12mm Spark Plugs for a Race Engine

[racing97]

Absolutely sounds like a very well done engine the M1 has a great sound program for detonation.

[winders]

Yes and the M130 works well with the Factory knock sensors.

[Neil Harvey]

Originally Posted by winders

Yes and the M130 works well with the Factory knock sensors.

Be careful here. I have corresponded with you on my suggestions. But maybe for others reading these posts, my advice is always start with the coldest most retracted plug if you are unsure. Understand how to read a plug too.

Heat range will not make any power. But it can hurt the power production. If you experience no misfiring from fouling, the plug may be the workable heat range. Then if you have enough piston clearance start moving the firing end out into the chamber. Along with this, you can select plugs with the same projection but with a wider gap. There may come a point where the plug will have trouble firing under cylinder pressure or as you move the plug out into the chamber will overheat. This is where understanding how to read a plug becomes extremely important.

NA engines can run a different plug to a boosted engine. High compression NA engines are limited to projected firing ends due to piston clearance. Air cooled engines add another element here too. They run hotter due to the head temps been higher compared to a water cooled head. Its often a trade off but like everything on your engine, you compromise the least to stay safe.

Knock control is definitely a great tool but it will not tell you if the plug is over heating and the cause.

The engine will tell you what it needs and the plug will tell you its happy. A race engine should not use a multi ground firing end in my opinion. This type is designed for long street use where fouling could occur. These block the flame kernel and lower the combustion a race engine needs. I have seen many instances where a poor choice of plug caused unnecessary engine damage, all because the installer had no idea how to read a plug. If in doubt, fit the coldest most retracted type and work up.

[winders]

That's why I ordered one DCPR9EIX and one KR9CI. Once we know if one or both have piston clearance, we will decide from there.

Engines using these heads with similar compression ratios and power output seem to run well on NGK heat range 9 plugs. Some have used heat range 8 plugs but I am starting at 9.

[winders]

I am going with the DCPR9EIX plugs.....

[Spotta]

Originally Posted by winders

I am going with the DCPR9EIX plugs.....

Hello, do you have any feedback on the spark plugs you ended up running. I am going through the same process now.

[gled49]

I ran XR2CS FOR 20 yrs in our race car without issue. They became unavailable a few years ago so switched to NGK iridium9’s, again no issues. Converted the car to the street with the same engine, got some NGK plugs 8’s in anticipation of of plug fouling, never happened. When I worked at Garretsons with Jerry Woods, he converted me from platinum Bosch to Silver. Like W4CS in my 73S.

[faapgar]

I have used W2CS and W3CS for many years with no issues with Motec.Fred

[winders]

Originally Posted by Spotta

Hello, do you have any feedback on the spark plugs you ended up running. I am going through the same process now.

The NGK DCPR9EIX plugs ended up being just a bit too cold so I switched to the NGK DCPR8EIX plugs and now all is well.

I have thought about trying the Brisk BR12S silver plugs to see if there is any benefit but my engine is working so well now with the iridium plugs I have not had enough motivation to bother. If Bosch still made a silver 12mm plug, I would probably be using it…

[faapgar]

There you go.Fred

[Rosco_NZ]

Nice one. What plugs in the 14mm side?

[winders]

Originally Posted by Rosco_NZ

Nice one. What plugs in the 14mm side?

I don't have a 14mm side....but, the NGK BKR8EIX would be the 14mm version of the DCPR8EIX plug.

[Rosco_NZ]

Thanks for prompt reply .. these would be right length / temp range ? Sounds like your head a bit different …??

[winders]

I can't say what the right temp range for your engine is....mine is a relatively high compression race engine running on 110 octane race fuel. I had to check to make sure there was enough clearance to run the DCPR8EIX plug.

I am using an aftermarket head (Xtreme). The 12mm plug size is used for a couple of reasons. Less effect on compression and less material removed from the head (less chance of cracking and more material for heat dissipation).

[Rosco_NZ]

Great, I’ve done some more research and I think 7 heat range will likely work better in a 10:1 CR street engine. Have ordered a set of each as a starting point to check clearance and for tuning. Running MFI on pump gas so temps should stay in check .. though air cooled generally run a bit hotter I think.

[Rosco_NZ]

Dcpr7eix
bkr7eix