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68Bug-lite
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Joined: July 31, 2005
Posts: 1087
Location: Tustin, CA
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 Posted: Sun Oct 12, 2008 7:58 am Post subject: VWarning CHT heat sensor gizmo... |
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VWarning sensor...
This is an old school device that is secured under the #3 cylinder shroud screw and piggybacks onto the oil pressure switch,(like the Berg temp stick).
Now I know nothing is going to come close to a real CHT sensor with full instrumentation, so please dont get all over me about this.
The fact is, I'm convinced that this little bugger has saved my bacon many times over.
It grounds/triggers your dash light when it senses 215 degrees at it's mount point.
My question for you thermodynamic guys out there, (Mr Raby?) is if that temp sounds about right?
Heres a qoute from the instructions...
" At what temperature does the VWarning activate?This is not an easy question. VW thermodynamics are extremely complicated. During normal operation (warm up, various loads, speeds, shutdown, restart) different areas heat and cool in a complex interrelationship. Cylinder head temps will actually rise in one spot and fall in another at the same time! Also there may be dramatic temperature differences between places only inches apart. For example, when the spark plug seating area is at about 435 degree (too hot for long term engine health) the VWarning mount site is at the trigger point of 215 degrees farenheit..."
So what say you experts? Is my faith misplaced in this thing or what?
Peace, Greg |
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krusher
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Joined: September 24, 2002
Posts: 7662
Location: europe
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| Posted: Sun Oct 12, 2008 11:07 am Post subject: |
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If when this device lights up the idiot light you then know the head at plug is up to 435 then its of use, I personally prefer to watch my cht (dakota digital gauge) and stop it getting much above 400 though.
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Jake Raby
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Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Sun Oct 12, 2008 4:04 pm Post subject: |
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Where the sensor is mounted will have everything to do with it's effectiveness.. Head temps vary greatly from one portion of the head to another.
I have thought about making a more advanced version of this and have a member of our team that could do it, but during testing we'd have to find the best location for sensor placement. This would be a compromise of sensor effectiveness, reaction speed and sensor longevity.
Where have you had this sensor mounted??
Using a temperature compensated gauge to calibrate the sensor for the point where it illuminates would be important... 435 is way too hot, at that point damage has already been done... 215 is way too low, when mounted anywhere close to the hottest portion of the head.
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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68Bug-lite
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Joined: July 31, 2005
Posts: 1087
Location: Tustin, CA
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| Posted: Sun Oct 12, 2008 6:55 pm Post subject: |
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| Jake Raby wrote: |
Where the sensor is mounted will have everything to do with it's effectiveness..
Where have you had this sensor mounted? |
I have the sensor pinned under the sheet metal screw on the cylinder head cooling tin nearest the # 3 spark plug, (as suggested in the instructions).Thats about what, a couple of inches from the sparkplug?
Interesting to watch the light come on after a brief shut down, and then to watch it flicker out after about a minute on the road. Theres times I'll see the light come on under load climbing a hill and then go out after I've crested it. Hot summer days on the freeway with passengers, I've seen It come on; once I reduced speed it would flicker out.
May be a lame way of keeping tabs on my head temps, but sure makes it simplistic and is all I really need to know -(Is it too hot?).
Assuming this thing is even accurately calibrated and such, I wonder if 215 degrees at that location would be an accurate indicator of potential trouble?
Thanks for replying Mr. Raby.
Peace, Greg |
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Jake Raby
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Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Sun Oct 12, 2008 7:02 pm Post subject: |
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1" away from the plug can be 100+ degrees cooler than at the plug, especially in the fins..
I'd quantify at what temp the head was at under the plug when that sucker lit up..
Not knowing exactly what temp you are at means the gizmo is giving unknown information and thats worse than none at all.
If the head is 215 there, who knows what the temp is under the plug.
it is a cool device, IF you know what the core temp is under the plug when it lights up.
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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Jody '71
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Joined: July 16, 2005
Posts: 2842
Location: Manassas VA
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| Posted: Mon Oct 13, 2008 9:22 am Post subject: |
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Jake,
I've given this some long thought about appropriate CHT readings, especially with us that still use the Type 1 engines, and this may apply to the Type 4's as well. Everyone knows how important the thermo coupler ring must seat between the plug and the head. If not absoulutey perfect, then problems arise.
Why not create a crush ring washer/thermo-coupling spark plug that elimintates all the installation problems???? Can't they be custom created by your establishment depending on what type plug is to be used? Would this be cost prohibitive in lieu of a profit return?
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Jake Raby
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Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Mon Oct 13, 2008 9:31 am Post subject: |
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The cost of such a device would be astronomical and no one would touch them for less than a quantity of 10,000 units.
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Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell" |
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