P38 on gas, Brisk plugs

Marcopolo · Aug 20, 2009

New to RRs recently bought 4 Ltr V8 SE 98 plate. P38? Had some problems missfires on gas and wondered if anyone here had tried Brisk plugs instead of standard. intend to invest in some magnycours leads so if anyone has used the plugs or leads are they all their cracked up to be. Cheers peeps

Gump · Sep 9, 2009

When I had my 4.6 LPG'd it didn't run well until I had Magny Cours put on it, after that it ran smooth as silk.

MirrorSignalSwerve · Sep 9, 2009

My gas 4.6 was lumpy until I had lambda (O2) sensor changed and a standard LPG service. Great now.

Marcopolo · Sep 10, 2009

Thanks for the replys, Since found gas pressure regulator valve was us, changed it out 7 problem improved but not totally gone. av to fit new leads 7 plugs 7 retune on gas. though the missfire does'nt seem to appear running on petrol ?

Gump · Sep 10, 2009

I was told that the firing voltage is higher when running on gas than on petrol (by the LPG bloke) and sure enough, the new leads had it running luvvly with nothing else touched, so maybe someone who knows about firing voltages could fill us in on that?

tufty · Sep 10, 2009

running on petrol dosent require much of a spark to ignite the fuel as the fuel air mix is very combustable.
however lpg is a much slower burning fuel and needs a strong spark to ignite it. the voltage does not change when you switch to lpg so you need every bit of spark you can get down your leads. if the leads are in the slightest bit lossy you will get missfires on lpg, petrol may well not be affected as it is getting enough of a spark.
hope this helps.

nathan5346 · Sep 10, 2009

standard plugs with a smaller gap is best... so they tell me and it suits mine

P38 on gas, Brisk plugs

Marcopolo

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Gump

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MirrorSignalSwerve

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Gump

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