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08/03/2005

  Tuning the system

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Installing the system
Tuning the system

 

Ford Scorpio 2.9 Cosworth LPG Conversion 
By Stephen Shaw



Tuning the system
After three weeks of sweat toil and cursing, It was off to the gas station for its first fill. 5 litres of gas was added, and a test made for leaks. Three leaking joints had to be tightened before filling up full.

Ideally the system should be tuned using an exhaust gas analyser, however it's not the sort of equipment I happen to keep in my toolbox. A good setting can be obtained by observing the red and green LED's on the rear of the Lambda ECU (red for rich, green for lean)

Firstly with the main mixture screw about half open, the engine was started, warmed up and switched to gas. The idle adjuster on the vaporiser I adjusted to obtain a good tick-over (under load). With the revs held at about 2500 (normal cruising revs), the main adjuster was turned until the red and green LED's where both on. After a test drive it was found to be much richer when under load, so small adjustments where made over the following weeks to obtain a good mixture when driving. Just a quarter of a turn on the main adjuster can equate to a loss or gain of up to 5 mpg.

The LED's and Lascare oxygen sensors voltmeters (purchased separately), were showing lean between tick over up to about 1500 rpm when driving. I also had problems with the engine surging at lower rpm's. The Vaporiser's second (Allen key) adjuster needed to be wound out about a turn and a half to enrich the mixtures at the lower driving speeds.

I had an initial problem with and a poor tick-over. I noticed the two oxygen voltmeters had uneven readings when idling. After spraying some WD40 around the intake manifold, a leak was detected on the left side. I again removed the manifold and refitted using a thin smear of silicon sealant on the gasket. The idle mixture was then reset. Problem solved.
The vaporiser will take about a 1000 miles to fully run in so I will continue to make occasional adjustments over the coming weeks.

At a later date I will try disabling the ERG valve to see if this makes any difference to the economy (it does on some cars), if so I will fit a solenoid to close the vacuum pipe when operating on gas.

MPG
Working out some figures over the first four fills I seem to be getting an average of 17% less on LPG, but at 0.35 per litre I am still making a good saving of over 40%. It must be noted that the system is running in and is still being tuned, so I expect to get the loss down to about 10%.

Overall opinion
The car runs lovely on the gas with no noticeable loss of power.

The only extra items I had to buy was 2 jubilee clips, a roll of insulating tape, tube of silicon sealant, Inlet manifold gasket, a handful of electrical Spade connectors, and set of spark plugs.

The fitting instructions could have been more vehicle specific.
Figuring out the wiring was a bit of a headache.

Not a weekend job. Best done a bit at a time, keeping the car on the road. Not one of the easiest cars to convert.

Seemed to be plagued by items going missing in the post even although sent by recorded delivery.

FES Top marks for the help and advice given during and after the installation. They obviously hadn't done a Cossie conversion before, so there was a lot of learning on both sides. They worked very hard to sort out all the problems encountered, and I now have a car which runs very nicely on LPG. A nice friendly company to do business with. Well recommended. If only they could sort out the Welsh postal service

Advice
If you are fitting a kit don't deviate from the instructions without first consulting the supplier

Ensure your ignition system is 100 % and there are no air leaks on the intake system

Avoid revving the engine when not under load, The mixtures are set for on the road, and may be lean when in neutral. This, coupled with an ignition problem caused a nasty backfire in mine causing 40 of damage.

Consider changing the spark plugs for a none platinum type. My plugs started to fail after about 300 miles on gas. Platinum and spitfire plugs are known to cause problems in some engines with LPG, I now use NGK double ground electrode plugs BCPR6EK. Other alternatives are
Champion EON, 2
NGK BCPR6ES,
NGK BCPR6ET (triple electrode)

I would also advise fitting a couple of dash mounted 0 to 1 volt Lascare meters to the oxygen sensors as these give a good indication of correct running and are a useful aid to tuning. See links.

Some Useful Links

Yahoo Groups lp-gas
http://groups.yahoo.com/group/lp-gas/

Lascare Electronics Mixture needle part No. EMA1710 http://www.lascarelectronics.com/index.cfm?CFID=179903&CFTOKEN=5449051

FES Autogas
www.fesautogas.co.uk

Autogas Refuelling Stations
http://www.lpga.co.uk/refueling_stations2.htm

 



 
 
   
   
   
   
   
   
   
   
   
   
   
   
   
 

 

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