Thinking ahead......

[gruntus]

Hi Chaps,

Sorry if this has been done to death but I am reassembling my 200TDi and will look to fit an EGT in a few years the distance.

I thought it worthwhile drilling and tapping the exhaust now and then plugging it until needed rather face the chance of getting unwanted swarf in the turbo at a later date.

So, is there a common size thread for most of the common probes?

And where am I best to put the temp probe in the exhaust manifold? Any particular cylinder preferred?

Your experience and knowledge greatly appreciated as always.

Cheers

Grant

[Pete Attryde]

Don't know if it's standard but, mine is 1/8th NPT for the thermocouple fitting.

HTH

Pete.

editted to add the madman system also uses 1/8th NPT

[Mo Murphy]

Yup, mines 1/8 npt too.

Mo

[gruntus]

Thanks Guys,

Looking up NPT its a tapered thread, is that correct ?

Regards

Grant

[white90]

[Guest WALFY]

Here's mine. Def manifolds on a Disco block. Using the MadMan setup purchased from Si R

[Pete Attryde]

Thanks Guys,

Looking up NPT its a tapered thread, is that correct ?

Regards

Grant

Yes, it is a tapered thread. As to wether it's correct for the application or not I couldn't say, but it seems to be an easily available fitting. If you need a tap I almost certainly have one you could borrow if needs be.

Pete.

[gruntus]

Thanks Walfy/Tony,

I had heard of people trying to catch the temperature as close to the exhuast port as possible but it makes more sense to have it on the collector just before the turbo thus catching all temperatures.

I imagine the temperature differences wouldn't be that much different anyway!

Getting a 1/8th NPT tap looks fairly straight forward from the web but I cant see my local bolt store having a blanking bolt...

Thanks again.

Grant

EDITED TO ADD: Thanks for the offer Pete, I should be ok just to buy one anyway, cheers.

[Guest WALFY]

If you have the boss to scrw in. Readily avail. Scew that in, and to seal it up use a small length of 6mm bar with an olive to seal it. Or pay the 25 quid ish for the EGT and fit it. And when you can afford the rest purchase it and plumb in.

[JimAttrill]

Just to be different, mine (which I fitted back in about Y2K) came with a 1/8" BSP thread. So I had to buy an expensive tap which has been used once. The two threads are not interchangeable because the NPT is 27tpi and the BSP is 28tpi.

[David Sparkes]

I had heard of people trying to catch the temperature as close to the exhuast port as possible

This comes from the world of petrol engines, where performance exhaust manifolds are often long tubular devices. The tubes are lighter than cast manifolds, and so don't retain as much heat. If the probe is placed where all the 4 or 6 pulses wipe the thermocouple tip it could be 2 feet from the exhaust valve. With the tubes losing so much heat (unless they are wrapped) the reading will be artificially low, but by a varying amount, not just 20 degrees (say) as the heat loss will depend very much on the amount of gas flowing.

For a diesel I think you are doing the right thing, if you think a thermocouple is a worthwhile investment (but don't let me spoil your fun!!).

[David Sparkes]

In my last post I was also going to comment on sourcing thermocouples by themselves, instead of part of a package.

However, when I checked I discovered my previous suppliers (Kalestead) only showed cables on their web site.

A phone call today revealed the thermocouple side had devolved to a firm called Alphatemp at http://www.k-instruments.co.uk/index.html

Browsing this site shows they do use the thread format I recall, BSPP and BSPT.

This doesn't help you decide what thread to create now, but for UK readers it does highlight a local, competitively priced, source of thermocouples. As these are all to a standard, they will work to any gauge / monitor, although one should always acknowledge the ability for some manufacturers to include non-standard connectors, hidden away, just to tie you into their product.

HTH

[gruntus]

Thanks for all the great advice Chaps,

I may stump up the cash and put the Thermocouple in place now as its something I will wish I had done at the time.

I currently have the turbo and manifold parted for cleaning/painting and could get the thermocouple spot on in place before reassemnbling.

Not to mention it being a bit easier drilling and tapping in a vice.....

