LPG spark plugs & leads

[Bru]

Hi all, just a quick question. I'm getting my 94 classic 3.9 hooked up to LPG next week. Any suggestions of plugs/leads or should I assume the LPG fitter will look after that end of things, I've been reading that ngk plugs are the go. Would appreciate any suggestions.
Bruce

[bee utey]

Hi all, just a quick question. I'm getting my 94 classic 3.9 hooked up to LPG next week. Any suggestions of plugs/leads or should I assume the LPG fitter will look after that end of things, I've been reading that ngk plugs are the go. Would appreciate any suggestions.
Bruce

Never assume anything. Ask the installer before you start!

As for LPG systems that I install, all vehicles leave with the compatible plugs and leads but I am personally aware of fitters that don't do this. I use Bosch plug leads and plugs because I've had an excellent run with them. The plug type I use is a Bosch WR7DC+ gapped to 0.7mm, or a platinum long life plug WR7KI33S gapped the same. Other people have different preferences but I'll stick with mine all the same.:)

[Listerdiesel]

We have a 1999 Discovery 2 V8, built in November 1998 so one of the first.

We run on Autogas in Europe and I use Champion 7318 double platinum plugs and STI leads, both brought in from the USA where they are a lot cheaper than buying in the UK.

Gaps I set to 0.8 for LPG.

We've covered just over 60k miles in four and a half years with no big issues, LPG controller is a Zavoli multipoint and we have 48 litres of gas capacity with 2 sill tanks.

The conversion was done in 2005 before we bought the truck, but the original installer is still in touch and has updated the zavolie software since we put it back on the road in 2009.

Bosch plugs are good, but tend to be expensive, the Champions are $US 3.00 or so in the 'States, we buy them in lots when we go over for vacations, we have two D2 V8's in the family :D

Peter

[ozscott]

I have a jerky throttle in my D2 v8 and wonder if the stock NGK LPG plugs i have had in there (running only petrol...another story) are the problem. They are 10,000 old and are gapped to LPG use. ..? I have a new MAF and cleaned the throttle body and IAC - no difference.

Should i go back to Iridiums or Platinums even if the LPG is going back on soon?

Cheers

[Pedro_The_Swift]

We have a 1999 Discovery 2 V8, built in November 1998 so one of the first.

we have two D2 V8's in the family :D

Peter

my apologies to the OP--

Peter, how long do your O2 sensors usually last?

[incisor]

The plug type I use is a Bosch WR7DC+ gapped to 0.7mm, or a platinum long life plug WR7KI33S gapped the same. Other people have different preferences but I'll stick with mine all the same.:)

much prefer the bosch over the ngk because i have seen too many issues with ngk plugs galling in alloy heads

the merc v8 uses the same plugs and they are often way cheaper from merc parts suppliers..

[ozscott]

What do you good people reckon about the recommendations on page 3 and the misfire possibility using a colder plug?

https://au.bosch-automotive-shop.com/documents/11095/0/SP+Info+Pack.pdf

Is the best option for running petrol and LPG the plug temp for petrol and reduced only .1mm?

Cheers

[ozscott]

Never assume anything. Ask the installer before you start!

As for LPG systems that I install, all vehicles leave with the compatible plugs and leads but I am personally aware of fitters that don't do this. I use Bosch plug leads and plugs because I've had an excellent run with them. The plug type I use is a Bosch WR7DC+ gapped to 0.7mm, or a platinum long life plug WR7KI33S gapped the same. Other people have different preferences but I'll stick with mine all the same.:)

According to the Bosch tech site the 133S "super plus" plug is gapped stock at .7mm...so a straight fit (checked I suppose first).

Cheers

[ozscott]

I just used the vehicle application search on the NGK site and the recommeded plug for D2 V8 is PFR5G-11 with a 1.1mm gap (way bigger than Bosch recommends. Non LPG...). Who knows!

Cheers

[bee utey]

I just used the vehicle application search on the NGK site and the recommeded plug for D2 V8 is PFR5G-11 with a 1.1mm gap (way bigger than Bosch recommends. Non LPG...). Who knows!

Cheers
The NGK plug listed there is a hot running plug, not suited to anything more than light service on LPG. Heat range 6 is more suited than a 5 . A 1.1mm gap for petrol is optimal. For sequential vapour injection you can safely run up to 0.9mm gap without straining the ignition system. If you're still running a mixer 0.7mm gap is safest to avoid lean mixture back fires blowing up your air box. Petrol will run adequately at the smaller gaps but will always be a compromise, mainly at low loads. I always check plug gaps when fitting them, saves nasty surprises.

As for favourite brands of plugs, I'm not really all that fussy any more so long as the gap and heat range are chosen correctly and the plugs are tightened strictly to manufacturers specifications. They should be checked every 20K to see how they are going, and to make sure they're not binding into the heads. A squirt of penetrating oil (CRC etc) on the plug threads before fitting helps them to glide in without picking up any metal out of the head. Never-seize or similar should be used very sparingly with plugs as it can alter the temperature at which the plug runs due to changing the thermal conductance to the head. I don't use it.