Would like any info on parts and experience with DD CHT

[cheesehead]

I am pretty sure I want to replace my non working VDO CHT with the dakota digital CHT but would like to ask of folks experience here.
Where and what parts did you order? I know to get the longer wire right? Who did you order from? Was it a kit or did you order from the dakota digital webpage? Inquiring minds want to know.
Thanks,
Meg

[poptop tom]

I ordered direct from Dakota Digital. http://www.dakotadigital.com

This is what I purchased:
http://www.dakotadigital.com/index.cfm/ ... prd347.htm
http://www.dakotadigital.com/index.cfm/ ... prd115.htm SEN-11-8 which is the 14 mm, 18'.

I installed at #3 cylinder. My engine was in rebuild process and heads were apart, so we notched a space in the head for the terminal ring to sit down flush between the spark plug and cylinder head surface.

It works really well, and I am glad I have it installed!

[cheesehead]

Thanks that is good info. I do have the CHT terminal on the spark plug as well so that is the way I will continue for now.

[BumbleBus]

Also ordered mine direct from Dakota Digital. Easy peasy. Have it installed under #3, but am not convinced it crushed/seated all that well because I've seen some insanely high readings this summer. Plug is seated as tight as I'm willing to make it for fear of stripping, but I might be getting a little exhaust blow by. Who knows. I topped out at 470-480 on a 90+ degree day climbing up a mountain and nearly panicked, but my oil temps never got over 220ish (taco plate install in the airstream a bit so may have read low also) so I kept going without issue. Bus seemed happy at the time so I listened to it. It routinely reads over 400 at 55-60mph on the highway. Hmm. Now I'm more into trending than moment to moment readings though. Some day soon I'd like to notch and seat the sender permanently on the head instead of under the plug. I do enjoy having a couple gauges to follow, but am training myself to take them all with a grain of salt.

[drober23]

Concurring with the rest. Direct from Dakota Digital, and get the 18' sender with the ring for 14mm spark plugs.

One thing to note. The VDO gauge is not cold junction compensated. This means that it typically will UNDER report CHT if the ambient temperature in your engine compartment is greater than 70 °F and OVER report CHT if the ambient temp is under 70 °F.

Geek alert! Stolen from Wikipedia:

Thermocouples measure the temperature difference between two points, not absolute temperature. To measure a single temperature one of the junctions—normally the cold junction—is maintained at a known reference temperature, and the other junction is at the temperature to be sensed. [7]
Having a junction of known temperature, while useful for laboratory calibration, is not convenient for most measurement and control applications. Instead, they incorporate an artificial cold junction using a thermally sensitive device such as a thermistor or diode to measure the temperature of the input connections at the instrument, with special care being taken to minimize any temperature gradient between terminals. Hence, the voltage from a known cold junction can be simulated, and the appropriate correction applied. This is known as cold junction compensation. Some integrated circuits are designed for cold junction temperature compensation for specific thermocouple types

The VDO sensor is a Type K thermocouple, but it transfers to copper wire just 1 foot from the sensor ring (still in your engine compartment). The gauge does not compensate for the cold junction temperature, and instead assumes the ambient temperature (at the junction in your engine compartment) should be around 70 °F.

The Dakota Digital gauge is cold junction compensated by running thermocouple wire all the way to the gauge, then sensing the temperature there. A small correction is applied to make the gauge read correctly. It should read correctly regardless of the ambient temperature in the engine compartment.

Bumble, 490??? Wow. Have you inspected your spark plug threads for signs of the blowby?

[56ovalbug]

I don't get it. Why would you want to 'compare' the cylinder head temperature with the temperature of the air under you dash? Wouldn't in be better to compare it to the temperature of the air that is cooling the cylinder head?

[BumbleBus]

Bumble, 490??? Wow. Have you inspected your spark plug threads for signs of the blowby?

I know right? I mean that was a burst temp, but still I've been over 450 a lot this summer it seems [well.. a lot being I've driven over 300 miles this summer, but that's a lot for Bumble haha]. Just had my plugs out the other day and while they were fairly black [too rich right?] there was no signs of blowby on #3. I'm starting to suspect that my timing may be off quite a bit, but thankfully my new aluminum timing scale arrives today so I'll see what's what.

[Amskeptic]

Bumble, 490??? Wow. Have you inspected your spark plug threads for signs of the blowby?

I know right? I mean that was a burst temp, but still I've been over 450 a lot this summer it seems [well.. a lot being I've driven over 300 miles this summer, but that's a lot for Bumble haha]. Just had my plugs out the other day and while they were fairly black [too rich right?] there was no signs of blowby on #3. I'm starting to suspect that my timing may be off quite a bit, but thankfully my new aluminum timing scale arrives today so I'll see what's what.

You will not have black plugs with 450*+ Dakota Digital readings. That is a fact. Do you have black plugs because you have been driving around town for the past 1,000 miles?
You *need* an Itinerant Air-Cooled visit.
Colin

[BumbleBus]

Do you have black plugs because you have been driving around town for the past 1,000 miles?

Probably.

You *need* an Itinerant Air-Cooled visit.

I know. I'm sorry this time around didn't work out. I will make it happen someday!!