Explain to me why I can't use the VDO 323092 Temp Sender

I've been reading for the last 2 days (on the forums and elsewhere) and doing maths (Jeremy Clarkson reference for those who are in the know   ) a bit beyond my understanding (ohm curves when compared to temperature for different temp ranges etc)...

I do not understand why I can't use the VDO 323092 temp sender, which has the proper threads for the LS block, but has a 50 degree higher temp range (300F vs 250F). How will this affect the calibration of the stock gauge? Is it even compatible with the stock gauge?

Can someone explain why everyone isn't using this bolt in option, even if the gauge lines will represent slightly different values? Does anyone know what the values (the stock temp lines on the late 944 gauge) will actually represent?

I've spec'd out all of the adapters for the 095 gauge etc etc, anyone running that sender successfully feel free to chime in. However I'm really looking for some in depth technical discussion on the problems or lack thereof running the 092 sender.

Input is appreciated guys!
Ethan

PS. This is going in a 1986 Porsche 951 LS swap, using a 2006 L33 with a LS6 intake and some other goodies...

I am not an expert, but here is my understanding of the potential problems. I'm sure you already know most of this, and where I'm wrong, I hope others will correct the details.

Most automotive analog gauge systems require a matched sensor and gauge to work. Typically automotive sensors are "active" and require a power input, and then change either the voltage or resistance in a way that the gauge can interpret and and turn into a usable display, like the movement of a needle on a specifically calibrated scale.

The factors that must work together are as follows:

The gauge and sensor must be designed to use essentially the same voltage and resistance range. A problem here means the the two components would either not function, give bad information, or possible even allow for damage to the components themselves.

The gauge and sensor pair must be matched and calibrated (contain analog logic) that allows the changes in voltage or resistance to be converted into a usable display. If the two components are compatible in voltage and/or resistance, but have differing values for what a given value represents, either in linear or non-linear calibration, or possibly even a linear and non-linear component mix, the rates of change may lead to a display, but it will be likely be inaccurate. Or at least not accurate across the whole range of the display.

Quite a lot of text to say they may not play nice with each other unless they are designed to.

That said, if a sensor sends the output through a modern ECU, PCM or computer before sending the signal on to the gauge, then it might be possible to change the code in the ECU to allow the sensor to match the gauge, assuming they are basically compatible.

I haven't spent any time working with GM PCM flashing software yet, but as an example, in my Evo, I could reprogram (change the base values and multipliers, and sometimes even the formulas) for much of the math used by sensor and gauge pairs. That allowed me me run a Mitsubishi 3 BAR intake manifold pressure sensor and GM boost controller together instead of the OE Mitsubishi 2 BAR manifold pressure sensor and OE Mitsubishi boost controller. That also allowed me to make my OE Mitsubishi optioned boost gauge work accurately with my modified combination.

A bit OT but related:

While not exactly the same as a sensor, essentially the same kind logic changes were required to run my aftermarket 1000 cc fuel injectors using e85 in place of the OE Evo fuel injectors. First I had to reset the fuel injector base size, then change it again as I figured out the actual difference in ratio of fuel use between e85 and gasoline in my specific engine, and finally make small changes to the injector activation curves as needed to help with issues like cold start, warm-up, and part-throttle dirveability and throttle response. It honestly took me about three months of continuous minor adjustments to achieve OEM class driveability on e85 with the larger injectors. But once set, the car ran lie OEM from -40 f to 110 f, regardless of start-up, restart, part throttle, full throttle, etc. Quite a bit of logging and tuning, but worth it, and not a result that typically comes from a quick afternoon tune on a dyno.

erioshi wrote:I am not an expert, but here is my understanding of the potential problems.  I'm sure you already know most of this, and where I'm wrong, I hope others will correct the details.

Most automotive analog gauge systems require a matched sensor and gauge to work.  Typically automotive sensors are "active" and require a power input, and then change either the voltage or resistance in a way that the gauge can interpret and and turn into a usable display, like the movement of a needle on a specifically calibrated scale.

The factors that must work together are as follows:

The gauge and sensor must be designed to use essentially the same voltage and resistance range.  A problem here means the the two components would either not function, give bad information, or possible even allow for damage to the components themselves.

The gauge and sensor pair must be matched and calibrated (contain analog logic) that allows the changes in voltage or resistance to be converted into a usable display.  If the two components are compatible in voltage and/or resistance, but have differing values for what a given value represents, either in linear or non-linear calibration, or possibly even a linear and non-linear component mix, the rates of change may lead to a display, but it will be likely be inaccurate.  Or at least not accurate across the whole range of the display.

