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Thu Feb 04, 2010 1:52 pm

Patrick199 wrote: I'll take a properly seated spark plug over an untrustworthy gauge any day.

the sender ring is very similar to the seal ring on the plug, in thickness and in hardness and a properly installed CHT sender ring will have zero negative impact on how the spark plug seals. the issue with the ring sender are wholly brought on by poor or lazy installation methods or techniques. we have vehicles into our shop where someone has simply jammed the sender over the plug and installed the plug. the wires are sticking through the plug hole with no protection or finesse. of course this will cause problems. it isn't the fault of the gauge or sender, it's the installer.

VDO CHT gauges are not perfect, but for 100.00 how can you expect them to be? there are plenty of better gauges available, some cost a lot more, some are in the same ballpark. for my uses the VDO units work well enough and tell me what i need to know, this is true for many others. some have installed aircraft 4-gang gauges to monitor all 4 cylinders. some have holes drilled in every available square inch of dash space with gauges everywhere. some have no gauges. in the end it's up to the user what they do and and how well they do it.

Thu Feb 04, 2010 2:29 pm

I use a VDO and #3 ring.....no problems IMO.
I understand the t-couple is based on 70-degree ambient. I notice when driving in 30-deg F temps at 60-mph my gauge reads high ~ 400 but on a 70-degree day at 60-mph reads ~ 375 and on a 95-deg day at 60-mph it reads ~ 350. Big or long hills make about a 30-deg increase. Silly it's designed to read low on a "hot" day.

For what it's worth the VDO gives me peace of mind and a possible warning of overheating. It's there to give some "trending" really.

Thu Feb 04, 2010 4:17 pm

rjonas wrote: I use a VDO and #3 ring.....no problems IMO.
I understand the t-couple is based on 70-degree ambient. I notice when driving in 30-deg F temps at 60-mph my gauge reads high ~ 400 but on a 70-degree day at 60-mph reads ~ 375 and on a 95-deg day at 60-mph it reads ~ 350. Big or long hills make about a 30-deg increase. Silly it's designed to read low on a "hot" day.

For what it's worth the VDO gives me peace of mind and a possible warning of overheating. It's there to give some "trending" really.

Hmm, I never read this in the DD manual though I'd heard talk of it in other posts. When I get in the bus in the morning it seems to read pretty darn accurately as to the outside temp then obviously ramps up quickly when I start 'er up.

This morning when I got to work the meter read 360 degrees and when I shot the infrared meter into the spark plug hole it was 305 and dropping about a degree a second. So, inconclusive. My concern about the "boiling water" test is that wouldn't test if I had any issues with how I mounted it. @#$% - pissed off as I did a *very good* job of securing the wires to the bus. Maybe I'll pull out the camp stove, get the water boiling and then quickly move the pot into the engine compartment to measure it... It's always somethin'!

Thu Feb 04, 2010 5:39 pm

Quote: rjonas wrote:
I use a VDO and #3 ring.....no problems IMO.
I understand the t-couple is based on 70-degree ambient. I notice when driving in 30-deg F temps at 60-mph my gauge reads high ~ 400 but on a 70-degree day at 60-mph reads ~ 375 and on a 95-deg day at 60-mph it reads ~ 350. Big or long hills make about a 30-deg increase. Silly it's designed to read low on a "hot" day.

For what it's worth the VDO gives me peace of mind and a possible warning of overheating. It's there to give some "trending" really.

Hmm, I never read this in the DD manual though I'd heard talk of it in other posts. When I get in the bus in the morning it seems to read pretty darn accurately as to the outside temp then obviously ramps up quickly when I start 'er up.

The DD does not have this problem as I understand it. And mine also seems to get the outside temp spot on according to the weather forecast. From 26 deg F in winter all through the summer. DD is ugly, but it's the best (next to that 4-gang Scott was mentioning; FYI, the stratomaster I believe).

Thu Feb 04, 2010 7:52 pm

Traveling Writer wrote: The DD does not have this problem as I understand it. And mine also seems to get the outside temp spot on according to the weather forecast. From 26 deg F in winter all through the summer. DD is ugly, but it's the best (next to that 4-gang Scott was mentioning; FYI, the stratomaster I believe).

When I drove home tonight I kept the engine running while testing. The gauge read about 330 while doing this - I pulled the plug and shot the tester down the hole it consistently read about 50 degrees higher then the meter showed. I would put the plug back on, let the meter move up again, pull the plug, shoot it, get the temp and repeat.

I'm guessing my next step is to pull the plug/ring and validate the ring is still ok. I'll then do the boiling water test...

Sat Feb 06, 2010 8:57 pm

I sometimes wish my Dakota Digital was wrong,...420 up hills in the heat of summer without h20 injection, 360 injected. In the winter time without injection, 365 up the same hills. I'm certain it's close but on the other hand, it takes away from the enjoyment of driving my bus.

Sat Mar 20, 2010 12:33 pm

I adjusted the brakes today and took my camper out for a drive.

Outside air temps today were around 45 F. My highest running head temps at 65 mph were 340 F.

I borrowed an IR thermometer from a buddy and used it to check the head temps against the DD CHT gage under #3 plug.

I turned the engine off and left the switch in the on position. The gage read 296 F and cooling slowly.

I removed the spark plug boot and pointed the laser several places close to the plug. With the gage reading 294 F, the hottest reading on the head was 236 F.

I'm not sure what this means, but I'll play around with it to see what else I can learn.

Sat Mar 20, 2010 12:42 pm

I removed the plug and read the ring sender at 143 F. The gage read 143 F

Sat Mar 20, 2010 1:26 pm

I got a digital food thermometer and checked it at boiling water, human body and freezing water temps. It checked out accurate to within a few degrees in all three cases. So I installed in the outer fins of #4 as it's easy to get at and I wanted to measure trends more than just raw temp data.

What I get consistantly is 340-350 degrees running 60 mph on mildly rolling hill terrain with 60 degree ambiant temp. On a very steep 1 mile hill climb it gets to about 380 degrees. Stop and go around town is ~300 degrees.

1600 DP. "71 Westy.

I also have a VDO oil temp gauge with the sensor mounted in the oil drain plug location. Takes 15 minutes to get to about 180 degrees at 60 mph, and at the top of that nasty hill it's about 200 degrees.