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View Full Version : Installing a Water Temperature Gauge



Jim Hubert
11-25-2007, 11:39 AM
Basically, I see three ways to go about doing this...

1. Tap into the existing water temperature sensor on the rear head. All automotive temperature sensors use an electrical part called a thermistor. It is a passive device and its resistance changes with temperature. Unfortunately, the change is not at all linear. You can put a voltmeter across the temperature sensor and make a look-up table that equates voltage to temperature. That is basically how the ECU works -- it injects a small current into the sensor and measures the voltage developed across it. You would not be able to read temperature directly on the voltmeter, but you would be able to infer it -- something like 2.5 volts means 40 degrees C. In a way, this is the preferred method because it represents the temperature the ECU is seeing. But is is not simple for the average guy to implement.

2. Install a temperature sensor in the front head. These sensors/readouts are available for about $100.

http://www.daytona.co.jp/motorcycle/export_p/temp.html

I have experience with Daytona's older battery-powered units. This unit has backlighting, so I assume it is powered from the bike's electrical system. The Aprilia sending unit has an M12 x 1.5 thread. If I recall correctly, the Daytona's sending unit uses a fine 10mm thread. Adapters may be available from Daytona, otherwise, you'd have to make one.

3. Something could be fabricated and installed in-line in the radiator hose leading to the water pump. The link below shows what I am talking about:

http://www.pegasusautoracing.com/productdetails.asp?RecID=2936

Unfortunately, that one is too big for the Aprilia (which has a 19mm ID hose).

That is the method I used to measure water temperature on my KX500. The outlet of the radiator shows the lowest coolant temperatures, and that was where I was accustomed to seeing temperature measured on a 2-stroke. I made an adapter that fit the 16mm hose, and epoxied-in the sending unit (it had no threads) from a cheap industrial temperature gauge. The gauge was battery powered. This was a lot of work, but it gave me all the features I wanted. Unfortunately, the readout was not immune to the CDIs electrical noise, and it did not work at all engine RPMs. But I suspect that would not be a problem with the Aprilia.

Finally, these three methods are all going to give different temperature readings, and it may not be straightforward to compare results from the various methods.

Edit: Hose to water pump is 19mm. Hoses to cylinders are 16mm.

irie
11-25-2007, 01:38 PM
I use a Hebo Rev/Temp/Hours display - I buy them from www.racespec.co.uk, but there's a direct pic here:

http://www.ooracing.com/store/index.php?act=viewProd&productId=889

Fabricated a 'T' which is 50mm x 20mm OD and plumbs into the Rad out pipe. It's mounted upside down to make sure there isn't an air lock. The Hebo display I use has a 10mm x 1mm fine pitch thread so the 'I' tube part of the 'T' is tapped 10mm x 1mm. There is more than one variant of this part. To see this search for Hebo Spain.

Under normal running conditions it show 50c which is obviously water temp exiting the radiator. Tells me all I want to know.

<edit>found these pics</edit>

RZRob
06-10-2008, 11:11 PM
I'm jonsing for a water temp gauge. I like Irie's gauge, but I want a little more "factory" looking install for the sensor. Frankly I'd like a really subtle, small, factory looking gauge and install. I can MacGyver, but want a tidy integration.

I really like Hubie's options. Anyone done anything really sano, or got any good advice on the subject?

Do Tell?

RZ Rob

cal550b
06-11-2008, 03:36 AM
I'm jonsing for a water temp gauge. I like Irie's gauge, but I want a little more "factory" looking install for the sensor. Frankly I'd like a really subtle, small, factory looking gauge and install. I can MacGyver, but want a tidy integration.

I really like Hubie's options. Anyone done anything really sano, or got any good advice on the subject?

Do Tell?

RZ Rob

on the r/h side of your front cylinder there is a water plug perfect for a standard temp sensor and then a simple 2 wire digital unit,keeps it all simple.:cheers:

duc slayer
06-11-2008, 09:13 AM
RZ, we want pic's and details :D

SLORider
06-11-2008, 12:22 PM
I'm jonsing for a water temp gauge. I like Irie's gauge, but I want a little more "factory" looking install for the sensor. Frankly I'd like a really subtle, small, factory looking gauge and install. I can MacGyver, but want a tidy integration.

I really like Hubie's options. Anyone done anything really sano, or got any good advice on the subject?

Do Tell?

RZ Rob

Haven't we discussed this previously? Last time I presented photos of a couple small display devices that could be suitable:
http://www.arrowne.com/innov/in176/pics/nkk_issue_9__image_1_lr.jpg

This project would take a fair amount of electronic and mechanical engineering--not beyond the members here, but still not trivial.

RZ--what is your idea of "factory looking" and "sano"?

RZRob
06-12-2008, 12:20 AM
Haven't we discussed this previously?

what is your idea of "factory looking" and "sano"?I did a search and found a lot of posts and fed the most relevant one looking for any late info on the subject. Definitely good info. Thanks!

Sano in this case means ideally guage that looks like it could've came with the bike, or been a factory option: no zip ties, true [looking] brackets, integrated without cutting factory harness and no dangling wires or clamps. The more I see and ideas I hear, the better I can brainstorm, and get closest to what I want.

RZ Rob