Ok, so First, Hello everybody :)
I've been lurking about for a while unregistered and I'm seriously considering an VEMS WBo2 for my Bus
I've a type 2 VW camper with a 2017cc carburated (Dual twin Dellorto DRLA 36's but maybe going bigger) type 1 aircooled engine that I need to keep an eye on to make sure it doesn't melt and to do that and make sure I get the best possible MPG, i'm going to go o2. Innovate motorsports LC-1 caught my eye but it doesn't do what I want it to. The VEMS unit nearly does and there are a couple of points I want to clear up before I stump up the cash.
My questions are several fold and begin with the cable.
I understand that the o2 sensor has to be where it has to be and that the Vems cable can't be altered in any way or it won't work properly. The only problem is that my exhaust is 13 feet away and 2 feet below my dash so I need a cable that is 18 feet long as a minimum.
How can the cable be extended especially without altering the accuracy of the thermocouple input to the gauge?
I am currently assuming that the cable is about 3 feet long and that I will have to make up the missing 15 feet or so out of suitable cable with suitable connectors. What is the gauge of cable that I will need to ensure there is no signal degradation and what are the part numbers of the connectors that I'm going to have to get?
Secondly, as my bus is aircooled, the exhaust gas temperature thermocouple is not as important as taking a reading of the cylinder head temperature on number 3 cylinder. it seems that the EGT sensor is a simple K thermocouple so switching this to a spark plug ring is not a difficult task, but the instructions do not clear up where the thermocouple connects to. Does it connect into the back of the gauge? If not, where. And if you don't order the EGT probe thermocouple, can you still connect a K thermocouple to it or is that part disabled?
In aircooled VW's, knowing what the exhaust gas temperature is won't be an indicator of your engines efficiency so much as CHT. VW heads are aluminium so they start to soften at around 400*C and melt not long afterwards. a quick way to a broken motor.
Thirdly, i'm also keen to carry out some datalogging on my laptop while i'm dailing in my carbs, but as it's an old technology vehicle, it runs from a bosch blue coil from brazil. I understand that the datalogging port is in the back of the gauge, but how would I go about collecting RPM data from the coil. I have a tachometer, but it's only got positive, earth and coil signal input as it's an aftermarket Elliot Design unit. No ECU output if you like.
The other thing I am keen to know is that, when my carbs are dialed in and the o2 has served it's main purpose, i'm going to disconnect the o2 and plug the boss and just use the system as a cold junction compensated CHT gauge. If I disconnect the o2 and essentially terminate that part of the systems function, will the gauge continue to display anything or can it be selectively turned off to preserve the display and internal gauge hardware, or will I have to almost permanently have the o2 running so as not to fry the thing?
Your help is greatly appreciated as the LC-1 just won't cut the mustard
Cheers
Marv
Hi Marv,
I've installed a VEMS wideband in a dyno cell with a 5meter extension without problems.
The rest of your questions are pretty straightforward, yes you can do pretty much all you want, but I'd leave the wideband in place.
YHPMBTW
Excellent :D
OK, now to the technical Q's
How do I extend it exactly? The connector at the end of the o2 cable will need a counterpart to extend it and then another one to sit in the back of the gauge. Where do I get the connectors and cable terminals from?
The o2 sensor heating element draws a current which I assume is supposed to be from a switched fused live connection. Given the geometry of my bus (engine in back, fuse box in front) running a cable from the battery to the fuse box, then from the fuse box back to the sensor is 26 feet of cable. My intention is to take a signal from the switched live on the coil, through a relay straight from the battery but i'll need to put a fuse inline. What is the current draw on the sensor and what is your recommended fuse size?
For the remaining connections, I'm going to use a length of multicore cable, but do you recommend shielded cable for the extension and what sort of shielding would be appropriate as I don't think the cable I have available is shielded, just insulated. What sort of signal voltages are likely to be seen through the cable so that I can make sure that the gauge of cable is sufficient?
How can I take an RPM signal from the coil without frying the electronics in the gauge. WHat is the max input signal strength so I can check my coil is not going to pump out voltages of gauge death
Where does the thermocouple connect to?
Cheers for the input
Marv
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PM
Excellent :D
OK, now to the technical Q's
:'( ;)
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMHow do I extend it exactly? The connector at the end of the o2 cable will need a counterpart to extend it and then another one to sit in the back of the gauge. Where do I get the connectors and cable terminals from?
In the one's I've extended I've spliced in the extra wire length.
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMThe o2 sensor heating element draws a current which I assume is supposed to be from a switched fused live connection. Given the geometry of my bus (engine in back, fuse box in front) running a cable from the battery to the fuse box, then from the fuse box back to the sensor is 26 feet of cable. My intention is to take a signal from the switched live on the coil, through a relay straight from the battery but i'll need to put a fuse inline. What is the current draw on the sensor and what is your recommended fuse size?
