LPG in the cold

[stuart_adair]

Is everyone enjoying the cold weather ?

I've heard that LPG doesnt perform well in the cold but my car ran absolutely fine today and the outside temperature was MINUS 14 !!!

Anyone having any problems ?

Stu

[junkcatcher]

During mid December I had more than a few instances of dropping back to petrol, much less so on my last couple of fill-ups, however if I have had badly iced road junction to deal with I have been switching back to petrol "just in case". This week it has been -8 to -10 in the mornings but it will run on gas after about 4 minutes.

The car is a Rover 75 1.8 with PRRT thermostat and I have been thinking about putting a flow restrictor in the very large bore (32mm) by-pass pipe on my engine restricting it down to about 25mm to force more flow through the vapouriser and heater but it is just too cold to do anything.

[magneto]

Well, I reckon my old Volvo 240 goes better in this weather on gas. I also may be kidding myself but the usually toasty heater doesn't seem as hot. Perhaps the vapouriser nicking the hot water?

[junkcatcher]

[quote="magneto"]Well, I reckon my old Volvo 240 goes better in this weather on gas. I also may be kidding myself but the usually toasty heater doesn't seem as hot. Perhaps the vapouriser nicking the hot water?[/quote]


Not imaginary combustion engines particularly modern ecu controlled ones are more powerful and more efficient in cold air and high atmospheric pressure, the colder air is more dense which gives a free supercharge and the because the temperature is lower at the end of compression stroke more ignition advance can be used without the danger of detonation.

[MEP]

Stilo returned alot lower MPG

But I was having a fair bit of fun in the snow

[junkcatcher]

[quote="MEP"]Stilo returned alot lower MPG :o

But I was having a fair bit of fun in the snow :D :lol:[/quote]

Warm up and defrosting has a big effect on fuel consumption typically petrol injector durations are at least 25% longer immediately after a cold start.
Coolant temperature has a big effect on required air/fuel ratio.

[Active_Lad]

Warm up and defrosting has a big effect on fuel consumption typically petrol injector durations are at least 25% longer immediately after a cold start. Coolant temperature has a big effect on required air/fuel ratio.

So you're actually better off leaving her ticking over until warm when the durations close up before driving off, rather than booting it from cold as the Eco-warriors would have you believe?

[magneto]

Well for my ha'porth of advice the best way to warm an engine up the fastest, but without abuse. All the clearances in an engine are worked out for normal operating temperature. I just start and go, but not hard. Some cars have a servicing calculator which I am told bases it's calculations on both mileage and the number of cold starts.
All above nowt to do with fuel efficiency just longevity. BTW I have built a few Rover V8 engines, and if there is no oil already in the system the design is such that the engine won't produce any oil pressure. You can either fill the oil pump with vaseline, use a primer shaft or a secret other way which I may reveal...
I made a dummy oil pump drive shaft, and with an ordinary electric drill started this priming process. Admittedly with 20/50 oil, I quickly kippered the drill, such was the loading on it. I have never revved a cold engine high since!
Incidentally, if anyone here is changing the oil on a Rover V8, don't go for a cuppa while it's draining - you may need to go through this priming routine to get oil pressure.

[junkcatcher]

The Rover V8 is notorious for problems getting the oil system primed after an overhaul, very few engines give anything like as much trouble in this respect, the only other I can think of off hand is the old MG XPAG which was a pre-ww2 design.

On most modern engines the secret is choose the correct engine oil. For most engines built in the last 12years a 5w-30 fully synthetic is a suitable choice for year round use in the UK climate. Fully synthetic oils are essential for extended service intervals, if you run an engine on fully synthetic from new you would be amazed how clean they remain inside.
Engines with hydraulic tappets work much better on these lower viscosity fully synthetic oil 5w/30 part or fully synthetic is essential for most Ford engines and Vauxhall and GM Saab engines can run into expensive valve gear problems if 5w/30 fully synthetic is not used.


Best buy fully synthetic is Havoline 5w/30 it can be found at Morrisions supermarket petrol stations for under £17 for a full 5 litres.

[rossko]

So you're actually better off leaving her ticking over until warm when the durations close up before driving off, rather than booting it from cold as the Eco-warriors would have you believe?

Well no, because leaving it ticking over burns fuel solely for warming up ; mpg = zero.
If you drive off cold, at least the fuel burnt is also getting you somewhere, though not as efficiently as when it is warm.
Booting it, hot or cold, always offends Eco-wotsits

[junkcatcher]

If you can park the car close to the house hang 240v hair dryer inside the car through car door seal it works wonders --- although at -12 it takes 15 minutes to work.

