MPG 5-speed vs CVT doesn't seem right.

[Basic]

It used to be cost effective to burn propane but over here, the price is too close to gas. The only benefit would be that the oil stays ridiculously clean for a long time when burning propane. At least that's what I've noticed on my junk and lpg forklifts. Downside is the crankcase turns to chocolate milk if the engine is never brought up to operating temp.

I've got propane powered Minneapolis-Molines from the 40s on Propane that haven't had the oil changed in 50 plus years and it looks like you put it in yesterday. Propane is so good.

[bunio14]

Interesting, I didn't know that was a thing. Does it run any differently?

No it does not, absolutely seamless experience (as long as you have good quality LPG kit installed).

I'm assuming it would run the same, a bit less mpg, a bit less power

It's not the case anymore, used to be back in the 90s with so called 2nd generation kits. Nowadays 3rd gen and later you have separate LPG injectors, it has a separate ECU which you tune as regular - fuel maps etc. The newest kits are having LPG injectors that are injecting LPG in a form of liquid and not gas hence (in theory) you could get rid of your regular petrol tank etc.
In general new kits are good for very sophisticated engine, you can have start&stop, turbo etc. It will work just fine.
Interesting fact: you can install LPG even in Diesel engines but the savings would not be spectacular - you could save up to 10% of diesel fuel and the conversion is 3k USD or more - some truck companies are doing it anyways, with their fleet and fuel consumption it's worth it.

The only benefit would be that the oil stays ridiculously clean for a long time when burning propane. At least that's what I've noticed on my junk and lpg forklifts. Downside is the crankcase turns to chocolate milk if the engine is never brought up to operating temp.

Indeed, the oil is cleaner way longer - LPG burns cleaner, less soot etc. About the operating temperatures - not a risk anymore. Back in time, you would have a manual switch from fuel to LPG and you would be instructed to switch it only when the temperature needle moves a bit - meaning the coolant is about 50*C or more - of course some people would just start up the engine and switch to LPG immediately which would cause the LPG evaporator to freeze, engine would stall etc.
Nowadays - it's all under control of LPG ECU connected partially to CAN, it switches to LPG at the programmed temp so this risk is eliminated, in case of any misfires, errors - it would switch back to petrol. Much more sophisticated versus the solutions from the 90s
About the price - in Poland the saving per litre is between 40-50% so there is an incentive for sure, also it burns cleaner, less CO and so on, of course whole European Union went nuts and just wants electric car (I am not a great fan of) - comparing an average buying and maintenance price my Mitsu on LPG wins when it comes to $$$ per 100km.

If you want to learn more - happy to answer

[Fummins]

The lpg vehicles I've had didn't have a gas tank. One was a 1970 Ford truck with a 390. It worked fine year round down to at least -30c. It did have what I thought was a primer button that let you give it a shot of propane on cold starts. Also had a high idle switch that was just a solenoid on the side of the carb.
I converted an 86 bronco with a 300 6 to propane just cause I got all the parts for free and could get pull propane from wrecks for free.
Work has 6-8 propane forklifts that are straight propane, they have individual injectors and have very few proplems other than operator failing to tighten tank fitting after replacing the tank.

The only dual fuel vehicle I've dealt with was a 3 ton tow truck with a tbi 427. That one didn't like to run on propane when cold, the piggy back propane system was finiky. It was a gutless pig running either fuel.

I've heard of propane injection on diesels used like nitrous to help lower egt's(I believe) but I've never heard of straight propane conversions for a diesel. But I have heard of natural gas conversions on diesels so propane isn't that weird I suppose. I wonder what's involved in pulling either one of those conversions off. Do you need spark plugs to ignite propane or natural gas?

[bunio14]

I've heard of propane injection on diesels used like nitrous to help lower egt's(I believe) but I've never heard of straight propane conversions for a diesel. But I have heard of natural gas conversions on diesels so propane isn't that weird I suppose. I wonder what's involved in pulling either one of those conversions off. Do you need spark plugs to ignite propane or natural gas?

You can read more on one of the Polish LPG system manufacturer's - here about diesel
https://stagdiesel.pl/en/

And to answer your question, yes - you need spark plugs, in general the car should be in good shape. LPG requires good spark, easiest to say - if it's running crappy on petrol it won't run great on LPG.
There are (according to marketing guys) dedicated LPG spark plugs, usually iridium or double/triple platinum. If coils/cables are fine - a good old regular NGK, Denso or any other works just fine.

