Hello,

Was just wondering what the pros and cons were for running a cooler thermostat on duel fuel LPG, like ,Fuel ecomony,engine longevity, freezing coverter problems????????,etc

I'm looking at sticking a 180 degree (195 original) into AU Wagon(6cyl) duel fuel
and a 160 degree (180 original) into a duel fuel KJ Laers 1.8l

Any info and exipirences would be appreciated.

Cheers Paul

I don't see any logic in using a cooler thermostat. Is there a problem? If so it should be fixed in other ways. Too cold and the converter will freeze.

I use the standard 92 degree with no issues. I do wonder if its stuffed again as the engine takes forever to heat up lately.

Last edited by Rick's EF Fairmont Wagon on Tue Jun 17, 2008 9:57 pm, edited 1 time in total.

In theory, a cooler t'stat would be better because LPG is injected as a gas, thus, the cooler the charge, the more dense it would be, thus enabling more fuel to be introduced to the combustion chamber which could (should??) equate to more power.

Petrol, on the other hand needs to be converted from a liquid to a gas, in the form of small droplets, thus it needs heat, among other things, to achieve this. Thus a higher t'stat may be needed.

Modern engines also run at higher temps in order to improve the combustion, thus putting out less polution. LPG by itself puts out less polution than petrol, so it doesn't need the heat.

Back in the old days, if you converted a car to run on LPG (only), you could dipense with the (anti)polution gear that was on the engine quite legaly. Thus a lot of mechanical fuel pumps were removed and replaced with electric ones sited where they couldn't be seen by the coppers. Well, at least mine were

By this do you mean the reduced head, bore and piston etc temperatures will mean better combustion and therefore that the HEGO lets more gas in and derives more power? I don't have much of an answer to that yet.

But i have read something along the lines that the hotter the combustion chamber is the greater will be the difference in intake and exhaust temps, due to more power being derived. It's covered in thermodynamics.


Petrol is converted to a mist by the injectors, then there's swirl, maybe it finally becomes a vapour before ignition. Heat probably just helps.


But why don't you think higher temps help the combustion of gas?


So you could still run it on petrol without the pollution gear? So if they couldn't see a fuel pump they would declare it gas only? Nowadays you have to have the tank out for an inspecion station to declare it decomissioned.

If you run the temperature too cold your heater wont work well for a start.
Yoy also have dirty oil that never gets up to temperature properly. Oil needs to run at the higher temperature to burn off the impurities and combustion by products. Short runs mean your oil gets far worse contamination as it never get up to temperature. Engines need to run up to proper operational temperature to stay healthy and tuned.

I find my factory LPG ute works much better when it is running at correct running temperature. I use the factory skirtless thermostat and it works fine.

I have a larger twin core radiator in the ute though ... and that makes it run a hell of a lot cooler ... can take a bit for it to warm up in winter ... but the heater works fine even when engine cylinder head temp reports it is still on C.

There was a dyno test a while back in Street Fords I remember when they tested a B-series EGAS sedan ... and they found the hotter the car got on the rollers the more power it made. They were surprised.

If lower engine temp causes converter to freeze, why does it not freeze on cold mornings before engine reaches operating temp? My engine temp runs to cool with the std t/stat and has never caused a problem on LPG. If you have a overheating problem fix the problem, dont put a bandaid on the result of the problem.

I disabled the thermostat in a vehicle i owned many years ago and after driving about 1 kilometre to work in the morning it cut out. I opened the bonnet and the converter was frozen. I left it for a few minutes and ambient temp warmed it up, and i drove off and it was okay.

I'm not saying a cooler thermostat will necessarily cause this, but it might, and would be dependent on conditions.