Quite a lot of text to say they may not play nice with each other unless they are designed to.

Lots of good info, I've copied the stuff I want to discuss further above.

The sending unit that a lot of people seem to use on this board is the 323095, which is the 250F gauge, and according to all of the documentation I've been able to find it is compatible with gauges using a 10-180 Ohm range.

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The 092 sending unit has a 300F peak, but also states that it is compatible with gauges using a 10-180 Ohm range (the same as the 095 sending unit that appears to work properly).

[You must be registered and logged in to see this image.]

looking at Clark's Garage, the stock gauge seems to function at a higher Ohm range than either of these VDO sending units (see below)...yet people seem to be using the 250F sender without issue.
[You must be registered and logged in to see this image.]

To me this will result in one of two things: either the gauge will function to the point that the lines in the stock gauge may not correspond to the same temperatures, but it will be usable for a daily driver. Or, the gauge will not function properly at all, or will indicate very inaccurately, to the point it is unusable.

Any thoughts guys?
Ethan

Found this interesting info in my search:

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Looks to me like this sender is a bit off in ohm-age (lol...puns could be made)...this shows 36.5 ohms at 120C, which corresponds very closely to the 100C mark on the stock gauge (Clark's garage shows 38.5 at 100C)

I'm starting to think I've found a rationally founded reason to not run this sending unit. Pretty sure I'm going to try the adapter route with the 095 unit.

Any final thoughts?
Ethan

I'm using the early 944 sender (047-919-501A-M82) with an adapter.  Works well and it's designed for our gauges.  

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supes6 wrote:I'm using the early 944 sender (047-919-501A-M82) with an adapter.  Works well and it's designed for our gauges.  

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I saw that in my searches (honestly I read every thread front to back to front 2-3 times on this entire forum having anything to do with temperature and oil pressure senders etc lol!)

Thanks for chiming in, I was looking at that actually...so you took the Autometer 2277 1/8x27 - M12x1.5 adapter and drilled the 1/8x27 female threaded portion out to accept the early 944 sender? Do you know what diameter and pitch you drilled the adapter to for the 944 sender? I have so many numbers in my head now I think I just need to go to bed lol.

Thanks again!
Ethan

I have threaded the stock sender to match the head dia./pitch multiple times. No issues.

scryfst wrote:I have threaded the stock sender to match the head dia./pitch multiple times. No issues.

No kidding! How did you manage that? Just run a die down over the threads?

scryfst wrote:I have threaded the stock sender to match the head dia./pitch multiple times. No issues.

ive been wondering about that myself. doing my ecotec swap i threaded the stock 944 n/a temp sensor right in place of the gm sensor. stock sensor is m12x1.5 on most ecotecs, same as the ls is.

sharkey wrote:

scryfst wrote:I have threaded the stock sender to match the head dia./pitch multiple times. No issues.

ive been wondering about that myself. doing my ecotec swap i threaded the stock 944 n/a temp sensor right in place of the gm sensor. stock sensor is m12x1.5 on most ecotecs, same as the ls is.

Do a search on this forum...I'm 99% sure the M12x1.5 stock 944 sending unit is the one for the DME, and does not work with the gauge...the gauge sending unit is a separate part, mounted in a separate place. If it uses a 2 pin harness plug, not 2 spade connectors, it is the DME sending unit.
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Ethan

this is the one i have for my gauges

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i used the one with the square plug first but found info saying that was the dme sensor. ive yet to get my swap running so i dont know.

bluehellfire666 wrote:

scryfst wrote:I have threaded the stock sender to match the head dia./pitch multiple times. No issues.

No kidding! How did you manage that? Just run a die down over the threads?

Yep.

scryfst wrote:

bluehellfire666 wrote:

scryfst wrote:I have threaded the stock sender to match the head dia./pitch multiple times. No issues.

No kidding! How did you manage that? Just run a die down over the threads?

Yep.

Awesome...that is so fricking simple! I can't believe I didn't think of that!

Thank you!
Ethan

How do you rethread the LS head on the engine to the size of the 944 na size without getting metal debris in the coolant passages?

He re-threaded the sensor, not the head.

spence wrote:He re-threaded the sensor, not the head.

ID like a pictures of that! My OEM one doesn't fit close to the size of the hole

At this point it's looking like the LS specific swap sensor is going to work out well. If you haven't seen it check out this thread for the part number [You must be registered and logged in to see this link.]

For 20 bucks, and proper compatibility (except for losing the warning light since the conversion sender is single post) there doesn't seem to be an easier/better option.