Multi Sender CHT Gauge

I believe Danny P is running one.

Thanks, Bill.

http://thesensorconnection.com...uple-pyrometer-gauge

Nice feature is the programable alarm limit to alert when parameter has been reached on any of the thermocouplers.

 

I found this Stratomaster LCD programable unit, but not sure if VDO had a unit, also?

I have two of these:

 

If you don't mind digital stuff in the cabin, these would work as well:

 

I've seen these in some guys cars as well. I'm 99% sure that Westach can set them up with a CHT gauge in each slot, if you so desire:

 

http://www.aircraftspruce.com/menus/in/chtgauges.html

 

Aircraft Spruce has what you need.

Thank you, Stan.  So far I like the Digital with limit alarm, etc.  I would mount under dash to keep the VDO: oil temp, press. and CHT look clean on dash face.

Thanks, again.

Tom

I also have a Bergmann 911 shroud and mounted K-type thermocouples on all 4 cylinders to be able to monitor all CHTs simultaneously.  

 

I used the 2 1/4" MGL Avionics TP-1 and the TC-1 gauges:

http://www.mglavionics.com/html/infinity.html#TC-1

 

To keep the dash as clean as possible, I installed the TC-1 4-channel CHT gauge and a TP-1 oil temperature and oil pressure gauge in a mount under the steering column.  I did have to bore it out a bit (made to fit only automotive 2 1/8" gauges).  Made by Airkewld:

http://www.airkewld.com/Billet...ne-Finish-p/7025.htm

 

It keeps most of the stock dash look and is not too intrusive.  To me, having the digital readouts of all my engine data in real time is worth it.  I run an AFR gauge also.

 

Here's how it turned out:

  

  

   

 

 

thank you for reference and photos showing details.  I like the Digital option you are using and the mounting location, also.

Tom

TP- How hard are they to see while driving?

Not too difficult to see while driving.  A quick head lean to either side makes them visible. 

I also have all alarm set points wired to one of the bulbs on the combo gauge.

That's a great arrangement.  I recall George Brown used to have both a visual and an audible alarm in his car for oil pressure.

I went simple. One Dakota Digital Gauge, four sensors, all thru a simple rotary switch from Radio Shack. I leave it on #3 and just turn the sw to see what the others are doing when I'm curious. The Dakota gauge is quite bright . The only time I have to shade it with my hand is when the sun is directly behind me and low.....Bruce

Pretty cool. But, you know that the rotary switch is a "cold joint", right?

Yup....The guys at Dakota told me that and said that as long as the switch doesn't get corroded or dirty it will work. Thanks for reminding me of that Stan. My plan is to remove all of this apparatus once I am comfortable with whats going on. I really don't like the looks of having the two gauges (oil and CHT)hanging under the dash. Anyway my comment before could be misleading and I'm glad you caught that. For some of you, What I think Stan is referring to is an electrical connection where the actual mechanical connection/contact is not ideal. ie, a "cold joint". An example of an ideal electrical connection would be a good mechanical connection (crimped) and then soldered thus pretty much eliminating the possibility of corrosion or loosening.

A rotary switch is not ideal, long term, for a CHT because they can corrode, create resistance. This is not good for CHTs because they are sensitive to changes in resistance.   Again ...Thanks Stan

I knew you knew, Bruce, and it really isn't that big a deal-- other than that the gauge is no longer 100% temperature compensated. Actually anything besides thermocouple wire running back to tha gauge introduces that same "cold joint", so unless a guy is ready to cut and solder thermocouple wire every time he removed the engine, the gauge will not be truly temperature compensated.

I've got a 9-pin connector on mine to connect the sensors on the engine to the thermocouple wire running to the dash, do I did the same thing. It's fine as long as you remember it's not truly "temperature compensated", for whatever that's worth.

OK, so let's say that you've installed this stuff the "quick and dirty" way and have some (gasp!) regular-old wire in the circuit, making it no longer 100% temperature compensated.  Let's say you've got 3 feet between the multi-sensor switch and your read-out (whatever that is).

 

Do you know what effect will that have on indicated readings?

Wow TP! Nice set up. Real quality wiring job. It's nice to see someone take that much pride in his ride.

I know all the theory, and I know what I think.

 

A CHT gauge works by means of a thermocouple, which generates a small electrical charge. This charge varies by temperature, which is what moves the needle on your gauge. The gauge is just a calibrated milivolt meter. A "cold junction" introduces resistance into the circuit, which varies by temperature (and a host of other factors) and effects the milvolt signal to the meter. The length of the wire, etc. also plays into the whole thing.

 

I know that for a gauge to be truly "temperature compensated", a pyrometer is going to be a laboratory-grade instrument. What we are doing is nowhere near that refined-- and the Dakota Digital, et al temperature compensated gauges available for a couple hundred bucks or less are going to have some digital algorithm or analog wizardry to factor in some fudge based on ambient temperature, etc.

