Installing gauges...have questions

[Leland Pate]

I want to add three VDO gauges to my car and have some install questions.
The voltmeter gauge I think is pretty straight forward.

The other two gauges I want are the 2 1/16th" oil pressure and clyinder head temp. gauge. I have even thought about adding another oil temp gauge too.

I would like to either mount them under the dash in one of the premade mounts, fabricate something in the stereo opening, or get a 930S center console to put them in.

My question is about the oil temp, oil pressure, and head temp gauges.

What is required to wire the cylinder head temp gauge? I have never seen a very good explaination of it before.

And as far as the oil pressure gauge, I don't want to disconnect the factory split gauge on the dash. I would like to end up with two functiioning gauges. For both oil temp and oil pressure.
It might not make sense to you at first, but I've thought about it and I want the 2" VDO gauges but don't want nonoperational factory gauges in the dash.
Is it possibe to wire the factory gauges with the seperate 2" gauges off of the same senders?

I was going to buy them last night but decided that I wasn't sure about what I was doing.
So I turn to you guys.


Flares, wings, and gauges rule...

[speeder]

I was going to ask why, but think I figured it out- looking at all those cockpits you are going guage-crazy. Probably stir-crazy too, any women in that god-forsaken place? Hope you hurry home, bro. SCWDP needs you here at home.

[Jack Olsen]

I added trans temp and battery gauges to my center console. Still room to hold CDs, too. (Click for a larger image.)

[Doug Zielke]

Lee,
Typically, a cylinder head temp gauge operates via a thermo-couple. I've installed them on racing m/c engines. The t-c goes between a spark plug and the head, like a spark plug washer does.

Now...
The 911 motor has 6 individual heads. To operate 1 gauge, would you need a 6 pole switch and 6 t-c's? Might be more trouble than it's worth.

[Leland Pate]

Hi guys,
Speeder, yes, I have gone "gauge crazy". I admit, i have a thing for gauges, I like to check my engines status often. It is just a habit- I glanse at all operating gauges while driving probably every 4 or 5 minutes.

Jack, that is a pretty trick looking little bracket, where did you get it?
I have been kicking around the idea of building myself a center console to look allot like the 930S console for a long time. I don't think it would be that hard.

Doug, thanks for the info. I too now wonder if the kit requires 6 t-c units. I don't see how it would matter because the gauge itself probably doesn't "average" the temps from each head. I would say that it simply reads the highest temp it is sensing. Can anyone clarify this?

Warren? Can I run two gauges off of the stock senders for the oil temp and oil pressure?
I would simply remove the factory temp and pressure gauges and install the 2" VDOs, but i don't want holes or dead gauges on my dash. I don't see how it could hurt anything, and what's the harm in having a "back-up" gauge system.
How many cars have "Back-up" guages...

[RoninLB]

CHT gauges are wonderful. They react much quicker than oil temp. You will be able to adjust driving style to prevent high oil temp. I use a dual CHT gauge from Aircraft Spruce cat. I use one sender under cyl #2 spark plug. One under #5 plug. You will be able to see immediately that you are lowering eng temp and then wait for oil temp to come down. In winter you will be able to see when engine starts warming up before oil temp reacts. Instant reaction of CHT ga. to 4%- 7% increase in road grade.

[Early_S_Man]

Lee,

A console-installation like Jack's seems ideal, though I probably won't have any space for tapes or CD's when I finish mine with a large 3-1/8" Voltmeter, dual 3-1/8" military CHT gauge, dual 3-1/8" oil temp gauge, and a fuse alarm monitor panel ...

The CHT requires thermocouple sensors that are a two-wire lead, and special extra-length extension cables for a 911 installation... all the way to the gauge, for each cylinder to be monitored. I recommend a dual gauge for aircraft, either new or military surplus. You could monitor just two cylinders, such as #3 and #6, or all six with a three-position selector switch. Here is a link to a popular light aircraft supplier, and some additional info sources:

http://www.aircraftspruce.com/catalog/inpages/westfaa_egtcht.php

http://www.google.com/search?q=+%22dual+cht+gauge%22&num=100&hl=en&as_qdr=all&filter=0

No, you can't run two gauges from one sender, but there is a dual-pole VDO sender that has both pressure sensor andd warning switch in the same size housing as a regular sender ... which you could install where your oil pressure switch is now, and run the 'spare' gauge from.

[Leland Pate]

Warren,
I have the dual pole sender on my SC. So your saying that I can unplug the warning light wire and attach the lead to the new pressure gauge? Or just splice it into the existing wire?

Ronin, Am i correct in thiking that these CHT gauges need a special wire from the thermo-coupler to the actual gauge? I couldn't just add generic wire to make up the distance...
Where did you get yours from? How many feet of "cable" did you need?

This all sounds very interesting!

Thanks!

