LPG Discussion Forum

Service life is a whole other issue. I didn't dare broach it. There's enough plates spinning now. As was my fear, if every aspect was covered this thread could go forever.

Who said anything about service life? the single point system on my car has been on for at least 14 years and almost 300,000 miles.

Let it go on forever, we are all learning things. So far we've concluded that brakes aren't an issue, steel tanks are heavy and because of the amount you need to carry, they are big too but there's still more questions.

Gilbertd wrote: Fri Oct 20, 2023 6:12 pm Who said anything about service life?

Stockton Rush didn't and that was his downfall

hitman2 wrote: Fri Oct 20, 2023 6:17 pm Stockton Rush didn't and that was his downfall

Yes, I think I've met mine.

I'll crawl back under my rock. It's a vast subject. I have failed. It's a rare thing to see on the internet- I will admit I was wrong. It is not my intention to mislead, upset or confuse. Save for Simon, I flat fail to communicate even basics.

Good luck in your quest, let us know if you ever manage to succeed

CNG wrote: Fri Oct 20, 2023 7:01 pm It's a vast subject. I have failed.

You haven't failed at all, you have educated us in the differences between LPG, which most of us are fully conversant with, and CNG which, as it is very rare in this country, most of us knew very little about.

I will admit I was wrong. It is not my intention to mislead, upset or confuse.

You weren't wrong either. It made me think, and probably others too. A single point system is pretty basic, all you need do is get the correct amount of fuel, irrespective of what it is, in the form of vapour, into the engine. Prior to that, the difference between LPG and CNG is that LPG arrives at the vaporiser in liquid form, vaporises and the pressure, and hence, the flow, is regulated but with CNG it is already a vapour, so all that is needed is to regulate the pressure. With Propane, 1 litre of liquid becomes around 270 litres of vapour but with CNG, as it is already a vapour, it will take up a lot more space in the storage tank. Consequently it has to be stored under pressure and even if the difference in energy was the same, I doubt you could compress it by a factor of 270 times so it stands to reason that tanks have to be bigger. A bigger tank, capable of holding a gas at a far greater pressure is therefore going to be heavier. Maybe not too heavy to be carried in even an average car (even my partner's Mercedes SLK280, a 2 seater sports car, can carry 100kg in the boot) so you may have over-estimated the weight problem.

Other than that, you didn't mislead, I don't think you upset anyone and while initially you may have confused some (my comment in your other thread about testing the gauge sender using a magnet is obviously complete rubbish once I realised that the tank doesn't contain a liquid with a float sitting on it), but we've all learnt something.

I'm also interested in CNG and for sure nothing about this thread has upset me lol.

Most of the electronics and injectors used for LPG sequential injection are also suitable for CNG sequential injection, it's only really the tank and pressure reducer that are different. That said, injectors nozzle size will usually need to be bigger for CNG applications due to the different stochiometric ratios and different weights per litre at a given pressure of LPG and CNG.

Besides the tank and plumbing there's all sorts of interesting technical aspects... Comparing energy density, weights, pressures, nozzle sizes, mixer venturi sizes (same or smaller size compared to LPG? If same size are CNG mixer system reducers more 'signal' sensitive), home filling options which for LPG would involve having either a bulk tank or having gas delivered in 47kg bottles (and a pump in either case), or for CNG could involve a never ending supply from piped mains gas feeding a CNG compressor with no need for home deliveries... And a cost aspect because running on CNG will be cheaper than running on LPG when setup costs (compressor) have been saved. I've looked into it before and wouldn't mind having a dabble.

There’s so many elements to this subject. I'll have a chat with Simon.