5Amps maximum
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMFor the remaining connections, I'm going to use a length of multicore cable, but do you recommend shielded cable for the extension and what sort of shielding would be appropriate as I don't think the cable I have available is shielded, just insulated. What sort of signal voltages are likely to be seen through the cable so that I can make sure that the gauge of cable is sufficient?
I've never used shielded I don't see that it would hurt as long as the sheild is grounded at only one end, most of the voltages are low current 5v, although the heater will draw 3A @Vbatt as it starts up.
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMHow can I take an RPM signal from the coil without frying the electronics in the gauge. WHat is the max input signal strength so I can check my coil is not going to pump out voltages of gauge death
A suitable Zener diode should ensure the voltage isnt too high, there is one inside the gauge, but an additional external one wouldnt be a bad idea.
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMWhere does the thermocouple connect to?
Theres a length of k-type wire on the back of the gauge, do you have a specific head temp sensor that you're planning on using?
Quote from: [email protected] on April 06, 2009, 05:19:36 PM
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PM
Excellent :D
OK, now to the technical Q's
:'( ;)
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMHow do I extend it exactly? The connector at the end of the o2 cable will need a counterpart to extend it and then another one to sit in the back of the gauge. Where do I get the connectors and cable terminals from?
In the one's I've extended I've spliced in the extra wire length.
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMThe o2 sensor heating element draws a current which I assume is supposed to be from a switched fused live connection. Given the geometry of my bus (engine in back, fuse box in front) running a cable from the battery to the fuse box, then from the fuse box back to the sensor is 26 feet of cable. My intention is to take a signal from the switched live on the coil, through a relay straight from the battery but i'll need to put a fuse inline. What is the current draw on the sensor and what is your recommended fuse size?
5Amps maximum
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMFor the remaining connections, I'm going to use a length of multicore cable, but do you recommend shielded cable for the extension and what sort of shielding would be appropriate as I don't think the cable I have available is shielded, just insulated. What sort of signal voltages are likely to be seen through the cable so that I can make sure that the gauge of cable is sufficient?
I've never used shielded I don't see that it would hurt as long as the sheild is grounded at only one end, most of the voltages are low current 5v, although the heater will draw 3A @Vbatt as it starts up.
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMHow can I take an RPM signal from the coil without frying the electronics in the gauge. WHat is the max input signal strength so I can check my coil is not going to pump out voltages of gauge death
A suitable Zener diode should ensure the voltage isnt too high, there is one inside the gauge, but an additional external one wouldnt be a bad idea.
Quote from: Marv [uk] on April 06, 2009, 04:04:33 PMWhere does the thermocouple connect to?
Theres a length of k-type wire on the back of the gauge, do you have a specific head temp sensor that you're planning on using?
Cheers Rob,
So, what you're saying is it's OK to take the connector off the end and splice in the extra required length of cable and then refit the connector on the end of the added in cable and plug it in.
Won't that invalidate any warranty?
What i'd prefer to do is have a couple of connector blocks and custom make an extension from the connector on the "factory" cable to the back of the gauge. I can then do a continuity test and voltage drop test on the separate wire before plugging everything in which should keep my warranty ticking over nicely ;)
Does the gauge run a comparison or calibration cycle once it's fully connected and the sensor is warm? The LC-1 system runs it's calibration from the factory wiring harness so i've assumed the VEMS unit does the same and altering the cable would be a bad thing. I'll be pleased if I'm wrong :) but i's still be worried about warranty over anything else.
Zener diode - Cool. What sort specification are we talking about? As it's just a counting signal required, i suspect the voltage is irrelevant, but what are the gauges trigger voltages for data logging? I can connect a multimeter and tune the input signal accordingly, but want to get the characteristics of the signal for the gauge as close as possible to maximise accuracy.
As for the head temperature thermocouple, a simple K type spark plug thermocouple was what I was looking at, it's just finding one that is long enough. Provided I can "plug" one in without having to fork out £60 for something i'll never use, thats fine :D
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMSo, what you're saying is it's OK to take the connector off the end and splice in the extra required length of cable and then refit the connector on the end of the added in cable and plug it in.
Yes.
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMWon't that invalidate any warranty?
I'm afraid so, the alternative is that I can ask the manufacturers to make a longer length cable - but I'm not sure if they'll go for it.
The problem with Warranty on products like this is that they're down to a "fair use" restriction, because its impossible to know if the purchaser installed the thing correctly they work on the understanding that if the gauge is DOA or fails after a short amount of time then it gets replaced, where as if it fails because someone connects it wrongly or burns/fouls their sensor during tuning experiements/crankcase breather failure/voltage spikes etc, it can't be said to be the gauge's fault.
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMWhat i'd prefer to do is have a couple of connector blocks and custom make an extension from the connector on the "factory" cable to the back of the gauge. I can then do a continuity test and voltage drop test on the separate wire before plugging everything in which should keep my warranty ticking over nicely ;)
I'd prefer this too - but the problem is that the male connector is unobtainable, the wideband connector has a calibration resistor built into it. You could get a dead wideband, cut the plug off and modify it, but it would be a pain (the pin crimps are tricky to find and you can't easily splice onto the wire as its stainless, then theres the butchering of the resistor to concern yourself with).
