Does anyone else have experience of running an engine into the ground?

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BritCNG
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Joined: Wed Jan 29, 2020 12:45 pm

Does anyone else have experience of running an engine into the ground?

Post by BritCNG »

Can an engine (motor) get so tired, it won’t run CNG yet still run Petrol?

First post gents, so be gentle with me. Please think in the context of barnyard engineering with this question….

Does anyone else have experience of running an engine into the ground?

I’ve a 60s Land rover with a low-comp cooking-engine so tired the oil-light goes on. Yes, I know I shouldn’t but to get round this I run snake-oil syrups in the thing (Lucas Oils Heavy Duty Oil Stabiliser’. The snake-oil has been in there for years. These Land rover engines are famous for two things, 40mph and not much more, and running forever.

I’ve been waiting for the day it finally stops, only it keeps running. I don’t need speed where I live so it’s fine.

UK petrol is four times what you’d pay anywhere else in the world, thus it runs CNG. This always killed any power it didn’t have anyway, yet this works for me.. The power has been getting less and less. Thing is, it still runs well enough on petrol. Runs on CNG provided you don’t give it any load. Compression-test shows all four pots are low but even.

I’ve checked all the obvious stuff, and minded to this thing, happy to run with vacuum leaks, timing way-off, and worn plugs etc. And I’ve fixed all that, I can’t understand why it won’t run on CNG. I’ve changed the reducer, fixed all the faults it was previously happy to cope with.

As I said, runs well enough on petrol. Runs on CNG provided you don’t give it any load.

I suppose what i’m asking is, assuming there’s no daft fault robbing power, is there a point where an engine can be so tired it won’t run on CNG, yet will run on petrol? Hence the day of the rebuild arrives, or should I keep looking for another reason?

storm
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Location: NSW, Australia

Re: Does anyone else have experience of running an engine into the ground?

Post by storm »

BritCNG wrote:
Tue Feb 04, 2020 5:54 am
UK petrol is four times what you’d pay anywhere else in the world, thus it runs CNG.
That's tiny bit of an exageration, it's only not quite twice as much as the cost in Australia :lol:
BritCNG wrote:
Tue Feb 04, 2020 5:54 am
I suppose what i’m asking is, assuming there’s no daft fault robbing power, is there a point where an engine can be so tired it won’t run on CNG, yet will run on petrol? Hence the day of the rebuild arrives, or should I keep looking for another reason?
If you have correct fuel mixtures this sounds like ignition timing to me. I'm no CNG expert but you'll never hear a low compression engine like the old Landrover ping on a fuel like CNG but engine timing will cause crippling power loss on any fuel. If it is to far retarded or advanced your engine wont produce the power you think it should have.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

BritCNG
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Joined: Wed Jan 29, 2020 12:45 pm

Re: Does anyone else have experience of running an engine into the ground?

Post by BritCNG »

OK, you might have a point. UK fuel is only near double what an Aussie pays, however I have it, this is broadly a Yank site - I'm reckoning UK prices could see 'em wince. Seems, across the pond, provided you remember to either blink or breathe, they give it to you.
You're also right in that I reckon as this engine gets ever more tired the poorly set ignition comes into play. It never did run well, more a case of 'well enough'. I'm looking at this side of the problem this week. I know I shouldn't, the poor thing has suffered enough. IMy barnyard abuse has gone on too long. Needs a bit of TLC.

Steptoe
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Re: Does anyone else have experience of running an engine into the ground?

Post by Steptoe »

Can an engine (motor) get so tired, it won’t run CNG yet still run Petrol?

yes..
CNG requires a high cylinder pressure at point of ignition to work correctly.. higher than lpg.
Forget compression ratio.. even high ratios can have low compression at point of ignition.. wear, cam profiles etc.

These old English engines where designed in their day to run even with high wear from bearing thru to rings , bore etc, and therefore would run fine of really crap fuels with very low octanes.. right down into the 50s..with cylinder pressures down into the 20 and 30 lbs... yeah the back fired going down hills etc but still pulled.
But run on high octanes over 95 and up into the low 100s (lpg) on run into problems even setting timing... then try cng which goes even higher...

I have several decades of playing with old English engines designed to run on British pool fuels (to 1956) . And even right up into the 60s (maybe early 70s??) due to British regulations on bore/ stroke requirements similar issues remained. Eventually killing the British automotive engine industry.
I have re designed heads, cam profiles, distributer curves and compressions for these engines to run modern low octane fuels more efficient.
My Spelling is Not Incorrect...It's 'Creative'

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