How to complete a compression test

[maddyaddy]

Could somebody give me step by step instructions on how to complete a compression test.  My friend has a compression tester but he has never performed one on a rotary engine:).  Many thanks

[mikeyh]

is it a rotary tester or piston one?

[maddyaddy]

its a piston one, it fits into the spark plug hole

[maddyaddy]

anyone??................

[David Nock (RIP)]

Done loads of piston cars, but I\'ve never had to do one on a rotary. I do know that you cannot do a test easily with a piston engine tester, plus you might knock the rotor tips off trying.
So if I were you I\'d make enquiries, see if you or your friend can hire or borrow a proper rotary tester.
Lindop, at top of page were offering free tests, but you\'d have to get car to Cheshire.

[mikeyh]

u cant test with a piston one as u dont get a true reading.
is there a problem with the car?

[maddyaddy]

no not atall just want to get a reading to sell it really

[Timmy]

It won\'t mean anything. As a rotary engine has three readings per rotor. Basicaly a piston engine compression tester only give the peak pressure where as for a rotary you need to see the 3 reading indivualy to know the condition of each tips.

[ro284]

copied from Clives thread,

Hi All

This may help,you can compression test a Rotary with a normal compression tester if you take the non return valve out then watch the 3 readings you get from each Rotor write them down then add 20% to your readings and you will get a close figure to work with,you need to do all this on a warm engine with the correct oil level.

All the best
Clive

also i think you have to remove a fuse to stop the fuel pump,and ignition to plug leads!  i think it\'s egi fuse, but do make sure, hopefully someone will be along shortly that knows more,

[pdtaylor18]

do a bit more research as there are a lot of threads about what the readings mean as well, can tell if a water seal has gone or a tip.

[Grizzly]

Tbh mate you can do it one of two ways, the side of the road way (checking the three bounces are roughly the same between the front and back rotors) and the proper way (book it into your local Engine builders and have them do it and give you the print out)

Simply using a Piston engine Comp tester is a pain in the rear to do because you have to remover the Shnider (sp) valve and this means it doesn\'t hold pressure (you get bounces rather than a constant pressure and have to be watching the Tester as a Third party turns it over). this is done because there is effectively three Compression chambers per Housing, this makes it a completely different task.

As said above, any time you turn a rotary over and don\'t want it to kick up remove the EGI fuse (it lives next to the battery)

[David Nock (RIP)]

Schraeder valve (sp).
And don\'t you still have to watch the depth of protrusion into the rotor chamber with an ordinary tester, in case it physically fouls the tips?

[ro284]

And don\'t you still have to watch the depth of protrusion into the rotor chamber with an ordinary tester, in case it physically fouls the tips?

Good tip David, I think i\'ll leave mine to Carl, its not worth risking damaging what you are trying to get a good reading on! :2eek

[Jürg Hensdiek]

Schraeder valve (sp).
And don\'t you still have to watch the depth of protrusion into the rotor chamber with an ordinary tester, in case it physically fouls the tips?

Hallo,
Simple cure...check the length of the tetser against the length of the spark plug. Don\'t tighten it any further.
 
Thanks
RH