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#1
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VDO head temp in a bus
Now that I've done some research here on ow the VDO cylinder head temp
gauge works I wonder if I did a bad thing. I have a 1971 Bay window bus with a sunroof and that means it has a belly pan which makes it almost impossible to run wires along the frame, so I have run all of them inside the interior down the left side and of course that left me about three feet short on the supplied lead length for the gauge. Thinking I was doing an ok thing I just spliced the needed length and checked polarity and hooked it up to the gauge. Then I found it too difficult to reach into the #3 plug hole so I attatced the sensor to the intake bolt, well that spot is of little use I now know but the gauge needle never moved at all. Thanks for your input. |
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#2
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VDO head temp in a bus
"Volksrod" > wrote in message
oups.com... > > Now that I've done some research here on ow the VDO cylinder head temp > gauge works I wonder if I did a bad thing. > I have a 1971 Bay window bus with a sunroof and that means it has a > belly pan which makes it almost impossible to run wires along the > frame, so I have run all of them inside the interior down the left side > and of course that left me about three feet short on the supplied lead > length for the gauge. > Thinking I was doing an ok thing I just spliced the needed length and > checked polarity and hooked it up to the gauge. > Then I found it too difficult to reach into the #3 plug hole so I > attatced the sensor to the intake bolt, well that spot is of little use > I now know but the gauge needle never moved at all. > Thanks for your input. > > ........The wire from the gauge to the connection with the sensor lead can be lengthened I would think. The voltage is low enough so that it shouldn't matter. The intake bolt location for the sensor is no good though. Under the #3 spark plug is where you need to put it. Just bend it so the ring shaped part is at an angle with the shank portion so that it'll fit down under the plug. .......I don't have much faith in mine. For a long time, I thought that my head temps were way too high until I checked with an IR temp gauge and discovered that the VDO was reading between 75 and 100 degrees F. too high in the 350+ range. Oddly enough, the IR gauge and the VDO agreed at 250 deg. You'd think that VDO would have calibrated them at about 400 instead of 250. |
#3
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VDO head temp in a bus
Yeah...they're an odd device to say the least...Actually because it's a
'thermal coupling' device..the temps vary with the ambient temp..opposite of what you'd think...most are 'zeroed' for proper temp at 68F....anything lower..and it appears to be running hotter...higher ambient temp makes it appear cooler!!..Very strange...wish they could develop a more precise, economical gauge. Pat Tim Rogers wrote: > "Volksrod" > wrote in message > oups.com... > > > > Now that I've done some research here on ow the VDO cylinder head temp > > gauge works I wonder if I did a bad thing. > > I have a 1971 Bay window bus with a sunroof and that means it has a > > belly pan which makes it almost impossible to run wires along the > > frame, so I have run all of them inside the interior down the left side > > and of course that left me about three feet short on the supplied lead > > length for the gauge. > > Thinking I was doing an ok thing I just spliced the needed length and > > checked polarity and hooked it up to the gauge. > > Then I found it too difficult to reach into the #3 plug hole so I > > attatced the sensor to the intake bolt, well that spot is of little use > > I now know but the gauge needle never moved at all. > > Thanks for your input. > > > > > > .......The wire from the gauge to the connection with the sensor lead can be > lengthened I would think. The voltage is low enough so that it shouldn't > matter. The intake bolt location for the sensor is no good though. Under the > #3 spark plug is where you need to put it. Just bend it so the ring shaped > part is at an angle with the shank portion so that it'll fit down under the > plug. > > ......I don't have much faith in mine. For a long time, I thought that my > head temps were way too high until I checked with an IR temp gauge and > discovered that the VDO was reading between 75 and 100 degrees F. too high > in the 350+ range. Oddly enough, the IR gauge and the VDO agreed at 250 deg. > You'd think that VDO would have calibrated them at about 400 instead of 250. |
#4
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VDO head temp in a bus
"pat" > wrote in
oups.com: > Yeah...they're an odd device to say the least...Actually because it's > a 'thermal coupling' device..the temps vary with the ambient > temp..opposite of what you'd think...most are 'zeroed' for proper temp > at 68F....anything lower..and it appears to be running hotter...higher > ambient temp makes it appear cooler!!..Very strange...wish they could > develop a more precise, economical gauge. Pat > Tim Rogers wrote: >> "Volksrod" > wrote in message >> oups.com... >> > >> > Now that I've done some research here on ow the VDO cylinder head >> > temp gauge works I wonder if I did a bad thing. >> > I have a 1971 Bay window bus with a sunroof and that means it has a >> > belly pan which makes it almost impossible to run wires along the >> > frame, so I have run all of them inside the interior down the left >> > side and of course that left me about three feet short on the >> > supplied lead length for the gauge. >> > Thinking I was doing an ok thing I just spliced the needed length >> > and checked polarity and hooked it up to the gauge. >> > Then I found it too difficult to reach into the #3 plug hole so I >> > attatced the sensor to the intake bolt, well that spot is of little >> > use I now know but the gauge needle never moved at all. >> > Thanks for your input. >> > >> > >> >> .......The wire from the gauge to the connection with the sensor lead >> can be lengthened I would think. The voltage is low enough so that it >> shouldn't matter. The intake bolt location for the sensor is no good >> though. Under the #3 spark plug is where you need to put it. Just >> bend it so the ring shaped part is at an angle with the shank portion >> so that it'll fit down under the plug. >> >> ......I don't have much faith in mine. For a long time, I thought >> that my head temps were way too high until I checked with an IR temp >> gauge and discovered that the VDO was reading between 75 and 100 >> degrees F. too high in the 350+ range. Oddly enough, the IR gauge and >> the VDO agreed at 250 deg. You'd think that VDO would have calibrated >> them at about 400 instead of 250. > > They're just a novelty item unless you run either a dually on a centrally located head bolt on each head, or a quad, preferably using the sparkplug sensors. When I bought my quad, it was about the same price as two VDO singles, but came with 48" stainless steel wrapped leads. With the quad gauge, you can, at a glance, see if any cylinder is out of range of the others. Ambient temp doesn't matter because it affects all 4 equally and the actual numbers mean little to nothing. Typical of my '79 bus, #1 would start out higher and the temp rise would be quicker than #2. Once up to operating range and pulling hard, they would all fall exactly in line with each other. Cooling down went the same way. I actually honed #3 cylinder an extra thousandth and it ran very close to #1. Prior to that, it ran 50 degrees hotter all the time. Before the quad gauge, I ran two VDO senders: one on #1 & one on #3. I had a single gauge and used a toggle switch. I usually monitored #3. With a brand new motor, it was #2 that the injector backed out from and seized up. If I had been running a dual gauge I might have seen the right side running hotter. With the quad gauge I definitely would have seen it. I highly recommend the quad CHT gauges. For FI engines, a CB mixture gauge with the oxy sensor in the #3 header runner (between the exhaust port and the heat exchanger) along with a quad CHT gauge will tell you everything you nedd to know to actually save your engine as they will indicate what is going wrong in time to avoid calamity, if you're paying any kind of attention. I was always anti- oil temp gauge, but have since figured out that the actual failure of my last T4 motor would have been indicated by an oil temp gauge but was not caught by the CHT / Mix combo. The failure was in the bottom end (where T4's are never supposed to fail!) When the oil temp started to go out of normal range, I would have consulted the CHT and Mix gauges and determined that I had either a main bearing or rod bearing heating up. I probably could not have saved it at that time, but would have at least had something rebuildable! Put your single VDO gauge in a pan of water on the stove. Watch the needle on the gauge rise as the water reaches boiling. Now point a hair dryer at the connector end of the sensor wire (not the sensor end which is in the water!) As you heat the connector end, the reading on the gauge drops. When in actual use, if your running on hot blacktop and your engine is running hotter than it should, it is very likely that your single VDO CHT gauge will have a reading lower than normal. With the 48" leads on the Westach Quad gauge (from Aircraft Spruce) I was able to put the connector ends on top of my tranny. I also placed a sensor for a thermometer there. The Westach gauge is calibrated for a 75 degree cabin temperature. That means that when the connectors were at 75 degrees, the gauge was calibrated to read correctly. If the temp on top of the tranny was 100 degrees, the gauge would read 25 degrees lower than actual temp. If the temp on top of the tranny was 50 degrees, the reading would be 25 degrees higher than actual. The only times it was drastically beyond the range of +/- 25 was when parked. In summer, the tranny case absorbed heat from the engine and at times the top of the tranny was over 200 degrees when not moving. Likewise, in winter, I saw the thermometer in the teens more than once, but once underway, it warmed up to the 50/60 range and likewise in summer, cooled to the 70/80 range. The important thing to remember is that all four readings are affected equally. You still look for one running out-of-range. Besides that, where I drive, the ambient temp is almost never above 80 or below 50 for very long at a time. It was interesting to see the actual temp trends, but of absolutely no value in monitoring safe engine operation. Freeway operation saw temps rise and fall more than 200 degrees in half a mile as hills were climbed and crested. As important as the proper gauges is the ability to make on-the-fly adjustments. Adding a slide-type adjustable resistor to the FI CHT sensor enabled me to enrichen the mixture as temps increased and when hard pulls were encountered. It also enabled speeds of over 100mph - coupled with a dashboard mounted momentary switch wired into the cold start injector, it enabled reaching that speed rather quickly! (Not as quickly or smoothly or effortlessly as the Subey though!) -- -BaH Dave Pearson 79 Bus w/ Subey 2.2 74 Bus Project |
#5
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VDO head temp in a bus
Here is an interesting write-up on VDO gauges. Scroll down to the cyl head temp section:
