Timing belt ?

[SJ]

> From: Kent McLean <kentmclean at mindspring.com>
> Subject: Re: Timing belt ?
>
> Huw Powell wrote:
>  > You could run the dizzy off the crankshaft, but then there'd be a
>  > wasted spark at TDC on the exhaust stroke.  And coil charging time
>  > would be halved...
>
> Some cars (the Miata comes to mind) have a wasted-spark by design.
> I think 1 coil powers 2 spark plugs, so one spark gets wasted each
> (every other?) cycle.

**** Yup, thats correct - no dizzy anymore. Each coil pack feeds 2 spark
plugs. Many newer cars (maybe all?) use this design.
No moving parts.
No dizzy with the gearing that goes along with it.
I guess they use crank positioning sensors(hall effect) to tell the computer
when to fire the coil packs.
With 4 coil packs on an 8 cylinder, if one fails the engine still runs.
Even with plugs firing twice as often as required, each coil gets more than
enough saturation time as its only handling 2 plugs instead of 8. So that
you dont need as big a coil.
Overall, a "simpler" design mechanically. The computer does all the "moving
parts" stuff. Since the car already has a computer, its not that complicated
to design a newer chip to handle this additional task.
I wouldnt be surprised if most of the car manufacturers use the same damn
chip. The chip does everything you can think of. Each model car uses what it
needs, the other chip functions are simply not used. This idea makes a lot
of sense from an inventory and qty price break point of view - less parts to
stock and a better price because of larger order quantity.
Anyhoooo, the end result is a more reliable system, and reduced costs in
manufacturing.

SJ
85 Dodge PU, D-250, 318, auto
85 Audi 4k - - sold but still on the road
88 Audi 5kq
90 Audi 100q



-- 
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.405 / Virus Database: 268.11.3/423 - Release Date: 8/18/2006