[Diy_efi] those bosch 4 point plugs

[Mike]

Hi chaps,

Some diagnostic experience for yesterday, Sat.

Have tuned ignition leads on my 3L turbo (same resistance of 2Kohms
for each leg) and noticed the new bosch 4-point plugs have trouble
firing smoothly under boost. So went to ngk 'ordinary' plugs
and no problem at all, even up to 10psi of a leaner mixture.
Over here the bosch 4-point at AUD55 per set of 6 vs ngk at AUD24.

The complication is that I am running a bit leaner than normal,
so its prob not that the bosch 4-point are faulty but that they
wont ignite a leaner charge under higher pressure. Looking at the sales
brochure it shows a spark can occur in the plug at the bottom,
this would not bode well if a greenfire type plug were used in
a lean charge...

Did a compression test, its 150KPa all round, ie Dry test, no
extra table spoon of oil in chamber, 2 valves per chamber, engine
done about 262,000Kms  etc, I think its a bit low but each
chamber is within 5% of the average...Right now the car is running
very smoothly on cruise but have a bit of tappet noise when
accelerating hard at 3,000+ rpm <sigh>

Comments, anyone know their last compression test on a 2-valve ?




Regards from


Mike
Perth, Western Australia
VL Commodore Fuse Rail that wont warp or melt !
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