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[Kevin Wood]

Right, the switch over to gas is based on 2 factors on the Stag ECU. Vapouriser temperature and time since start. You can also set RPM thresholds, etc. but it switches over smoothly with no tendency to stall so there's no need, IMHO.

The vapouriser temperature is close to (but lags slightly behind) coolant temperature since the vapouriser has a water jacket around it.

The vapouriser doesn't actually need to be that hot to operate. It just needs a good flow of coolant that ensures it doesn't ice up. It does take a lot of heat out of that coolant under sustained engine load (about a kilowatt during a fast motorway cruise) but rarely is that experienced on a stone cold engine, so I find 20-25 degrees C will work fine.

The engine ECU will apply enrichment after starting (even when hot) based on the assumption that it is running on petrol. These enrichments don't work for LPG (LPG doesn't condense on the walls of the inlet manifold, for example) so if you let it switch over straight after startup (whether hot or cold) it will run lumpy.

For this reason I tend to set a low switchover temperature (20-25 deg. c) but quite a long delay (15-30 seconds) to allow the startup enrichment to decay before it switches to LPG.

During the summer, it has switched to LPG before I get to the end of my road (a few hundred yards). In winter it takes perhaps 0.25-0.5 miles.

Some would argue that switching over when the vapouriser is cool will lead to more "heavy ends" being deposited in the vapouriser. That may be true, but they will surely be "boiled off" again when the engine reaches full working temperature IMHO. As long as you generally do long enough journeys that the engine gets to full working temperature I don't see a problem.

Kevin

[feeutfo]

There, what he said. :-)

Certainly no problems here Kev, thanks to your fine tuning and experience. Well happy :-)

[tunnie]

Very interesting Kevin, thanks for that. Only experience with LPG i had was that horrid mixer system, its good to know it can switch over within half a mile!

This is totally automatic as well? Its set in the ECU, I was thinking i might forget sometimes to switch it over on a morning commute 

[Kevin Wood]

Yes, it's automatic. Bit of a pain, IME, because if the tank is empty and you've switched to petrol it still tries to switch over every time you start the car, and then beeps at you.

Kevin

[Ian_D]

Thanks for that Kevin. I thought that in summer I would be looking at half a mile before I could switch to gas, and a couple of miles in winter! I was 'miles' off literally!

I’m still amazed that the vaporiser can take up to a kw of heat out of the coolant. Now I know that butane / propane can be used as a refrigerant, so it makes perfect sense, but still amazing!

You say the switchover from Petrol to LPG is automatic. What about the other way round? If your driving down the motorway and you run out of LPG, what happens?

And again, if your LPG tank is empty, I assume that it wont automatically switch over to the find out that there’s no gas left!   :-?

[Kevin Wood]

I’m still amazed that the vaporiser can take up to a kw of heat out of the coolant. Now I know that butane / propane can be used as a refrigerant, so it makes perfect sense, but still amazing! Lips Sealed

Well, it has to boil the fuel to turn liquid into vapour. That might seem silly when the liquid boils at -40, but it's still taking heat from its' environment to do so. If you don't provide heat from somewhere the vapouriser will ice up.

If you multiply the rate of fuel consumption by the latent heat of vapourisation of propane you do get about 1kw IIRC. Did the csums once out of interest.

You say the switchover from Petrol to LPG is automatic. What about the other way round? If your driving down the motorway and you run out of LPG, what happens? Roll Eyes

Yep. It's automatic. First thing you know about it is when it beeps at you. As soon as the vapour pressure drops it flicks back to petrol without so much as a misfire.

And again, if your LPG tank is empty, I assume that it wont automatically switch over to the find out that there’s no gas left!   Huh

Well, yes, it does - once, when you start up. The only way it knows it's empty is when the pressure drops as soon as it starts injecting vapour.

Kevin

[feeutfo]

i have noticed you can milk it even if it has run out once. For instance, your blasting down the motorway.sorry, my own private test track, at 90 say. Then the beeper goes off, the red light is on the little gauge, you press the button to turn the beeper off and confirm you know its run out....or has it? Slow down to 70 and press the button again to turn it back to lpg and it will run for while at that speed and so on until it really has run out. Or turn off the motor way and drive at 30 you can get more out of it. But by that stage if you boot it obviously the buzzer goes off and your straight back on petrol, gets boring after a while, but hope that gives an idea how it works. :-)

[Ian_D]

Right... Balls to it... Just looked on petrol prices website. Asda is the only LPG station inside York (I thought it was).

49.9p Per Litre! 

So, what do I need to do to get the ball rolling? 

TBH, I would be daft not to convert to LPG the more and more I think about it...

[feeutfo]

Pm Lazydocker for Tailo's phone number.

[tunnie]

Pm Lazydocker for Tailo's phone number.

He's been really busy lately, i need to ring back for the 3rd time today to get a quote from him. But he is a top bloke, just mega busy it seams

[tunnie]

Right... Balls to it... Just looked on petrol prices website. Asda is the only LPG station inside York (I thought it was).

49.9p Per Litre! 

So, what do I need to do to get the ball rolling? 

TBH, I would be daft not to convert to LPG the more and more I think about it...

Fek sake, BP here, its 57p 

[feeutfo]

paid 59.9 at the shell services on the m40 near wycombe. Yet the BP just south off jcn 11 on the m4 is 53.9, cheapest round here afaik.

[Ian_D]

Pm Lazydocker for Tailo's phone number.

He's been really busy lately, i need to ring back for the 3rd time today to get a quote from him. But he is a top bloke, just mega busy it seams

Cheers I will send him a PM later on

[Ian_D]

Right... Balls to it... Just looked on petrol prices website. Asda is the only LPG station inside York (I thought it was).

49.9p Per Litre! 

So, what do I need to do to get the ball rolling? 

TBH, I would be daft not to convert to LPG the more and more I think about it...

Fek sake, BP here, its 57p 

8-) 8-)

[Ken T]

There's a small garage in Batley doing it for 49.9p AND they have a loyalty card scheme, fill up with stamps and get 35L free 

er do any petrol stations do that 

ken