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMDoes the gauge run a comparison or calibration cycle once it's fully connected and the sensor is warm? The LC-1 system runs it's calibration from the factory wiring harness so i've assumed the VEMS unit does the same and altering the cable would be a bad thing. I'll be pleased if I'm wrong :) but i's still be worried about warranty over anything else.
We use the calibration resistor, so as long as the wires are all good quality and roughly the same length theres not a problem, I was concerned about the dyno install but had a crack at it anyway because I wanted to see how it performed - the result was that it gave pretty much the same values as their existing sensor (that used the expensive NTK sensors) errors tended to be in the 0.0x region of the Lambda reading which can be down to filtering or sensor differences.
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMZener diode - Cool. What sort specification are we talking about? As it's just a counting signal required, i suspect the voltage is irrelevant, but what are the gauges trigger voltages for data logging? I can connect a multimeter and tune the input signal accordingly, but want to get the characteristics of the signal for the gauge as close as possible to maximise accuracy.
I'll double check with the design team.
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMAs for the head temperature thermocouple, a simple K type spark plug thermocouple was what I was looking at, it's just finding one that is long enough. Provided I can "plug" one in without having to fork out £60 for something i'll never use, thats fine :D
This is something you can plug extensions on to, the k-type plugs cost a bit mind you.
Quote from: [email protected] on April 06, 2009, 06:51:55 PM
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMSo, what you're saying is it's OK to take the connector off the end and splice in the extra required length of cable and then refit the connector on the end of the added in cable and plug it in.
Yes.
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMWon't that invalidate any warranty?
I'm afraid so, the alternative is that I can ask the manufacturers to make a longer length cable - but I'm not sure if they'll go for it.
The problem with Warranty on products like this is that they're down to a "fair use" restriction, because its impossible to know if the purchaser installed the thing correctly they work on the understanding that if the gauge is DOA or fails after a short amount of time then it gets replaced, where as if it fails because someone connects it wrongly or burns/fouls their sensor during tuning experiements/crankcase breather failure/voltage spikes etc, it can't be said to be the gauge's fault.
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMWhat i'd prefer to do is have a couple of connector blocks and custom make an extension from the connector on the "factory" cable to the back of the gauge. I can then do a continuity test and voltage drop test on the separate wire before plugging everything in which should keep my warranty ticking over nicely ;)
I'd prefer this too - but the problem is that the male connector is unobtainable, the wideband connector has a calibration resistor built into it. You could get a dead wideband, cut the plug off and modify it, but it would be a pain (the pin crimps are tricky to find and you can't easily splice onto the wire as its stainless, then theres the butchering of the resistor to concern yourself with).
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMDoes the gauge run a comparison or calibration cycle once it's fully connected and the sensor is warm? The LC-1 system runs it's calibration from the factory wiring harness so i've assumed the VEMS unit does the same and altering the cable would be a bad thing. I'll be pleased if I'm wrong :) but i's still be worried about warranty over anything else.
We use the calibration resistor, so as long as the wires are all good quality and roughly the same length theres not a problem, I was concerned about the dyno install but had a crack at it anyway because I wanted to see how it performed - the result was that it gave pretty much the same values as their existing sensor (that used the expensive NTK sensors) errors tended to be in the 0.0x region of the Lambda reading which can be down to filtering or sensor differences.
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMZener diode - Cool. What sort specification are we talking about? As it's just a counting signal required, i suspect the voltage is irrelevant, but what are the gauges trigger voltages for data logging? I can connect a multimeter and tune the input signal accordingly, but want to get the characteristics of the signal for the gauge as close as possible to maximise accuracy.
I'll double check with the design team.
Quote from: Marv [uk] on April 06, 2009, 05:54:14 PMAs for the head temperature thermocouple, a simple K type spark plug thermocouple was what I was looking at, it's just finding one that is long enough. Provided I can "plug" one in without having to fork out £60 for something i'll never use, thats fine :D
This is something you can plug extensions on to, the k-type plugs cost a bit mind you.
well thats a PITA aint it :( Would said manufacturers produce a 20 foot cable for the same price as the normal one or at least supply a different connector on the end to make fabricating an extension cable easy. Bear in mind the damn things going to have to go through 2 bulkheads not to mention a load of tinware. I'd have to strip the connectors out of the terminal block anyway
(Techedge can supply the connectors so I don't see why VEMS can't :( on the plus side though, techedge are australian and not entirely round the corner :))
As for the K thermocouple..... 25 quid and another 25 for the 15 foot extension. But the cables are red and yellow, not green and white even though it's a K thermocouple. At the very worst, it'd be a 2mm thermocouple soldered into a 14mm ring terminal, not the hugely expensive things that the tuner websites offer
Quote from: Marv [uk] on April 06, 2009, 07:30:17 PMwell thats a PITA aint it :( Would said manufacturers produce a 20 foot cable for the same price as the normal one or at least supply a different connector on the end to make fabricating an extension cable easy. Bear in mind the damn things going to have to go through 2 bulkheads not to mention a load of tinware. I'd have to strip the connectors out of the terminal block anyway
When it comes it comes with the wires crimped - but out of the plug, which is why splicing an extra length doesnt seem such a bad idea. They've added an extra meter of wire on my request for MR2's at the cost of £10. If you want I can ask them.
