CHT Nirvana (cylinder head temperature) gauge/sender FAQ

Randy in Maine · Posted: Fri Feb 15, 2013 11:54 am Post subject:

What happens temperature wise if you put the spark plug sealing washer back on the the plug (closer to the plug tip)? That is how I do mine.

cardinal0128 · Posted: Fri Feb 15, 2013 11:59 am Post subject:

Looks like that's now on my project list for tomorrow. I believe I cut off the crush washer last time I installed a new set of NGK's.

345 is way too hot for idle on a DD, right? Even if I was running way lean at idle? And timing at idle isn't going to cause that much heat, is it?
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1978 Westy, stock
1967 Beetle (sold)
1993 Ford F-150 v8 5 sp
1965 Jeep CJ-5
2002 Jetta TDI

Randy in Maine · Posted: Fri Feb 15, 2013 12:31 pm Post subject:

It seems a bit warm to me at idle, but I can't remember the exacts anymore for a stock engine.

Put a spark plug washer on first andd see if that changes anything. It might.

I always set the timing to 28º BTDC when it is all in (~3500 RPMs or so) with no vacuum hoses attached. I don't care where it falls at idle but mine was pretty close to 8º BTDC when it was stock.

My Camper Special runs like crap until the heads warm up to 200º and tooling down the road they hang about 380º or so. 20º if I am pulling my trailer. That is its sweet spot and it will stay there pretty much all day.

Is your fan nice and clean? Engine to body seall all good? Is your "muffler shield" on and good?

cardinal0128 · Posted: Fri Feb 15, 2013 12:53 pm Post subject:

Yes, just had a new fan installed and bead blasted. Shield on. Tin tight. New foam seal. But I'll have to double-check everthing, obviously.

Will start with timing and the spark plug. Then mixture I guess if necessary.
_________________
1978 Westy, stock
1967 Beetle (sold)
1993 Ford F-150 v8 5 sp
1965 Jeep CJ-5
2002 Jetta TDI

SGKent · Posted: Fri Feb 15, 2013 1:51 pm Post subject:

We had abnormally high temps. We pulled the engine to replace the cam gear because of a knock and pulled the plugs and sender in the process. The sending ring was already elongating from one use. Looking at the plug, the NGK used has a flat shoulder but the crush washers are thicker in the middle and narrow towards the outside with a profile like () but lying down whereas my () is standing up. I think that because the sender is loose enough around the plug, the crush washer not only grabs it but pushes it out, elongating it, allowing it to leak a little. I cut the crush washer off and uses the sender to seal it to the head. Temps dropped about 50F to 75F. I believe it was seeing gasses escape through the threads. On my T1 I drilled it and mounted the sender permanently into the head near the plugs. On the T4 head I could not find a spot I was comfortable drilling that would yield close to the plug temps.

Also - the heat range of a plug is really about how fast it conducts heat away from the tip of the plug. Plugs that run cooler do so by conducting heat away faster - hence a cooler plug will carry a little more heat to the sender than a hotter plug.

I haven't tired Randy's method or perhaps using a pre-flattened crush washer.
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airkooledchris · Samba Member Joined: January 25, 2005 Posts: 2713

cardinal0128 · Posted: Mon Feb 18, 2013 12:52 pm Post subject:

I checked my timing and it was 28 with out the vac hose connected. Plug was installed sans crush washer. BUT my plug was loose when i went to check it.

Replaced the spark plug with another one with crush washer (kept the crush washer on the plug side of the ring terminal, not the head side). Rats. Darn thing is still running 380-400 on a cool day on the freeway. Idling a bit cooler now at 333. Still seems high to me. How much is an NOS AFM?

I wish there was an easier way to install a 'cheater' switch in the circuit somehow so with freeway driving and on uphills you could richen up the mixture by some pre-set amount.

I have an aftermarket exhaust... think it makes any sense to tap a bung into it and install an aftermarket mixture gauge? LM1s are expensive anyway.
_________________
1978 Westy, stock
1967 Beetle (sold)
1993 Ford F-150 v8 5 sp
1965 Jeep CJ-5
2002 Jetta TDI

58deadhead · Posted: Sun May 04, 2014 1:33 pm Post subject:

I ordered and installed the Dakota Digital CHT after reading this and also having wasted time and money on a VDO.

