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Page last modified 21:03, 5 Jan 2012 by internetscooter
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Vespa Labs > Vespa Tuning > Gadgets > Cylinder Head Temperature Gauge

Cylinder Head Temperature Gauge

From $1

    A very valuable gadget to have is a CHT gauge. This will give you a relative reading of how well your engine is cooling. There seems to be no hard and fast rule of what is a good temperature, however it is obvious that hotter engines can lead to heat seizures. A CHT will quickly tell you if a new fuel is bad or if some modification you have done is causing your engine to run hotter. 

    Roughly a Vespa engine will run at between 320F and 380F, different engine set-ups will run different temperatures. The CHT is not a replacement for listening for engine problems (you are unlikely to be staring at it constantly), however it will tell you when to listen more carefully or not.
     

    ./Cht gauge.jpg

    Pictured above Exhaust Gas and Cyclinder Head Temp Gauges. The hardest part was making the hole in the glovebox, I made a bit of a mess but most of what you see in the pic is due to dodgey touchup paint. Cyclinder Head Temp Gauges supplied to me by http://www.wadeair.com.au/ for AUS$126. 

    Tips:

    • straighten out a coat hanger and push that through the frame, through the clutch cable hole.
    • label the wires from each sender (because they are both the same colour
    • when drilling the hole in the glovebox, I found taking short jabs, made it easy to get the teeth cutting in the same spot

    Notes:

    • EGT changes quickly with engine speed
    • CHT change slowly

    Although the above is not detailed, the following links will show you all you need to know about fitting a CHT

    Cylinder head temperature gauge installation

    Installing a Cylinder Head Temperature Gauge

    Alternative CHT

    One experience with the Westach gauge was that it lost accuracy after a while and started reading high. The gauge was replaced with the following more accurate guage
     

    MICRO 1000 CHT
    http://www.aircraftspruce.com/catalo...HT_gauges2.php

    and sender:
    http://www.aircraftspruce.com/catalo...1chtPROBES.php

    which is an E type. You will need to order the 7 foot extension:
    http://www.aircraftspruce.com/catalo...o1chtLEADS.php

    Exhaust Gas Temperature Gauges

    The gauge above has a EGT (Exhaust Gas Temp), this may be very valuable for a mircolight aircraft where the engine runs at a constant RPM. In that case the EGT will quickly tell you if the engine is in trouble. However, the EGT reading changes quickly with RPM, so for a scooter it's use is limited. It "might" prove a useful tuning tool in conjunction with a rev counter.
     

    More Information?

    It would be nice to find the following information: 

    • Is there a digital CHT with programmable warning light or beeper?
    • Is there a cheap digital CHT with backlight?
    • Is there a EGT/RPM gauge? 
    • Is there a cheap CHT temperature switch? It would be nice to switch something off/on to save the engine
       
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    Viewing 10 of 10 comments: view all
    #1
    Chispas says:
    Notes for page clean up. "The hardest part was making the hole in the glovebox..." is repeated at the end of the third paragraph. Fourth bullet in More Information, says are when it should say a.
    Posted 06:08, 27 Jan 2009
    #2
    internetscooter says:
    updated thanks - email alerts have also stopped working so I'll sus that out too
    Posted 06:52, 16 Feb 2009
    #3
    Dedalo says:
    First, while the CHT gauges you cite are still available from www.aircraftspruce.com, the links are no longer up to date.

    1. Cheap digital CHT (don't think it has beeper/ warning light, or backlight):

    http://trailtech.net/tto_temperature.html

    It's US$40.

