Help - Search - Members - Calendar
Full Version: Head Temp
914World.com > The 914 Forums > The Paddock
hedfurst
Rebuilding a track-car I haven't used for 10 years, it has 2 VDO head temp gauges and was set up for #s 1 and 3. I'd like to be able to watch all four.
Has anybody ever set any thing up for this before? I'd like a switch to change from 1 & 3 to 2 & 4?
brant
QUOTE(hedfurst @ Feb 23 2018, 08:25 AM) *

Rebuilding a track-car I haven't used for 10 years, it has 2 VDO head temp gauges and was set up for #s 1 and 3. I'd like to be able to watch all four.
Has anybody ever set any thing up for this before? I'd like a switch to change from 1 & 3 to 2 & 4?



a lot of people have done it
check the air craft suppliers for the gauges like that
spruce is one...


but you probably would be better off monitoring EGT on each cylinder than 4x- headtemps.....


the EGT is going to be more money but more useful
I think a single CHT on #3 is adequate if you know your mixture and your EGT

brant
hedfurst
QUOTE(brant @ Feb 23 2018, 07:52 AM) *

QUOTE(hedfurst @ Feb 23 2018, 08:25 AM) *

Rebuilding a track-car I haven't used for 10 years, it has 2 VDO head temp gauges and was set up for #s 1 and 3. I'd like to be able to watch all four.
Has anybody ever set any thing up for this before? I'd like a switch to change from 1 & 3 to 2 & 4?



a lot of people have done it
check the air craft suppliers for the gauges like that
spruce is one...


but you probably would be better off monitoring EGT on each cylinder than 4x- headtemps.....


the EGT is going to be more money but more useful
I think a single CHT on #3 is adequate if you know your mixture and your EGT

brant


Hey, appreciate it but what I was wondering was if there was a way to rig up a switch for an extra two sending units to use the gauges I have!
brant
QUOTE(hedfurst @ Feb 23 2018, 09:39 AM) *

QUOTE(brant @ Feb 23 2018, 07:52 AM) *

QUOTE(hedfurst @ Feb 23 2018, 08:25 AM) *

Rebuilding a track-car I haven't used for 10 years, it has 2 VDO head temp gauges and was set up for #s 1 and 3. I'd like to be able to watch all four.
Has anybody ever set any thing up for this before? I'd like a switch to change from 1 & 3 to 2 & 4?



a lot of people have done it
check the air craft suppliers for the gauges like that
spruce is one...


but you probably would be better off monitoring EGT on each cylinder than 4x- headtemps.....


the EGT is going to be more money but more useful
I think a single CHT on #3 is adequate if you know your mixture and your EGT

brant


Hey, appreciate it but what I was wondering was if there was a way to rig up a switch for an extra two sending units to use the gauges I have!



probably....


but why..
again CHT on #3 is going to tell you the whole story
and you can't use CHT to judge mixture

EGT will not only tell you mixture
but will give you real time info about what is going to happen to head temps before there is a problem
much better info
info available to prevent a problem
plus perfect mixture and max performance

not sure there is a benefit what so ever to adding 4 CHT readings.

I don't even run CHT on my race car at all
I use innovate wide band O2 for mixture
but in order to cut weight no CHT what so ever
jd74914
QUOTE(hedfurst @ Feb 23 2018, 11:39 AM) *

Hey, appreciate it but what I was wondering was if there was a way to rig up a switch for an extra two sending units to use the gauges I have!

Just buy a thermocouple selector switch. smile.gif

Cheap surplus one with 4 channels:
https://obtainsurplus.com/electrical/compon...917024jj17store
jd74914
The less costly and more space saving way is to buy any double-pole, double-throw (DPDT) switch and wire each side of the TC to it's respective pole.

CAVEAT: IF YOU GO THIS WAY YOU NEED THE SWITCH TO BE NEAR THE GAUGE.

The reason is that by using a generic switch (without special Nickel-Chromium amd Nickel-Alumel wires, assuming you're using Type K), you introduce cold junction error which puts a bias on your measurement. As long as the switch and your gauge are at the same temperature you're good to go because the compensation is the same. smile.gif

See the picture for a wiring example. For some reason you need to click on it, it's not displaying all of the test otherwise.
hedfurst
Thanks to you all! Appreciate your expertise.
Obviously some things to think about.
This is a "lo-fi" version of our main content. To view the full version with more information, formatting and images, please click here.
Invision Power Board © 2001-2019 Invision Power Services, Inc.