Cylinder Head Temps, My Experience + lessons learned Options

[rwilner]

Don't forget we're going to need about 40' of K-type TC wire as well (purple jacket). A complete kit would include the wire, gauge, sensors, and enough terminals / splices to get the job done.

And oh yeah, probably 3 beers.

Any connections added to the thermocouple wires may mean the cold junction compensation feature of the instrument won't work. FYI

Chris
My understanding is that the compensation feature will work correctly if the splices for all 4 TC channels are at the same temperature (i.e. in the same location).

From the TC-2 manual:

9.4 Extending leads of thermocouple probes
Thermocouple leads as used with the EGT and CHT probes can be extended either with ordinary copper cable or with
special K-Type extension cable. The choice of either depends on your desired accuracy. If it is possible in your installation
to ensure that both ends of a copper extension cable will be at the same temperature (or very close), then it is quite
possible to use the copper cable. In most open-air installations this will be the case. Should this not be possible or you
require best possible accuracy at all times, you can obtain a special K-type extension cable. This cable is made from the
same metals as your probes cable and uses ordinary plastic sleeving as insulation. In either case, ensure that the cable is
not routed close to sources of electromagnetic interference of any kind. The voltages present in this cable are very small
and are subject to changes applied by external fields. This can lead to false temperature indications. You can check your
installation by using a hand-held transmitter, such as an air band radio. If you transmit a signal, no change in temperature
reading should occur.

[ww914]

This all sounds really exciting, but aside from having to make the clock hole larger (no big deal), I like the idea of a larger display for these old eyes. The other side of the coin is that Chris' set up has been tried and trued, let alone customized for the 914. That might be worth the extra bucks. From reading posts on this thread, some guys have spent a lot of money trying to get it right. Just my thoughts. (IMG:style_emoticons/default/idea.gif)

[jsayre914]

Don't forget we're going to need about 40' of K-type TC wire as well (purple jacket). A complete kit would include the wire, gauge, sensors, and enough terminals / splices to get the job done.

And oh yeah, probably 3 beers.

I forgot to mention, the quote was for the guage and four J style 10 foot wires with the 14mm rings. No splicing or cutting neccessary. I should have somthing in writing this afternoon.

as far as the beer.... your on your own (IMG:style_emoticons/default/beer3.gif)


(IMG:style_emoticons/default/popcorn[1].gif)

[jsayre914]

I was told the J style was 1/2 percent more accurate (IMG:style_emoticons/default/confused24.gif) and the cost would be about the same.

Does this sound the right way to go??

[rwilner]

I was told the J style was 1/2 percent more accurate (IMG:style_emoticons/default/confused24.gif) and the cost would be about the same.

Does this sound the right way to go??

Joe
The J type will give slightly better *precision* because it is more sensitive (1mV per 25 deg C for J and 1mv per 18 deg C for K), but I believe the *accuracy* of the J and K will be the same.

HOWEVER:

The J type TC uses iron (iron-constantan) as one of the metals. Iron = rust. The K type uses aluminum (cromel-alumel).

I'd recommend going with the K.

here's a decent discussion of thermocouples.

[jsayre914]

so, so far no go.

I have heard from both vendors and they both cried me a river, no margin, no room, etc. I just left a message for Matt, the owner of MGL located in Torrence. I am not trying to make money here, I just want to give his company some good publicity. Heck, he might even own a Porsche (IMG:style_emoticons/default/biggrin.gif)

I see no reason to move foreward on the sensors until I can get the best price possible on the guages.


...to be continued.... hopefully within the hour

(IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif)


btw: sensor connection said 10 @ 242 ea
aircraft spruce said 10 @ 246 ea

i think we can do better (IMG:style_emoticons/default/smile.gif)

[ChrisFoley]

This all sounds really exciting, but aside from having to make the clock hole larger (no big deal), I like the idea of a larger display for these old eyes. The other side of the coin is that Chris' set up has been tried and trued, let alone customized for the 914. That might be worth the extra bucks. From reading posts on this thread, some guys have spent a lot of money trying to get it right. Just my thoughts. (IMG:style_emoticons/default/idea.gif)

I just looked at my supplier's website and their listed price for the units I've sold (but without the custom mods I have them make for me) at the same price for at least 5 years appears to have gone up.
I don't have any in stock (can't afford the inventory in this economy) so I may have to increase my price by $50 to keep offering them on my website.
Such a dilemma. (IMG:style_emoticons/default/unsure.gif)

[falconfp2001]

so, so far no go.

I have heard from both vendors and they both cried me a river, no margin, no room, etc. I just left a message for Matt, the owner of MGL located in Torrence. I am not trying to make money here, I just want to give his company some good publicity. Heck, he might even own a Porsche (IMG:style_emoticons/default/biggrin.gif)

I see no reason to move foreward on the sensors until I can get the best price possible on the guages.


