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Old Aug 26, 2011, 05:12 AM
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JoseLuis28's Avatar
Colmenar Viejo - Madrid - Spain
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Question
the highest temperature in a gasoline engine , (heat cylinder & exhaust gas)

Change name of threadHello everybody,

I want to make an electronic circuit that it should disconnect the electronnic ignition if temperature is above the highest one.

Could someone tell me which is the highest temperature in order to avoid any damage ?

Thank you

Enjoy flying

Jose Luis
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Last edited by JoseLuis28; Sep 02, 2011 at 04:59 PM. Reason: Change name of thread
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Old Aug 26, 2011, 05:57 AM
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Canada, NS, Greenwood
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I could see this for electric motors, but there too many variables in IC engines for failure other than temperature. Wrist pin snap rings, stuck ring etc. You can have a catastrophic failure without high temperatures.
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Old Aug 26, 2011, 02:35 PM
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USA, CA, San Diego
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Quote:
Originally Posted by ACS tech View Post
I could see this for electric motors, but there too many variables in IC engines for failure other than temperature. Wrist pin snap rings, stuck ring etc. You can have a catastrophic failure without high temperatures.
You missed the point entirely. He's looking to create a circuit the kills the ignition to prevent heat damage. This would potentially remove one of those variables. You're right, not all failures cause excessive heat but excessive heat can/will cause various failures (stuck ring, siezed piston, bearing failure) so while it wouldn't be a catch-all solution, it may prevent some failures.

OP, A nice feature would be some sort of audible alarm thar sounds a few degrees before the ignition is killed.
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Old Aug 26, 2011, 03:06 PM
TigreJohn
United States, CA, Corona
Joined Aug 2008
996 Posts
You may want to start searching snowmobile sites. Umpteen years ago I had a racing snowmobile that had temperature sensors that ran gauges. Basically the sensor was a thick sparkplug gasket which was wired to a gauge box. I think at one point in time it was an OEM option on one of the brands.

The only other non-water temp sensor available for any gas motor was a exhaust gas temp sensor which indicated if your mixture was rich or lean. I wonder if todays auto oxygen sensors in the exhaust pipe would be similar or the same as.
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Old Aug 26, 2011, 03:35 PM
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The temperatures can vary depending on the engine brand and type, how much cooling it gets from the fins and air flow and so on.
But the temps seem to be around 200 degrees Farenheit give or take a little.
ref: http://www.troybuiltmodels.com/ns/in...g_easier.shtml
So if you set your temperature cutoff to 220 degrees F, that would be a good starting point.
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Old Aug 26, 2011, 04:29 PM
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You don't need to build one. Nobody does this however.
http://www.venom-group.com/itemdesc.asp?ic=0605

The answer is proper cooling and monitoring temperatures. Many carry an onboard temperature sensor that records peak temps and if things get hot, you make adjustments to your baffling to improve cooling.

http://prme.nl/forum/viewforum.php?f...23912c2c33cef5
http://www.venom-group.com/itemdesc.asp?ic=0602

Gas engines can handle more than than 220°F without damage. Try to keep it under 250°F. Even higher peak temperatures can be acceptable.

Greg
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Old Aug 26, 2011, 04:50 PM
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Enhaust gas temperatures will be the highest and from 600 to 1000 degrees F. Diesel tractors use pyrometers to monitor exhaust gas temperatures in the turbos to get a feel for how hard the engine is working. Once you start pushing past 900 F on the pyrometer engine life is shortned.

A K type or T type thermocouple should work for your application. You will need a cold junction compensated thermocouple to digital converter for your microcontroller such as a Maxim MAX31855.

http://www.maxim-ic.com/datasheet/index.mvp/id/7273

I have used the MAX6674/MAX6675 before with good results.

Jason
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Old Aug 27, 2011, 05:03 PM
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Sorry
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Old Aug 27, 2011, 05:05 PM
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Oh no I lost my answer.

Ok doesn't matter, as on monday, I'll be at home , I'll reply that day or next tuesday.

Thanks a lot everyone , very good info to start.

Enjoy flying

Jose Luis
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Old Aug 30, 2011, 04:16 PM
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Hi, just at home, easy to write with keyboard, not mobile phone as before.

The idea is to design an electronic CDI , and this circuit will be an auxiliary one, only to prevent damage due higher temperatures. If every engineīs model has its ideal temperature cut off, I have to ask the manufacturers about it, of course I need that info , I must indicate it in manual and user could program the right cut off temperature, also could disconnect the preventive circuit.

Jason, that Maxim thermocouples looks very good, 14 bits resolution is excellent, maybe Iīll use it, but my initial idea was that a PIC including A/C converter with 8 bits resolution would be good for my application.

Anyway, I have to study every detail, every component carefully.

Any idea, any circuit to prevent damage, please tell me.

Thanks

Enjoy flying

Jose Luis

,
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Old Aug 30, 2011, 04:21 PM
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Where would you measure/monitor the temperature?
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Old Aug 30, 2011, 05:25 PM
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Colmenar Viejo - Madrid - Spain
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I donīt need it. My circuit must be simple, cheap to build, adding few components and using the PIC of CDI circuit.

Of course, I have to use precision tester in order to know
real temperature

JOse Luis
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Last edited by JoseLuis28; Sep 01, 2011 at 05:03 AM. Reason: My stupid reply
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Old Aug 30, 2011, 09:46 PM
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When I worked on snowmobile engines back in the 70s, the operating temp was between 250 and 300F with a thermocouple under the sparkplug. 350 was getting dangerous.

Gord.
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Old Aug 30, 2011, 09:48 PM
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Old Sep 01, 2011, 05:24 AM
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I think I must give some option between 220F to 350F.

Using the info you are telling me, I think it would be a good range.

Flypaper2, you install the thermocouple under the sparkplug in order to aviod aircooling refreshing the sensor, donīt you ?

Now I have to ask manufacturers about cut off temperature, and "ignition advance curve". I donīt know if in english it would be its technnical name.

Also, I have to open new thread.

Thanks

Enjoy flying

Jose Luis
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