----- Original Message -----
From: "Carol Kenyon" <Da-Kenyons@webtv.net>
To: "Military Vehicles Mailing List" <mil-veh@mil-veh.org>
Sent: Saturday, April 07, 2001 9:00 PM
Subject: [MV] Bosch Platinum Plugs
> I was removing yet ANOTHER set of Bosch Platinum sparkplugs from a
> customer's car that
> good people on this list mght have fallen into this trap.
>
Yup.
> In my part of the world the DIY auto parts
> stores push these pieces of junk. They are completely unacceptable for
> most U.S. cars
> and just about ANY older vehicle I can think of.
>
Yup.
> If you have a BMW, Volvo, Mercedes-Benz, maybe...
> Here's what's wrong. I call it "running out of
> spark". On the 'scope, a good sparkplug requires 7 to 13kV to fire.
> Most systems will
> max out (12v electronic ignition) at around 30 to
> 35 kV. Older 6v systems will be less, 20kV?
> The difference between firing voltage and maximum output is like a
> reserve. As soon as you put the pedal to the metal that reserve begins
> to narrow. Add a heavy GVW, lean mixture, too wide of plug gap, etc, and
> the reserve is JUST enough to prevent misfire.
> Let's add Bosch Platinum plugs to the mix!
> They require somewhere around 80% of max output AT IDLE! You can see
> that your ignition
> system will "run out of spark" very quickly.
> God forbid you forgot to take the choke off or
> you happen to be running old gasoline! The
> spark will completely bypass this "huge resistor"
> of platinum electrodes and just run down the coated insulator.
> There MUST be someone on this list who has
> had problems with "high performance-long life"
> platinum plugs.
>
Yup.
> I'm not just picking on Bosch, "Split fires", and
> other platinum plugs are just as bad.
> I know that certain vehicles REQUIRE platinum plugs. Use what came in
> them originally.
> If I hurt someone's feeling with this, too bad!
> It's the truth!
>
Yup.
In every instance I too have found them next to useless and at variance with
the claims. My motor sport competing chums report exactly the same
findings.
Actuality:
1) Ford RS 2000 (broadly a Pinto with a twin-choke Weber) very hard starting
and complete failure to start after 2/3 days use. Replaced with anything
and first one up fires.
2) Yamaha XV750 (probably a Virago in the US) electronic ignition and
happily makes a 1/2" spark. See above.
3) Base model Renault 5 (old model) very ordinary, 35HP, cooking 1 litre
motor. See above. Parts store exchanged three sets (Bosch) and gave up,
offered part refund and regular items.
4) H-D 883 Sportster. See above. (Should have learnt by now)
5) All RR B Range engines (Champ-Ferret-Saracen-Stalwart-432 etc) are
specified for RSN 13P (Champion only), a screened, fine wire, platinum plug,
new plugs are instant starters after that it gets difficult. On
high-volatility UK pump petrol first start idle icing is very prevalent on
the 48NNIP carburetted eights, once the 13P's are fouled thank heavens they
are a dismantle type, its the only cure.
I currently use Scorpion/Fox RSN 12Y, an extended nose plug of conventional
configuration, first one up fires and although it will idle ice after a
couple of minutes and stall in black smoke, the next start after letting the
carb warm up is instant and on all eight rather than the usual 6. The two
that fail are, of course, 4 & 5 being nearest the very short tract from the
single, central carb and also awkwardly placed either side of the
distributor.
Apart from the specialist mil screened and sealed types, we have had nothing
but success (and availability) with NGK, the stocked range here even
includes equivalents for every old WWII truck we've looked at and pre-war
cars too, including 18mm types.
What they claim for fine-wire platinum plugs and what actually happens are
two very different things we have found, if it didn't come with them
originally, ignore the hype.
Richard
Southampton - England
This archive was generated by hypermail 2b29 : Tue May 01 2001 - 07:42:39 PDT