[RoninLB]

Leland....better than "sounds interesting", it's a home run. CHT ga. gets my attention any time conditions of driving change. When on Hy 10 in S.Calif. in 112 deg. desert heat at 3,700 rpm CHT looked great for hours. During that time 3,900 rpm showed an immediate 10 deg. rise in CHT. Doesn't sound like much but I had a complete view of what is happening heat wise with out waiting for oil temp. to catch up with what is happening. I returned to 3,700 rpm to be consertative on a big ride. I bought dual ga. from Aircraft Spruce. The extension from eng. to ga. is in their cat. or web site. Whole package is around $125. Worth every penny to someone who is 911 mechanically neurotic. The sender that replaces spark plug washer is what I use. I had to chop a plug socket to allow sender wire to fit into. I use one sender on #2 and one on #5 to assist future carb. tweaking. Don't get me started on exhaust temp system, which will be a wild install on SSI to monitor future carb. install. If you don't use carbs a single ga. will be good enough.

[Early_S_Man]

Lee,

No, I was suggesting adding a second oil pressure sender up on top of the engine near the thermostat, where it was located on 2.7 engines and earlier. I believe SC's originally had the oil pressure switch located there.

Here is a good article on the istallation of cylinder head temperature gauges:

http://www.ultralightnews.com/engineinfo/chtwirdia.htm

[Doug Zielke]

If you have a thermo-couple on only 2 cylinder heads (#2 & #5), how do you know what's happening with the other 4 heads?

[RoninLB]

Doug...not being an expert, IMHO, The 2 center cyl. will give a good indication of what is happening else where. In a CIS system I believe that a cyl. running lean is remote, unlike carbs which has 6 seperate systems to cause problems. In a 911 CHT is operating temp of eng., used for monitoring load heat, IMHO. Exhaust Gas Temp. is another story, IMHO. 6 EGT probes will enable the driver to detect a lean condition caused by a single carb problem, which may not be detected early any other way. [also to help tuning] Also, IMHO, you monitor eng. w/CHT and tune and monitor each cyl. with EGT. The site on Westach CHT ga. is good. I use the dual Westach CHT pictured. The site info is OK for a 911 engine. I found that what they considered normal CHT is too high, based on my experience, although they may be refering to Wide Open Throttle. The EGT numbers of 1,200 deg only applies to WOT in a 911, which is borderline excessive without using heat protection on pistons. IMHO, on a CIS one CHT is plenty, I would do two CHT because it's an easy install to do a dual set up. 6 EGT probes on a carb 911 will relax me on monitoring. They will be installed on SSI one inch from flange.

[Leland Pate]

Lots of great info!

Warren, now i'm tracking... so your saying I can remove my oil pressure switch and "backdate' to the older 2.7, era oil pressure sender.

I am also considering adding a fuel/air mixture gauge.

Am I correct in understanding that these CHT gauges are more less "self powered" and require no wiring to the fuse panel except to add a light?









Give me gauges or give me death...

[RoninLB]

Leland...yes. elec. for lite only. Fuel/air mix ga. is accurate around a set "so called perfect" mix unless you spend big bucks. Depends what you want fuel/air mix for and in what application, IMHO. To my understanding the acuracy falls off the further you go from "perfect". Research this one out.

[Early_S_Man]

Lee,

Yes, I was suggesting adding either the 2.4/2.7 or aftermarket VDO sender for the 2-1/8" gauge ... up where it was mounted on 2.7 rngines -- where the pressure switch was moubted on SC engines.

As far as the CHT needing +12 Volt power power, it is only for illumination on the Westach light aircraft gauge, but on my military Boeing CHT gauge by Lewis Engineering, it has separate inputs for +14 Volts or +24-28 Volts, and I am certain that it is NOT for illumination, as I have had the gauge apart, and there aren't any internal light bulb(s). There is a bridge circuit, and the thermocouple side generates one Voltage, and it is compared against the system Voltage and dropping resistors for a reference.

Ron,

Idon't think your assumptions about CIS having no separate control paths or circuits is valid, as there are six separate control pistons in your CIS fuel distributor, and individual injectors can stick open or get clogged! So, for accurate assesment of engine health, six thermocouples and a selector switch is needed, unless you put in three of the dual-gauges.

[RoninLB]

Warren....Thanks for info on CIS..Didn't realise it was a possible problem....Seems like a fuel dis problem could burn a valve? I don't have much local knowledge of CIS. Do you think this fuel dis prob would happen without other CIS fuel dis problems showing up? Seems like 6 probe EGT install will be of some use while waiting carb install.

[Early_S_Man]

Ron,


CORRECTION --- there is only one milled and slotted control piston in the fuel distributor.

What I should have said is that there are individual check valves and filter screens in the injectors, and injector problems caused by water, rust, carbonate, and silicate contamination in the fuel, courtesy of the petroleum plants and transport companies, and that injector problems in individual cylinders can and do occur with high frequency these days!

[RoninLB]

Warren---thanks for the "heads up" Sometimes when I reach for the stars I don't always get one. I don't wind up with a handful of mud either...

[Mike Feinstein]

Leland,

Are there Porsche parts available in the sandbox (Qatar)?

"I was going to buy them last night but decided that I wasn't sure about what I was doing."

Just wondering how you're accomplishing all this from the far side of the globe.

Be safe and happy holidays,

[RarlyL8]

Lee-
Several of the aftermarket mags sell dual senders for oil temperature. You use the stock guage and a conventional round one. Have a friend who did this on his 930. Very nice option, especially if you have the "no numbers" crappy guage.