[Gilbertd]

I used to use a 3kW fan heater in my car when it was really cold. Defrosts all the windows too.....

[MEP]

Warm up and defrosting has a big effect on fuel consumption typically petrol injector durations are at least 25% longer immediately after a cold start.
Coolant temperature has a big effect on required air/fuel ratio.

Although when warming up and defrosting its normally still running on Petrol as coolant isn't warm enough for LPG switch-over.

[junkcatcher]

[quote="MEP"][quote="junkcatcher"]
Warm up and defrosting has a big effect on fuel consumption typically petrol injector durations are at least 25% longer immediately after a cold start.
Coolant temperature has a big effect on required air/fuel ratio.[/quote]

Although when warming up and defrosting its normally still running on Petrol as coolant isn't warm enough for LPG switch-over.[/quote]

The petrol ECU sets 25% longer petrol injector durations for cold start enrichment nothing to do with the LPG system, the richment tapers off as the coolant temperature rises only when the temperature of the coolant at exit from the cylinder head exceeds about 70c to 80c will the engine switch to closed loop most LPG conversion would have switched to gas before that.

[SimonHobson]

BTW I have built a few Rover V8 engines, and if there is no oil already in the system the design is such that the engine won't produce any oil pressure. You can either fill the oil pump with vaseline, use a primer shaft or a secret other way which I may reveal...
I made a dummy oil pump drive shaft, and with an ordinary electric drill started this priming process. Admittedly with 20/50 oil, I quickly kippered the drill, such was the loading on it. I have never revved a cold engine high since!
Incidentally, if anyone here is changing the oil on a Rover V8, don't go for a cuppa while it's draining - you may need to go through this priming routine to get oil pressure.

A 12mm (IIRC) single hex socket fits as well ! I have a better story about Rover V8s priming though - and also proof that they can actually self prime. I would welcome any explanation as to cause because I'm out of ideas Well not quite, I have a theory that involves the differential expansion of aluminium vs steel and internal clearances.

My last engine in the 110 developed a fault. Ran fine, on cold start it came up to pressure quickly, etc. Then one day (on the way back from some greenlaning down on Salisbury plain) we stopped for lunch - and when I came out later (about 1/2 hour), it had no oil pressure. Nothing, just the warning light goading me and quickly followed by the rattling sound. It was fine when we stopped, and there was no oil on the road.

Came home on the back of a recovery vehicle - how embarrassing.

When I came to check it, dizzy was going round, so I pulled dizzy out to see if the pump drive had sheared off (though no idea why it should have). All normal - so whizzed it round with a drill and it primed. Stuck everything back together and it worked fine

Now here's where it gets interesting. If I ran it till hot, stopped for a while (eg 5 mins), and then started up - it had no oil pressure. Leave it for a couple of hours and it would rattle a bit and then the pressure would come up as it primed itself.

As it happened, I was already planning to swap the engine (the EFI engine that's in it now), just brought it forwards a bit. I scrapped the old engine as the block was cracked - common fault, the webs crack where the big end bolts screw in.


PS - Mines been fine on gas all through this cold weather. Fires up on petrol and I switch it straight to gas (single point mixer).

[MEP]

The petrol ECU sets 25% longer petrol injector durations for cold start enrichment nothing to do with the LPG system, the richment tapers off as the coolant temperature rises only when the temperature of the coolant at exit from the cylinder head exceeds about 70c to 80c will the engine switch to closed loop most LPG conversion would have switched to gas before that.

Well I know that the richment tappers off in my Stilo after about 90sec after start up as thats when the rev's drop off and it returns to it normal 'warm state' rpm.

Gas then switches over after a few more minutes.

So you saying that often the gas has switched over before my BRC guage light has gone from red to green

[magneto]

A 12mm (IIRC) single hex socket fits as well ! I have a better story about Rover V8s priming though - and also proof that they can actually self prime. I would welcome any explanation as to cause because I'm out of ideas Well not quite, I have a theory that involves the differential expansion of aluminium vs steel and internal clearances.