...to be continued.... hopefully within the hour

(IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif)


btw: sensor connection said 10 @ 242 ea
aircraft spruce said 10 @ 246 ea

i think we can do better (IMG:style_emoticons/default/smile.gif)

For what ever discount they give on the gauge, they should make up on the sensors. Just like popcorn at the movies.

[jsayre914]

I am satisfied now. I cant get the price any lower. We are getting custom 10 foot sensor's K style (they ended up being the better buy, and they are more common) and the gauge is top of the line.

GROUP BUY is open.

375.00 plus shipping

[grogthegreat]

Does anyone know if this kit could be used with Megasquirt to provide the MS ECU with temp info for things like cold start enrichment?

[shuie]

Those of you who have spent time on the Pelican tech forums over the years probably know who Grady Clay is. If you don't know him, he is a really sharp retired ex-racer & Ace mechanic who raced a 917, owned a 904, Abarth Carrera, currently owns a 2.8L MFI RSR powered -6, etc., and then ran a shop in the Denver area for many years. Anyway, he has posted there many times about his 'rubbermaid solution' for keeping -6 cylinder head temps down during tracks days in Denver at high altitude with crappy fuel. Grady's rubbermaid solution is basically just a cool water reservoir/bladder, a stock VDO windshield washer pump, and a stock washer nozzle that is fixed in front of the cooling fan. The water gets pumped and sprayed into the fan when a switch is flipped from the passenger compartment.

It all sounds pretty hokey when you read about it for the first time on the interweb, but it really works. Grady knows his stuff and has posted the math about how much heat the cool water vapor that is sprayed through the fan sucks out of the -6 heads and the hp figures to back it up over on Pelican for years.

I have seriously thought of implementing something this on my 914 just because of the ambient temps here in the summer months and crappy fuel. I sent Grady a PM about it on Pelican a couple of months back and didn't get a response. I don't know if this kind of thing is necessary for a big IV, but it seems like it might be worth a shot.

Here is an old thread from Pelican where Grady posted the details.

http://forums.pelicanparts.com/porsche-911...d-solution.html

[rwilner]

Does anyone know if this kit could be used with Megasquirt to provide the MS ECU with temp info for things like cold start enrichment?

You can use the stock 914 CHT sensor for this, if you're willing to tie the sensor ground to the engine ground.

[grogthegreat]

Unfortunately me heads no longer have the stock CHT sensor.

[rwilner]

Unfortunately me heads no longer have the stock CHT sensor.

hm...

MS is looking for a NTC (negative temperature coefficient) resistance for head (or coolant) temperature. This is a signal whose resistance is inversely proportional to temperature, i.e., higher temps = lower resistance. The device that accomplishes this is called a thermistor.

The CHT gauges use thermocouples. These devices output a voltage in response to a temperature change -- not a resistance.

Off the top of my head I can think of 3 options for you:

• Do a blind drill and tap in your head to receive a stock CHT...this is really the best option IMO. The location isn't very important.
• Locate or fabricate an NTC thermistor (parts are at digikey, mouser or similar) with a 14mm ring terminal end and put it under #3...this is the least complicated if this device exists or can be easily fabricated
• Purchase a CHT gauge with a resistive output to feed MS...that might be a tall order to locate. I don't think the gauge in this thread has any outputs to feed downstream devices.

Good luck
Rich

[brant]

Those of you who have spent time on the Pelican tech forums over the years probably know who Grady Clay is. If you don't know him, he is a really sharp retired ex-racer & Ace mechanic who raced a 917, owned a 904, Abarth Carrera, currently owns a 2.8L MFI RSR powered -6, etc., and then ran a shop in the Denver area for many years. Anyway, he has posted there many times about his 'rubbermaid solution' for keeping -6 cylinder head temps down during tracks days in Denver at high altitude with crappy fuel. Grady's rubbermaid solution is basically just a cool water reservoir/bladder, a stock VDO windshield washer pump, and a stock washer nozzle that is fixed in front of the cooling fan. The water gets pumped and sprayed into the fan when a switch is flipped from the passenger compartment.

It all sounds pretty hokey when you read about it for the first time on the interweb, but it really works. Grady knows his stuff and has posted the math about how much heat the cool water vapor that is sprayed through the fan sucks out of the -6 heads and the hp figures to back it up over on Pelican for years.

I have seriously thought of implementing something this on my 914 just because of the ambient temps here in the summer months and crappy fuel. I sent Grady a PM about it on Pelican a couple of months back and didn't get a response. I don't know if this kind of thing is necessary for a big IV, but it seems like it might be worth a shot.

Here is an old thread from Pelican where Grady posted the details.

http://forums.pelicanparts.com/porsche-911...d-solution.html

We used to do that back in the 80's on a track 914/4
This was before I knew Grady... but it was really a common practice at the time.
it is not ideal for a number of reasons but yes it will work with trade offs.
brant