CHT II, replacement question Options

[jim_hoyland]

Does part # 311-906-041-A work on both 1.8 and 2.0 motors ? Seems like there were separate CHT II sensors for each, but PP shows one for all years

[pilothyer]

Jim, Ideally you would replace the CHT with the one specified for the year and engine size for D-Jet or L-jet. Now days it seems as thought the one you mentioned, and Bosch 280130012 are the ones available for all years and engines D-Jet or L-jet with the exception of the 73 2.0 D-jet. That one just seems to be left out.
The main thing I suppose is that the CHT should measure high OHMS (2 to 3 KOHMS) when cold and very low when warmed up (less than 1KOHM) and most older CHT sensors could benefit by replacement if the tolerance has changed with age. For the 73 you would probably have to make your own using a variable thermistor.

[jim_hoyland]

Thanks for that; that' sweat I am curios about. I did find a link to AutohausAZ for a Google price....

http://www.autohausaz.com/pn/0280130012

[pilothyer]

http://www.rmeuropean.com/Part-Number/Head...S_94E6B777.aspx

[jim_hoyland]

http://www.rmeuropean.com/Part-Number/Head...S_94E6B777.aspx

Good link, I see they have the good ignition switches too.. Got a question : What is the trick to removing the old CHT II ? It'so a tight fit......

[BeatNavy]

Deepwell 13mm socket. Coil the lead up inside the socket. People have also used a 3-inch extension and ground off a corner so the lead can fit through that (if it won't fit coiled up inside the deepwell).

[jim_hoyland]

Deepwell 13mm socket. Coil the lead up inside the socket. People have also used a 3-inch extension and ground off a corner so the lead can fit through that (if it won't fit coiled up inside the deepwell).

Thanks ! Am I correct that it's kind of a blind spot I am tring to reach... (IMG:style_emoticons/default/sad.gif)

[Olympic 914]

Jim, Ideally you would replace the CHT with the one specified for the year and engine size for D-Jet or L-jet. Now days it seems as thought the one you mentioned, and Bosch 280130012 are the ones available for all years and engines D-Jet or L-jet with the exception of the 73 2.0 D-jet. That one just seems to be left out.
The main thing I suppose is that the CHT should measure high OHMS (2 to 3 KOHMS) when cold and very low when warmed up (less than 1KOHM) and most older CHT sensors could benefit by replacement if the tolerance has changed with age. For the 73 you would probably have to make your own using a variable thermistor.

Why would the 73 2.0 be different?

didn't the 74 -76 2.0 also run the d-jet?

[mepstein]

Deepwell 13mm socket. Coil the lead up inside the socket. People have also used a 3-inch extension and ground off a corner so the lead can fit through that (if it won't fit coiled up inside the deepwell).

Thanks ! Am I correct that it's kind of a blind spot I am tring to reach... (IMG:style_emoticons/default/sad.gif)

beatnavy is right. a $5 deep well socket from the home store. wire will fit inside the socket. Nothing fancy. It's easy but i think i needed to remove a bit of the FI to get to the spot. a small flashlight will let you see the hole. start it in by hand. I don't believe it needs to be tight, just snug.

[Bleyseng]

Jim, Ideally you would replace the CHT with the one specified for the year and engine size for D-Jet or L-jet. Now days it seems as thought the one you mentioned, and Bosch 280130012 are the ones available for all years and engines D-Jet or L-jet with the exception of the 73 2.0 D-jet. That one just seems to be left out.
The main thing I suppose is that the CHT should measure high OHMS (2 to 3 KOHMS) when cold and very low when warmed up (less than 1KOHM) and most older CHT sensors could benefit by replacement if the tolerance has changed with age. For the 73 you would probably have to make your own using a variable thermistor.

Why would the 73 2.0 be different?

didn't the 74 -76 2.0 also run the d-jet?

With the 2.0L six killed Porsche rushed the development of the 2.0L four. VW engineering was saying the type 4 was stuck at 1.8L due to the cam to crank clearance. Porsche offset ground the crank for the 71mm stroke, developed the 3 bolt heads etc to get the 100hp 2.0L 914. But Bosch didn't have time to develop the ECU so the 73 uses a 1.7L ECU, special MPS and one year CHT to work. All this development was done in less than a year but for Porsche with their racing background engineering not too hard a feat.

[jim_hoyland]

Interesting

[Olympic 914]

Jim, Ideally you would replace the CHT with the one specified for the year and engine size for D-Jet or L-jet. Now days it seems as thought the one you mentioned, and Bosch 280130012 are the ones available for all years and engines D-Jet or L-jet with the exception of the 73 2.0 D-jet. That one just seems to be left out.
The main thing I suppose is that the CHT should measure high OHMS (2 to 3 KOHMS) when cold and very low when warmed up (less than 1KOHM) and most older CHT sensors could benefit by replacement if the tolerance has changed with age. For the 73 you would probably have to make your own using a variable thermistor.

Why would the 73 2.0 be different?

didn't the 74 -76 2.0 also run the d-jet?

With the 2.0L six killed Porsche rushed the development of the 2.0L four. VW engineering was saying the type 4 was stuck at 1.8L due to the cam to crank clearance. Porsche offset ground the crank for the 71mm stroke, developed the 3 bolt heads etc to get the 100hp 2.0L 914. But Bosch didn't have time to develop the ECU so the 73 uses a 1.7L ECU, special MPS and one year CHT to work. All this development was done in less than a year but for Porsche with their racing background engineering not too hard a feat.

Interesting to me also.... Although my car is far from running the engine is built.

I have a '73 that was running the stock D-jet setup. and I took it to 2056. adding a Raby 9590 cam and new heads worked by HAM.

My plan was to run the original ECU... I don't know what the special MPS is, but hope my 049 MPS can be modded to work. either by using the Tangerine kit or adding some type of ballast resistor if necessary. maybe both.
Right now I have the 1.7 CHT installed.

I didn't think that this was a total Frankenstein setup. but the more I am reading it gets me to thinking there may be more problems with this than I anticipated...

If any of you have put together a similar setup to mine I would really appreciate hearing what you did, any problems encountered and how you solved them

BTW I have looked at P.B. Anders site quite a bit and thought that tuning the MPS would be the biggest headache. but not undoable.

(IMG:style_emoticons/default/confused24.gif)

[Olympic 914]

Bleyseng

I see in your sig you are running a 2.1 with a Raby 9550 cam.

I may be trying to pick your brain when the time comes to finally start this thing up...

[BeatNavy]

I have a '73 that was running the stock D-jet setup. and I took it to 2056. adding a Raby 9590 cam and new heads worked by HAM.

My plan was to run the original ECU... I don't know what the special MPS is, but hope my 049 MPS can be modded to work. either by using the Tangerine kit or adding some type of ballast resistor if necessary. maybe both.

You may have some minor issues with that 049. That's stock for the 1.7. I'm about to install a 2056, and the PO of the engine said he ran it fine with the 049. We'll see. I ended up buying a busted 043 that I'm going to fix.

Anyway, if you get a chance, read this thread: ECU/MPS Compatibility