 

Know what? It works. My take on it is that the "cold joint" is probably nowhere near as big a deal as the talking heads over on The Samba act like it is. The purported net/net of your (purely hypothetical) non-approved set-up is that the gauge will read low in high ambient conditions, and high in low ambient conditions. It might vary up to (gasp) 20* or so.

 

I'd bet, however, that it is more of a reference tool than an absolute indication of exactly what your head temps are. I know where mine run when things are happy. I can watch one head cool off when I start to have an issue with an idle jet. I know instantly which one is the offending menace, and how bad it is. It's a pretty great tool to have out on the road.

 

In short (well... too late for that now), to answer your question: IMHO, you are none the worse for the wear doing it just like you are doing it. You too, Bruce- as long as that rotary switch has nice and clean contacts. You aren't going to get it down the gnat's eyelash, but this is a bit like we used to say in high-school woodshop class:

 

We measure it with a micrometer,

mark it with a crayon,

and cut it with an axe.

 

There's no point in pretending any of this is a mico-measurement, unless you have a lab-grade pyrometer. I'm just trying to avoid cutting this thing with an axe, but I'm pretty sure we're marking it with a big-'ol Crayola.

I saw that instantly. Forget the gauges: check out that dude's terminal strip.

 

Nice!

Stan,
What you have explained here is exactly my intent.
Example: same ambient conditions, RPM, MPH (for airflow) and all 4 CHT are say 350 F, + or - a few deg.   Next time under very similar conditions #4 is showing 450 F.  I would then have a "relative" indication that something may be wrong?
Again, not exact value readings, but a reference point to determine abnormalities from previous known standards on my engine.
Monitoring all 4 CHT would serve the same "relative" reference point. Kind of like Cyl. Compression numbers from one to the other.
BTW, today vendor selling GEL told me J or K specific joint connectors were $15/ea (metal is specific to metals used on wires) to connect to DB9 connector in back of Gauge.  8 x $15= $120.00 in connectors. Ouch.....
Thanks for all the input offered here.
Tom L

Really  nice insulation of wiring and gauges .  I don't quite understand why you are so worried about the engine temperatures, unless someone built the engine with too much compression, requiring octane we cannot buy at the pump.  I drive my air cooled cars in stop and go traffic in the summer time and never have any overheating problems, but I do build my own engines.  Suggest only 8:1 CR on mild cam engines and an air/fuel ratio meter, to me, would be more important to show the engine is tuned properly.  Then, there should be no concern about the temperatures and save someone hundreds of dollars in gauges and sensors. 

 

Last time I looked, aircraft gauges are expensive.  Just build the engine correctly with good quality parts and that solves the overheating problems.  I test the temperature( with a $100 red laser heat gun)  on my engines, only when test run and break in on my engine test stand.  I run them at  2500rpm for at least 20 minutes and look for any questionable temperature reading at about 20 different places on the engine.  When tuned properly, that solves the overheating problems. 

 

Here is a very cheap method to check your engine's temperature. Drive your car for one hour at 60mph , then pull off the road and see if you burn your fingers when you touch the dip stick. If so, there is a problem with your engine, which the gauges cannot fix.  Again, built right, I have not seen any overheating problems with my air cooled engines, in many different models, kit cars, dune buggies, etc. in the 40 years I have been driving these air cooled engine powered cars. 

 

But, am impressed with the engineering and wiring.  Looks beautiful !  --George K.---

You're right, George-- when everything is working correctly, gauges are just car jewelry. Gauges are useful only when something is wrong, when they can save a LOT of money if you look at them. A few hundred bucks to save a multi-thousand dollar engine seems like money well spent, at least to me. I really do believe that forewarned is forearmed.

 

Tom-- That's it! The CHT gauge provides me a relative reference, rather than an absolute number. There's a lot of value in that for me. After I went through the whole rigmarole, I (like George) wondered if it was just a complication that was going to end up being more for looks than having any real use. When things are going well, it's a lot of complexity that's not really needed. But when things are not going well, monitoring all 4 helps me pinpoint the offending cylinder without even leaving the driver's seat. That saves huge amounts of frustration in troubleshooting issues. I like it.

George...Welcome Back !

 

Stan....You gave me the best laugh of the day with your Measure-Mark-Cut procedure! Never heard that one before but will use it where appropriate !...Bruce

Some gratuitous fuse panel p o r n:

  

 

oh... that's really nice.  I'm mortified by comparison to the rats nest under my dash.

Challenge accepted.

 

Ted

Beautiful wiring for sure. TP, are those crimped or soldered connectors ? Any special brand or supplier ? What type of wire do you use....straight from the auto supply house or something special ? Thanks.

That is beautifully done!

TP,
Terminal Block or Work of Art. LOL
Nice job.

TP, you out did yourself. If I ever unravel my rats nest of wiring you're the man I'll consult with!

How are your relays attached to the panel, 3M?