http://www.ratwell.com/technical/VDOGauges.html "Tim Rogers" > wrote in message ... > "Volksrod" > wrote in message > oups.com... > > > > Now that I've done some research here on ow the VDO cylinder head temp > > gauge works I wonder if I did a bad thing. > > I have a 1971 Bay window bus with a sunroof and that means it has a > > belly pan which makes it almost impossible to run wires along the > > frame, so I have run all of them inside the interior down the left side > > and of course that left me about three feet short on the supplied lead > > length for the gauge. > > Thinking I was doing an ok thing I just spliced the needed length and > > checked polarity and hooked it up to the gauge. > > Then I found it too difficult to reach into the #3 plug hole so I > > attatced the sensor to the intake bolt, well that spot is of little use > > I now know but the gauge needle never moved at all. > > Thanks for your input. > > > > > > .......The wire from the gauge to the connection with the sensor lead can be > lengthened I would think. The voltage is low enough so that it shouldn't > matter. The intake bolt location for the sensor is no good though. Under the > #3 spark plug is where you need to put it. Just bend it so the ring shaped > part is at an angle with the shank portion so that it'll fit down under the > plug. > > ......I don't have much faith in mine. For a long time, I thought that my > head temps were way too high until I checked with an IR temp gauge and > discovered that the VDO was reading between 75 and 100 degrees F. too high > in the 350+ range. Oddly enough, the IR gauge and the VDO agreed at 250 deg. > You'd think that VDO would have calibrated them at about 400 instead of 250. > > |
#6
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VDO head temp in a bus
"Karl" > wrote in message
m... > > Here is an interesting write-up on VDO gauges. Scroll down to the cyl head temp section: > http://www.ratwell.com/technical/VDOGauges.html > > .......Thanks for that link Karl. I'm going to buy one of those Dakota Digital head temp gauges. |
#7
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VDO head temp in a bus
"Tim Rogers" > wrote in message
... > "Karl" > wrote in message > m... > > > > Here is an interesting write-up on VDO gauges. Scroll down to the cyl head > temp section: > > http://www.ratwell.com/technical/VDOGauges.html > > > > > > ......Thanks for that link Karl. I'm going to buy one of those Dakota > Digital head temp gauges. > > ...........I just placed my order today. They have a special sensor lead for acvws that is 18 feet long and has the correct 14mm ring for sitting under the spark plug. Its number is SEN-11-8 but doesn't come up on their website so I had to place my order over the telephone. My total expense is about $160 which includes about $25 for 2nd day UPS from South Dakota to NY. ........It's going to be great to have an accurate cylinder head temp at last to look at while driving. |
#8
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VDO head temp in a bus
Thanks to all for your input.
I will try hooking up the CHT gauge again today. As advised I will use them for trend rather than actual. Plus they do fill up an unsightly hole the PO left in the dash. |
#9
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VDO head temp in a bus
"Tim Rogers" > wrote in
: > "Tim Rogers" > wrote in message > ... >> "Karl" > wrote in message >> m... >> > >> > Here is an interesting write-up on VDO gauges. Scroll down to the >> > cyl > head >> temp section: >> > http://www.ratwell.com/technical/VDOGauges.html >> > >> > >> >> ......Thanks for that link Karl. I'm going to buy one of those Dakota >> Digital head temp gauges. >> >> > > ..........I just placed my order today. They have a special sensor > lead for acvws that is 18 feet long and has the correct 14mm ring for > sitting under the spark plug. Its number is SEN-11-8 but doesn't come > up on their website so I had to place my order over the telephone. My > total expense is about $160 which includes about $25 for 2nd day UPS > from South Dakota to NY. > > .......It's going to be great to have an accurate cylinder head temp > at last to look at while driving. > > Huh! I guess the simple basic lack of understanding runs much deeper than I possibly could have imagined. I wish you the luck that I didn't have: The luck that the cylinder you place your monitor on is the one out of 4 that fails! For that much $$ you could have had a system that actually works. Ah, well. I guess it's time to go back into hibernation. -- -BaH Dave Pearson 79 Bus w/ Subey 2.2 74 Bus Project |
#10
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VDO head temp in a bus
"Busahaulic" > wrote in message
... > > Huh! I guess the simple basic lack of understanding runs much deeper than > I possibly could have imagined. I wish you the luck that I didn't have: > The luck that the cylinder you place your monitor on is the one out of 4 > that fails! For that much $$ you could have had a system that actually > works. Ah, well. I guess it's time to go back into hibernation. > > ........Sorry Dave, but my brain could never process four Westach CHT readings while talking on the cellphone and eating a Big Mac and playing with the adjustment on that dash mounted potentiometer and lastly trying not to wander across the centerline into oncoming traffic..<g>...... My Berg 1679 has about 20K miles on it now and still has no changes in exhaust valve length during adjustment/checking so I'm not too worried about whether 1, 2 & 4 are acting up for now. This Dakota Digital CHT gauge really does look like a good upgrade over the VDO unit and I'll report back on how it's working maybe next week after I get it installed this weekend. |
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