Broken Spark Plug--Why?
Turbo Mini Forums

I've finally installed a used metro turbo lump I bought as an assembled unit. It runs, but at idle there's a steady build-up of blue smoke and I was having an unsteady idle. I've found a vacuum leak at the inlet manifold where I plumbed in the vacuum/boost gauge and the blow-off valve (red alloy--already installed on plenum).

The plugs that were in the motor when it was shipped to me were missing the metal hook that gaps to the electrode on ALL FOUR PLUGS! I replaced those prior to my install and ...

BEHOLD! I have one plug (#4) that the same hook was nearly broken clear through. I pulled on it and it came apart in my hands. Why did this happen?

Plug spec: NGKBP6ES Engine at standard bore (compression psi is 127-135 across all cylinders), carb at standard still with factory star-type screws sealing it up. Only mod seems to be the alloy blow-off valve int eh plenum. It is running at about 6psi max boost according to my gauge when my foot is really in it. Not sure if this picture will appear. If not, check out the link and offer input, please.

Thanks!
--Spank

http://im1.shutterfly.com/procserv/47b6da3...16102CZM2rJozY2

spank ,this is often caused by detonation ,i have some plgs from a car ,that had no centre electrode or side or porcelain!! check mixture ,and timing,and use the highest octane you can ,eg optimax or that tesco 99 i think its called ,also try runnig a b7 plug instead of a b6 .oh and check the timing at 3500 with the vacuum advance off to see you total timing ,regards robert.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Could be detonation. I'd be tempted to change to the 7ES plugs rather than the 6ES to start with. Then, as you don't know the setup of the car, get it rolling roaded. this could save you melting a piston rather than a spark plug next time.

Where are you by the way? I'm assuming not the UK as you use the word 'shipped'

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

i won these the other day, bargain i thought:


http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...AMEWN%3AIT&rd=1

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

bollocks..why didnt i think to look on ebay for cheap plugs. i end up paying £16 a set in halfrauds for the bpr7es's

I'm in the US. A "rolling road" would cost $350 US minimum, or about 160 GBP and it's not like they are on every corner here.

I'll check the timing figures and post back later. I've never run above N for temp, though, so I would think a timing issue would have manifested itself in temperature reading.

I am running 91 octane, the highest I can get from a normal petrol station here in Southern California.

Here are some other pictures of the same plug along side another plug. These were used plugs (little use) I installed, btw.

http://im1.shutterfly.com/procserv/47b6da3...16102CZM2rJozY2

The broken plug was from cylinder #4.

I've had the dish of the pistons fill with fuel early on in my install... probably float valve blockage. I ran bowl dry a couple of times at idle and allowed to refill (as suggested in other posts), reset the pressure to 4psi, and haven't had the problem again since.

http://im1.shutterfly.com/procserv/47b6da3...16102CZM2rJozY2

Thanks,
--Spank

mine was eating spark plugs until I done the T peice trick and blocked the vent valve

Metro turbo weekend driver,Mini turbo in the making again!

Hi,
The standard plugs for the turbo engine are BPR7ES. Those plugs will cause detonation as they will run too hot! Get the correct plugs, check timing and condition of carb, it may well be gummed up with carbon deposits. Get some octane booster in the tank, unless you can confirm what octane your fuel is, as you measure it differently over the pond!
Have a look at
Cheers,
Gavin :)

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