Exhaust temperatures?

[Alan Lee]

I've got the SO Guzzi running reasonably well now after a few weeks of
meesing around with it (1979 V50). The carbs have been balanced, and
throttle cables adjusted etc to give a smooth tickover and take up of
revs. It also starts pretty much immediately, which it wouldnt do
previously.
I had it running for 15 minutes last night to get it nice and warm, and
tried my IR temperature meter to see what the 2 exhaust temperatures
were. Something I've never done before, so thought that now it's running
well, it should be close to the same temperature on both exhausts, but
no, it was ~130 degrees on one,and ~178 on the other. Both measured at
the same distance from the head.
Clearly they should be about the same temperature if it is running
correctly.
Do these IR Temp meters give a pretty accurate temperature reading from
chrome pipes?
If yes, any ideas why it has differing exhaust temperatures?
Thanks.

--
Remove the '+' and replace with 'plus' to reply by email

[bob prohaska]

Alan Lee <al...@darkroom.plus.com> wrote:
> the same distance from the head.
> Clearly they should be about the same temperature if it is running
> correctly.
> Do these IR Temp meters give a pretty accurate temperature reading from
> chrome pipes?

In general, no. Surface finish plays a huge role. Rusty vs chromed,
for example.

> If yes, any ideas why it has differing exhaust temperatures?

IR thermometers measure radiated power, not temperature. If the
surfaces have similar emissivity then temp and radiated power
are related. I'd start by applying heat resistant paint or some
other coating that will survive intact long enough to take your
measurements. The absolute value of the temp probably won't be
correct, but at least the numbers can be compared.

It'd help if you posted the actual measurements. 100 C out of
1000 C isn't a big deal. Out of 200 C it's a very big deal.

A group of measurements on or near the pipes might be helpful
as well. I'd expect the pipe to read hotter than the port
area, for example. If not, that's worth investigating.

HTH,

bob prohaska

>

[Andy Burns]

Alan Lee wrote:

> Do these IR Temp meters give a pretty accurate temperature reading from
> chrome pipes?

Shiny is probably not the ideal emissivity for the thermometer, the
usual trick of sticking on some black insulating tape is probably not a
brilliant idea though, also does what is within the cone-of-view vary
from side to side? They usually tell you the angle they "look" at, or
the circle size at a given distance ...

[Bruce Horrocks]

Do you (Alan) have a multi-meter that can take a k-type thermocouple?

<https://www.amazon.co.uk/Multimeter-Temperature-TP-01A-Humidity-Thermocouple/dp/B093Q9M9HB>

Just tape the wire to a piece of wooden dowel and bend the end over the
end of the dowel so that you can press it onto the pipe without burning
yourself.

--
Bruce Horrocks
FJR1300AS

[Pipl]

On Sun, 19 Mar 2023 14:13:27 +0000, Bruce Horrocks
<07....@scorecrow.com> wrote:

>Do you (Alan) have a multi-meter that can take a k-type thermocouple?

My thought too.

--

-Pip

[Eddie]

On 18/03/2023 20:44, bob prohaska wrote:
> Alan Lee <al...@darkroom.plus.com> wrote:
>> the same distance from the head.
>> Clearly they should be about the same temperature if it is running
>> correctly.

<snip>

> It'd help if you posted the actual measurements. 100 C out of
> 1000 C isn't a big deal. Out of 200 C it's a very big deal.

It was in the bit you snipped:

> it was ~130 degrees on one,and ~178 on the other

--
Eddie ed...@deguello.org

[Andy Burns]

Bruce Horrocks wrote:

> Do you (Alan) have a multi-meter that can take a k-type thermocouple?

If not, and he's still in Blaby, I could drop one round ...

[Champ]

On Sat, 18 Mar 2023 20:14:36 +0000, Alan Lee <al...@darkroom.plus.com>
wrote:

How serendipitious [1]

I got my ZXR750 post-classic racer fired up on Friday [2]. It hadn't
run for at least six months, and did it's usual thing of starting on
2, then 3, then finally 4 cylinders, but still sounded pretty lumpy.
So I got my newly aquired IR thermometer out, with the exact same
thought, and had a very similar experience - huge variability across
the four exhausts.

My first suspicion was that a curved shiny surface, with different
levels of shiny-ness, would likely give inconsistent results, so I'm
glad that the follow-ups to your post have suggested the same.

[1] One of my favourite words
[2] And then on Sunday I rode it at one session at the ACU Test Day I
(part) organised and officiated at. Blimey, it was fucking brilliant!
Any fluffiness while blipping the throttle on the paddock stand
completely disappeared under full load in gear. I came back in
whooping inside my helmet, with a huge grin on my face.
--
Champ
neal at champ dot org dot uk

I don't know, but I been told
You never slow down, you never grow old

[Spike]

What the OP is looking for is similar readings from both exhausts; it
doesn’t matter if the readings are accurate in temperature, so long as all
other things are equal.

Shiny metals that have been chemically cleaned have an emissivity of around
0.2, and oils, paints, plastics, etc are around 0.8.

The thing is, energy is radiated from the first few microns of the surface,
and in real life shiny-looking metal is going to have surface contamination
of one thing or another, so the emissivity is going to be nearer 0.8 than
0.2. ISTR a 2 micron layer of oil can change the emissivity of a clean
metal surface from 0.2 to above 0.7.

It’s why domestic radiators are painted white; the IR emission comes mostly
from the matrix that the white colourant is bound by. Painting a radiator
black won’t change the amount of radiated heat much at all.