My shaky memory tells me that there are 2 types of oil pump gear? Mine had a slot, hence the tool.
Maybe your motor had some oil pump/pressure release valve issues?
I'll reveal my priming trick, but keep it to yourself... Block the breathers on the rocker boxes then use an airline 'squirter?' either on the dipstick tube or oil filler. As long as you can put light pressure in the crankcase somehow it will then prime at cranking speed, plugs out.
Lovely, simple old engines though, nonetheless. I once took 3 months to build one. While I was doing chamber volumes (individually) I thought, hang on, one head seems heavier than the other - different casting firm! And the bugger had run all it's life with an exhaust rocker on an inlet valve, pad touching about half the valve stem! 246bhp at the end of the day so reasonably nippy in an MGB. Amongst several others I now have a Subaru SVX - similar BHP but thank God there is an excellent forum...

[SimonHobson]

My shaky memory tells me that there are 2 types of oil pump gear? Mine had a slot, hence the tool.

An early one then - I think they changed in the late 70's to early 80's. Early ones had a drive tang on the dizzy and a slot in the pump shaft, later ones switched round to have a slot on the dizzy (on a flexible coupling to allow for any alignment errors) and a tang on the pump shaft.

Maybe your motor had some oil pump/pressure release valve issues?

Who knows - all I know is it was a strange one

I'll reveal my priming trick, but keep it to yourself...

OK, no-oone else will know about it

[Gilbertd]

Although this thread seems to have drifted way off topic, it's made an interesting read. On the original subject, my car seems to be using more gas than before it got cold, but that may just be because I'm using it for more short journeys (like taking the missus to work).

My ex used to leave for work at some ridiculously early hour on a Saturday morning so, if the weather forecast said there would be a frost, I used to put a 3kW fan heater (but on the 1 kW setting) inside her car the night before. This was powered through one of those digital timers to switch on 15 minutes before she had to leave. By the time she went outside, the car was warm and defrosted without me having to get up and go out and scrape it for her....

But, the posts about Landy V8s lack of oil pressure are very interesting. I have a periodic need to transport cars between UK and the South of France. Up until now I have been borrowing a car transporter and was considering buying one specifically to do the job. The downsides are that I'd need a Good Vehicle Operators Licence, the ferry companies charge as freight, the French Motorway tolls are double what they are for a car and then there's all the tacho regs and driving hours complications. As an alternative, I'm now looking at getting a Range Rover and trailer instead where none of the above apply. I'm looking at something around the 96-99 age, early P38, and will be going for a petrol engine with LPG rather than a diseasel. This means I'll probably be getting something like a 4.6 HSE. I assume that at that age the engine is still a development of the original Buick design? Does it suffer from this oil pressure problem and are there any other major flaws that I need to be aware of?

[rossko]

This means I'll probably be getting something like a 4.6 HSE. I assume that at that age the engine is still a development of the original Buick design? Does it suffer from this oil pressure problem and are there any other major flaws that I need to be aware of?

Waay off topic
Yep, same basic engine. Oil pump priming isn't an issue for in-service engines; but regular oil changes are very important for overall life so look for a car that appears to be have been serviced.

Earlier P38s have a Lucas management system (box plenum), later have Bosch (banana plenum) which are superior due to other small changes. Don't dismiss 4.0 versions, which seem to run sweeter and have less block failures (see below).
Avoid singlepoint LPG systems on either, hopelessly unsuitable, or budget for a sequential upgrade. No distributor but still need to keep on top of plugs and leads, and the odd coil, for good LPG running.

Biggest horror stories for these revolve around cooling issues. Like any of the V8s, overheating due to say water loss (burst or seeping rad) or inefficiency (low level, clagged rad) leads to head gasket failure which leads to water loss ... vigilance is need to prevent one issue from becoming a cycle of knock-on parts replacements.
Biggest bills come from "porous block" syndrome - in reality loose liners - mystery unfixable water loss, gets bad enough to pressurise water system - leading to burst hoses, seeping rad cyclic horror story. In theory all the blocks that were going to fail should have failed by now and only good ones are left...

So have a very close look at water system condition - bubbles and smells in header tank, pressurising after a run, sniff when opening bonnet for antifreeze smell (you won't see a seeping rad but you can smell it) etc.

Rest of car has many electric systems, usual check everything functions advice.
Air suspension can get leaky bags, fixable at sensible cost ; unattended leaks lead to worn out pumps though. Check it goes up and down in sensible timescales, no listing after long parkup.
Usual landrover 4WD, listen for clonks whines and rumbles, these cars should be quieter than earlier models.

And do avoid pimpmobiles with skinny tyres, black windows and upholstery ... yukk ... it's a landrover for heavens sake !!