-----Original Message-----
From: Peter Stoneberg [SMTP:pstoneberg@usa.net]
Sent: Tuesday, April 27, 1999 11:07 AM
To: 'MHKitchen@aol.com'
Subject: Bosch Motronic 1.7
Hi Myles, good explanation of CD vs. inductive. I've seen you at several
CSRG events in your pretty Lotus. Have you had any experience or know
anyone w/ experience on Motronic (esp 1.7) ignitions? I've been struggling
to get one fixed in my Porsche 962 and it seems we have to send it back to
Germany for every repair for big bucks. If someone could repair and/or
clone one here they would be in great demand.
Thanks,
Peter
On Tuesday, April 27, 1999 9:14 AM, MHKitchen@aol.com
[SMTP:MHKitchen@aol.com] wrote:
> To the List:
>
> Just thought I'd throw my 2 cents worth in here as I formerly designed
> electronic ignition systems for Motorola.
>
> A common misconception is that a CD ignition is a "high performance"
> ignition. Acutally, most CD's produce far lower spark energy than
> conventional inductive storage types. What CD's do, is produce a very
quick,
> high voltage pulse that's helpful in lighting oil-fouled plugs. However,
the
> spark duration is much shorter (usually 10 times) than an inductive
storage
> signal.
>
> The spark energy is determined by the product of the voltage times the
> current times the duration, or the area under the spark pulse.
>
> Lean burning engines (which most should be if they're producing maximum
power
> and minimum emissions) need lots of spark energy to keep the mixture
ignited
> under the high turbulence and swirling conditions in the cylinder. High
> energy, inductive storage systems are better at delivering this energy
than
> CDs, usually. Multiple spark systems also have advantages, as they can
> re-light the fire if it goes out, but this is done at the expense of
total
> energy as multiple sparks must now fit into the same spark time as one
long,
> high energy spark.
>
> After studying and benchmarking MANY ignitions, including magnetos, I
> recommend a good, high energy inductive storage ignition. To get high
> energy, you usually have to go breakerless as the ignition current at
idle is
> too high for points to live reliably. Unless you have bad rings and an
> engine that regularly fouls plugs (then you really have other problems),
you
> really don't need the 40KV - 80KV initial spike a CD provides. What's
more
> important is burn time.....go inductive storage.
>
> OK, I'll shut up now.
>
> Myles H. Kitchen
> 1965 Lotus Cortina Mk1 #128
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