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Suitable Spark Plug For Supercharger Engine


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#1 sam138

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Posted 26 November 2021 - 03:41 PM

Could anyone recommend a suitable NGK spark plug for the following spec supercharged 1275 engine please ? I've guessing as this is tuned and runs hotter that a cooler plug is needed ?

 

 

1275cc engine  suck through  m45 supercharger set up with hif 44 carb 

 

- Aldon electronic Ignitor fitted inside my old 59D distributor body. 

 

- Running with a Aldon amethyst mapping unit. 

 

 

The car runs but seems to take a some time to fire or doesn't on the first try like the spark is weak and I feel the current NGK BR7ES might not be suitable ? 

 

 

I've installed a brand new starter motor and coil etc when building the engine so can't see any of these being an issue. 



#2 nicklouse

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Posted 26 November 2021 - 06:44 PM

Then try a 6 and see how they look like after a run.

 

how do your 7s look after a run?



#3 postve

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Posted 07 June 2023 - 01:54 AM

Hey Sam,'

 

 

What did you conclude regarding spark plugs and likewise the appropriate gap??



#4 Steve220

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Posted 08 June 2023 - 08:34 AM

For boosted, i'd always run an NGK 7 plug with a 0.85mm gap.



#5 mini13

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Posted 08 June 2023 - 10:07 AM

i know of loads that have run 6's on decent boost and been fine, that may be forth a try if they are fouling when cold



#6 postve

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Posted 08 June 2023 - 10:51 AM

Thx guys as I now have cooler plugs on 0.85 gap. I had NGK 7’s with .25 and another set at .28 and destroyed them with my super charger as engine kept creeping up to 90-92C and believe cooked the electrodes ? Dropping in an oil cooler next week - thoughts?

#7 postve

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Posted 29 June 2023 - 02:58 AM

Ok all heating issues resolved as my SC mini runs at a respectable 82c all day long and figured I would show you guys the new plumbing and grill I made up to help with air flow - so glad I finally resolved the over heating issue - thx again for all those who helped

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#8 postve

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Posted 29 June 2023 - 02:59 AM

Big pic

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Edited by postve, 29 June 2023 - 02:59 AM.


#9 nicklouse

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Posted 29 June 2023 - 10:27 AM

Thx guys as I now have cooler plugs on 0.85 gap. I had NGK 7’s with .25 and another set at .28 and destroyed them with my super charger as engine kept creeping up to 90-92C and believe cooked the electrodes ? Dropping in an oil cooler next week - thoughts?

Engine temp has little to do with spark plugs. If you are killing the plugs is is an ignition thing. The heat rating is to do with cylinder temp (combustion temp).

 

would interested to see images of the dead plugs.



#10 postve

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Posted 29 June 2023 - 11:26 AM

Hey Nick and thx for the response - in regards to the plugs let’s just agree to disagree as at the end of the day swapped in new NGK 6’s as well as eliminating the vacuum advance and problem disappeared completely as no more erratic idle, engine mis-fire, and plugs no longer dying after a few cycles. Seems quite a few others with SC mini are adopting the 6’s although blows in the face of conventional logic to use a slightly colder plug.

Also I did the usual to deal with any pre-ignition issues such as;

- check timing - confirmed 26/4000
- run slightly Rich
- I run 91 as opposed to 94 - no ethanol

Compression sits at 8.5 with the decompression plate so I believe I eliminated most issues and truly narrowed it down to the NGK 7’s as went through 3 sets and mirrored this with my m8 in the UK who was running into the exact same issue. In both cases we tried multiple gaps ..24/.28/.32 and absolutely nothing worked with these plugs - settled on .35 with NGK 6’s, problem solved!

Edited by postve, 29 June 2023 - 11:36 AM.


#11 sonscar

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Posted 29 June 2023 - 12:18 PM

I thought colder plugs have a shorter nose bringing the sparky bit closer to the heat sinking ability of the cylinder head?I an with Nick that the engine running temp has little to do with destroying plugs or that the plugs affect the engine temp.I am not an expert.Steve..

#12 postve

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Posted 29 June 2023 - 12:33 PM

Humm well I cannot disagree with both you’re and Nicks logic Steve and have to agree.

My earlier point said differently is that repeated overheating can cause the plugs to prematurely fail which from my internet research is what I believe happened with the 7’s and interestingly enough not the 6’s? That is the relationship I was trying to establish between spark plugs and engine heat.

What I am trying to figure out is why the 6’s work and 7’s don’t when every thing - to your last post - suggests the 7’s would be appropriate given the setup???

Edited by postve, 29 June 2023 - 12:34 PM.


#13 postve

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Posted 29 June 2023 - 12:51 PM



Thx guys as I now have cooler plugs on 0.85 gap. I had NGK 7’s with .25 and another set at .28 and destroyed them with my super charger as engine kept creeping up to 90-92C and believe cooked the electrodes ? Dropping in an oil cooler next week - thoughts?

Engine temp has little to do with spark plugs. If you are killing the plugs is is an ignition thing. The heat rating is to do with cylinder temp (combustion temp).

would interested to see images of the dead plugs.

Nick, will get a few pics shortly and again cad simply will not run properly on these things and furthermore will not even start up with them -

#14 sonscar

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Posted 29 June 2023 - 08:29 PM

I am not disputing the car runs better on colder plugs.The hotter plugs may well be overheating due to their lesser ability to transfer heat to the head.The combustion temperature affects this.The colder plugs more quickly dissipate the combustion heat to the head and may,just may,be masking a timing/ fuelling problem.As I said I am not an expert and the plugs may well be correct.I like to learn.Steve..

#15 postve

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Posted 29 June 2023 - 09:01 PM

Steve no one least of all me, is saying whether you disputed this or that as I am simply responding to you’re post which based on the logic - provided by VMAX as well as multiple sources on line is correct (shorter spark) as a point of clarity constant overheating of the engine, as I explained was my situation, can and absolutely will destroy spark plugs as it basically eroded the electrodes from my sourcing of information and personal experience.

That being the case I adjusted to 6’s and will try, at some point, 7’s again to experiment as could be simply due to the constant overheating that cooked the 7’s. Furthermore there is no timing or fueling issue as set to 26/4000 and fuel pressure @2.5 which is bang on for my setup. Idles at 1100, afr 12.9 (richer on purpose) and 13.4 cruising - engine purrs like a kitten now that the spark plug issue has been sorted. in addition engine sits between 82-85c all day long - had it out for a run today for 3 hours - all is good and just concluding on my story.

As a side note, in fairness to all on this forum, no one is an expert and certainly would be foolish to put oneself out as such.

Edited by postve, 29 June 2023 - 09:02 PM.





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