VSS

[Guenther,Max]

What do you do if you dont have one?  Can you put one in a turbo 400?

>----------
>From: 	rauscher at icst.com[SMTP:rauscher at icst.com]
>Reply To: 	diy_efi at efi332.eng.ohio-state.edu
>Sent: 	Wednesday, January 27, 1999 9:00 AM
>To: 	DIY_EFI at efi332.eng.ohio-state.edu
>Subject: 	Re: VSS
>
>
>
>Mike Pilkenton wrote:
>
>>Could someone tell me what functions the VSS signal might affect in the 92
>>3.1L V6 Camaro ECM.  The motor/ECM came off a manual tranny car and my
>>project car application won't have this signal available unless I install an
>>aftermarket speed sensor.  Do I need this signal?
>>
>>Mike
>>V6 Opel GT
>
>
>Mike, there is a ton of information in the archives, to go the DIY EFI home
>page and follow the links. Personally, I believe that the VSS is important,
>there is also info on what the signal looks like and some ideas and also
>off the shelf solutions to this.
>
>http://efi332.eng.ohio-state.edu/diy_efi
>
>I got the following from there:
>
>the following text is from:
>http://www.jagsthatrun.com/Pages/SpeedSensors_Speedometer.html
>
>-------- quoted text from webpage ------------
>
>Without a VSS, the Chevrolet Fuel Injected engines will not run correctly,
>and they will not pass a smog test.
>
>Basically, the VSS tells the ECM how fast the vehicle is going. Most
>people think the VSS is only used for the lock-up torque converter. The
>VSS is also used to control the EGR valve, the charcoal canister purge
>valve, the electric cooling fans, idle speed, and air/fuel ratio. This is
>all explained in the Chevrolet shop manuals. 
>
>It must be emphasized that the VSS is used to control the idle speed when
>the vehicle is moving. Without the VSS, a vehicle may have stalling
>problems under certain conditions.  Needless to say, this is dangerous. 
>Raising the minimum idle speed with the adjusting screw can eliminate
>stalling, but the engine will still not run optimally without a VSS. 
>
>A lot of people think that running "closed loop" is best for fuel mileage. 
>Closed loop simply means that the oxygen sensor is being used to monitor
>the fuel/air ratio. Some of the Chevrolet fuel-injected engines are
>programmed to run lean under certain conditions (called "highway mode") to
>improve fuel mileage during steady cruise conditions. Without a VSS, the
>engine computer (ECM) will not get the correct signals to run the engine
>for best fuel mileage. There are a lot of programs in the ECM that depend
>on the VSS. For best operation, the VSS needs to be connected and
>functioning.
>
>-------- end quoted text from webpage ------------
>
>Here is a list of things affected by the VSS sensor.  This list covers
>three different engines, two of them 4 cylinder TBIs.  All three
>applications are from the same era as the 1226867 2.0 TBI.
>
>Code 24
>TCC lockup (auto)
>Upshift light (manual)
>IAC position learning (above 30 MPH)
>Cooling fan control (not used in these applications)
>Determine if manual transmission is in gear (compare VSS vs RPM)
>Disable some idle speed control if manual in gear (see previous item)
>Disable idle learn if moving
>Enable idle learn if moving with manual in neutral
>Prevent DecelFuelCutOff if manual in neutral
>Prevent DecelFuelCutOff at very slow speeds
>Top speed limiter (not used in these applications)
>
>The third application adds one more item:
>
>Amount to open IAC and rate at which to close it upon throttle closing
>
>Note - the idle speed control logic is a rats nest of complicated code. 
>It is hard to figure what really happens.
>
>--
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