Just curious really but I keep seeing people referring to having to drive 1 mile, 2 miles, 5 miles or whatever on petrol before their system switches over to gas. Are modern injection systems more critical in this respect? My own system is a Leonardo controller with a single mixer stuffed in the top of the airbox directly above the main intake venturi. The vapouriser is a very elderly looking Italian thing of unknown parentage (or I can't read it anyway). The car is a '96 Saab 900 non-turbo and it was converted quite some time ago.
However, I start my car from cold and it starts on petrol. I immediately blip it up to 2000 rpm and it changes over to gas as the throttle closes. This morning it was cold, it had been a clear night with a bitter wind and the temperature gauge in the car told me that the external temperature was 6 degrees C. I had to blip the throttle twice before it changed over! That means I was running on petrol for at least 15 seconds! Damn me, at this rate I'll have to put some more in it. I've got just over 1/2 a tankful that was put in it in May so if it carries on like this it'll last less than a year!!
It pulls cleanly from cold, or as cleanly as any car of it's age and technology, and I have never had a problem with icing. So why do the modern systems have to run on petrol for as long as they do?
Warm up times
Injection systems will not change over until the temperature in the vapouriser is upto a preset level. This is because the delivery of the gas to each piston has to be more accurate on modern cars or emissions will rise and the OBD system will detect errors.
Slight blockages due to iceing or incorrect mixtures due to lower gas temperatures cause problems for more modern cars. Older cars don't have such sophisticated diagnostic systems and if the mixture strays from lambda=1 it's not as cruicial.
Slight blockages due to iceing or incorrect mixtures due to lower gas temperatures cause problems for more modern cars. Older cars don't have such sophisticated diagnostic systems and if the mixture strays from lambda=1 it's not as cruicial.
single point systems on cars with the correct amount of coolant with a healthy dose of antifreeze will generally run from cold without any problems. Freezing usually occurs from low coolant or air in the coolant system.
My discovery used to start from cold even on the worst winters day on LPG and would drive fine straight away. My boats which are on converted start on LPG and even though in winter they will have lake water at less than 10 degrees running through them very rarely suffer freezing problems. The only time its been an issue is if they are driven flat out straight away. A couple of mins below half throttle will get enough warmth to no longer cause an issue.
Look at countries like canada where LPG is very popular. They use these fuels out there as the are usually easier to start an engine than gasoline when the temperatures are well below zero.
Like has been said modern injection systems do require a bit longer warm up times though.
My discovery used to start from cold even on the worst winters day on LPG and would drive fine straight away. My boats which are on converted start on LPG and even though in winter they will have lake water at less than 10 degrees running through them very rarely suffer freezing problems. The only time its been an issue is if they are driven flat out straight away. A couple of mins below half throttle will get enough warmth to no longer cause an issue.
Look at countries like canada where LPG is very popular. They use these fuels out there as the are usually easier to start an engine than gasoline when the temperatures are well below zero.
Like has been said modern injection systems do require a bit longer warm up times though.
So the moral is to stick with an older motor then..... I must admit, it has made me think. Since I filled the tank with petrol in May (in Belarus at only 53p a litre), I've done another 11,000 miles. This will result in having done about 22,000 miles in May next year. Assuming I've used half a tankfull now, it'll be about empty by May. That's a petrol consumption of 2000 miles per gallon!
I suppose if I never switched the engine off it would get even better because I'd never use any petrol at all.....
I suppose if I never switched the engine off it would get even better because I'd never use any petrol at all.....
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Heggsy
Is this the reason for my car struggling on LPG this morning? It was v. cold and icy. The system swapped over to gas after about 2 mins of idling (as usua), but ran poorly on gas and stalled a couple of times when I blipped the throttle.johnnygas wrote:Injection systems will not change over until the temperature in the vapouriser is upto a preset level. This is because the delivery of the gas to each piston has to be more accurate on modern cars or emissions will rise and the OBD system will detect errors.
Slight blockages due to iceing or incorrect mixtures due to lower gas temperatures cause problems for more modern cars. Older cars don't have such sophisticated diagnostic systems and if the mixture strays from lambda=1 it's not as cruicial.
I've only had the system for about a week, and it has yet to have its 1K check and adjustment.