When it comes to the tanks - the best and most common place to install them is taking out your spare wheel, depends on the size of your tires you can have different mileage. If that's not enough, there's plenty of cylinder shaped ones - had 90 litres LPG tank if my Odyssey's trunk. Worth to remember - it will only allow to top up 80% of the tanks capacity for safety reasons. You wouldn't like to fill it up on winter with cold and dense LPG, park in your cosy and heated garage making the gas to extend... KABOOM! The mechanism inside of the tank works exactly like a float in the toilet flush and shuts off the valve. I have seen some video of geniuses bending it to make just few more litres to extend the range - that usually does not end up well.

[Fummins]

You can read more on one of the Polish LPG system manufacturer's - here about diesel
https://stagdiesel.pl/en/

And to answer your question, yes - you need spark plugs, in general the car should be in good shape. LPG requires good spark, easiest to say - if it's running crappy on petrol it won't run great on LPG.
There are (according to marketing guys) dedicated LPG spark plugs, usually iridium or double/triple platinum. If coils/cables are fine - a good old regular NGK, Denso or any other works just fine.

When it comes to the tanks - the best and most common place to install them is taking out your spare wheel, depends on the size of your tires you can have different mileage. If that's not enough, there's plenty of cylinder shaped ones - had 90 litres LPG tank if my Odyssey's trunk. Worth to remember - it will only allow to top up 80% of the tanks capacity for safety reasons. You wouldn't like to fill it up on winter with cold and dense LPG, park in your cosy and heated garage making the gas to extend... KABOOM! The mechanism inside of the tank works exactly like a float in the toilet flush and shuts off the valve. I have seen some video of geniuses bending it to make just few more litres to extend the range - that usually does not end up well.

I guess no lpg for my diesel. It doesn't have glow plugs so no place for spark plugs.

I don't know if I read it wrong(probably) but it looks like that Stagdiesel conversion still uses diesel but adds propane to the mix rather than run on one or the other.

[bunio14]

Posting few pictures if anyone is interested how it looks in practice (seems I stole the show and it became solely LPG topic - sorry!)

The meter below serves several functions
1. When you start up your car (cold) - the LED bar will rise from one (red) LED into green ones showing your car temperature. When it reaches 5 green LEDs it means the coolant reached the desired temperature and the ECU will switch the engine into LPG - if you listen carefully you can hear a solenoid click in the LPG tank - louder when empty
Once the meter switches into LPG mode it acts as an indicator of your LPG - this can be programmed and played around, this particular one is RGB so you can even change the color of the LEDs.


LPG valve nicely hidden


The LPG tank took the place of the spare wheel


Engine bay view - some would not even notice there is something extra added


LPG dedicated injectors


Location of the liquid LPG filter on the so called LPG reducer - it turns the LPG from liquid into vapor as well as reduces pressure and keeps it under control


And location of the vapor filter on the LPG line


And that's the whole magic of topping up half price!

[bunio14]

II don't know if I read it wrong(probably) but it looks like that Stagdiesel conversion still uses diesel but adds propane to the mix rather than run on one or the other.

You are absolutely correct, it's just an addition of about 10% unlike with petrol engines in which case (mostly) they run 100% on LPG. In this case I assume diesel would not necessarily need glow plugs (I am not mechanic).
Of course there are exceptions like...
GDI engines - fuel injectors built in directly in the engine - need to be cooled by the fuel flow so every other injection it switches between LPG and petrol to cool them down still providing some savings.
My Mitsubishi was programmed in a way - if I rev over 3500 RPMs - it will add some fuel (like in the above example).

Possibilities are limitless
Scroll down under this link to see a simplified schematic of the installation
https://www.stag.pl/en/

[Fummins]

I initially thought you meant there was a diesel to propane conversion where spark plugs were added to the glow plug holes.
I found this conversion site that looks like they might machine spark plug holes into a diesel cylinder head. Looks like a lot of work, basically re-inventing the wheel. https://www.omnitekcorp.com/altfuel.htm

[bunio14]

Call me stupid but I see no obvious reason for such a conversion - must have some use though, marginal cases I would assume