Temp gauge

[9sixty4]

92 964 3.6L. I want to use a cylinder head temp gauge. I figure the best place to pick up the temp is from the taped hole in the head(s) were the factory sensor is located only on a different head. Two questions: which head should I use to pick up the temp and were can I find a 12mm 1.0 pitch bolt/plug to use to mount the temp sensor pick-up wire?

[Flat6pac]

The only other place the tap is available that you can see would be on the #4 but the chain box is in the way for that one. You might be able to tap in another area on #3 but #6 is covered with the PS pump.

[Henry Schmidt]

I haven't seen them in years, but back in the day, you could buy a head temp sensor that used a pickup that went under the spark plug. No drilling needed.
As I recall they worked pretty good.
Try a VW performance shop.

[Jeff Alton]

Or an aircraft supply house, they will likely have the sensor too.

[MrPerkles]

I am using one of these with my efi.oil temp lags behind head temp
PROBES, Sensors and Sundries for MGL Avionics

[RoninLB]

Pilot Supplies, Avionics, and Homebuilt Aircraft Parts from Aircraft Spruce and Specialty Co.


spark plug thermocouples on #2 & 5 worked good for me as a relative average of hotter and colder heads

my new system has digital readings on all 6 heads. On x-country rides and steady 90-100 mph 30mi runs temps didn't vary more than 25F, and then only for a few seconds

sorry.. no track info

[Walt Fricke]

Ron

My experience with dash mounted LCD displays has been bad - after a while they are too hot, the display blackens, and I can't read it.

I suspect my dash area - where clock would be - is hotter than most because I have a 4 gallon oil tank in the smuggler's box, and no air flow stuff or windshield wipers, far less a cardboard valance, to keep heat away from the back of the dash.

I have used inexpensive displays - 0.2V panel meters modified to read O2 sensors (yes, poorly). I don't know if a fully cased aircraft grade instrument would better resist display blackening.

Do you?

That 12 channel aircraft instrument which could be used for 6 CHTs and 6 EGTs in one display sounds like it might be quite useful for a hot rod race motor. I have 3.2 heads, so could screw a short bolt and washer through the 10mm spark plug sensors. I could lead the wires from all but #3 down through the space between cylinders, and then to a loom somewhere.

Walt

[RoninLB]

QUOTE=Walt Fricke;5210877

My experience with dash mounted LCD displays has been bad - after a while they are too hot, the display blackens, and I can't read it.
I don't know if a fully cased aircraft grade instrument would better resist display blackening.
Do you?



Hi Walt

----------- I don't know anything about LCD
But... At one time I was on the phone with Westach Instruments, who mfg the above aircraft dual CHT ga, about making me a tripple fuel ga set to fit in the clock hole. They said they could make just about anything I want. [So I plumbed 3 fittings into my fuel lines for senders when I re-did it for carbs]
Maybe call up the aircraft gauge mfg's ?





That 12 channel aircraft instrument which could be used for 6 CHTs and 6 EGTs in one display sounds like it might be quite useful for a hot rod race motor.

---------- it's extraordinary
Not only can you tune as close to the edge as can be under real world conditions but that edge can be monitored. Besides the fact that, from my experiences, even though you may be experiencing a cylinder miss you don't know if a jet is lean from being partially clogged or the jet is completely clogged and dead. It doesn't take much of a lean to send EGT's way over 1,500F... very scary the first time it happened. My set allowed me to get home safely w/peace of mind.







I have 3.2 heads, so could screw a short bolt and washer through the 10mm spark plug sensors.

--------- from my research before buying my unit attaching custom CHT probes to different places on 911 heads can be very problematic. Not only is cooling air an issue but the incorrect placement of the sensor in the head can lead to improper CHT info.

The spark plug thermocouple placement isn't the greatest and you have to develop an eyeball on why the CHT is increasing as the spark plug heat under different loading affects readings.

This subject came up a few years ago and Grady chipped in on different areas of the head he tapped into for racing. I could probably dig it out easier than you if needed?


Anyway if I would suggest the most accurate and inexpensive tool to install it would be a single digital EGT. The digital is usually accurate within 2% and easier to read.

