Compression Test
 

I'm able to do compression testing on rotary engines.

If you want to have the compression tested on your rotory engine, let me know.

I'm charging $50 to $100 per car, depending on the difficulty of pulling the lower spark plugs and installing the test plug. If you pull them, then the charge will be $50; If I pull them then the charge will be $100.

Before anyone goes crazy about the cost and thinks it should be less (or free); check what the dealerships charge for the test.

If you feel the cost is too much then don't bother saying (or posting) so. I'm not interested in hearing a bunch of whining about the price. There is a simple solution for your problem; don't get your compression tested by me, have it done elsewhere.

Considerable time and expense have been invested in equipment and training, so I feel justified in charging for the service.

When the local Mazda dealership's compression tester was broken, they called me to do compression tests for their customers.

Good price! I take it you have the Mazda tester if your doing side jobs for the dealer.

you don't just have a regular ....piston compression tester right?

Basically what I do is put my ear against the lower spark plug hole so that there is a tight fit and then turn over the engine. Depending on how much my eyes bulge out, I can determine the engine's compression.

OK, here's the truth: I have an oscilloscope hooked up to a custom made part that is a combination of two basic pieces. One piece is from an air conditioning sensor which sends an electrical current to the oscilloscope. That piece is connected to the threaded part of a spark plug that has had a hole drilled in the end to allow the engine compression to be sensed by the air conditioning sensor piece. The tool is screwed into the spark hole in the engine and a wire is attached to it that plugs into the oscilloscope. As the engine is turned over, the compression is converted into a wave form. The strength of the compression causes the wave to react according to the voltage sensed by the air conditioning part of the tool.

To calibrate the tool, another tool was built and hooked up to the tester tool, that showed the psi and the voltage generated from a specific psi. For example, a psi of 10 lbs showed a voltage of .010; a psi of 15 showed a voltage of .015, etc. PSI and corresponding voltage were calibrated and recorded up to 125 psi.

So when I hook up the tool and turn over the engine, a wave form is generated that has a voltage. I take the recorded voltage and compare it to my cheat-sheet to get the associated compression.

Simple in a complicated way, but it works.

Thanks to Gambone for conceiving the idea and building the prototype (and teaching me how to use it)!

:)

How does this compare to how the mazda tool functions? Have you ever done a test back to back with your tool vs the factory tool? What were the results?

What an AWESOME idea! Is this an estimated reading or did you have a scale burned onto your eyeball for an accurate reading? This is absolute dedication folks. Who else is willing to risk vision AND hearing for your benefit, and at such a reasonable cost?
PROPS TO YOU HOOFHEARTED!!!:icon_tup: :icon_tup: :icon_tup:

I've not done a back to back test against the Mazda tool.

Because mine took a known psi and recorded the voltage for that psi; I'm reasonably certain that the voltage registered, while doing a compression test, equates back to a known psi.

I would have responded back earlier but I just did the ear/eyes compression test and I'm having a little problem seeing the screen. WHAT!? WHAT!?

He tested my old RX2 a few years back, and its seemed very accurate.
He is a great guy, and I would get this service form him if i needed it.

Compression tested:
1) Black FD. front: 97lbs psi; rear: 96lbs psi.
2) Bridgeported 13b w/Dellorto's. front: 138lbs psi; rear: 135lbs psi.
3) 13b w/Dellorto's. front: 135lbs psi; rear: 137lbs psi.
4) Stock '86 FC. front: 125lbs psi; rear: 128lbs psi.

Notice the difference between the turbo engine, which has lower compression rotors ,and the non-turbo engines, which have high compression rotors.

notice that all these motors must be runners..
all my compression tests have some zeros in them!

Two of the four engines are installed and drivable. The other two are out of the vehicle(s). I have a special engine stand head that has a starter motor built into it; for the "out of body" engines.

Having zeros in them is OK, as long as the zeros are preceded by a one.