Thread: isuzu & LPG

Originally Posted by lambrover

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Dougle to me it seems abit far fetched that just because you add double the fuel you will double the engine out put and that sounds like the way you are approaching it.

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With a turbo diesel, if you double the fuel at the same engine rpm and have upgraded the turbo and suitable intercooler to provide the air needed to burn it properly, then the power and torque should be approximately doubled.

(edit) there are some reasons why they won't double, but will approximately double.

The need for increased mass airflow, means the air density in the combustion chamber is increased, and so the spray pattern from the injectors is affected - injectors need to be reset for higher pressure if you want to get back same effect.

To get double fuel rate the injection event finishes later - to finish earlier will need larger elements in the pump and more nozzle holes in the injectors.
(end edit)

The facts are that the later 4BD1T engines produce 90 kW at 3000 rpm in stock condition i.e pump calibrated to provide 70 mm^3 per pump stroke.

My stock pump has been on a test bench and calibrated to provide 170+ mm^3 per stroke (test bench showed that it could go to 180 mm^3 per stroke).

I have seen evidence that the 4BD1T can easily exceed 600Nm torque with pump adjustment and suitable turbo.

The way I read the posts, Dougal's comment regarding increased power adequate for most people here by tweaking the fuel injection pump was directed at big guy.

It seems to me that big guy is a self appointed expert on how bad Isuzu engines are and how good the Land Rover 300TDi is in comparison. He takes every opportunity to heap rubbish on the Isuzu engine and the drivers of same. In my opinion he knows very little about them and my guess is that what knowledge he has is probably based on the series 3 with 4BD1 - not a very good reference for what a 4BD1T intended for vehicle use is like.

It was big guy that showed how little he knows and claimed:

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A pump tweak will get 600 nm.
Pie in the sky me thinks ...

He is a big guy when it comes to slinging insults, but he can't take it when he is called out.

And now for some hypothetical numbers for Dougal. Imagine an Isuzu powered 110 travelling on a flat 100km stretch (hard to do in the Shakey Isles I suppose) at 100km/h. It used 12l/100km before d-gas, now uses 9 l/1ookm diesel and 3l/100km lpg. The 3 litres of LPG will produce 710 litres of vapour. I found this figure from a cursory Google search:

"From a USA Website, that is supplying Propane to households, they indicate the liquid to vapor conversion factor at 1:270 which sound reasonable."

Now work out your CFM multiplied by 60 minutes multiplied by 28.37 l/cf and divide the 710 by this figure, there's your ratio. What I can get without sweat.

Originally Posted by yt110

I'm having dgas fitted tuesday,I have dyno print outs for each change I have made,(first turbo,then intercooler,and last 3" exhaust)when the gas is fitted I'll try to get another one,currently 80kw at wheels.

Looking forward to it

Originally Posted by clean32

with a machine that supposedly spins all 4 wheels on bitumen etc etc

Hehe

One thing you kids need to remember

"whats the difference between argueing with an engineer and wrestleing with a pig in the mud?"








Nothing, after a few hours you realise they both enjoy it

The argument/questions presented by Dougal seem to me to be reasonable, there hasn't been much of substance from the other camp.


From my point of view, the idea of adding LPG and diesel at the same time, to my Isuzu engine has always been a very attractive idea.


But it seems to me that the lack of technical knowledge throughout the industry and installers is alarming.


Also I find it somewhat condescending, that others assume that we have absolutely no idea what Dougal is talking about.


Therefore, my choice is, at ths stage, is to refrain, until I can ensure the longevity of the engine of my Landrover will not be adversely affected by adding LPG.


I fully intend to hand this vehicle down to my son in a servicable condition.


So lets hear and see some figures, guys, lets cut out the emotive abuse, it serves no one and demeans your point.

Perhaps you just need to agree to disagree. I have read this thread and do not feel there are the insults people believe there are. Concentrating on the facts instead of having a go at the person will certainly improve the enjoyment factor of reading any thread.

fact: there are diesel trucks using gas systems.

conjecture: truck drivers/companies try to reduce costs and damaging engines would not be consistent with reducing costs, therefore if gas damaged diesel engines the trucking industry would not use gas.

fact: not all gas fitters understand the details of the systems they are installing or how they work.

In support of the last fact, I have a mate that put gas onto his diesel prado and he had to drive over to Adelaide to get it sorted as the bloke who fitted it in Ballarat kept tweaking it and changing parts but could not sort it out.

I too have considered the use of gas in my diesel, more from the point of reducing running costs as LPG is cheaper than diesel around here. The extra power if it is to be had would be a bonus.

Mechanically injected diesel can produce extra power as a result of tweaking the pump but it appears to be difficult to get the extra power without black smoke. Is this what limits the power output of diesels or is it just a detuned engine has greater longivety?

Originally Posted by bee utey

And now for some hypothetical numbers for Dougal. Imagine an Isuzu powered 110 travelling on a flat 100km stretch (hard to do in the Shakey Isles I suppose) at 100km/h. It used 12l/100km before d-gas, now uses 9 l/1ookm diesel and 3l/100km lpg. The 3 litres of LPG will produce 710 litres of vapour. I found this figure from a cursory Google search:

"From a USA Website, that is supplying Propane to households, they indicate the liquid to vapor conversion factor at 1:270 which sound reasonable."

Now work out your CFM multiplied by 60 minutes multiplied by 28.37 l/cf and divide the 710 by this figure, there's your ratio. What I can get without sweat.

Thought about this after I went to bed (kept me awake) it's simple really. Make a few rough calcs and you get: 4litre 4 stroke engine at 2000rpm displaces 4000 litres per min, or 240 000 litre per hour. Allow for pumping losses, say 210 000 litre per hour. Divide 700 litres of gas by 210 000 and you get 1 in 3000 or 0.3% fumigation That, Dougal is about 10 times less fumigation that you added in your "test". Fine tune the calcs by all means but you were adding LPG at a rate of around 30 litres per 100km which is squarely in 400 cubic inch petrol engine regions. Happy now?

And thanks to all those who weighed in on both sides of the debate, just please try not to read insults where there none and keep cool, there's probably a Land Rover about that needs your attention too.