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DIY compression tester

Old 03-17-19, 12:01 AM
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DIY compression tester



OK, bear with me, because this might be stupid.

But it as I live in a new fear of needing to rebuild my engine (and lack of parts), I have been wanting to do a compression test, and while I have read on how to use a standard gauge w/o check valve, I started thinking...

why not try to use an automotive pressure sensor like you would find on a injection rail. Something like the attached.

for less than $15, you can buy a usb adc that does up to ten single ended channels, and feed straight to a pc or Mac, and then use excel or the like to get the compression data. Sure, would not be as slick as the multi-hundred dollar option, but it would be less than $50, and all you would need to do is to tap/die an aluminum rod to connect it right to the spark plug hole.

In fact, you could run both (in my case) housing at the same time. Or, if you were bold enough to own a Dodge Viper, you could get it all at once?

am I missing something here, any reasons not to give it a shot?

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Old 03-17-19, 05:37 AM
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^Yup, this stuff isn't rocket science, but you'll need a bit more than just a pressure transducer to build a decent DIY compression tester. Especially if you want it to provide readings that compensate for cranking RPMs and altitude. Here's a pretty good DIY set of instructions I found online with recommended parts list, that would probably cost about $150 in hardware for everything if you opted for quality parts; the software needed to run it is free/open source.:

https://www.instructables.com/id/TR-...ession-Tester/

Or, if you don't want to deal with the hassle of a DIY project, or worrying about the unknowns on how accurate your DIY creation is, you can buy a really nice compression tester from these guys for about $300 (sometimes less when they run special sales on FB or this forum):

https://rotarycompressiontester.com/
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Old 03-17-19, 02:11 PM
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