[Diy_efi] those bosch 4 point plugs

[Mike]

At 06:53 AM 10/10/05, you wrote:
>Mike I dont think it is the plugs fault, sounds like
>your coil output is low.  A combination of the plugs
>and a lean mixture is working your coil to the max.  A
>hotter coil will do it for you.   Dustin Lof

Yeah thought that at the time, have spare coil, spare power
transistor and I changed the rotor too - pain that one as the
rotor was a skyline part not compatible with the holden one
so had to use a mitsubishi part... So the end result is low
probability the spares also have low coil voltage, the standard
coil for the VL and VLT is considered a high performance part.
I guess the only way to be sure is put it on one of the engine
analysers at a dealer or procure a proper high voltage probe.
I guess I should also check the O2 sensor output so I know
just how lean its running - which I think is pretty lean, might drop
it back a tad when summer hits with a vengeance but getting
around 12L/100Kms in city at moment, I'll give it a country test
this w/end... Right now I'm more worried about the tappet
growl - its starting to be noticeable at lower revs <sigh> Have
to take the top off the engine soon if it gets any worse :(



Regards from


Mike
Perth, Western Australia
VL Commodore Fuse Rail that wont warp or melt !
Twin tyres for most sedans, trikes and motorcycle sidecars
http://niche.iinet.net.au







>--- Mike <niche at iinet.net.au> wrote:
>
>> 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 ?