Quote from: Marv [uk] on April 06, 2009, 07:30:17 PM(Techedge can supply the connectors so I don't see why VEMS can't :( on the plus side though, techedge are australian and not entirely round the corner :))
I can't see the male connectors on their site, it seems that they have an 8meter controller to sensor cable, that ends with an 8pin DIN connector, you could easily follow that model.
Quote from: Marv [uk] on April 06, 2009, 07:30:17 PMAs for the K thermocouple..... 25 quid and another 25 for the 15 foot extension. But the cables are red and yellow, not green and white even though it's a K thermocouple. At the very worst, it'd be a 2mm thermocouple soldered into a 14mm ring terminal, not the hugely expensive things that the tuner websites offer
I'd just be cautious of the soldering as it might form a cold junction between the thermocouple wire and the solder material - the worst that happens is that you have to buy plugs if you're not happy with the temperature reading - you seem hands-on enough for this not to worry you.
Quote from: [email protected] on April 06, 2009, 08:18:12 PM
Quote from: Marv [uk] on April 06, 2009, 07:30:17 PMwell thats a PITA aint it :( Would said manufacturers produce a 20 foot cable for the same price as the normal one or at least supply a different connector on the end to make fabricating an extension cable easy. Bear in mind the damn things going to have to go through 2 bulkheads not to mention a load of tinware. I'd have to strip the connectors out of the terminal block anyway
When it comes it comes with the wires crimped - but out of the plug, which is why splicing an extra length doesnt seem such a bad idea. They've added an extra meter of wire on my request for MR2's at the cost of £10. If you want I can ask them.
Quote from: Marv [uk] on April 06, 2009, 07:30:17 PM(Techedge can supply the connectors so I don't see why VEMS can't :( on the plus side though, techedge are australian and not entirely round the corner :))
I can't see the male connectors on their site, it seems that they have an 8meter controller to sensor cable, that ends with an 8pin DIN connector, you could easily follow that model.
Quote from: Marv [uk] on April 06, 2009, 07:30:17 PMAs for the K thermocouple..... 25 quid and another 25 for the 15 foot extension. But the cables are red and yellow, not green and white even though it's a K thermocouple. At the very worst, it'd be a 2mm thermocouple soldered into a 14mm ring terminal, not the hugely expensive things that the tuner websites offer
I'd just be cautious of the soldering as it might form a cold junction between the thermocouple wire and the solder material - the worst that happens is that you have to buy plugs if you're not happy with the temperature reading - you seem hands-on enough for this not to worry you.
If you wouldn't mind asking if they would do it and for how much, yes please. I know dakota digital have a thermocouple cable of 18 feet to reach from engine to cab in a type 2 VW so (without actually measuring) i'm guessing 20 feet would be ideal for this application and I wouldn't mind spending an extra tenner or so on it to cut out a ball of work for myself, but lets just leave it as an enquiry for now :) I've got to see whether it'd be worth it or whether a case of splicing for a day or so would be economic. Maybe the DIN cable connector would be a good idea.
Either way with the thermocouple, providing it's a K type, there should be no compatability problems. It's just a case of making sure that the polarity is the right way around. I'm assuming here that the insulation colour doesn't mean anything though. It's not green and white as an ISO thing is it?
Quote from: Marv [uk] on April 06, 2009, 08:37:45 PMIf you wouldn't mind asking if they would do it and for how much, yes please. I know dakota digital have a thermocouple cable of 18 feet to reach from engine to cab in a type 2 VW so (without actually measuring) i'm guessing 20 feet would be ideal for this application and I wouldn't mind spending an extra tenner or so on it to cut out a ball of work for myself, but lets just leave it as an enquiry for now :) I've got to see whether it'd be worth it or whether a case of splicing for a day or so would be economic. Maybe the DIN cable connector would be a good idea.
Okay I'll ask them and point out that Tech Edge do 8 meters. It would make sense to leave the wires uncrimped then you can cut it to size without a problem.
Quote from: Marv [uk] on April 06, 2009, 08:37:45 PMEither way with the thermocouple, providing it's a K type, there should be no compatability problems. It's just a case of making sure that the polarity is the right way around. I'm assuming here that the insulation colour doesn't mean anything though. It's not green and white as an ISO thing is it?
