CHT EGT Gauges

[StepVino]

Finally took the plunge and got a CHT gauge. Got the round
one, with the bullet case, and lighting kit.

Have to put in a plug for these guys:
http://airstuff.com/eshop/10browse.asp

Their prices are very good. For a few bucks more, they will
send you an extension cable for the sender, whatever length
you want. You can also get replacement spark plug ring sensors
of various sizes... lots of great stuff.

I looked at their dual CHT EGT gauges, almost went for it. The
single one should be easier to read, has C anf F scales, plus
a red line starting at 450F. Seemed perfect. I'll get the EGT
gauge next time.

They also have a $35 tach, similar to Tiny Tach.

[burnt_toast]

i hope this doesnt get flagged for the parts link, those are some good prices..

[StepVino]

Yup, it's always uncomfortable having to post links. They don't
sell scooter parts though, and this was just too good a find.

Looks like we have a lot in common with the ultra light crowd!

[burnt_toast]

on a side note, you less than 100posts behind me, no wonder you got super poster status so quickly. :8wave:

[str8dum]

you think 50 degree marking will be fine enough? i woulda went with the 100$ koso unit and the 20$ cht sender. digital resolution at 1 degree plus it have rev meter.

good luck with that one though. it will be harder to disquish those 10 degree jumps.

[Jack B]

I have the Koso unit on my two Zumas with the spark plug sensor unit. The problem is the unit only goes up to 230 degrees and both my scoots run hotter than that. I am not running over lean and it is not even summer yet. I mainly bought the units for the tach anyway. The temp part of the unit is worthless to me.

[StepVino]

My current setup.. 135lbs compression, 135 main jet, can run
about 10 seconds at wot, then overheats and looses power.
It will run all day at part throttle, 45mph.

Hopefully the gauge will have enough resolution to show a clear
difference between these two conditions. Then I can try lowering
the compression till wot temps match current 45mph temps.. or
something along those lines.

Burn't I tend to ramble on about my projects :).. maybe that's
where most of the volume comes from.

[burnt_toast]

I have the Koso unit on my two Zumas with the spark plug sensor unit. The problem is the unit only goes up to 230 degrees and both my scoots run hotter than that. I am not running over lean and it is not even summer yet. I mainly bought the units for the tach anyway. The temp part of the unit is worthless to me.

exactly, I have the same koso deluxe tach too and its great, just hate that temp limit. thats why I relocated my temp sender to a different part so i can atleast use it, but it just gives an approx temp relative to sender placement.

[str8dum]

ahh ok, my bike is LC and doesnt run over 190.

Still I think the resolution on that aircraft cht gauge is pretty wide.

[StepVino]

Just got it this afternoon....

It seems to read a bit low in a boiling water test (first pic).

Investigating further (meaning actually reading the instructions),
the connection (pic 2) between the cable that goes to the gauge,
and the cable attached to the sensor, is a *cold junction*. The
gauge is calibrated to read accurately when this cold junction
connection is at 75 degrees F. Gauge reads one degree low, for
every degree that this junction is above 75F, and vice versa.
This aparently is a characteristic of all self powered temp gauges.
A fact mentioned in the instructions, but left out of the online
description. Maybe it's no biggie... let's see :)

Next two pics are with the junction covered in ice, and last with
the junction in the boiling water, with the sender.

Cold junction in ice:
Ice is 32F... that's 43 degrees F lower than 75... so gauge should
read 43 degrees higher than before... looks correct.

Cold junction in boiling water:
Water boils at 212F.. digital thermometer is reading 215.. that's pretty
good! Maybe I should use that for my cylinder head gauge :). Anyways..
212 - 75 (cold junction reference) = 137 degrees. So gauge should
be reading 215 (boiling water) - 137 (cold junction error) = 78F
It reads around 50, maybe just above...

What's the point... well, I guess since summer will soon be here..
with 90-100 degree temps, the gauge is going to be reading 20-30
low. Add the 10 degrees or so which it appears to be low anyways,
it could be as much as 40 degrees off in summer.

Basically str8 is correct, it's not very usefull for precise work.
Still worth the $50 bucks.. with sender and all...

[Lennox]

i love how you forced the morton salt girl to keep your ice cool!! LOL!! ..laugh.. ..pics..

[StepVino]

I thought the test would be more interesting than the
salt... oh well....