You should mass produce some panels...

No kidding 35+ years of Shade Tree wiring can be pretty scary to contend with! My philosopy is IF it works don't screw with it or it WILL scew up. So When I want to shut off my engine I HAVE to press the Break or it keeps running! Solution ALWAYS press the Break! LoL You ever see the fuse box on a REAL 356? Simplisity it's wonderful! But of course IF you want a priemum Bose system, Air conditioning, Seat warmers and coffee cup warmer in your "Spartan" Speedster I guess you need wiring like were talking about! LoL Looks more the underdash of a H2! LoL

The connectors are female blade terminals and ring terminals, all soldered with shrink wrap.  I found a few rolls of automotive wire on Amazon.  Most is 14AWG, the big stuff is 10AWG.  Relays, fuse blocks, and wire terminals are attached with hardware through the panel.

 

I also realized even with my hidden starter kill switch, anyone could hotwire the car in a few seconds because of the labeling!

That is some really nice work T P. You did it right!

 

T P, is that a one-point rule around the borders of the relay labels?

 

Did you do that to distinguish relays from other connections?

 

I'm out on a limb here, but I'm guessing that your sock drawer looks a whole lot different than my sock drawer.

 

 

 

 

Do I detect a Graphics Artist?

 

Or maybe a publisher?

Just a little anal-retentive.

 

Newspaper photo dude. One of the great battles of the twentieth century was waged by newspaper photo dudes trying to get editors to put one-point rules around photos.

 

And now, here those rules are under the dash of a Speedster - the last place on earth I'd expect to find them. They, and the neat little labels they surround, would serve no purpose whatsoever under my dash, where any label would be lost behind an impenetrable snarl of wires.

 

One of the reasons I'm careful about making good connections under the dash is that I know, once the crimp is made, I'll never be able to find that joint again.

 

 

 

Ya think?

 

Excellent use of a soldering iron and heat-gun. Not everything strictly NEEDS to be nuke-plant grade, but boy is it nice when it is!

 

You sir, are the man.

T.P., just curious, is there much difference in individual head temperatures with the BB shroud?

Sorry, this thread has gotten a bit off topic...

 

Ron, yes when I started I measured about a 90F CHT delta between the 1-2 side and the 3-4 side cylinders.  Cylinders 1/2 were being way over cooled, 3/4 were being way undercooled.  I've since gone through 2 iterations of air diverter designs and placement in the back of the shroud to grab air and re-direct it to the 3/4 side.

 

Below are some CHT temps at a 70-80MPH cruise at 3500-3800RPM.  Ambient around 75F.

 

No mods:

Cylinder 1: 295F

Cylinder 2: 303F

Cylinder 3: 380F

Cylinder 4: 386F

 

Largest delta = ~90F

  

 

1st diverter design:

Cylinder 1: 319F

Cylinder 2: 326F

Cylinder 3: 365F

Cylinder 4: 370F

 

Largest delta = ~50F

 

 

 

 

2nd diverter design (offset diverter farther to the right):

Cylinder 1: 332F

Cylinder 2: 339F

Cylinder 3: 370F

Cylinder 4: 373F

 

Largest delta = ~40F

 

 

3rd diverter design:

In progress

 

 

I'll be happy when I can get the 1/2 to 3/4 side temp delta to around 10-15F.  Cylinder to cylinder on the same side seems to be within 3-8F always.  All numbers are averaged.  I have a ton of data at various speeds and RPMs as well.  Idle, 20MPH, 50MPH, etc.  The 911 shroud cooling varies greatly depending on how fast the fan is spinning.  My current 2nd diverter design is actually about perfectly matched (0-5F) at 800RPM at idle on all 4 cylinders.  It isn't until higher RPMs that the temperature differences start.

 

 

TP,
Will you keep us advised of 3rd Diverter results. Having 911 shroud, very interested in your findings. Thanks.
Tom L

This kind of stuff really lights me up.

 

For years, all we heard was how awesome a 911 shroud was (all the cool kids in Australia/Europe/et al are running them). Then all we heard was how horrible they are (over/under-cooling banks, etc.). Every thread- every single one of them- on the subject has somebody saying, "I really love how the shrouds look, but I wish somebody would work on helping them cool better".

 

Nobody ever does. From everything I've seen so far from TP, I think he just may be the guy to do it. The dude is methodical, careful, persistent, and does clean work.

 

I've got a DTM. There's nothing especially nice about it, except that it works really, really well. I remember when Jake Raby was figuring it out 12 years ago (or so)-- he was just trying to do better than a VW shroud. I think it took about 15 different arrangements of the air-deflectors inside before he found the sweet-spot. Once that was done, he moved on to other things. Nobody has ever cracked the 911/4 shroud nut, because nobody has ever thrown everything they had behind it.

 

If you can get this done, TP- you will have accomplished something that has needed to get done for years.

 

I'm seriously impressed.