quoted a few pages back showed. Any claim of environmental benefit would need to be scrutinised. Sure you may get up to a 10% reduction in CO2, an increase in some pollutants and a decrease of others.

the review paper you posted and as you pointed out was for a dule fule system, running bio gas or methane irrelevant to this debate

Originally Posted by clean32

why are they BS?
\

true you can over fuel lpg fumigated systems and up the Emissions just like any other fueled vehicle, but I think the claim is that there are less emissions when producing the same amount of power mainly



the review paper you posted and as you pointed out was for a dule fule system, running bio gas or methane irrelevant to this debate

In reverse order...

Go back further - that wasn't the review paper. The review paper was a review of all literature on duel fuel (diesel+gas) systems, in amounts varying from "fumigation" levels to 80-90% gas.

When producing the same amount of power you are still using a greater quantity of gas than the quantity of diesel you have replaced. Let's say you use 10L/100km of diesel, which will produce ~2.7kg CO2/L when combusted. For every litre you substitute, you will need ~1.33 L of LPG (in an ideal case). So although LPG is only ~1.5kg CO2/L, the extra 33% means that any reduction in CO2 emissions is minimal. e.g. - if you use 10% less diesel then you will reduce CO2 emissions by 3%. This may easily be offset by increases in other emissions, as mentioned in the review paper.

LPG/Propane/Butane is a fuel, not a catalyst, and diesels combust >99% of all fuel injected. The claims about catalysis or a much cleaner burn have been disproven.

Isuzu relevant news!
Well, I now have preliminary results for a 4BD1T fumigation system. My first run up Adelaide's SE freeway at a steady 100km/h showed a peak (post turbo) EGT of 440C. This did not vary with diesel only or diesel+gas. Activating the gas flow produced a nearly instant boost pressure increase of 2-4 psi, depending on accelerator position. As this hill isn't steep enough to tax the 4BD1T I had to back off to the same boost pressure as before to maintain an even 100km/h. At this level of fuelling there was no smoke visible or any hint of detonation. The maximum boost pressure under full power was about 16psi, 1psi greater than achieved with diesel alone. Without a 2 ton extra load I could only hold full power for a short time, and also it's not my vehicle so I am handing it back intact. As the owner's primary requirement was for reduced running costs further adjustment may be necessary. I am sure he will be happy to post his findings when he has them.

My Tdi is the same,on cold start up it drives normally and as the coolant temp hits 45 degree's the gas solinoid clicks on and I get a push from behind,without moving my foot the speed increase from say 60 to 70 and I then lift off back to 60.Not having to use as much throttle to maintain speed is were you start to save a couple of ltres per hundred. Pat

Originally Posted by PAT303

My Tdi is the same,on cold start up it drives normally and as the coolant temp hits 45 degree's the gas solinoid clicks on and I get a push from behind,without moving my foot the speed increase from say 60 to 70 and I then lift off back to 60.Not having to use as much throttle to maintain speed is were you start to save a couple of ltres per hundred. Pat

Nobody is disputing anything in what you have just said.

When your engine gets to 45oC, your fuelling is effectively "turned up" through the addition of LPG. You then back off the accelerator, and as a result inject ~2 litres less diesel per hundred km, as it has been replaced ~2.66 litres of LPG.

Originally Posted by bee utey

Isuzu relevant news!
Well, I now have preliminary results for a 4BD1T fumigation system. My first run up Adelaide's SE freeway at a steady 100km/h showed a peak (post turbo) EGT of 440C. This did not vary with diesel only or diesel+gas. Activating the gas flow produced a nearly instant boost pressure increase of 2-4 psi, depending on accelerator position. As this hill isn't steep enough to tax the 4BD1T I had to back off to the same boost pressure as before to maintain an even 100km/h. At this level of fuelling there was no smoke visible or any hint of detonation. The maximum boost pressure under full power was about 16psi, 1psi greater than achieved with diesel alone. Without a 2 ton extra load I could only hold full power for a short time, and also it's not my vehicle so I am handing it back intact. As the owner's primary requirement was for reduced running costs further adjustment may be necessary. I am sure he will be happy to post his findings when he has them.

Thanks for that test.

How much boost was this one running at 100km/h?
Do you know which turbo was on this engine? Factory has at least 3 different turbos, two wastegated and one not. It's hard to guess which as some wastegated turbos will creep up the boost when given more fuel, just not as much as a freefloating turbo.

Was there any smoke before?