Club 80-90 Forums

What is the code for the Bosch spark plugs when using LPG? I have been told to change from the multi point plugs to the single points but need to know which ones to get.

Thanks Steve

Hi Steve
Hope your conversion went well and your very pleased with it..i'm sure you will be..
Spark Plugs listings can be found here look for you type of engine..

Brickyard Engine Data

Cheers
Al

Thanks for the reply. I had a look at the spec's but are they not the multi type of plug? I have a new set of these fitted, it is the single type I need.

WR7DC+ is the Bosch code for single electrode spark plugs as fitted to my 2.1 LPG'd van. Thank Matt as he's the one who told me and Peter (Headley 18) told me the gap, but can't remember it now.

That's great thanks.

I have been advised to use single tip spark plugs.
I have been using multi tipped ones for 4 years no problems till I fitted the current set. Misfire I have been advised by people on a LPG forum site to fit NGK plugs and one grade cooler (higher number). Spoke to Spark Plugs.co.uk who sell them they said try a grade cooler because of LPG causing localised higher temp and always use single point.
Also reduce gap by 0.2mm that would be 0.5 or . 020 on a 2.1 T25
they also said the Iridium tipped were better with LPG due to reduced
voltage required.
Iridium Plug BPR7EIX ONE GRADE COOLER £6.99 each
Ordinary Plug BP7ES ONE GRADE COOLER £1.91 each

Any one any thoughts or used the NGK plugs

Interesting, I was told not to use NGK and stick to Bosch.
I look forward to your test.

I fitted the NGK BP7ES spark plugs last night (bought from Andrew Page for £1.32 + vat ) and gapped them to 0.5mm There is a an improvement over the previous plugs, that were not that old. The engine pulls better and feels stronger. I shall see if the colder plug makes any difference on motorways or long journeys. I will pull th plugs out and have a look.

An interesting Bullitin on the NGK website

THE INFLUENCE OF LPG

An engine converted from petrol to L.P.G. (liquefied petroleum gas) will cause a change in the spark plug operating conditions. Therefore, some consideration should be made on the type of spark plug being installed.

As L.P.G. has different properties to petrol it influences the spark plug operating temperature and required voltage. The extent of this influence can be seen when comparisons are made on spark plugs which were fitted in an engine using L.P.G. and petrol.

Typical results are as follows :


1. Spark Plug Temperature



Temperatures are higher with L.P.G.
compared to petrol. This occurs due
to L.P.G.'s reduced cooling effect.

2. Spark Plug Required Voltage



Required voltage increases with L.P.G.
because of the difference in the bonding
of gas particles between the two fuels.


Recommendation

To eliminate the influence of L.P.G. and to obtain optimum spark plug performance, NGK recommends:

-The use of a spark plug with one heat range colder (if possible) than that listed in the catalogue: eg, BPR6EFS-13 (L.P.G.) instead of BPR5EFS-13 (petrol) for VN 6 Cylinder Commodore.

AND

-The reduction of the electrode gap by 0.1 mm (which lowers the spark plug required voltage)

Pickles
How does the engine perform when you switch over to petrol using the colder plugs?

Went to local motor parts for the Bosch or NKG one range cooler plugs and he had these on the shelf which are the equivalents and which I had for half price as he isnt doing champion plugs any more;

Champion RNY7C

Gapped them to 0.5mm and my stutteiring & popping 2ltr Aircooled is running like a dream, returned an average of 21 mpg, (yes 21mpg) on a trip to Ynys Las this last weekend from North Worcestershire. This was at around 55mph

Took them out after the trip and they look like model plugs displayed in the Haynes manual, light brown and lovely!!!

THis is a top useful thread - thanks for the info guys.

Will look for those plugs as mine's spluttering a bit and kind of needs the pugs sorting.

Can info get wiki'd?

(Anyone know how to add stuff to wiki? I want to add info on insulation but can't register/add)

Apparently, LPG needs a slightly "fatter spark". A single-electrode plug tends to give a fatter spark than the multi-electrode ones. The only advantage of the multi-electrode plug is longer life as the erosion of the centre electrode is more distributed around its circumference.

To be honest, I haven't noticed any difference in the way the engine runs between the two types but have used the single electrode type for the majority of the 100k miles I've done on gas on the advice of my converter.