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I have a new air-cooled history book and in the chapter about the 1997 993 it states that there were a few engine changes, namely revisions to pistons and cylinders as well as new valve guides.
Does anyone have more details about what these changes were?
I might have to email the author (Brian Long) and see what he’s talking about. He was very good about detailing minor changes across all the years, so he must have had some factory documentation that led him to write this. I just wished he’d given some specifics!
I have a new air-cooled history book and in the chapter about the 1997 993 it states that there were a few engine changes, namely revisions to pistons and cylinders as well as new valve guides.
Does anyone have more details about what these changes were?
for '95(Feb production) piston oil cooling jet for #4 was changed
Rings were changed for '96 and again for '97,
for '96 base valve guide spec was changed to 1st oversize, turbos tail pipes and cats were revised, US cars got OBD2 spec equipment & 1 year only DME
for '97 head studs were changed, heat exchanger hoses changed, rear drive shafts changed, updated DME
What does first oversize mean for the 1996 valve guide change? Was that changed in 1996 for the 1997 model year? If so, maybe that’s what Brian was talking about, since he was referencing model years in the text.
I understand the Motronic software changed after 1996 as
the improved reliability of its communications with OBDC readers;
the ability to report individual readiness code status were added and;
the unit allowed for programming updates via physical chip replacement.
The posting above notes a change in the oxygen sensors, did Porsche go to wideband sensors in 97'?
Andy
all 55 pin OBD1, w/ user replaceable chip. ie All '94-95 and all RoW n/a '96 up
'96 one year only US 88 pin OBD2, twin chip design not flashable
'97-98 US 88 pin OBD2, single chip design, flashable w/ the right equipment, not something a typical owner would be able to do.
All the 55 pin are motronic 2.10.1, all the 88 pin are Motronic 5.2
main difference is that 5.2 adds/changes
separate fuel mixture control for left & right banks
NTC based intake temp sensor
plausibility check & provision for replacement values
NTC engine temp sensor
all 55 pin OBD1, w/ user replaceable chip. ie All '94-95 and all RoW n/a '96 up
'96 one year only US 88 pin OBD2, twin chip design not flashable
'97-98 US 88 pin OBD2, single chip design, flashable w/ the right equipment, not something a typical owner would be able to do.
All the 55 pin are motronic 2.10.1, all the 88 pin are Motronic 5.2, main difference is that 5.2 adds/changes, separate fuel mixture control for left & right banks, NTC based intake temp sensor, plausibility check & provision for replacement values, NTC engine temp sensor
I stand corrected, thanks for clearing this up and providing outstanding detail.
Andy
01-13-2019, 01:30 PM
Engine changed for 1997 model year
