Leakage tester, not comp test
05-08-07, 01:24 AM
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Leakage tester, not comp test
Hey guys, I was wondering what kind of #'s a rotary engine should put out on a leakage tester, not a compression test. Im thinking of buying a used engine, and it wont have the tranny and starter hooked up. Thanks
05-09-07, 02:02 AM
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Really? On cyl engines you can pinpoint stuff like valves, headgasket, or piston rings problems better than you can with a compression tester. Im not sure what #'s rotaries shoudl put out. I wont have a starter to crank the engine , so I want some way to test if its good
05-10-07, 08:38 PM
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05-10-07, 11:36 PM
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Try searching around. This might be a good place to start:
http://en.wikipedia.org/wiki/Wankel_engine
http://en.wikipedia.org/wiki/Wankel_engine
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05-10-07, 11:47 PM
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Try searching around. This might be a good place to start:
http://en.wikipedia.org/wiki/Wankel_engine
http://en.wikipedia.org/wiki/Wankel_engine
I know how rotaries work. Im still wondering why a leakage tester wouild not work on a rotary? Shooting compressed air in the cyl and checking the % leakage will not work??? The seals wont hold compressed air? Im not new to engines or cars, how they work, or how to rebuild them. My searches have come up with 0. Im having trouble figureing out why a compression test is ok on a rotary but a cyl leakage wont give reliable results. Couild someone please explain to me why? Thanks
05-11-07, 12:01 AM
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The "combustion chamber" is dynamic, unlike a piston engine, which the piston bore and piston (dimensions) do not change.
I guess you can dial the rotor to TDC and do a leak-down, but that's only for one rotor face.
Are you going to do this for all 5 rotor faces?
Sounds like a pain in the ***...
No one that I know of does such a thing.
-Ted
I guess you can dial the rotor to TDC and do a leak-down, but that's only for one rotor face.
Are you going to do this for all 5 rotor faces?
Sounds like a pain in the ***...
No one that I know of does such a thing.
-Ted
05-11-07, 12:09 AM
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Yeah, I have leak tested cyl engines without even having to figure TDC and giving it compressed air. I just rotate it over slowley untill I get my lowest amount of leakage. With the compressed air, its not impossible to turn the engine over.
BTW, it would b 6 faces of the 2 rotor engine
Since were on the subject. A compression test, we look for 3 even bumps of compression. You have to be alert and watch the gauge while it quickley gives fast readings.
Wouildnt you be able to tell which seal is leaking more by listening to exhaust and intake?? And you would get a percent of leakage. And leakage testers are not biased on compression of the engine.
Even for cyl engines, barely anyone does a cyl leakage test, but im wondering why its "useless"? Thanks for your input guys
BTW, it would b 6 faces of the 2 rotor engine
Since were on the subject. A compression test, we look for 3 even bumps of compression. You have to be alert and watch the gauge while it quickley gives fast readings.
Wouildnt you be able to tell which seal is leaking more by listening to exhaust and intake?? And you would get a percent of leakage. And leakage testers are not biased on compression of the engine.
Even for cyl engines, barely anyone does a cyl leakage test, but im wondering why its "useless"? Thanks for your input guys
05-11-07, 07:33 AM
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Sorry about that, my wording was bad.
It was supposed to be "to test the other 5 rotor faces"...
Yes, but it's not that bad.
Mazda gives a variation of 20psi between rotor faces, but if they are close enough, it's good.
If there is something seriously wrong with the engine, you'll see the differences in the bumps!
Hard to say, since I would think some of the pressure would leak past the apex seals / side seals / corner seals / oil control rings...
I dunno...I did leak-down testing all the time on piston engines, especially when we were looking to buy one of them. 
It's a good indicator of the condition of the engine without getting too involved or dirty with the engine itself.
Damage to the piston or cylinders would be obvious with this test.
I just haven't heard too many rotary engine guys bothering with a leak-down test for their rotary engines?
