[Gmecm] Re: VSS help needed

[DOZIERHC at aol.com]

Decel fuel cutoff and also enleanment typically would NOT use a VSS  input.

Think about it this way.  

You have a manual trans (or  automatic with aggressive lockup) and put it in 
a high gear, and decel  from that with the clutch engaged.
When you get close to idle, you dump the  clutch (or torque converter clutch 
is uncoupled).
If the decel cutoff worked  off VSS, this would cause a stall due to the low 
speed engine unloading while  the engine was being motored (dry-fired), as 
there is insufficient time to  execute a rewet of the manifold/cylinders to get 
combustion restarted with  efficiency (combustion chambers dry and cold).

So instead, decel fuel  cutoff works as a function of (ECT, RPM, TPS, and 
MAP/MAF).  Additionally,  catalyst heating and O2 heating can also be included 
for optimizing of the  algorithm if necessary.

H. Dozier


Date: Wed, 6 Jun 2007 13:20:39 -0500 From: "James Panter" 
<_9jim30 at charter.net_ (mailto:9jim30 at charter.net) >
 Subject: Re: [Gmecm] VSS help needed
 To: <_gmecm at diy-efi.org_ (mailto:gmecm at diy-efi.org) >
 Message-ID: <000b01c7a867$63ee2dc0$6401a8c0 at COMPY>
 Content-Type: text/plain; format=flowed; charset="iso-8859-1";
     reply-type=original
 
 Only other way for decel enleanment is the TPS I guess!  I'm currently 
 working with a 7749 and have the VSS hooked up but don't really know if the 
 VSS is responsible for enleanment.
 I am also working with a FAST ECM and it requires no VSS signal for it to 
 function properly.  Must mean it uses the TPS for the ECM to know what's 
 happening.       Jim----- Original Message ----- 
 From: "Cowen" <_captain_krill at yahoo.com_ (mailto:captain_krill at yahoo.com) >
 To: <_gmecm at diy-efi.org_ (mailto:gmecm at diy-efi.org) >
 Sent: Wednesday, June 06, 2007 12:44 PM
 Subject: RE: [Gmecm] VSS help needed
 
 
 > Just a comment...
 > I don't know for sure if VSS is required for decel fuel enleanment, as I 
 > was surprised to find a VSS is NOT required for decel fuel cutoff with a 
 > '7730.
 >



 



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