Durable Small Temp Sensor Wanted

SCCA_Racer

I am working on my senior college project and I am in need of a temperature sensor which is small enough to fit into a 1/4" hole, but it need to be durable enough to handle high heat and air flow. The use is to monitor air flow at different point inside an air intake tube on a car. I also want to use it to measure the heat under the hood in various locations. The accuracy needs to only be +- 1 degree but I want to be able to take sample data every 0.1 sec especially while in the air intake stream. Let me know what sensor you guys would recommend for using with my Basic Stamp or if I need to upgrade to a different unit.
Thanks for the help.

Mike Green

What's "high heat"?

The National Semiconductor LM34 is good from -50F to 300F and has an output voltage proportional to the temperature. The BS2 doesn't have a built-in analog to digital converter (ADC), but works nicely with a variety of ADCs including the MCP3202 that Parallax sells. There's sample code and documentation on Parallax's webstore page for the MCP3202.

If you are willing to change to a BS2p/pe/px Stamp, you could use a 1-Wire temperature sensor from Maxim/Dallas like the DS18B20 which is good from -55C to +125C and does its own ADC internally.

Both are available in TO-92 packages which should fit in a 1/4" hole

SCCA_Racer

I am not 100% sure on the heat range. Nobody knows how hot it gets under the hood but I think 300F should be good until I get around the exhaust side of the motor. I think the intake air should be well below 300F, so it should work fine there.
Thanks for the recommendation and I will check into those.

Kevin Wood

Years ago a friend of mine was big time into customizing his truck, and one day we were installing a new exhaust header. When we pulled off the old one, out fell a 10" flat head screwdriver that had no handle.

Apparently it had slid in there somehow when he had done some previous work, and was sitting in the pipe where it bent to the main pipe at the bottom of the engine. The plastic was completely melted away!

So, yeah, engine exhaust gets hot.

Franklin

For the exhaust you will need thermocouples or you might be able to modify the output of a standard EGT sensor.

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- Stephen

SCCA_Racer

I am not looking to measure the exhaust temperature for this project, but I am looking at measuring the air in the engine bay while the car is traveling at race·track speeds to find the lowest temperature area to mount my air cleaner. I also want to see how much the temperature changes at the·intake manifold in relation to changes in the air coming into the air filter.

mikediv

SCCA you are not saying what type of car/engine but I have a very basic stock oval track race car its basically a mote carlo frame some of the other guys use fords but I to had measured the under hood car temp and I was very surprised I am sure you have to follow rules just like we do for venting and construction of the race car. mine is just a stock car
Chevy 350 sheet metal body panels and plastic hood the engine makes around 700HP top speed of around 180 MPH on top of manifold I have seen temps of over 300 F at speed under 90MPH 275 F at over 100MPH and by the exhaust manifolds about 4 inches away right near the spark plugs I have seen temps of over 600 F now I know why I melt so many spark plug wires
I have EGT's for the exhaust 6 inches from heads in pipes I regularly see 1375 F we have to use radiator shrouds so the air just flows over the radiator and then down under the engine
I have seen my poly hood actually deform from the heat when we are bunched up in a group I hope that helps . Depending on where you are going to mount your Temp Sensor under your hood you might end up needing more temp range than you think .. I also wanted to know what the carb temperature is under my Holly 1050D we can not use spacers I routinely see 240F idle is much higher

SCCA_Racer

Mike,
I did not realize I was not posting my signature.
The car is a 1991 Mazda Miata. The class I am building it for is SCCA Spec Miata. As far as I know no one ever did a study on the engine bay temps like I will. Thanks for the info on what your engine temp under hood.
The car will see outside temperatures as high as about 110F and as low as about 40F. The 300F sensor might be a good start but like you said I may have to go up from there.

Capt. Quirk

Seems like you really need a more complete data acquisition system to measure and then verify performance. A Propeller, with 4 EGT's, Barometer, Humidity, Temp, Crankshaft position, and a 3 axis accelerometer be a good start. Open ended thermocouples for your exhaust and air temp. Closed ended for coolant and oil temps. You could use a smaller diameter wire connected to extension wire for the air temps. With this set-up you could measure air density and calculate density-altitude at your air box. With the CPS, Accelerometer, Density Altitude, and important car weight data you could calculate engine acceleration, torque, and horsepower anywhere on the track to confirm your findings.

Mikediv's post demonstrates your project so clearly, and how temps near your intake could torpedo your horsepower and jack-up the fuel air ratio.

After reading your rules, they would allow Water Wetter from Redline instead of coolant. http://www.redlineoil.com/product.aspx?pid=74&pcid=10 Race Gas is a curious topic (If they do not provide you with a spec fuel). As air temps go up and air density drops, the EFI may go beyond it's normal map, and run rich as a result. And at what point does the ignition go into full retard for a given load. How far will the engine rev past peak horsepower, and how fast does engine accelleration fall off. Through testing you could develop a set of "ideal parameters".

With Ideal Parameters, you could discover just how much octane really necessary. Unleaded fuel with increased octane only (no oxygenation), will provide less horsepower. You could create your own mixture of pump gas mixed with race gas that best suits your car and driving style.

Good Luck

Bill M.