Ignition Only

[Shannen Durphey]

Axel Rietschin wrote:
> 
> ----- Original Message -----
> From: "Shannen Durphey" <shannen at grolen.com>
> > > A wasted spark DIS doubles the rpm limit of the ignition system since
> you
> > > have twice the number of coils.
> > This is not correct.  The max RPM for a distributor based system is
> > higher provided sufficient firing voltage can be maintained.
> 
> Sufficient voltage is precisely the main problem overcomed by a DIS setup.
> 
> >  The
> > waste spark of the DIS system will cause problems in engines with
> > exhaust/intake valve opening overlap as rpm increases.  The waste
> > spark can fire the incoming intake charge at high rpm.  There are
> > posts discussing this in the DIY_EFI archives.
> 
> I was not aware of this potential issue and I don't believe it happens in
> practice. 
I don't believe ...

>First, why only at high rpm when you have the most spark advance
> thus the less fresh gases in the cylinder, if any at all? If you use such a
> radical cam and highly tuned exhaust manifold as to fill the cylinder with
> enough fresh gases to be ignited, some 30 or so degrees BTDC, consider
> upgrading to a coil-per-cylinder setup. 


>Also, at that particular moment, a
> significant part of the fuel will probably 
probably....

still be in liquid form thus is
> is very unlikely 

unlikely...

that the super-lean, very-diluted (by burned gases) low
> pressure and low temperature (due to pressure drop and partial fuel
> evaporation) will ignite at all. That said, you never know :)

Ok, honest question.  What is high rpm, how many engines capable of
attaining it do you know of that are running a DIS system?  

If you want some information, search the archives.  I though I'd give
you something useful, not an argument.

Shannen
> 
> > Distributor systems with 2 coils, which can alternate between coils
> > for firing events can significantly increase available spark voltage
> > at high rpm.
> 
> By far not as much as a coil-per-plug setup, which is also "DIS".
 
> 
> --Axel
> 
> ----------------------------------------------------------------------------
> To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
> in the body of a message (not the subject) to majordomo at lists.diy-efi.org
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org