[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

SVO: Re: old missives -- new meaning



> >>what i gleened from this is that the pip does 2 things:
> >>1) it lets the eec know how fast the engine is turning (frequency
alone)

True.

> >>2) it gives a base signal to be sent back to the tfi after being
delayed 
> >>   a bit.  this delay or phase change (realitive to the pip) is what
lets
> >>   the eec control timing, but indirectly, the tfi is doing _most_ of
the 
> >>   work.

Not true.

The PIP MODULE amplifes and waveshapes a signal from a hall effect sensor
in the distributor.  It sends this on to the the TFI which sends it to the
EEC.  When no signal is present from the EEC,  ie... starting, the TFI
sends it to the ignition coil.  When a signal DOES come back from the EEC, 
the TFI sends IT to the coil.  Incidentally, this signal is called SPOUT
and it's coming out of the EEC.  When you pull the plug in your distributor
wiring to set the timing, you are running on the PIP signal thru the TFI,
with no EEC correction. The signal from the EEC is the *previously*
received PIP signal, time-shifted to allow the EEC to have a signal to fire
the current cylinder on.  If you followed the flow path, it wouldn't have
received the current cylinder's PIP yet, so it's using the last one. IOW,
how can it delay an event to happen at 30 BTDC, when it doesn't get the
signal it's using until 10 Btdc, which is a later occurence?

So, the TFI ain't doin much...

TFI's are all the same, barring some physical mounting differences between
carlines.  EDIS, I dunno.

USE MOTORCRAFT TFIs ONLY!!!!  I have wasted lots of time chasing problems
that a redbox TFI cured.  Also, make sure the connections to the TFI are
sanitary.  For a good deal on TFIs, see my sig block, TurboTekToys, $49
delivered.

> >>
> 
> The return signal from the EEC to the EDIS is unrelated to the PIP.

Not true, it's the last PIP signal.

> It purely indicates to the EDIS unit the amount of spark advance
required. 

True.

The EECs are very different.  There's little chance you can transplant them
across disimilar engine combos.  Injector drivers, are different for some
of the different engine families, etc.  Somewhere mid to later 80s, a lot
of the boxes doubled their processor clock speed, and the size of the
EEPROM code.  I  assume this because the 4 cyl turbo calibrations did this
in 87.

CU
Dave
Home Page:  http://www.SmartWorx.com/Dcompton
Subscriptions to SVO and TC Listservers: 
http://www.SmartWorx.com/Listserver
Turbo Tek Toys  http://www.SmartWorx.com/TurboTekToys