Yes and no, the wire colours are important as they indicate the different metals that the wires are made from, and this dictates the polarity, the British standard is Green and White, while our American cousins favoru Yellow and Red
| British standard | American Standard |
| Connector | Green | Yellow |
| Wire insulation | Green | Yellow |
| + wire | Green | Yellow |
| - wire | White | Red |
Quote from: [email protected] on April 06, 2009, 09:40:57 PM
Quote from: Marv [uk] on April 06, 2009, 08:37:45 PMIf you wouldn't mind asking if they would do it and for how much, yes please. I know dakota digital have a thermocouple cable of 18 feet to reach from engine to cab in a type 2 VW so (without actually measuring) i'm guessing 20 feet would be ideal for this application and I wouldn't mind spending an extra tenner or so on it to cut out a ball of work for myself, but lets just leave it as an enquiry for now :) I've got to see whether it'd be worth it or whether a case of splicing for a day or so would be economic. Maybe the DIN cable connector would be a good idea.
Okay I'll ask them and point out that Tech Edge do 8 meters. It would make sense to leave the wires uncrimped then you can cut it to size without a problem.
Quote from: Marv [uk] on April 06, 2009, 08:37:45 PMEither way with the thermocouple, providing it's a K type, there should be no compatability problems. It's just a case of making sure that the polarity is the right way around. I'm assuming here that the insulation colour doesn't mean anything though. It's not green and white as an ISO thing is it?
Yes and no, the wire colours are important as they indicate the different metals that the wires are made from, and this dictates the polarity, the British standard is Green and White, while our American cousins favoru Yellow and Red
| British standard | American Standard |
| Connector | Green | Yellow |
| Wire insulation | Green | Yellow |
| + wire | Green | Yellow |
| - wire | White | Red |
That would make sense provided they are not some weird specialist crimps. I'm quite capable in many things, but fiddly things and my fat fingers don't mix very well ;)
So, let me summarize so far, and please correct me if i'm wrong
The cable length is not as important as the o2 connector as this is where the calibration resistor is, but, the cable can be spliced if you use correct gauge cable and equal lengths. THis invalidates the warranty though
Secondly, the EGT gauge can be used as a CHT gauge as the thermocouple cable connects into the back of gauge to two tails of (British Standard) K thermocouple cable. American standard K thermocouple cable can be used providing the polarity is consistent as the metals that the cables are made of SHOULD be the same. (white to red, green to yellow connectivity)
Once the gauge is connected, it's not really a good idea to disconnect the o2 and just use it as a CHT gauge as it might break it.
Are you sure there is no way that the software can temporarily disable the Wideband part of the gauge while the sensor is disconnected? I don't want it all the time, just for tuning.
Oh yeah, and one more thing,
A coil can be used as an RPM source to log data provided a zener diode is used to moderate voltage.
What would the software settings be for a coil input on a 4 cylinder engine?
Its a case of experimenting starting from
Toothcount of 2
Multiplier of 228
Hi,
Unplugging the sensor from the gauge shouldn't be a problem from the gauges point of view, it'll just show "e" on the display.
However what you don't want to do is leave a WBO2 sensor in the exhaust without it being powered up as that does kill the sensor.
Personally I'd leave it in and working, you only need something like a fuel pressure problem to leave you running lean at WOT and you're in trouble!
Cheers,
Gavin :)
Kool and his entire gang :)
It's all doable then. Just waiting on some info before I decide whether to press go or not :D
Gavin, my plan was to take the o2 sensor out. The cheap header I have won't take a decent weld, let alone a decent bung so I'm resorting to a slip in piece with flanges and a bung, about 2 inches long like this one but from Aircooled.net (this one has a pic!)
http://cbperformance.com/catalog.asp?ProductID=598
Leaving the section in there is not advised by the manufacturers so the o2 IS coming out. I just don't want to break the gauge until I can get a half decent stainless header with a bung already welded in.
any spec on the zener diode yet? :)
Just one more piece of information required to get it straight in my head... :)
The gauge is compensated for EGT as in if it's 30 degrees outsides but the EGT is 650 degrees, the gauge automatically compensates for ambient temperature showing the EGT as an absolute temperature.
Question - Is this compensated to the temperature at the gauge (inside the gauge) or does it require a temperature compensated K thermocouple cable?
The thermocouple has to use k-type cable all the way through or it forms a cold junction at the dissimilar metal joint and starts messing with the temperature reading. The temperature reading is the temperature at the tip of the sensor.
Quote from: [email protected] on April 17, 2009, 06:27:02 PM
The thermocouple has to use k-type cable all the way through or it forms a cold junction at the dissimilar metal joint and starts messing with the temperature reading. The temperature reading is the temperature at the tip of the sensor.
