RE: [DMCForum] freq valve question

["Dave Stragand" <dave.stragand@xxxxxxxxxxxxxxx>]

I concur.  But isn't it too lean when it's off, not too rich?

I have three emissions machines so when Mike comes up, maybe we can find
the answer.

-Dave

-----Original Message-----
From: Walter Coe [mailto:Whalt@xxxxxxx] 
Sent: Thursday, May 29, 2003 1:45 PM
To: DMCForum
Subject: Re: [DMCForum] freq valve question


> should the frequency valve buzz non-stop when the engine is running?

That's a damn good question, and I'm still not sure of the answer.  Mine
would run all the time which made me wonder why they even had a Lambda
relay
which could shut it off.  That could be done switched straight off the
ignition.

The first time I heard one cycling on/off was on Jim Reeve's car at the
Memphis show.  I have since seen many DeLoreans that do this.  When the
frequency valve "cycles" it is due to the Lambda ECU switching it off
and
not due to an intermittent electrical connection.  Now that I bought a
dwell
meter and have used it on a few cars, I have come up with the following
theory:

DeLoreans are set up such that if the frequency valve is switched off or
non-functional then the engine runs lean.  The Lambda system monitors
the
exhaust to determine the optimum duty cycle for the frequency valve so
that
the engine isn't either too rich or too lean.  The effect of a high duty
cycle is to make the fuel mixture richer; and inversely, the effect of a
low
duty cycle is to make the fuel mixture leaner.  If the Lambda ECU
determines
that the engine is running so rich that the frequency valve can't do
enough
to lean it properly, then it will just shut the valve off completely.
The
logic behind this is that if a low duty cycle won't lean out the fuel
mixture then as a last ditch effort the Lambda ECU will try using no
duty
cycle at all which is technically an infinitely low duty cycle.  Hence
the
frequency valve cycles off.

On a properly running engine, the frequency valve should never have to
cycle
off.  If it does cycle off then the engine is set to run too rich.  To
make
matters more complicated, if you have a vacuum leak then it could be
compensated for by mis-adjusting the air/fuel mixture.  Now you have two
problems that cancel each other out -- vacuum leaks and a dorked with
fuel
adjustment.

This is just a theory guys.  Do any of you concur?  Am I full of shit?
Well, we already know the answer to that last question. ;-)  I'm an
expert
bullshitter.  I keep a turd in each pocket.

Walt



[Non-text portions of this message have been removed]



Yahoo! Groups Sponsor	 

ADVERTISEMENT
 
<http://rd.yahoo.com/M=244522.3313099.4604523.1512248/D=egroupweb/S=170512
6215:HM/A=1595053/R=0/*http://ashnin.com/clk/muryutaitakenattogyo?YH=33130
99&yhad=1595053> Click Here!	
 
<http://us.adserver.yahoo.com/l?M=244522.3313099.4604523.1512248/D=egroupm
ail/S=:HM/A=1595053/rand=662530582> 	

To unsubscribe from this group, send an email to:
DMCForum-unsubscribe@xxxxxxxxxxxxxxx



Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service
<http://docs.yahoo.com/info/terms/> .

<<attachment: winmail.dat>>