Spark Plugs

[Lionheart]

Having just acquired the G40, we are carrying out a full service check over. Also encouraged to do this as goes so well on the open road but in town after 15 mins or so starts to miss the odd spark on constant low throttle but all seems well once cleared with a quick blast.

Read through the forum threads on plugs and decided Std W5DPO is the way to go.

Have spent two days trying to find spark plugs, i thought the following info would be helpful.
We were looking for W5DPO s, the std plug. Also vag part no VW P/N 101-000-006AG sparlk plug.
Bosch's ref no 0 241 247 500 and apparently also short tag of W 235 P 21

Search results:
GSF have had them, now totally out and not sure when or if they will get them back in, thought £17 each
Halfords have had them £48 for a pack of 4, but not getting them again
VAG totally out, should get them but not sure when, no price available, but thought £22
Bar-Tek, Germany, have them 89 euros plus post
Mister-Auto.co.uk have them in stock at £11.71 post free

But they also have listed a plug for the Polo G40 (115bhp - the Original Mk1 G40?) for this they have listed Bosch WR 5 D+ also called WR 5 DC (at £2.26 each) - these look like a much more normal plug, cheaper and appear to be more available - has anyone used them? Even as emergency plugs?

The more I dig into the forum the more I am appreciating it, fantastic info! Thank you to those running it, supporting it adding to it, cheers James

[hayesey]

I think W5DPO are discontinued now.  They were replaced with a plug with a suppression resistor in them.  Something like WR5DPO or possibly that WR5D+ code you mentioned.

A lot of people used NGK BP7EVX but they are now also discontinued!  BPR7EIX are supposed to be the replacement. 

NGKs are a fair bit cheaper than the Bosch ones but they are all expensive plugs because they are platinum tipped.  They are often listed on ebay for some older Ferraris

[Jezza-7]

Can still get BP7EVX

http://www.ebay.co.uk/itm/NGK-Platinum-VX-Spark-Plug-BP7EVX-7270-/290400910757?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item439d3e3da5

Is it BP8EVX that ferrari use? I think yoof ran them for use with nitrous.

[PeteG40]

Biy them and youll gey replacement ones. Trust me.

[hayesey]

Yeah I found the same as Pete!  I ordered a set from Camskill not long ago (well BP8EVX actually but the same applies) and they emailed me to say that despite their website saying the old part, the ones they had were the replacements. 

I suspect the same will happen for anyone claiming to have W5DPO in stock too, they've not existed for some time now.

[Jezza-7]

Oh right, is there really much difference between them?

[hayesey]

which ones the new NGK ones or the new Bosch ones?

The main difference is supposed to be that they have a suppression resistor in them.  G40s already have one in the rotor arm so this means there are now too.  I don't know enough how what these resistors actually do to say what effect this might have.  Needs a reply from yoof and/or andy I think when they look at this

[JoeH]

I bought those BP7EVX of ebay and what arrived was some BPR7EIX and the g40 has been fine.

I've noticed no difference to what i had before, some random bosch ones:
http://www.polog40.co.uk/forum/index.php?topic=8999.0

There must be some technical explanation, the purpose of the resisters

No idea about the WR 5 DC @ £2.86 though, but good question

[sparkz786]

I bought a set of WD5P0 spark plugs from euros about a month and a half ago, luckily got some discount so ended up about 12.50 each, but are listed for about 16 i think :/ platinum iridium tipped. Came up with the reg and are g40 specific if im not mistaken!

[Lionheart]

Just looked those up, think its these
http://www.eurocarparts.com/ecp/c/Volkswagen_Polo+Coupe_1.3_1991/p/car-parts/car-service-parts/regular-service/spark-plugs/?408770730&1&670231ce9c441fc8d9dc7e7d4b3fdf94e990b770&000301

Don't say the 'W5DPO' any where but give a Bosch supplier no 0 241 247 500

And they turned up as W5DPO s ?

Will contact them and Bosch tomorrow. Will also post up what arrives!

[Lionheart]

Plot thickens- a bit. Went into GSF to day to pik up the rest of the service parts and with them was a set of original W5DPO s, te called around and found so else where 14.25 each.

Mister Autos have not arrived yet, so still don't know what these will be, update when they arrive.

[Yoof]

which ones the new NGK ones or the new Bosch ones?

The main difference is supposed to be that they have a suppression resistor in them.  G40s already have one in the rotor arm so this means there are now too.  I don't know enough how what these resistors actually do to say what effect this might have.  Needs a reply from yoof and/or andy I think when they look at this

Correct Hayesy, resistors are basically to supress noise on any other electrical items in close proximity to the HT circuit. I think a Polo rotor arm is circa 6k ohms (from memory).

Obviously the more resistance you put in any circuit, the more work or energy has to be put in for the output to remain constant. So fitting a set of resistor plugs, and a rotor arm resistor means the spark energy is reduced in comparison to having resistor-less plugs and a standard rotor arm.

I've never seen this lead to a miss fire (spark being 'blown out') on anything sub 200bhp in a Polo, however when you run harsher combustion conditions (addition of nitrous, large amounts of boost, different AFR/fuels) the demand on the ignition system increases as the density/composition of the mixture changes.

I now run the NGK replacement which is a BPR8EIX I think... now iridium not platinum.