[StepVino]

Changed my avatar to Rodney Dangerfield.... no respect :D

[Lennox]

I thought the test would be more interesting than the
salt... oh well....


i didn't mean to rain on your parade.... ,.,.

why do you need that cold joint? having to have a thermometer on board and doing math while riding seams like alot of work. i don;t remember having that joint on digital guages I have used.... are they just for analog?

[StepVino]

It's a little vague, but I think the junction is needed as a reference.
I don't know why. I guess the math isn't so bad... just need to
know how far ambient temp is from 75, then add/subtract from
meter reading. Have yet to see how it helps for tuning, or at least
avoid engine overheating.

Not knowing anything more, it seems like the best choice would be
a digital gauge, with cold junction compensation. I'll get something
like that for EGT, and not this same type. Glad I didn't get the dual
CHT/EGT now.

[str8dum]

autometer sells a analog temp gauge for like 30$. you can get the spark plug sender for under 20$

[StepVino]

I was looking at some in the autoparts stores.. never saw one
that went higher than 280.

[str8dum]

I think if your motor is hotter than 280, you might be in trouble.
The digital ones for use with the under the plug sensor dont even go to 280 i dont think.

[StepVino]

Just tried it out.. wires hanging everywhere... wot is
just under 400, maybe 350. Then I go and drop the
d@n thing and broke it!!!

Needle stuck at 100. Tore it apart (all plastic glued together),
and I found a piece of wire stuck to the movement magnet.
Someone must have left it in there while putting it together,
and the drop made it jump to the magnet. These things are
pretty low quality.

Took the oportunity to recalibrate it back in the kitchen. House
temp just happened to be 74 something, so set it in boiling
water, and made it match the digital meter exactly. There's a
small tab, on the needle axis that you can turn.

Anyway, I guess water temp would be way lower. Good part
of the plug sender is that it reads very quickly. You can actually
see the temperature rise as you accelerate. Almost instantaneous.

[str8dum]

wow really 400 under the plug.
hopefully u can find some numbers to get a comparison.

[StepVino]

It's kind of a big number isn't it?

Here's blurb I found this morning on CHT temps:

*ultralightnews.com/engineinfo/chtwirdia.htm

(Include asterisk in google search)

[burnt_toast]

400degrees F on a 50cc??? that doesn't seem right man..

In conjuction with my koso deluxe gauge, I sometimes use this to get measurements at different parts on both bikes:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93984

it reads up to almost 500deg F, so I use it to check cyl temps on the stroker and even thats usually under 300F. The triton is usually under 200F.

I suggest you get something like that to check intermittent temps, but having a guage is handy too. And are you sure everything is ok with your cooling system??

[str8dum]

airplane temps cant even be correlated with a 50cc motor. 400 has to be way off. it shouldnt be that much higher than a LC motor. over 250 would be serious problems.

[StepVino]

Wow!!! That's a great price.

400 was an overestime.. it was much closer to 350. Took it
out last night again, in chilly temps, and it stayed around
300. Came back and set the timing back to stock, from -2 degr,
temp maybe went up a hair above 300 at wot. Idles around 200,
maybe less (darn memory).

Cooling system is air... but I do have the big Jog fan on. Sucks
noticeable power btw. Have to compare temps to stock fan, and
hopefully take it off.

It's possible that the handheld meter might read a hair lower,
just a guess though. The temp sender, under the spark plug,
should be reading more of the internal engine heat (conducted
through spark plug threads) than a measurement taken on the
cylinder head surface. The sender is sitting on the cylinder
head too.. but you know what I mean...

[StepVino]

The spark plug sensor end is broken. That lasted a whole month...
Pretty sure I installed it correctly, nice loop out of the cylinder
head cooling shroud. If I wiggle the lead coming out of the shroud,
it will work intermittently, so it must be right where the lead
attaches to the ring.

[str8dum]

that sucks, hopefully you can resolder it or something

[OldGuy1]

The neat part of that is, you can tell how much heat your soldering iron puts out.

[StepVino]

Well I tried soldering, but didn't work, ended up trying the welder.

Seems like overkill but it managed to get the wires stuck back together.
Will find out tomorrow if it did anything. I was too lazy to put the
spark plug back, partly because it's raining, and partly because there's
a James Bond movie starting. I used the lighter on it, and the meter
responded. Need to try it with boiling water, and another thermometer.

Best setting on the welder was full power, and zero wire feed speed.
Just a couple of quick zaps.