I sort of understand all this
the K thermocouple measures the temperature difference between the two ends of the twin cable by producing a millivoltage current depending on the temperature gradient. This is casued by the dissimilar metals. Know the voltage, know the temperature difference. Cold junction compensation references the ambient temperature at the cold junction which in turn references the cold junction temperature to "a bucket of ice" or 0 degrees C. Because K thermocouple properties are well known, electronics can be set up to measure a reference voltage of the cold junction against the known voltage of a k type at 0 degrees so the electronics can then work out exactly what the real temperature in degrees celcius is being measured at the hot end
The display on the gauge then is electronically wombled with and shows the actual temperature in degrees celcius. I.e. you can get a thermometer and read the same temperature (if it doesn't melt) at the hot end if you so fancied making the effort
Thermocouple cables can be extended provided that the extension cable is of the same stuff and polarity and that the junctions are made on a "similar material" so there is no temperature difference between the + ve and - ve wires to monkey about with the data
The question really is do I go out and buy a standard K thermocouple with 2 wires, or do I have to get a temperature compensated cable? Does the gauge itself carry out the compensation or does it have to be supplied with the induced voltage already compensated to freezing point? I'm currently assuming the that the gauge does, but i've read 2 different explanations on the Wiki and it's confused me :(
I've got a supplier of K thermocouple cable (with american insulation) complete with a 14mm spark plug end and an extension cable (again american spec insulation) and a couple of proper connectors lined up, but it's all non compensated cable. Is it the right stuff? :-\ ??? :'(
Sorry for being a PITA :) and thanks for humouring my stupid questions :D
Use standard normal k-type wire, the gauge has an internal temperature measurement which I understand the AD597AR chip uses to compensate.
Corking!
Got my WBo2 gauge and it looks great and everything is there. Chuffed to bits :D
But the instruction SUCK :(
Still, i'll get there :D really looking forward to having it all plugged in. Going off to get a couple of grommets now :D:D
Even these instructions suck:
http://www.vems.co.uk/VEMSWB/UserGuide/README.html
If you have any questions on information that is missing please ask and I can make the documentation better.
Not exactly sucky Rob :D , much better than the ones that don't even come in the box for crying out loud! :(
The wiki is pants, there is no two ways about it. What this product needs is a decent wiring diagram that does not continually go on about R232 this and that when it doesn't even show what they all are
Simple would be good
on the separate wiring harness, connect the red to the switched live ignition at the fuse box. connect the blue to a suitable earth
connect the o2 sensor connection as the diagram shows on your instructions cos thats a good one. the ones in the box were crap and obviously babelfished
what is the other cable for? I know it's for connecting to an engine management box but it never actually says what it for
Someone REALLY needs to write proper instructions for this as the wiki is crap and speaks in technobabble that even a geek friend of mine has difficulty with.
I really really REALLY hope the gauge is better than the instructions else i'll be fuming! ;)
Hi,
The Gauges are good, I've sold a couple to some very impressed customers ;D
Cheers,
Gavin :)
One cable is for power and external connections.
One with a 9pin plug is to connect to a serial port on a PC/Laptop.
Then theres the wideband connector, and finally the green and white thermocouple wire.
Well I finally got it all installed and connected up and I is a very happy bunny :)
Feedback!
For future reference a 5m cable is perhaps half a meter too short for a VW camper given the length of the wideband sensor cable but I got mine to work with no splices :D The rubber boot is most definitely impossible to thread through the wireways on a bus so has to come off, might as well not put it on. Had a bit of difficulty threading the 6 crimps through at times and they could do with a bit of staggering but no big deal.
All in all, a very simple install complicated by the type of vehicle :D
One problem though...... the EGT just will not hold still on a number and fluctuates wildly. On start up while the o2 sensor is heating the EGT fluctuates between say about 200 and 400 *C then as the sensor heats, the value drops down to 0 and fluctuates up to about 100. The fluctuations are rapid, say 5 or 6 a second and are seemingly random. I've been through the system from end to end and, Although I have 2 thermocouple connectors in there, all polarities are correct. When the thermocouple is diconnected, the gauge reads a steady 1174*C. I have a copper ring K thermocouple from the states clamped beneath #3 spark plug which is connected to a 15 foot extension which is then connected to the cable in the back of the gauge.
Any ideas what the problem is?
Cheers :D
Good news on the install.
As for the thermocouple reading, I've not seen anything like that before, do you think you could test the thing by connecting a thermocouple directly to the gauge? It uses such small voltage differences, and the cable is so long that it could potentially be acting as an antenna for noise.
Quote from: [email protected] on May 26, 2009, 01:21:04 AM
Good news on the install.
As for the thermocouple reading, I've not seen anything like that before, do you think you could test the thing by connecting a thermocouple directly to the gauge? It uses such small voltage differences, and the cable is so long that it could potentially be acting as an antenna for noise.
Funny you should say that but that is what I was originally thinking as it is so close to a spark plug.
Plugging the thing directly into the gauge is a bit of a no no. It took me for f'n-ever to get it in there as #3 is a pig to reach, especially with twin carbs so i'll not be taking it out in a hurry!! Any ideas for some electronic shielding? bit of stainless braiding perhaps?
If you connect the two wires on a k-type together they create a thermocouple, how is the extension connected to the thermocouple wires that come out of the gauge?
Quote from: [email protected] on May 26, 2009, 04:59:25 AM
If you connect the two wires on a k-type together they create a thermocouple, how is the extension connected to the thermocouple wires that come out of the gauge?
It's got a proper K type thermocouple connector on it as per the destructions :)
I checked the end of the extension after i connected it but before i threaded it through all the really hard to get places beneath the floorpan and when touched together, the two wires registered a steady 23 degrees which was a few degrees higher than ambient but probably the same as my finger temperature so I was happy that it all worked and was connected properly.
