My new vdo head temp gage reads high by 50 - 60 degrees. Could it be the way it I bent the wire when putting the sensor on plug #3?

I got back from a ride and gage shows 300, ir sensor showed ~ 245

Did I get a bad sensor/gage or is typical?

When I get in the car on a cool day about 50deg the gage read half way between 100-150 deg before I start the car for the 1st time that day. Is that a bad gage or a bad sensor or something that I should live with. Do I subtrack about 60 degrees from my readings while driving. at 3000 RPMs i'm seeing almost 400 deg.

Don't you have to subtract the ambient air temp from the reading ?

Yes. VDO CHT's are not accurate unless it's 70F outside or somewhere around there. Other than that you have to do some math. You should get a temperature compensated gauge. This will be accurate at any ambient temp.

I won't recommend a certain model as some people don't like the one I use (Jim Hoyland).

Who can tell me which sensor and gage I should use?

Where do you ambient, is that at tha gage or is there a point on the wire?

Do I have a bad sensor, a bad gage or is this normal and I just have to live with it?

I did check with an IR sensor which confirms that I'm reading high by about 60deg.

I bought VDO gauges because they were inexpensive, looked good, and I would be looking for relative temperature values. For competition one might want absolute values.

My oil temp gauge reads the same as IR temps on the sump and oil filter just after shut down. So that one checks out. The oil pressure reads what it should on a normal engine so I assume its accurate without verifying it on a mechanical gauge.

CHT varies around 325 in this cold weather and 350 in the hot summer weather. After shutdown I pull the #3 plug wire and get several readings aroung the spark plug. It usually is nowhere near the CHT readings by more than 50 degrees, lets say about 250 degrees, but it really varies. I suspect you need a perpendicular flat surface to get a really accurate IR reading and flashing that IR around blind off the cooling fins may in itself not be accurate. A reading off the steel valve covers also shows a cooler temp but they are insulated from the heads by a cork gasket. And I suspect the exhaust side of the head will be a different temp than the intake side...

Given all that, I assumed my HAM rebuilt heads are performing flawlessly for my normal driving and take the CHT reading as a relative value. The indicated temp will vary a little depending on the terrain and how hard I drive but regardless of the number, if it ever starts to point way off from where it usually is I'll start looking for a cause.

That's my story...

PS Even tho my thermostat works, the oil takes forever to get even close to 180 degreees in cold - below 40 - weather. In the 100 degree summer weather it slowly climbs up to 240. Gosh, the things we didn't worry about with just a green and a red idiot light!

Before you start your car for the day and the weather is cool about 50-60deg does you gage read >100deg? Mine is half way between the 100 and 150 mark when connected to the sensor before I even start the car on a cold morning.

this supplier has been recommended by some.

http://www.dakotadigital.com/index.cfm/pag...prod/prd347.htm

it is supposed to compensate for tempature.

[Before you start your car for the day and the weather is cool about 50-60deg does you gage read >100deg? Mine is half way between the 100 and 150 mark when connected to the sensor before I even start the car on a cold morning.
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At rest, the gauge reads just off 100 degrees but I don't believe that is reading ambient temperature. I assume most gauges read in a certain range and anything outside that range will be irrelevant. The needle is in the same position when it is below freezing here as it is today at about 60 degrees. Also the gauge reads based on resistance to current flow. Resistance changes as the temperature changes. The gauge reads the resultant change in current.

At least I think that's right. If anybody wants to jump in here to clarify...

When I got the gauge I thought about dropping the sender in hot water but then I would need to hook up a battery...too much to mess with but it would be a good test.