Wideband 02 install questions

[Marv [uk]]

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....

  thermocouple reading from twisted together wires read from about 10 - 13 degrees with a bit of a wobble... much better

reconnected connector and thermocouple together, turned on ignition and




same random readings again 

not a happy bunny....

Any ideas?

thanks

[rob@vems.co.uk]

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?

[Marv [uk]]

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 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. The chart HERE 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

[rob@vems.co.uk]

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

[Marv [uk]]

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?

[rob@vems.co.uk]

Calibration is done through MegaSquirt - if the setting is not there - it cannot be calibrated

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.

[Marv [uk]]

Right, I'm armed with barbeque paint and heat sink paste to eliminate the ground loop.... Wish me luck  


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' 

Cheers

[rob@vems.co.uk]

You should be able to setup the display to show what you want using MegaTune, once burnt it should remain set.

[Bat]

Hi,
MAT = Manifold Air Temperature also known as Intake Air Temp. or charge temp.
Cheers,
Gavin

[Marv [uk]]

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


anyway, rain and TFL stopped play so no closer to sorting it out just yet..... but I will

[Marv [uk]]

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

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

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

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?

[Marv [uk]]

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


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?

[gunni]

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.