A rough test of the balance of your exhaust temperatures could be done by
starting from cold and, with a hand on each exhaust pipe, see if one starts
to heat up before the other, perhaps six inches down from the ports.

Another method might be to wind some black plastic tape round each pipe,
well away from the ports, and do an IR check on each as things warm up,
holding the sensor head up against the tape each time.

--
Spike

[ts]

Alan Lee <al...@darkroom.plus.com> wrote:

> I've got the SO Guzzi running reasonably well now after a few weeks of
> meesing around with it (1979 V50). The carbs have been balanced, and
> throttle cables adjusted etc to give a smooth tickover and take up of
> revs.

(snip)

> Clearly they should be about the same temperature if it is running
> correctly.
> Do these IR Temp meters give a pretty accurate temperature reading from
> chrome pipes?
> If yes, any ideas why it has differing exhaust temperatures?

I've also used my IR temp meter to check the exhaust sides of my boxer
cylinder heads to monitor temperatures, and believe it to give useful
readings. Measuring at a few different places is as always wise. Dull
aluminium is probably better than shiny chrome, as mentioned.

Even if you have synced the carbs, and got the engine to run smoothly,
the air-fuel mixture at different revs/engine loads can differ quite
much. With ethanol laced fuel, it is supposedly more difficult to check
for excessive lean or rich conditions by looking at the spark plugs, but
that was one way to check the A/F ratio in the old days. Have you looked
at your plugs?

Have you adjusted the idle jet settings of your carbs? With too rich
fueling the extra petrol acts as a coolant, resulting in lower cylinder
head/exhaust valve temperatures. At mid engine load, the needle jets and
needles determine the A/F ratio. They certainly wear in my Bings, and
can result in too high fuel consumption, possibly also different
fuelling conditions. For the Bing carbs, the needles can furthermore be
set in four different positions, if not at he same setting for both
carbs, one can run richer than the other. Not sure to what this applies
for your Dell'Ortos - but the principle is the same.

Another reason for one cylinder running cooler than another can be poor
piston ring sealing - lower compression. Compession of air warms it up,
and the heat has to go or stay somewhere.

--
ts // scrap vehicle to send e-mail
Four Boxers
Kawa GPz750

[RustyHinge]

On 21/03/2023 17:12, Spike wrote:
> Andy Burns <use...@andyburns.uk> wrote:
>> Alan Lee wrote:
>>
>>> Do these IR Temp meters give a pretty accurate temperature reading from
>>> chrome pipes?
>>
>> Shiny is probably not the ideal emissivity for the thermometer, the
>> usual trick of sticking on some black insulating tape is probably not a
>> brilliant idea though, also does what is within the cone-of-view vary
>> from side to side? They usually tell you the angle they "look" at, or
>> the circle size at a given distance ...
>
> What the OP is looking for is similar readings from both exhausts; it
> doesn’t matter if the readings are accurate in temperature, so long as all
> other things are equal.
>
> Shiny metals that have been chemically cleaned have an emissivity of around
> 0.2, and oils, paints, plastics, etc are around 0.8.
>
> The thing is, energy is radiated from the first few microns of the surface,
> and in real life shiny-looking metal is going to have surface contamination
> of one thing or another, so the emissivity is going to be nearer 0.8 than
> 0.2. ISTR a 2 micron layer of oil can change the emissivity of a clean
> metal surface from 0.2 to above 0.7.
>
> It’s why domestic radiators are painted white; the IR emission comes mostly
> from the matrix that the white colourant is bound by. Painting a radiator
> black won’t change the amount of radiated heat much at all.

It will if your (very) off-white paint is graphite paint

--
Rusty Hinge
To err is human. To really foul things up requires a computer and the BOFH.

[Alan Lee]

I'll try again with a bit of tape on it. Getting 15 minutes spare is the
problem.
Yes, I'm still in Blaby, but not for much longer hopefully,the Estate
Agent comes round today to take the photos etc, I'm pricing it to sell,
we're moving to Southern Scotland.
I've been hectic for the last few weeks, cleaning and decorating, still
haven't finished, though it'll have to do. I also started a new job on
Monday, and promptly finished yesterday, it was shite, so am unemployed
again! Not really a problem, I'll get something pretty quick I think.

[Alan Lee]

On 18/03/2023 20:44, bob prohaska wrote:

> Alan Lee<al...@darkroom.plus.com> wrote:
>> the same distance from the head.
>> Clearly they should be about the same temperature if it is running
>> correctly.
>> Do these IR Temp meters give a pretty accurate temperature reading from
>> chrome pipes?
> In general, no. Surface finish plays a huge role. Rusty vs chromed,
> for example.
>

Thankyou, I wondered if it was something like that. I'll try again with
some heat resisting tape.

[Alan Lee]

On 20/03/2023 15:39, Champ wrote:
>> Do these IR Temp meters give a pretty accurate temperature reading from
>> chrome pipes?
>> If yes, any ideas why it has differing exhaust temperatures?
> How serendipitious [1]
>
> I got my ZXR750 post-classic racer fired up on Friday [2]. It hadn't
> run for at least six months, and did it's usual thing of starting on
> 2, then 3, then finally 4 cylinders, but still sounded pretty lumpy.
> So I got my newly aquired IR thermometer out, with the exact same
> thought, and had a very similar experience - huge variability across
> the four exhausts.

Yep, too much tech, and too little training!
40 years ago, we'd be happy if it started and ran well. Now we want to
balance the exhaust temperatures.

[chrisnd @ukrm]

Nicely put :-)

Chris
--
The Deuchars BBB#40 COFF#14
Yamaha XV750SE & Suzuki GS550t
http://www.Deuchars.org.uk