Cheers

Grant

[Guest WALFY]

The probe that I use is a K type. Not sure if that relates to the temp range or style of guage you use. But on research that I did they all seem to mention that it was compatable to a K type guage.

As for being tied in with trange thread sizes. The t/c is just a small 6mm dia tube with the magic bits inside. What boss you choose to fit it with is up to you. As long as it corresponds to either the 6mm (what people seem to use) or a 3mm you should be fine.

[David Sparkes]

The probe that I use is a K type. Not sure if that relates to the temp range or style of guage you use. But on research that I did they all seem to mention that it was compatable to a K type guage.

Yes, it's the electronics in the gauge that has to match the type of thermocouple, and I agree, K type is normal for EGT usage.

As for being tied in with trange thread sizes. The t/c is just a small 6mm dia tube with the magic bits inside. What boss you choose to fit it with is up to you. As long as it corresponds to either the 6mm (what people seem to use) or a 3mm you should be fine.

I confess I was thinking more of the gauge end. The threaded fitting is normally chosen to meet local practise, thus BSP or NPT, whatever. I use a 3mm probe.

A stand alone thermocouple will end in a pair of wires, and these have to be ordered to be long enough in the first place. Unless the user is 'in the trade', these leads can only be shortened, not lengthened (without adversely affecting accuracy). If the chosen gauge uses some form of special connector, or it is hidden behind a crimped fastening, it just makes the whole installation process a little more 'stimulating'.

HTH

[Guest WALFY]

The MadMan setup I have has a tail of about a dozen wires out the back of the guage. Then all the senders including the EGT just join the tail. I have crimped mine and it seems to be a good solution for me. The EGT came with a long tail, about 2m IIRC ending in bare wires. As it was a kit I assume that the componants were chosen for the ease of fitting factor, which helped me no end.

[white90]

there are a few more UK suppliers

I've used all of them

http://www.tc.co.uk/guides/therm.htm

http://www.labfacility.co.uk/ my preferred supplier

K type is a Temp range Mark

after having x2 3mm ones snap I've reverted to 6mm

Ps joining the TC wires shouldn't be done with solder or crimps as dis-similar metals affect the reading

[Guest WALFY]

So if you can't solder or crimp, what you supposed to do? Are there other methods of joining 2 sets of bare wires which is what you get with the MM setup?

[white90]

Tape joint/resin epoxy pot

or order a longer lead.

Soldering/crimping will give incorrect readings.

This info from the suppliers

not something I thought up

[Guest WALFY]

I discounted a taped joint for the simple reason is that we used to use them at work to join cables and it proved to be problematic, so it is no longer a recognised method unless in a real emergency. Resin I hadn't thought of. But it would be nice to be able to remove the dash without breaking the joint everytime.

I didn't think for 1 minute that you had made it up, just that I'd never heard of that before. So I'm now assuming that my readings are duff then. Does it say which way the readings go? Reading high or low? Or couldn't they say. If it's reading high I can live with that but if it's low then I'll have to readdress the issue.

[Pete Attryde]

You can use something like this from RS Thermocouple connectors other suppliers are available.

As Tony says you can twist the similar metal wires together and then tape, spot with epoxy or apply glued heatshrink also.

Pete.

editted link as I linked to the wrong thing. DOH!

[white90]

Mark contact Labfacility

they sell the connectors that are made of similar metals as mine came with crimps fitted already to the ends.

they are very helpful on the phone, I have an account if you need to place an order.

I used previously self amalgamating tape to join one of the 3mm ones worked well and water proof

I also have the spring reliefs fitted to my TCs as this save wires breaking down over time through fatigue.

[gruntus]

Just a quick update.

I was able to get a 1/8 NPT brass plug for a couple of quid from e-bay and more interestingly the cheap tap and die set I have has a 1/8 NPT-27 tap included.

In fact, most of the tap and die sets I looked at had a 1/8NPT-27 tap as standard so no need to spend £17 for a tap you may only use once!

A reasonable Draper set could be had for about the same price.

I was also able to drill and tap the hole at the right angle so that I shouldnt need to bend the thermocouple when it eventually gets fitted.

HTH someone in the future.

Cheers

G