    This guy is selling an analog version for US$22 which many Vespa riders seem to use (don't know how accurate it is!):

    http://cgi.ebay.com/ebaymotors/NEW-2-Ultralight-Aircraft-CHT-Gauge-50-375-Celcius_W0QQitemZ260392829000QQcmdZViewItemQQptZMotors_Aviation_Parts_Gear?hash=item3ca09f4048&_trksid=p3911.c0.m14&_trkparms=72%3A1205|66%3A2|65%3A12|39%3A1|240%3A1318


    See pictures (pinched from internet fora) for installation

    2. a more expensive (and much bigger unit) with backlight
    and other functions:

    http://trailtech.net/vapor.html

    and then there's this one from SIP included with speedo for
    SS90, Rally etc.:

    http://www.sip-scootershop.com/EN/Products/50000600/Rev+counter+Speedometer+Vespa+Vespa+SS50SS90125PVET3+SuperSprintVGTRTSRally.aspx

    or older style P200 etc with smaller hole for speedo:

    http://www.sip-scootershop.com/EN/Products/50000400/Rev+counter+Speedometer+Vespa+P80150XPX80200+EP200E.aspx

    There are also other temperature gauges on SIP site. edited 01:33, 28 Aug 2010
    Posted 01:00, 28 Aug 2010
    #4
    internetscooter says:
    Thanks for the links:

    One thing though, take care that the temp is actually CHT from the sparkplug. Some are just water temp levels which are much lower.

    I got the Trailtech Vapor when it first came out and it was rubbish. They told me that CHT worked then after I got it, said that it didn't. The website now claims that it now works but I would hunt around for actual users before buying one - if anyone wants to find out just how bad their service was, feel free to email me for the woeful service email thread I have.

    I like the SIP one and have added it to my wishlist :)
    Posted 20:28, 29 Aug 2010
    #5
    vesparados says:
    I recently bought a trailtech CHT. I must say the 7 sec delay is quite long although i don't have much experience. Maybe its meant to be that way? I dont know. Besides that, I was wondering how you extended the wire as the one i had purchased had a short sensor wire??
    Posted 09:29, 7 Jun 2011
    #6
    internetscooter says:
    I had a trailtech but I gave it away - they sold it before CHT actually worked. I suspect with all the other features that the processor could not keep up with the CHT as well. With your unit they may have slowed it down to get it to work. When I had it I had a data cable running through the frame and just hooked up what wires I needed - so I probably chopped it and extended it that way.

    The nice thing about the Trailtech is that it does have a warning light and that did work for me and warned me the scooter was overheating with a HP4 flywheel attached.

    oh - and check out www.vespalabs.org/qa edited 10:13, 7 Jun 2011
    Posted 10:11, 7 Jun 2011
    #7
    vesparados says:
    dear internet scooter, i must say that your site is amazing!! thank you very much for replying. Mine was Trailtech TTO CHT with only a single function. the wires are quite small and i have no idea what type of wire to use for extension.

    recently i had started "Project reed valve" which i had welded a reed block right on top of the crankcase using a Suzuki RG125 reed valve. i had the scooter running and i must say it is quite impressive especially the top speed. Sadly, the "sudden reed valve boost" that i had anticipated are not as quick. I would like to share the project rite here and ask for suggestions with your approval on how to improve the design by working as a community. can you point me the rite way?
    Posted 00:41, 8 Jun 2011
    #8
    internetscooter says:
    I'm toying with the idea of changing the format the Vespa Labs - it currently is open to everyone but the idea of first starting in your own lab area and then migrating the information to main page doesn't seem to be working.

    The format change would be project focused and have people (probably mostly me to start with) launching projects on the main area. Then people can jump in and help each other succeed in the projects and documentation.

    A project could be as big as a scooter or a technique - "Project reed valve" would be perfect :).
    Posted 11:41, 8 Jun 2011
    #9
    vesparados says:
    what about forums?...i ll be following updates from vespa Labs.
    Keep up the good work..=)
    Posted 05:38, 9 Jun 2011
    #10
    internetscooter says:
    I'm trying to do something different to the typical forums - the www.vespalabs.org/qa section can be considered the forum, but the idea is to allow people to fix up mistakes, improve content etc. The Q&A section allows you to do this and vote up/down answers.

    BTW - I think for my CHT gauge I had some (maybe bought) spare connectors with the Trailtech. I was able to make an extender cable. The connectors are quite big so the have to be attached after the cable is threaded through the frame.
    Posted 10:17, 9 Jun 2011
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