Current choices or options for a compression tester
 

So far for 2019, my searches and reading only turn up two possible choices for a rotary compression tester - one USA at rotarycompressiontester.com and one in Australia. I was looking for possible comparison review but couldn't locate any. There are some diy and pc alternatives but I'm looking for something self contained and reliable. I can use it to check out a possible purchase but I'd like to use it as a regular baseline measurement to monitor engine condition. In the case of possible unexpected problems it can also help (99%) eliminate certain issues and help to locate problems lurking elsewhere. Kind of like an angiogram in cardiology. I also occasionally see sale of testers on ebay but I'd like to go with something new. Am I missing something here? Thanks.

I have chosen to manufacture one, starting with a ceramic pressure sensor (€ 17) and a digital oscilloscope, in my case a model that connects to PC (if you do not have it you can get it for around € 125).
It is handmade and therefore not approved, but it has the advantage over the classic meters, which only give you the numerical results, which in addition to those numbers helps you determine the condition of the rotors, seals and houses, from the profile of the compression curve; something like the angiogram you mentioned.
https://cimg6.ibsrv.net/gimg/www.rx8...e54d681b00.jpg

Naturally, doing so requires some knowledge and / or previous documentation (basic operation of the oscilloscope, connection of the sensor to the PC, etc.) but it is not complicated and it is truly useful.

Cool. What mods or how did you adapt the sensor? Is a compression curve profile documented for the Renesis engine? I know there are some design documents available but haven't yet looked. Could be useful as a secondary tester. Oscilloscope or PC isn't a problem just not that convenient if on the road.

^^

https://www.rx8club.com/series-i-do-...%24100-261310/

In my case I had to add an adapter between the sensor and the spark plug hole, and account for the volume of that adapter so it doesn't read artifically low. I think I posted the excel sheet for conversion in that thread.

Of course, the PC or oscilloscope should not be used on the road, but that is not a problem since the compression test can not be done on the road.

For the sensor, since I could not find an adapter, I chose to do it myself: starting with an old spark plug, I removed the insulating porcelain core and screwed the hole with the sensor's measurement.

To connect and feed the sensor use a USB cable recovered from an old mouse, taking the positive and negative cables I got the 5V needed by the sensor. The rest of the USB cables are not used, so simply leave them there, covered with an insulator to avoid problems. In this way, when performing the test, I use a USB on the PC to power the sensor and another to connect the Oscilloscope. There is no need for this any auxiliary circuit, circuit board, or anything else, just the USB cable.

On the profile of the compression curve, I had not found many examples, but I got the idea from jird20, an enthusiast and good connoisseur of rotary engines and who has a website ( http://www.rotarypit.com/ ) with plenty of information about our engines.

There are a couple of images on your website that illustrate the profile of the curve and can help you interpret some of the problems of engine from that profile:

In page ( Encendido ) see ( http://i1.wp.com/www.rotarypit.com/w...de3.jpg?w=1500 )

In page ( Núcleo del motor ) see ( http://i0.wp.com/www.rotarypit.com/w...Pit.jpg?w=1105 )

As Loki says in the previous message, the compression data taken from the graph must be compensated in RPMs, altitude and, if you want more precision, also compensate the extra volume added by the sensor adapter. Anyway, these compensations are easy to do with an Excel spreadsheet.