Choosing Plug Temps for FI

[Vettezuki]

So, what are the parameters for choosing the right plug tempratures for forced induction? Also, what effect might other fuels, particularly E85 or even E100 have on choosing plugs?

[st-evo-9*corn fed-8urvet*]

So, what are the parameters for choosing the right plug tempratures for forced induction? Also, what effect might other fuels, particularly E85 or even E100 have on choosing plugs?


hmmm how do i wanna answer this it can get tricky and long!!

basic answer = e85-e100 u want a hotter burning spark, petrol based fuels u want a colder spark

long answer.........

platinum or iriduim ngk or denso spark plug in the 6-7 head range with a small gap *.018-.022* for e85-e100 and 8-9 heat range with a tad bigger gap *.024-.030 for 100oct- c16/q16

reason i said what i did for e85-e100
- it takes a little longer to burn and its a tad harder to ignite *mainly at start up when its cold- because cold air or cold engine mixed with cool ethonal mixed with its cooling propertys will put out ur average spark really easily and start up can be a bitch sometimes.*...so u would want a quick hot ass spark to get it going...but you dont want a big gap because it will transfer too much heat to the fuel making it burn hotter then it needs too and pretty much nullifying the cooling property of ethonal

reasons i said what i did for petrol based fuels
- when you get past the 105 octane level shit starts getting harder to ignite but will burn super fast and super hot compared to e85.
-so you give stuff like 110 leaded to c16 a nice colder spark to keep combustion temps down but a bigger gap to make sure that colder spark can ignite that hard to ignite fuel.

also the platinum or iridium transfer a more consistant spark because they better conducting metals then copper.

now if you want to get deeper ignition.....make sure you have a good ignition system!! distibutors will only take you so far...before ull need to go coil on plug....and hold a harder charge.......and jesus dont get me started on fuel systems!!!

its kinda crazy that you asked this because yesterday i was messing around with my gaps and lowering them made all my knock go away! by the way im on ngk 7 heat range iridium parks plugs...freakin cost $15 each from dealership :-( i cracked 2

[Vettezuki]

hmmm how do i wanna answer this it can get tricky and long!!

basic answer = e85-e100 u want a hotter burning spark, petrol based fuels u want a colder spark

long answer.........

platinum or iriduim ngk or denso spark plug in the 6-7 head range with a small gap *.018-.022* for e85-e100 and 8-9 heat range with a tad bigger gap *.024-.030 for 100oct- c16/q16

reason i said what i did for e85-e100
- it takes a little longer to burn and its a tad harder to ignite *mainly at start up when its cold- because cold air or cold engine mixed with cool ethonal mixed with its cooling propertys will put out ur average spark really easily and start up can be a bitch sometimes.*...so u would want a quick hot ass spark to get it going...but you dont want a big gap because it will transfer too much heat to the fuel making it burn hotter then it needs too and pretty much nullifying the cooling property of ethonal

reasons i said what i did for petrol based fuels
- when you get past the 105 octane level shit starts getting harder to ignite but will burn super fast and super hot compared to e85.
-so you give stuff like 110 leaded to c16 a nice colder spark to keep combustion temps down but a bigger gap to make sure that colder spark can ignite that hard to ignite fuel.

also the platinum or iridium transfer a more consistant spark because they better conducting metals then copper.

now if you want to get deeper ignition.....make sure you have a good ignition system!! distibutors will only take you so far...before ull need to go coil on plug....and hold a harder charge.......and jesus dont get me started on fuel systems!!!

its kinda crazy that you asked this because yesterday i was messing around with my gaps and lowering them made all my knock go away! by the way im on ngk 7 heat range iridium parks plugs...freakin cost $15 each from dealership :-( i cracked 2

I'm asking in preparation for RX-Snake, but asked here because it's a good general info topic.

- We will be using an HEI Distributor.
- The motor is setup with something like 9.x:1 static compression.
- I'm really hoping we can fix the 174 Blower. It's a roots style blower than can get up to about 12psi boost on that motor.

I was thinking of using E85 because a) the cooling properties help mitigate the very hot nature of a roots blower b) will allow us to run more timing c) is half the price of race gas d) I'm looking for an extra quirk on the project car for that cool factor.

Plus, as the hippie tree huggers continue their reign of terror, no matter how poorly reasoned E85 should become more readily available, so I'm interested in this fuel as a performance fuel.