The other thing I was thinking was that, as the thermocouple cable is laid alongside the power cable for the wideband, interference from the wideband heater cable would explain the weird behaviour of the thermocouple as it's high during heating, then falls off to zero ish after the heat cycle has finished. They really are side by side for nearly 5 meters. They are also very close to the main power cable.
Hmmmm, I think, first, I'm going to have to separate the thermocouple cable from the wideband cable for as much distance as I can and see if that has any effect. If it doesn't then I'm going to have to think of something else.
As a minimum, i think the 1m thermocouple itself, from the end of the extension to the spark plug, needs a steel overbraid to shield it from the ignition leads though.
Perhaps Mr Hungarian needs to do a bit of research to see just how the o2 cable interferes with the thermocouple cable just so it can be added to the instructions or perhaps shielded at source.
UPDATE:
:(
haven't had time to do much recently but now i've done a bit of work and the following was observed
disconnected connector in engine bay and removed connector to end of extension cable (furthest away from gauge) and twisted the two wires together, turned on ignition but didn't start motor.... same thing happened as before... random readings
faffed about underneath the van and separated the cables where they were running side by side to eliminate as much noise as possible... turned on ignition....
;D thermocouple reading from twisted together wires read from about 10 - 13 degrees with a bit of a wobble... much better ;D
reconnected connector and thermocouple together, turned on ignition and
same random readings again >:( >:( >:(
not a happy bunny....
Any ideas?
thanks :)
If I'm reading this right, it does suggest that its noise related because the gauge was happy away from the wire, but that the thermocouple has introduced noise back into the setup.
I'll have to ask some of the others what they might suggest, I know that I've seen thermocouples with separate grounds for their outer casing. What thermocouple are you using?
Quote from: [email protected] on June 04, 2009, 02:13:26 PM
If I'm reading this right, it does suggest that its noise related because the gauge was happy away from the wire, but that the thermocouple has introduced noise back into the setup.
I'll have to ask some of the others what they might suggest, I know that I've seen thermocouples with separate grounds for their outer casing. What thermocouple are you using?
Yep, thats pretty much what I was thinking. I'm not going to be able to play with it for a couple of days but i'm going to go through the wiring again and make sure that they are totally separate except for where it just isn't possible to do so.
The thermocouple i am using is THIS ONE (http://shop1.actinicexpress.co.uk/shops/partsforaircraft/images/catalog/cht.jpglarge.JPG) and it's an american one with a 14mm copper ring for the spark plug with glass fibre insulation.
Had a couple of installation problems with it. VW heads have recessed spark plugs and the outer diameter of the copper ring is too big. Additionally, the one i was sent had the thermocouple connection welded (or soldered) on to the copper ring far too close to the ring so it ended up scoring a groove around the plug and frayed off the insulation protecting it. Anyway, I removed it, reinsulated it and put it back in. The deformities in the copper ring that took so long to put in the first time meant that the second installation went smoothly.
I have been doing some reading and thinking and discovered that the red sheathing does not necessarily indicate a negative connection depending on where it's manufactured. The chart [url=http://www.omega.com/techref/thermcolorcodes.html]HERE (http://[/url). The chart HERE (http://www.omega.com/techref/thermcolorcodes.html) shows the relative colours known about and there are some with red + ve's so I reckon i'll have a play and see if there is any difference if i swap the connections around on the thermocouple connector.
Apart from that, the only other thing I can think of is that there is some interference coming from the cylinder head, perhaps a voltage leak or bad earth connection.... I get lost on the finer points of electrickery.... so I think i might also have to clean the earth connection from the gearbox to the chassis and make sure i have no bare cable anywhere. I still can't quite reconcile this with my knowledge as the voltage would cause the gauge to read a big fat error, not just a couple of hundred degrees though...
I'm officially stumped
Noise is odd, it may be presenting itself on the gauge input as a few millivolts or as a huge spike - the huge spike would probably rail the reading at its maximum- but it would happen very quickly, so if theres any sample averaging in the gauge it will lessen the effect of the spike reading. Does that make any sense because it may potentially be a load of old twaddle... A scope on the wires would be the only way to find out.
Rob
Quote from: [email protected] on June 04, 2009, 09:43:16 PM
Noise is odd, it may be presenting itself on the gauge input as a few millivolts or as a huge spike - the huge spike would probably rail the reading at its maximum- but it would happen very quickly, so if theres any sample averaging in the gauge it will lessen the effect of the spike reading. Does that make any sense because it may potentially be a load of old twaddle... A scope on the wires would be the only way to find out.
Rob
That sort of makes sense, i think ???
