OP
UTC

Hooked
P200
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Location: Alabama
 
Hooked
P200
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UTC quote
Damn, wrote long post and it disappeared while doing attachments.

This one will be short. Did a quick dirty test, here are some numbers....

Average Difference from Under the plug to the Under the Stud #1
9.61 deg F
Average Difference from Under the plug to the Under the Stud #2
12.58 deg F
Average Difference from Under the Stud #1 to the Under the Stud #2
2.97 deg F

Max Difference from Under the plug to the Under the Stud #1
15.52 deg F
Max Difference from Under the plug to the Under the Stud #2
17.61 deg F
Max Difference from Under the Stud #1 to the Under the Stud #2
6.23 deg F

Short on time these days, anyone wanna take this hardware and log some real data? I'll mail ya the HW and the TrailTechs, just mail back when done. Also allows ya to control timing (retard only), has 3 Trail Tech inputs and 1 K-type thermocouple input. I log using my little Asus Eee through USB.

Plots of data and OpenOffice SS attached. Data labeled IAT and TPS are the under the stud TTs. The CHT is for the under the plug TT. The EGT is for the K type, in the exhaust. The TT are in F and the EGT in C.

I did this in a hurry. Tell me if I messed something up.
Forum member supplied image with no explanatory text
Forum member supplied image with no explanatory text
OP
UTC

Hooked
P200
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Location: Alabama
 
Hooked
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UTC quote
I give up on adding the attachments. PM me if you want the spreadsheet or wanna get the stuff to log your own data.
@oopsclunkthud avatar
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UTC quote
great info, what two studs were used?
@vader19 avatar
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Mr. Clean
P,SUPER,V90, 50 Special
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Mr. Clean
@vader19 avatar
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UTC quote
Yeah!!! Fantastic.. thanks brother!

same question which studs!

Cheers man! err guy!
OP
UTC

Hooked
P200
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Hooked
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UTC quote
I had to leave on travel unexpectedly, hence the rush job. I don't recall which 2 studs. Will take pic when I get home sunday or monday. I'm in spotty wifi hell. Will do better info uploads when I get back too.
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Mostly Lambrettisti
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UTC quote
I just go under the plug. Good enough for me.
Forum member supplied image with no explanatory text
OP
UTC

Hooked
P200
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UTC quote
Location of studs and their corresponding labels used in plot and data.

Offer still stands, anyone wanna borrow hardware and do some logging on their engine? I'm not gonna get to this again for a while. Would be nice to see some RPM/CHTs/EGT plots.
Forum member supplied image with no explanatory text
OP
UTC

Hooked
P200
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UTC quote
Hell, image got rotated after I uploaded to MV. Hmmm, well, you can probably sort it out based on plug position.
@ginch avatar
UTC

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
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Location: Victoria, Australia
 
Veni, Vidi, Posti
@ginch avatar
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
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Location: Victoria, Australia
UTC quote
Excellent info, thanks for that!

So you're saying that the stud furthest from the plug gave a reading that was closest in temperature to the plug?

Also, I don't know if that's where you always place the plug sensor, but I found if you turn it around so that the sensor lead is at the bottom (in your picture), then when you put the plug in and do it up, the ends of the fins either side hold it from turning. That position doesn't block the airflow as much either.
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UTC quote
I'll try that, its always seems like a pain to hold the CHT and seat the plug.

Yes, the stud further from the plug did track a bit closer to the plug CHT, but that stud is closer to the exhaust side.
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UTC quote
this_guy wrote:
Yes, the stud further from the plug did track a bit closer to the plug CHT, but that stud is closer to the exhaust side.
and furthest from the fresh cooling air. That's the stud I tend to use.
@chandlerman avatar
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Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
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21 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
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21 Days Since Last Explosion
UTC quote
What's the X axis on those graphs? Elapsed time in seconds?
OP
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Hooked
P200
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Hooked
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UTC quote
Its crank syncronous. So the x axis is just the sample number. The time varies with rpm. The cht values are sampled many times between revs, but the last sample before cdi trigger is what's logged.
@bigben avatar
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Evil
p2, jet2, lml166
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Evil
@bigben avatar
p2, jet2, lml166
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UTC quote
i just got a new cht, for one my old sensor got bent a bit attempting to seat the plug - as it was used on both my lambretta and my vespa, and for the other because some runt stole my digital gauge. i'm drilling holes and bolting this new one down.

perfect timing, perhaps ill seat the old sensor under a nut and not have to run the new wire through the frame.
⬆️    About 4 years elapsed    ⬇️
@ginch avatar
UTC

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
Joined: UTC
Posts: 8648
Location: Victoria, Australia
 
Veni, Vidi, Posti
@ginch avatar
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
Joined: UTC
Posts: 8648
Location: Victoria, Australia
UTC quote
Just found this again in a FB group and thought it could be useful. This was written by a friend of mine.
Derek wrote:
TTO vs SIP temp gauges

Tony and I have both been 'double probed ' recently to see the difference between my benchmark TTO readings and the sip speedo readings.

Prelim results indicate that they read exactly the same in a STILL AIR environment albeit with a slight delay on the sip probe.

The big differences are related to engine speed or, more correctly, air flow over the probe connection. The material and extra protrusion into the cooling air flow in the sip robe cause an increasingly lower reading as speed increases.

Tony might pipe in with some stats here. Hypothetically.....

At rest sip:28; tto:28
Around town sip 94; tto:112
Flat knacker: sip150; tto:200

All my learned 'scare points' after years of using tto on dozens of scooters need to be shifted down considerably

Conclusion: beware when asking what is a safe temperature without referencing the gauge used in the question AND answer.

Next: I will experiment with shielding the probe from air flow while we have the luxury of the tto control probe still installed. Stay tuned.
Tony wrote:
Agree with you about the cause of the difference in readings. I experienced a difference of up to 80 deg F at high cruising speeds, which backs up the hypothesis that as speeds increase, so does the airflow and cooling effect on the SIP probe
Derek wrote:
I have some more test results for the panel, thanks to Tony and my good self. As you know we have been double probed for a better world.

Test 1- Tony with both tto and sip sensors under his plug

Result- low Rev : both results similar with sip slightly delayed. High Rev: sip showing significantly cooler results.

Test2- derek double probed (ooh matron)
Working on the theory that the high Rev discrepancy was due to the Aluminium sip probe sensor being higher up in the cooling airstream, resulting in incorrect readings, I did the following. I wrapped the sip probe arm in double sided tape then aluminium shield tape. This made it quite a squeeze in there but it is well worth cutting away some fin and some shroud to allow smooth fastening of the plug without cross threading.

Result: 200 km of various hard riding resulted in the Guages showing the same results all the time.

CONCLUSION: 1- shielding the sip speedo cht sensor from cooling air shows the same results as a tto, allowing the existing mental database of 'safe' temps to be used with the fancy Guages. Proving they are both accurate temperature sensors calibrated the same.

2- Going from a tto to a straight out of the packet sip speedo will show temperatures at higher speeds as lower than what they are, creating a danger of overheating or incorrect jetting.

ALSO It is worth noting that in both cases the spark plug popped out unexpectedly.
Tony's late last year. Mine popped out yesterday , bringing me to the conclusion that the alloy vs copper with no crush washer at standard torque is not conducive to staying in. Don't Try it at home. I hope our great sacrifice helps make the cht world a better place.

ps. I have run the tto without the crush washer without hassle for years.
This issue is when you use both sensors.
Personally I will use the crush with the alloy sip sensor from here on in.
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