LPG tune up

[yoda960]

Hi chaps, i'm sure my lpg system must need a tune up as I was getting 21/22mpg when I first got then system about 2.5k ago, but now it seems like i'm getting 18mpg... Does it mean I need a so called 'tune up'?

I see people saying that after a tune up their system runs better and they get better mpg etc, but i'm confused - what exactly is a tune up and why is it needed? How does it get out of calibration in the first place?!

My lpg installer is a bit to far to be going to for 'tune ups'...Half wondering if I can get the software and plug myself and have a crack unless its quite complicated!



EDIT: Just seen this: http://www.ebay.co.uk/itm/King-AEB-L...-/360479608664

I've got a King ECU, wonder if that cable/software would be useful, seems a bit dear for a cable and some software though...More research needed

[capt jack]

Not sure what is meant by 'tune-up' either, unless you're planning to 're-map' or 'chip' the fuel system. In the old days it meant fiddling around with carburettors and mixtures, chokes and needles. These days, cars have pretty much sealed-for-life electronics, and tuning for more oomph means playing with the engine control software. This is OK, but can have all sorts of implications if you don't really know what you're doing.

I'd forget all that stuff to be honest and go with the basics: New spark plugs (copper core single point), air filter, clean up the rotor and dissy cap if fitted, etc.

Is the temp gauge sitting at 3 o'clock? If not then a new thermostat is needed.

LPG needs to have tip-top electrics and optimum temperature otherwise it won't work properly - oh and use the air-con with care. Air conditioning can clobber fuel consumption.

Cheers

Jack

[CNGBiFuel]

An aside, but this amused me.

I know the guv'nor of the local cycle shop. He does a roarign trade in tune-ups, and when I asked him what he meant by a 'tune-up' (on a bike FFS) he smiled and repleied with a wry grin, "I really don't know, but my customers seem to".

He admitted along with simple punctures half his workshop staff were employed doing these. I had to agree with him, he used to offer a specoifed service, but tune-ups are far more lucrative.

[yoda960]

I agree, the term tune up doesn't make sense but I have seen posts whereby people have said they have had their lpg system fettled and tuned and now they run better/more economically, i'm just confused as to how that can be! Its has a service inc plugs, filters etc just before the lpg was installed so very recent, dissy cap etc clean. I might check the dissy cap again just to make sure no oil is leaking into it. I know a seal has blown somewhere as its leaking oil

[classicswede]

Try resetting the petrol ECU and see how that effects it

[yoda960]

Hi Dai, how do I go about doing that? Unplug the battery for a few hours?

[classicswede]

Disconnecting the battery will do the trick. Let it run on petrol for a few miles before switching to LPG

[yoda960]

Ok thanks will give that a go, what does it do though?

[capt jack]

As I understand things it works something like this:

When a car is converted to LPG, the original petrol ECU is retained, and the LPG ECU becomes a 'slave' unit to it. The engines sensors (O2 mostly) still send information about the exhaust gases to the petrol ECU.

The LPG ECU sends information about fuelling to the petrol ECU, and provided that the petrol ECU can make sense of these two inputs, all will be well and the car will run happily on both.

However, if the LPG system fails to run properly for whatever reason, the O2 sensor will detect this and tell the petrol ECU. The petrol ECU will then try to make adjustments to the petrol fuel map. But of course it can't alter the LPG fuel map and continues to get information that the fuelling is wrong, and so tries to adjust some more. In other words, it tries to compensate for a perceived 'fault' in the LPG system by adjusting the petrol, and in effect gets it's little silicone-chip knickers in twist.

By disconnecting the car battery for a while and then running on petrol, the petrol ECU resets itself to it's correct petrol settings. Then by switching to LPG, provided that whatever caused the LPG system to run badly has been addressed, the petrol ECU and the LPG ECU should be communicating happily again.

If the same symptoms start to occur then the LPG ECU will need attention. However, before anyone starts to connect up their LPG re-mapping laptop, it makes sense to ensure that the basics are sorted - plugs, leads, dissy cap, rotor, LPG filter etc. Then if any further intervention is needed, you know that you've eliminated all the things that might be affecting the way that the LPG is burning.

If the system is a new installation then this is probably just a part of what you can view as a 'settling in ' period. It's very likely that you will need to take the car back to the installer so that he can re-adjust things.

Finally, you say the car has had new plugs. What type are they? Anything other than simple single-point copper-cored plugs is going to give you problems as LPG does not like fancy multi-pronged non-copper spark plugs.

Hope that helps!

Jack

[yoda960]

Hi Jack, thanks for the detailed reply, great info there

I've got bogstandard ngk plugs that were recommended by Dai so they should be fine, not that old either so should be fine, will see how I get on with the unplugging battery