Which spark plug?

[davvide]

Hi guys,

on my engine, 90,5 x 76 with 48 IDA and 9:7:1 rc, I used untill last year NGK spark plug D7EA. Last year I have reworked the heads (cb 044) but now the spark plug after few km are burned.
I know that the heads temperature is increased after the job and now I'm waiting to try NGK D6EA, a little bit hottest than the 7. or maybe is better a coldest one?!

Which kind of spark plug do you use on your street/strip engine?

Thank in advance!

[richie]

What is the compression now?
It sounds like it is maybe lean,or to much timing,not a spark plug issue,I have used d7ea in 500hp turbo engines and 12/1 compression N/A without any problems,if you want to try a diffeent plug you need to go to a d8ea not a d6ea

cheers richie

[davvide]

Hi Richie,
thanks for your suggestion. Now the compression ratio is 9:9:1
So is better a coldest one not the hottest?
if I have more degrees on the heads I need a spark more cold?

[richie]

Hi Richie,
thanks for your suggestion. Now the compression ratio is 9:9:1
So is better a coldest one not the hottest?
if I have more degrees on the heads I need a spark more cold?

Higher compression=more heat needs a "colder plug" [runs colder so less likely to create detonation] but you really shouldnt need to move on the heat range from the d7ea,it proberly needs more fuel[bigger jet] how much total timing do you have?

cheers richie

[davvide]

I had 10° to advanced but I need to check it to be sure.
I've 165 for main jet with F7 emulsion tube

[richie]

I had 10° to advanced but I need to check it to be sure.
I've 165 for main jet with F7 emulsion tube

Total timing try max 30,and what size idle jets?

cheers richie

[richie]

Can you post a pcture of the spark plugs so we can see what they look like?

[davvide]

Yes,of course:

 

idle jet is 55 f10

Thank you very much Richie for your help

[richie]

Yes,of course:

 

idle jet is 55 f10

Thank you very much Richie for your help

That doesnt look to bad to me,it really depends on how you were driving it just before you turned the engine off,to long idleing and it will only show whats happening in that period,maybe try a 60 idle and see how it behaves,whan you mentioned it being to hot in the 1st post,do you mean just cruising or when you are pushing it hard?

No problem to help,I am supposed to be building an engine,but everyone needs a break for a beverage/Tea

[davvide]

or a beer!   

I haven't this kind of problem on the strip but in that case I usually change the main jet from 165 to 175.
The spark burned only in normal use, when I don't go too much fast.
Before the job at the heads I had no problem. After that I used for 2 month the car with the same setting but I thought was more rich and I moved to 165 main jet. Maybe the problem is only that 

Maybe I can try to use the 175 all time and try 185 on strip

[richie]

or a beer!   

I haven't this kind of problem on the strip but in that case I usually change the main jet from 165 to 175.
The spark burned only in normal use, when I don't go too much fast.
Before the job at the heads I had no problem. After that I used for 2 month the car with the same setting but I thought was more rich and I moved to 165 main jet. Maybe the problem is only that 

Maybe I can try to use the 175 all time and try 185 on strip

With normal road use you are mainly on the idle circuit which is why i sugested going up a size on the idle,most of your driving will be done on this jet



cheers richie

[davvide]

I will try when stop raining!

 

thanks for help

[DWL_Puavo]

I made this cross-reference table for 044 spark plugs as I found out that these were quite often asked in finnish vw forum: http://dwl.fi/044_sparkplugs.xls

I've used D8EA (a bit colder plug) in our endurance racer without problems. Annoying thing BTW is that NGK (as well as Denso) plugs go hotter when the number decreases, and Bosch (as well as Champion and Brosk) ones get colder as their number decreases.

[davvide]

Hi, I know that NGK became colder when number increase, maybe my reasoning was wrong!

Thank you for sharing, it will be useful and thanks for explain your experience

Davide