LPG Sparkplugs
 

99 EB Exp Bifuel 5.4L. Plan to change sparkplugs soon, slight miss when running on LPG. I have been told platinum plugs do not like LPG and I should use a little colder plug for propane which I run 90% of the time. Up to now my research points to NGK TR55IX. Anyone have experience with these or other recommendation.

My mazda loves the copper plugs. I'm running to much boost on a way to big turbo but with a colder copper plug it seems to do ok.

With propane you want to run at least a stage colder. I have a buddy that runs propane in a big 454 with high comp and he runs 2 or more stages colder. There are a lot of benifits to propane in a gas truck. Like $2.25 galon and over 100 octane.

Thanks orng1
The NGK TR55IX is the one recommended for gasoline and I can't find the # for one a step colder.

Talk to the parts guy at a hot rod shop or performance shop. They know which heat range is the right one, ask two people there and go with the answer that they both say. I forget if it's less -1 is colder or more +1 is colder. But ask and they will know.

NGK heat range numbers go up for colder plugs.
TR55IX is a special 1.5mm gap iridium plug not made in other heat ranges.
The closest design made one step colder is the TR7IX with a 1mm gap.

Jim

The electrode is so small on iridium spark plugs, I would be surprised if traditional differences between various heat range plugs had any effect.

I prefer to run coppers for that reason too. I can't see a tiny piece of metal transfering that much of a spark.

You dont understand how fine wire electrode plugs work. They, with the proper wide gap, transfer more electrical energy, making for a more reliable "light off" of the fuel-air mixture. Iridium alloy withstands the heat much better, allowing for the fine wire, than traditional nickel, that need to be relatively big and thick. Platinum is in between the two in cost and longevity.

On the NGK site, they explain why LPG engines need a colder heat range. Since it is already a gas in the mixer, there is no cooling effect as there is with evaporating liguid fuels such as gasolne or alcohol.

Jim

Yeah I know in theory how it works, and they do work fine. It's my thinking that if something were to go wrong it will leave a very small room for error. Running big boost will make you worry. I have worn through a lot of plugs to find the right combo for me. It's me preference to run the widder electrode, I know it's everybodies choice and we all have to make our own.

I have had good luck at sparkplugs.com for finding the same plugs in different heat ranges. What you may have to do is move to a traditional plug instead of the iridium. My previous post was just to give some reasoning as to why there are not different heat ranges for the iridium plug. I worked on a sport bike engine for an engineering project at school and we would always install traditional plugs instead of the iridiums that were stock in the bike because of the price difference mainly, but also so we could run a colder plug with the turbo/E85 setup we were running on stock 12:1 compression. Never had a bit of trouble with plugs.