LPG Explained... An Intro to LPG

[Beej GrpA]

6 years old but a very good read

[Beej GrpA]

this is interesting, regarding butane content and octane..
http://www.deh.gov.au/atmosphere/fue...ubs/paper5.pdf

and some interesting stuff in fuel tax submissions..
http://fueltaxinquiry.treasury.gov.a.../ALPGA_224.asp


is liquid LPG viable yet? how do they compenate for varying tank pressures and temperature?
i'd like to start with vapour injection, and then later move to liquid if it becomes (more)easily available...ie, you can buy the parts..

problems of varying fuel tank pressure can be overcome with a high pressure pump and swirl tank

[oldcorollas]

if you look on page 25 of the first link above...
the (aussie) MON rating of propane is 97, for butane it's 89
they suggest a minimum MON of 90.5, and international practice is that MON is more important than RON for LPG...

for injecting vapour or liquid LPG, the fuel requirements (esp in Aus) are different, ie volatility...

[oldcorollas]

6 years old but a very good read

might be 6 years old, but the recommendations were adopted into practice
http://www.deh.gov.au/atmosphere/fue...lpg/index.html

i thought some people might like to see the reasoning behind it also...

[Cool1]

Has anyone done any reseach into CNG? I know its not easily available to the public as yet, but if you were serious you could import a pump from the US to fill up at home

[oldcorollas]

CNG = much higher pressures because it doesn't convert to liquid phase... means heavier stronger tank, but no problems with trying to make it into a vapour
also no chance of liquid injection (and cooling benefits), but could be more consistent with vapour injction.
main issue now is the infrastructure. LPG has a pretty good infrastructure going now, but CNG is still not a widespread...

[Norbie]

personally i couldnt find any specifications direct from distributors/prodcuers on the specifics of their LPG. Shell, Mobil, BP or Caltex.

It took me all of 5 minutes to find it. Where were you looking?

BP: 50/50 propane/butane, 100RON, 93MON
http://www.bp.com.au/products/LPG/lpg_product_info.asp

Shell: 50/50 propane/butane, 92MON
http://www.shell.com/static/au-en/do...g_fuel_pds.pdf

Caltex: up to 60% butane, 100RON
http://www.caltex.com.au/products_oil_detail.asp?id=179

While it's true that the mix of gases can vary specifically in any given tank of fuel, and if you get pure propane it might be 110RON, you can't tune your car for that scenario if you're just as likely to get 100RON or less. The fact is you never know exactly what you're getting, so you have to tune for the minimum guaranteed numbers - as listed above.

[stradlater]

Unless you buy straight propane every time Norbie, then you know what your getting.

[stradlater]

Another common mis-conception..

Adding LPG to your air stream DOES NOT cool the air temperature an iota.

All the heat loss is in the converters, where the engine coolant gets cooled a little (more to the point the coolant HEATS the converters to stop them from freezing). Once the LPG is in gas form, adding it to the air stream does squat to the temperature.

If you were injecting straight LPG liquid into the cylinder, THAT would be a different kettle of fish... (Imagines frozen pistons smashing..)

for the introduction of LPG into the air stream? or for the expansion of liquid to gas in the convertor, which is usually heated by the engines coolant (iirc )

[Norbie]

Unless you buy straight propane every time Norbie, then you know what your getting.

Entirely true, but this discussion is about LPG not propane. If you look at the product specifications it seems they throw whatever leftover gases they have lying around into the LPG mix, and only guarantee about 50% propane. No wonder it's hard to tune LPG setups properly when the fuel properties change from tank to tank!

[stradlater]

Yeah, But Propane is Supposed to be of higher percentage during winter to stop the lines from freezing.

It's convention, but it's hardly law, and it seems they are doing it less and less. I wouldn't guarantee anything these days

[Norbie]

As I said above, you have to tune for the lowest common denominator. Even if you get pure propane 90% of the time, what happens the other 10% of the time when you get a tankful of butane and other cheap shit? If your engine has been tuned for 110RON, kaboom!

Unless of course you have some way of detecting the fuel properties and can adjust the engine management on the fly, but I think this is beyond the scope of most backyard modders.

[stradlater]

Your hardly making a hugely necessary point, ofcourse it's safer to tune it to the lowest common denominator. I was merely saying if you can get propane, why not....

[Norbie]

Not very practical for a daily driven streeter, but OK you have a point.

[Big rob]

does anyone know how far away that joint is from doing liquid LPG injection? I'm going for GRA at the end of the year but these guys seem they think they can do it for the same price. I guess we'll see what happens.