[RoninLB]

how about some eye candy







This reading was w/car stopped so I could take the pic. My CHT usually run about 170-180F and EGT around 1,325-1,350 in 5th from 3.5-4k rpm. When above 4k in 5th my EGTs start to decrease about 25F. The CHTs slowly increase relative to output above 4k in 5th. That confirmed to me I had nice E-tubes for my act.
The dot under #4 means which cylinder is being read.






This reading was with the car in 5th at about a steady 3.2k rpm. The "Dif" readings means the differential between the hottest and coolest cylinder for EGT. When I was adjusting carb jetting and screw adjustments this was my bible message for getting all 6 cyl putting out equal power. In other gears EGT's are inaccurate and scattered all over. From some readings I found carb differentials are 125F and over and FI is 60-75F. I did notice that as you squeeze the power envelope the Diff increases. Not an issue as idle screw adj deceases it back down. A minor screw adj can move EGT 25-50F

[Walt Fricke]

Eye candy indeed!

Because I have 3.2 heads, I could use the factory CHT sensor in the factory location. Our host sells them for $69.25 each, making six of them a bit pricey. Also, except for where the factory used them, the sensor and its wire might be a bit bulkey. Hence my interest in bolting the spark plug type in that location. However, it would be reading the aluminum farther from the bottom of the threaded hole than I suppose the factory sensor would be doing.

Grady built a 914/6 track car which had six EGT (or maybe CHT) gauges in an angled dash panel over by the shifter. Most who saw that marveled at it, then wondered how a driver on the track could take it all in.

I'm wondering if a guy might not be better off (for racing applications) just using one or two (I have two EGTs with a dual pointer gauge plugged into #3 and 5 exhausts) showing on a gauge, and maybe recording the rest for later tuning review? The older my eyes get, I find that on the track, and especially when racing, I don't have much ability to do much gauge monitoring. Then there is the question of where the sun is (I race an open cockpit car).

Those graphic displays should be easy to read at a glance, especially if just looking for one which was out of line with the others.

To get my EGT information to the gauge I just use some more or less ordinary wire in a loom I made up (saved maybe one pound by removing factory wiring). I did not use K thermocouple wire. If the electrical properties of both of the wires I use are identical, will that suffice to give me proper readings? Or the red and yellow wires both of different composition (as in being the thermocouple itself at the exhaust end), and maintaining that difference all the way to the gauge is important despite the fact that temperature differences are no longer being measured by that part of the wiring?

Walt

[RoninLB]

Walt Fricke;5213967

However, it would be reading the aluminum farther from the bottom of the threaded hole than I suppose the factory sensor would be doing.

---------- and then again the spark plug heat is connected into the combustion chamber. I'd guess the plug thermocouple has to be somewhat reliable an indicator to be used in planes?




Grady built a 914/6 track car which had six EGT (or maybe CHT) gauges in an angled dash panel over by the shifter.

----------- Grady also posted names of these track digital EGT/CHT multiplex mfg's. Seems $3-400 more than cost of thremocouples and probes. Costs for them have been coming down.




I'm wondering if a guy might not be better off (for racing applications) just using one or two (I have two EGTs with a dual pointer gauge plugged into #3 and 5 exhausts) showing on a gauge, and maybe recording the rest for later tuning review?

-------- I posted above that I think a single digital reading EGT would be excellent for tuning instead of a analog reading for being able to discern 25-50F differences when figuring mixture. I figure that it's not a gauge you have to monitor constantly like a volt or oil temp gauge. You wouldn't be able to troubleshoot using it but it still would be an excellent tuning guide. It's interesting watching what happens when tuning carb accelerator pumps when you take that "seat of pants" issue out of the equation.





Those graphic displays should be easy to read at a glance, especially if just looking for one which was out of line with the others.

--------- I know which jet is plugged immediately. More than once I thought I cleaned the jet and I had to go back and redo the jet again or clean it's passage. Saved me all kinds of agrivation on the side of the road.




I did not use K thermocouple wire.

--------- I don't know enough how it would affect an analog gauge? In my digital system I wasn't about to experminent considering the imense # of hours for the install. My extension 12 pair cost around $300 from JPI



I'll try to find Grady's thread




.

[RoninLB]

CHT probe placement - Pelican Parts Technical BBS