Spark Plugs - Projected or not ?

[Holden202T]

So with most everything i've done, i've used projected tip plugs, and just changed heat range to suit.

With my brother and i getting more into nitrous we've been trying to read up on best practices and such and one thing i see alot is to run a non-projected tip plug, and on further investigation i've seen even people with boost running them ....

From what i can see projected tip will give a better ignition due to being further into the cylinder but because of this it also means it will knock with less timing, whereas a non-projected plug will not ignite quite as good but will take more timing without knocking.

It also seems that the projected tip will suck more heat from the cylinder into the cooling system as apposed to the non .... which for nitrous i can see how this is not so much of an issue heat wise because the intake charge is so cold anyways, but chance of detonation is more of a factor with more gases in there and a projected tip etc ....

So im just interested to see what other people have done and if theres any definate benefit one way or another ?

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[vlad01]

get projected with a cooler range.

[Holden202T]

ahh yes but if you go too cold they foul all the time, its a fine balancing act!

[Charlescrown]

I was led to believe (fact or fallacy) that Mitsubishi used the non projected tip on their turbo engines because it was in a less turbulent area of the combustion chamber and hence had a better chance of igniting the mixture. Heat range can be the same with both designs.

[HQ355]

Plugs are cheap and easy to change on a 202 so I'd try both and see which one suits your combo ?

[slewinson]

Plugs are cheap and easy to change on a 202 so I'd try both and see which one suits your combo ?

Depending on the combo a retracted gap plug can work well too. They tend to survive better in really harsh conditions. My experience is that you need have good spark.

Simon.

[delcowizzid]

Non projected are less likely to turn into a glow plug in the cylinder. They act one range colder true.yanks run them in turbo buicks on high boost to stop preignition damage ie Big holes in pistons and bent rods

[Holden202T]

yeah that's what I've heard, a ngk 7 in non projected will be like an 8 in a projected!

and yeah can only try, its cheap enough!

[Charlescrown]

It's only cheap if it doesn't detonate.

[slewinson]

It's only cheap if it doesn't detonate.

My advice is to start with a plug that you know is too cold and adjust the heat range hotter to prevent any fouling.

Many years ago I ran NGK 9.5 or 10.5 heat range retracted gap plugs and found that careful tuning of idle mixtures was critical to minimizing fouling. With EFI and good ignition this should be less of an issue today.

Simon