-Ted
It was supposed to be "to test the other 5 rotor faces"...
Since were on the subject. A compression test, we look for 3 even bumps of compression. You have to be alert and watch the gauge while it quickley gives fast readings.
Mazda gives a variation of 20psi between rotor faces, but if they are close enough, it's good.
If there is something seriously wrong with the engine, you'll see the differences in the bumps!
Wouildnt you be able to tell which seal is leaking more by listening to exhaust and intake?? And you would get a percent of leakage. And leakage testers are not biased on compression of the engine.
Even for cyl engines, barely anyone does a cyl leakage test, but im wondering why its "useless"? Thanks for your input guys
It's a good indicator of the condition of the engine without getting too involved or dirty with the engine itself.
Damage to the piston or cylinders would be obvious with this test.
I just haven't heard too many rotary engine guys bothering with a leak-down test for their rotary engines?
-Ted
05-12-07, 03:59 PM
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Sorry about that, my wording was bad.
It was supposed to be "to test the other 5 rotor faces"...
Yes, but it's not that bad.
Mazda gives a variation of 20psi between rotor faces, but if they are close enough, it's good.
If there is something seriously wrong with the engine, you'll see the differences in the bumps!
Hard to say, since I would think some of the pressure would leak past the apex seals / side seals / corner seals / oil control rings...
I dunno...I did leak-down testing all the time on piston engines, especially when we were looking to buy one of them.
It's a good indicator of the condition of the engine without getting too involved or dirty with the engine itself.
Damage to the piston or cylinders would be obvious with this test.
I just haven't heard too many rotary engine guys bothering with a leak-down test for their rotary engines?
-Ted
It was supposed to be "to test the other 5 rotor faces"...
Yes, but it's not that bad.
Mazda gives a variation of 20psi between rotor faces, but if they are close enough, it's good.
If there is something seriously wrong with the engine, you'll see the differences in the bumps!
Hard to say, since I would think some of the pressure would leak past the apex seals / side seals / corner seals / oil control rings...
I dunno...I did leak-down testing all the time on piston engines, especially when we were looking to buy one of them.
It's a good indicator of the condition of the engine without getting too involved or dirty with the engine itself.
Damage to the piston or cylinders would be obvious with this test.
I just haven't heard too many rotary engine guys bothering with a leak-down test for their rotary engines?
-Ted
05-12-07, 05:16 PM
#13
The problem with leakdown testing is that all the seals in the rotary are spring loaded. Apply enough pressure and the compressed air will just push past them. By the same token that piston engines usually generate 180-220psi compression and rotary engines only generate 90-125psi compression, piston engines leak down air slowly while rotaries leak down quickly because the seals do not hold air while at rest (or at low rpm) well. This is also why piston engines are easy to hydrolock, while rotaries are almost impossible. IF you get water/oil/atf/whatever in a rotary combustion chamber and excess pressure is generated, the pressure just pushes the seals into their groove and goes around, then the seals pop back out.
You could try it, but you'd have nothing to reference your results with, so the test would be useless.
You could try it, but you'd have nothing to reference your results with, so the test would be useless.
05-13-07, 06:26 PM
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The problem with leakdown testing is that all the seals in the rotary are spring loaded. Apply enough pressure and the compressed air will just push past them. By the same token that piston engines usually generate 180-220psi compression and rotary engines only generate 90-125psi compression, piston engines leak down air slowly while rotaries leak down quickly because the seals do not hold air while at rest (or at low rpm) well. This is also why piston engines are easy to hydrolock, while rotaries are almost impossible. IF you get water/oil/atf/whatever in a rotary combustion chamber and excess pressure is generated, the pressure just pushes the seals into their groove and goes around, then the seals pop back out.
You could try it, but you'd have nothing to reference your results with, so the test would be useless.
You could try it, but you'd have nothing to reference your results with, so the test would be useless.
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