Thread: isuzu & LPG

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.

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

Clean
As you know I am all for the D-gas and have similar.

Your consumption of Gas does seem a little high though and if you have a similar system as mine, perhaps wind the flow a little down would be my suggestion.
I am only going on what research I have read, personnel experience and that of others I have noted.

The extra power is quite addictive so cation is advised.

I use roughly 4L gas per100 km's.

I still find good power and good economy.

Just my 2c worth.

Originally Posted by big guy

Clean
As you know I am all for the D-gas and have similar.

Your consumption of Gas does seem a little high though and if you have a similar system as mine, perhaps wind the flow a little down would be my suggestion.
I am only going on what research I have read, personnel experience and that of others I have noted.

The extra power is quite addictive so cation is advised.

I use roughly 4L gas per100 km's.

I still find good power and good economy.

Just my 2c worth.

That's the first sensible thing you have said in this thread - keep up the good work

Originally Posted by isuzurover

So how are you measuring your combustion chamber and head temperatures??? And what are they?

Replaced a cold start thingy with a temp thingy

1090 light peek 1250 ish under full load IE dropping revs, no change with or with out LPG. NB it is un calibrated, I also have a ring thingy to measure soak, this is under a valve spring. I would love to measure piston temps but don’t have the $$$.

anyway just shy of 20 ltrs in 300 klms of quite hard hilly driving, nothing went bang, nothing melted, peek temps didn’t go off the scope. Seems like to me the hole LPG bun fight is just that, a bun fight.

HEE HEE a lot more scientific than stuffing a BBQ hose up some where aye???

Originally Posted by clean32

Replaced a cold start thingy with a temp thingy

[COLOR=black][FONT=Verdana]1090 light peek 1250 ish under full load IE dropping revs, no change with or with out LPG. NB it is un calibrated, I also have a ring thingy to measure soak, this is under a valve spring. I would love to measure piston temps but don’t have the $$$.

Any pics of your setup???

Speaking of being scientific, some tests/plots of combustion temp vs LPG injection (I assume from BG's post above that you can adjust peak fuelling) would be interesting and useful.

Originally Posted by big guy

Clean
As you know I am all for the D-gas and have similar.

Your consumption of Gas does seem a little high though and if you have a similar system as mine, perhaps wind the flow a little down would be my suggestion.
I am only going on what research I have read, personnel experience and that of others I have noted.

The extra power is quite addictive so cation is advised.

I use roughly 4L gas per100 km's.

I still find good power and good economy.

Just my 2c worth.

ah well, thank you for your concern.

There are a couple of indicators when pushing the lpg
Firstly you can see CCT rise when lpg stops becoming the additive and starts to become a fuel in its own way. I think this point is at about the 14-15 lters per 100. Its this scenario that dougal bases his arguments on.

Another thing that you notice is partial throttle temps rise, indicating a lean mix as with a petrol or dedicated lpg system. At this point there is only a partial brake down of the lpg as well as a burn of lpg, gives good power but its to much of a fine line to manage though the rev range.

10 lters per hundred is miniscule 2 kw at the wheels improvement over 6 liters per hundred, which seemed to give the best power results but the worse economy.

i think you are correct at 3-4 lters per hundred as giving a good balance of power and economy.

Interesting to note, at the high lpg low diesel usage power was dropping, i assume that just because diesel has more energy than LPG. i only have 1 more day of playing before i have to return most of the toys before its noticed they are missing.

Only one thing left to do, is sort out how to disassemble a BBQ

I have run a glow plug as a cylinder head thermocouple before. They work as a Type B and tables are available to correlate voltages to temperatures.

They read average temps which include the cooling effect of each new induction and indeed the exhaust before it is expelled. Peak temperatures or even actual combustion temps can't be measured that way. I was running approx 905C at 100km/h cruise. Turbocharged engines obviously run cooler than NA.

I found the EGT gauge more accurate and far more useful.

Originally Posted by isuzurover

Any pics of your setup???

Speaking of being scientific, some tests/plots of combustion temp vs LPG injection (I assume from BG's post above that you can adjust peak fuelling) would be interesting and useful.

lol the set up is 2 lcd gauges screwed to a bit of plywood, as are all my other gauges. Yes peek fueling was pulled back, so as you see from my previous post I did get to the point where LPG was replacing diesel.

the only other instrument is a side exiting tail pipe and an adjusted rear view mirror.

Dyno,s have there limits and in the wrong hands can be a bit dangerous. I haven’t come across a 4 wheel dybo that will take higher loads ie torque for sustained periods, they start to get a weeeeee bit worm. While CCT temps are good to know and an indicator if things are going to go bang. soak is just if not more important as its an indicator of how the motor will live or how long it will live

Originally Posted by Dougal

I have run a glow plug as a cylinder head thermocouple before. They work as a Type B and tables are available to correlate voltages to temperatures.

They read average temps which include the cooling effect of each new induction and indeed the exhaust before it is expelled. Peak temperatures or even actual combustion temps can't be measured that way. I was running approx 905C at 100km/h cruise. Turbocharged engines obviously run cooler than NA.

I found the EGT gauge more accurate and far more useful.

of course you would, you cant let yourself deviate from your original argument. And you have an EGT gauge already and probably don’t have access to any thing else high end. Add to that we can all see how you are able to adjust your thinking or logic to fit what ever information you have at hand. Which are not bad skill in themselves.


the temp setups can give a high and a low as well as an average, you can set the time period for the average, high and low have a maxim duty cycle of 300 per second after that they act as you have pointed out, or start to depending on the difference in charge temp and peek temp.