Anyway, as i don't have access to a scope, other than a tele ;) i'm kinda screwed and have to do it by trial and error
Anyway, i'm going to bite the bullet and take the washer out from beneath the spark plug and see if that does anything. If it solves it, i've been told that it could be an earth potential difference causing the millivolts of difference required to produce the fluctuations. The fact that it's synchronous with the heating current may be a red herring as that could be the cycle rate of the gauge, but the incidence of the temperature readings altering from high to 0 in line with the heating voltage leads this person to think that there is an difference in earth potential between the earth point of the gauge at the front of the van, and the earth point of the thermocouple some 12 feet away, but 8 feet closer to the battery earth. If this turns out to be the case, it may be necessary to earth the gauge at the same point, or at least close to, the cylinder head.
If, when it is out and it continues to happen, i'm going to swap the polarity of the thermocouple and see if that affects it in any way.
Is there any way that you know of to test the thermocouple to see if it is a K type or something else? It's been suggested that I might have been mis sold a J type. The colours say it's a K but you never know for sure
Something completely different though.... there are 7 cylces of info on the gauge depending on button presses. I've guessed that there is the option of AFR or Lambda for each one and celcius and farenheit for each one but what are the settings exactly... EGT i know, ambient gauge i know, I'm sure that one of them is revs..... have i missed any out? Also, how do you choose which one comes on when you turn it on as it isn't the one that you switch it off at if you change it. Mine always comes on at lambda and egt but i want it on AFR and egt. It seems that the ambient temperature setting is slightly off by maybe 5 degrees or so, how do i calibrate the temp?
Calibration is done through MegaSquirt - if the setting is not there - it cannot be calibrated :o
The modes of the button are listed on the documentation page but I'll paste it in here:
The button on the front of the gauge display allows you to cycle through the 14 different display modes:
1. Lambda & Internal temp C,
2. AFR & Internal temp C,
3. Lambda & EGT C,
4. AFR & EGT C,
5. Lambda & Internal temp F,
6. AFR & Internal temp F,
7. Lambda & EGT F,
8. AFR & EGT F,
9. Lambda & MAT C,
10. AFR & MAT C,
11. Lambda & RPM,
12. AFR & RPM,
13. Lambda & MAT F,
14. AFR & MAT F.
Right, I'm armed with barbeque paint and heat sink paste to eliminate the ground loop.... Wish me luck :) ;D
By the way, I knew the different cycles were on the destruction page but I didn't know what some of them were, my mistake for not asking the full question of course, but what is MAT?
Also, how do you get it to turn on with a certain display. The default of lambda and EGT C is not what I want most of the time and I want to set it to AFR and EGT F as 'default' :D
Cheers
You should be able to setup the display to show what you want using MegaTune, once burnt it should remain set.
Hi,
MAT = Manifold Air Temperature also known as Intake Air Temp. or charge temp.
Cheers,
Gavin :)
Quote from: Bat on June 09, 2009, 03:39:14 AM
Hi,
MAT = Manifold Air Temperature also known as Intake Air Temp. or charge temp.
Cheers,
Gavin :)
hmmmmm :thinks:
Anyone know what the input signal characteristics are? I could use that as an oil temp gauge :D
anyway, rain and TFL stopped play so no closer to sorting it out just yet..... but I will :D
after a lovely day I finally managed to get my arse in gear and got ~3 spark plug out and the thermocouple too
BONUS!!!!! the thing read right :D:D:D:D:D
Ok, so it fluctuates by a degree or 3 a few times a second, but at least it's more or less the right temperature. A couple of degrees I can live with ;D
Well, it's a ground loop problem so the thing to put in the WIKI is that, if a non EGT thermocouple is used, it must be an isolated, not a grounded one to avoid this problem.
Anyway, out came the barbeque paint.... it was like spraying it with chewing gum >:( so off it all came again and now the hammerite has gone on it in an effort to electrically isolate the thermocouple from the head. When I actually get around to putting it back in again, there is also going to be a generous coating of heatsink paste ;D
All in all, I am a very happy bunny.
Is there any way of reducing the sampling frequency of the EGT without affecting the wideband though?
well it's been a while and I've had a few issues
the barbeque paint and heat sink paste didn't work at all.... fluctuating readings did y head in so i left it unplugged for a few weeks.
I ordered a different CHT sender for £40 but I had some work to do to intall it properly. The old one was a pig to install. The problem lies with VW cylinder heads where the plug recess is really tight. It mangled the sender right up, exposing the copper ring and the ground loop.
I had some work to do to the motor so out it came. fan shroud swapped but the main thing was taking the dremel to the cylinder head to chase out the side of the plug recess to accomodate the new thermocouple ring and to prevent it moving while being tightened.
Engine went nicely back in, hooked up, turned it on and.....
BINGO
It works, properly, no feedback ;D;D;D;D;D;D;D
I am chuffed. Quality Gauge
One small query.... one thing I have noticed is that the internal temperature keeps rising as you go along, even blatantly out of whack.... 16 degrees, wearing jumper.... gauge says 27 degrees. Is this normal? Is this caused by heat being generated in the electronics or is this something that would need 'fettling' in megatune?
I believe the heat things is within the gauge itself and it´s pretty close to the electronics that drive the pump ont he sensor.
That creates the higher internal heat.