It is reading 70s and 80s haven't really driven it much past a few miles at 55-60 and my bug generally runs pretty cool. Wasn't sure if it maybe had something to do with the way I wired it in because my bugs wiring harness is next to be replaced and is pretty ratty. I ask because in the directions it says it won't read accurate below 150 degrees but I should at least be that warm after a few miles and some idling right?

Bleyseng · Posted: Sun May 04, 2014 2:48 pm Post subject:

airschooled · Posted: Sun May 04, 2014 3:25 pm Post subject:

58deadhead · Posted: Mon May 05, 2014 6:16 pm Post subject:

airschooled · Posted: Mon May 05, 2014 6:19 pm Post subject:

58deadhead · Posted: Tue May 06, 2014 5:28 am Post subject:

Hahaha that is the worst part of the job!!! Hopefully that is all that is wrong. I really appreciate your input, I will definitely post what happens for others in the same boat.

58deadhead · Posted: Tue May 06, 2014 2:26 pm Post subject:

airschooled · Posted: Tue May 06, 2014 3:25 pm Post subject:

Sure thing! I'd hate for someone to have to go through what my poor bus did. Several full throttle runs got the gauge up to 70*!! So Joe the Thermocoupler didn't pay attention to yours either; if the wire bunching doesn't bother you then run with it.
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58deadhead · Posted: Tue May 06, 2014 4:21 pm Post subject:

I'm gonna leave it. The bad is I am running hot but glad to be aware of it. I have done a number of things to mend it with no luck. Switching back to my 009 distributor tomorrow and getting rid of this Chinese pertronix unit. If this doesn't fix the problem then I can only conclude that I did damage to my heads due to overheating before parking it for the winter or my oil cooler is clogged or faulty. The engine is almost brand new and spitting oil out the front pulley like crazy. I have a breather box and stock pulley on order for that but something is telling me it is due to heat. Lol it is always something, getting mentally prepared to pull the engine and make a new thread..

airschooled · Posted: Tue May 06, 2014 9:44 pm Post subject:

aerosurfer · Posted: Wed May 07, 2014 8:03 am Post subject:

Im piecing together the parts needed for my CHT guage from the 'poor man's Dakota' thread

http://www.thesamba.com/vw/forum/viewtopic.php?t=592584&sid=ae96549144a41ec9cfe24211a3616c6c

The motor is not coming out to do the install so I wont be able to do any head modifications or drilling into. I had to make my own ring terminal using a 1/2" one from the FLAPS, I think bending it and fitting it went pretty well. Im using an old head and sparkplug to mock it up and it seams like it seals up nice. My only question is the junction where I will fit the TC wire is relatively large and therefore farther away from the head and ring, will I likely be losing a bit in heat transfer or in the cooling air?

Image may have been reduced in size. Click image to view fullscreen.

It looks askew in the picture, but is very nicely round and flat, with clearance where it bends up between the sparkplug and head.
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Rebuild your own FI Harness..My Harness

77 Westy 2.0L Rockin and Rolling Resto!

72 Sportsmobile (sold)
79 Tran$porter... Parts car money machine (gone)

aerosurfer · Posted: Wed May 07, 2014 8:08 am Post subject:

wow those are a lot more out of focus than I hoped, but you get the gist
_________________
Rebuild your own FI Harness..My Harness

77 Westy 2.0L Rockin and Rolling Resto!

72 Sportsmobile (sold)
79 Tran$porter... Parts car money machine (gone)

58deadhead · Posted: Wed May 07, 2014 10:07 pm Post subject:

Huh, I had thought about that but didn't really pay a whole lot of mind. I am on to the distributor but I am gonna pull that back out tomorrow. I was having that sealing problem with the vdo sender and gauge. When I got this one I was sure to bend it that direction but still had that annoying catch. I had to or thought I had to use the socket to tighten it down. I have always found it habit to hand tighten plugs whenever possible and couldn't seem to. Even against my better judgment, I locked it down with the socket to flatten any potential bends that might of happened. This truly is a pain in the ass to do, I did it at least three times with the VDO trying to sort it out before ruling it a faulty gauge and buying this one. I'll pull it out in the morning and do my best to keep it flat and not catch to hand tighten. I'll let you know how it goes.


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CHT Nirvana (cylinder head temperature) gauge/sender FAQ
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