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Multi69s
Samba Member
Joined: January 24, 2006
Posts: 5364
Location: Lefty, CA
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 Posted: Sat Jun 27, 2015 3:02 pm Post subject: School me on installing a CHT sender in a Type 4 engine |
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Since I just lost a valve seat in my 2L Type 4 engine, I will be installing a CHT gauge. However, after reading all of the horror stories about the VDO unit, I will be using an aircraft unit (my brother in law owns a repair facility). Since I have never used one, I have some questions about the installation of the sender. I am using 1700 heads, so would this be the best method of installing the sender?
http://www.germansupply.com/xcart/skin1/images/tech/cht/SenderClip.jpg
If so, what are people using to hold the sender in place? Also, how are you routing the wire out of the stock tin? Lastly, what do you do when it is time to pull the engine? Is there a connection inside of the engine compartment, if so is that the cold junction that everyone is talking about
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saw2
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Joined: November 06, 2008
Posts: 321
Location: nw Oregon
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| Posted: Sat Jun 27, 2015 3:44 pm Post subject: |
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Yes, the thermocouple ring that goes under the spark plug does have ring terminals that connect together the wire that go to the gauge. I didn't connect the ring or cable anyway to the head, just used a Dremel with a small bit to put a small notch in to keep terminal front turning when tightening plug. Have also just used a small screwdriver to hold ring from turning on heads that I haven't put the notch in. Most the gauges have different thermocouple ring sizes available to match spark plug size.
Here is a link for pictures of the plug thermocouple. It is also nice if your cht gauge is temperature compesated, which the VDO gauge is not. Do a search on this link for cht gauges. Lots of info there, aviation parts site. I have had several of the Micro 1000 cht gauges which are temperature compesated and never had any problems with these.
On the engine tin I just drill a close to the spark plug just
big enough to get ring terminals through. Pig tail off thermocouple is about 10" long. Just disconnect there for engine removal.
http://www.aircraftspruce.com/catalog/inpages/chtgrasketprobe.php?clickkey=2394959 |
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jomamma
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Joined: March 11, 2013
Posts: 10
Location: St Louis
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| Posted: Wed Nov 11, 2015 11:27 am Post subject: Re: School me on installing a CHT sender in a Type 4 engine |
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| Does the ring from the sending wire go above or below the spark plug gasket? |
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nextgen
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Joined: August 19, 2004
Posts: 6031
Location: CONGERS, N.Y.
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Steve Arndt
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Joined: August 01, 2005
Posts: 1780
Location: Boise, Idaho
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| Posted: Wed Nov 11, 2015 12:07 pm Post subject: Re: School me on installing a CHT sender in a Type 4 engine |
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| jomamma wrote: |
| Does the ring from the sending wire go above or below the spark plug gasket? |
Some people remove the crush washer and use just the ring.
I like to remove the washer from my plug, put the ring on (make sure it spins easily, but not too loose), then re-install the crush washer.
Some people dremel a groove in the head so that the crimp and wires lay in the groove instead of bending and breaking. It keeps it from rotating on ya as well. |
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jomamma
Samba Member
Joined: March 11, 2013
Posts: 10
Location: St Louis
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| Posted: Wed Nov 11, 2015 12:40 pm Post subject: Re: School me on installing a CHT sender in a Type 4 engine |
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| Can you just install it to the tempII sensor? |
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arizonabuckeye
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Joined: November 10, 2013
Posts: 544
Location: SLC
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Steve Arndt
Samba Member
Joined: August 01, 2005
Posts: 1780
Location: Boise, Idaho
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| Posted: Wed Nov 11, 2015 1:39 pm Post subject: Re: School me on installing a CHT sender in a Type 4 engine |
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To get valid temperature readings for tuning or warning, it needs to be under the plug.
The thermistors mounted further away show warm up trends for the EFI, not for a warning or operating temperature. |
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arizonabuckeye
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Joined: November 10, 2013
Posts: 544
Location: SLC
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| Posted: Wed Nov 11, 2015 1:46 pm Post subject: Re: School me on installing a CHT sender in a Type 4 engine |
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| Steve Arndt wrote: |
To get valid temperature readings for tuning or warning, it needs to be under the plug.
The thermistors mounted further away show warm up trends for the EFI, not for a warning or operating temperature. |
You could still use the $10 thermocouple I recomended and just braze/weld it to a spark plug wire instead of the $140 option. Or epoxy the lead right next to the spark plug - they are small enough you could probably snug it right up there without issue. |
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nextgen
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Joined: August 19, 2004
Posts: 6031
Location: CONGERS, N.Y.
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