Compressioin test results?
11-20-09, 03:14 PM
#1
Compressioin test results?
Did a compression test today with a piston tester. Front and rear housings both had 3 even bumps of 35...with the release valve held it...and with it not held it it would pump the gauge up to about 100 or maybe a little over....is this normal or did i not do it right? engine was warm and throttle held open...
11-20-09, 04:05 PM
#3
Did a compression test today with a piston tester. Front and rear housings both had 3 even bumps of 35...with the release valve held it...and with it not held it it would pump the gauge up to about 100 or maybe a little over....is this normal or did i not do it right? engine was warm and throttle held open...
11-21-09, 05:51 PM
#7
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+1
A piston tester is NOT appropriate to test a rotary engine.
With the release valve held in, you will not see the true pressure of the rotor face.
With the release valve in normal position, you will not see the three faces individually.
There is no winning way to use one and get an accurate picture of how the engine is performing. You're better off saving your cash on the tester and removing the leading spark plug and listening the the air pulses... Or if you've got cash, get a tester...
The best alternative is to find your local dealer that has a tester or find a local rotor head that has one.
+1
A piston tester is NOT appropriate to test a rotary engine.
With the release valve held in, you will not see the true pressure of the rotor face.
With the release valve in normal position, you will not see the three faces individually.
There is no winning way to use one and get an accurate picture of how the engine is performing. You're better off saving your cash on the tester and removing the leading spark plug and listening the the air pulses... Or if you've got cash, get a tester...
The best alternative is to find your local dealer that has a tester or find a local rotor head that has one.
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11-21-09, 06:11 PM
#8
And why is that? From my understanding with the release valve held in it becomes just like any other pressure tester. The only difference is that it lets the pressure escape through the valve so the readings must be taken quickly. The reading is probably lower since the valve is open allowing some pressure to escape but still closer and more useful from a diagnostics standpoint than listening to the pulses...Last time the test on my engine I got 105psi for every face which is normal.
11-21-09, 07:52 PM
#10
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Proper compression test procedure using standard tester. HERE
Having the valve open will tell you if you have even pulses on each rotor face.
Having the valve closed will tell you the compression itself.
How is this not better than listening with your ear?
Get a brain morans!
Having the valve open will tell you if you have even pulses on each rotor face.
Having the valve closed will tell you the compression itself.
How is this not better than listening with your ear?
Get a brain morans!
11-21-09, 09:14 PM
#13
zoom zoom go boom
When did a conventional compression tester ever become an unacceptable method? Its been used by thousands for a long while now. I think the problem lies in the fact that there's a procedure to follow and when people don't follow it they get incorrect readings so they blow the whole thing off as wildly inaccurate.
11-21-09, 09:29 PM
#14
When did a conventional compression tester ever become an unacceptable method? Its been used by thousands for a long while now. I think the problem lies in the fact that there's a procedure to follow and when people don't follow it they get incorrect readings so they blow the whole thing off as wildly inaccurate.
11-22-09, 02:53 PM
#15
Proper compression test procedure using standard tester. HERE Having the valve closed will tell you the compression itself.
Get a brain morans!
Get a brain morans!
Second, take a look at the attached graphic. This is from a compression test of an engine with one failed apex seal. As you can see, with one bad apex seal, two faces are reading low but one is showing reasonable compression of ~107 PSI. Now, if using a conventional compression tester, with the schraeder valve removed or the button held in, on this rotor housing, you would likely get one decent bounce and two that are considerably less. Agreed?
Then if you let the compression build by not releasing the pressure in the conventional tester it will build to ~107 PSI. Does that mean the compression in this housing is at an acceptible level? I don't think so.
BTW, you might want to ask Banzai which compression tester system they use.
11-22-09, 03:30 PM
#16
Hmmm, first of all it's MORON.
Second, take a look at the attached graphic. This is from a compression test of an engine with one failed apex seal. As you can see, with one bad apex seal, two faces are reading low but one is showing reasonable compression of ~107 PSI. Now, if using a conventional compression tester, with the schraeder valve removed or the button held in, on this rotor housing, you would likely get one decent bounce and two that are considerably less. Agreed?
Then if you let the compression build by not releasing the pressure in the conventional tester it will build to ~107 PSI. Does that mean the compression in this housing is at an acceptible level? I don't think so.
BTW, you might want to ask Banzai which compression tester system they use.
Second, take a look at the attached graphic. This is from a compression test of an engine with one failed apex seal. As you can see, with one bad apex seal, two faces are reading low but one is showing reasonable compression of ~107 PSI. Now, if using a conventional compression tester, with the schraeder valve removed or the button held in, on this rotor housing, you would likely get one decent bounce and two that are considerably less. Agreed?
Then if you let the compression build by not releasing the pressure in the conventional tester it will build to ~107 PSI. Does that mean the compression in this housing is at an acceptible level? I don't think so.
BTW, you might want to ask Banzai which compression tester system they use.
11-22-09, 08:06 PM
#18
zoom zoom go boom
You'll still see that compression is wrong. There's entirely too much emphasis here being placed on overall compression. Its the bounces. Overall like stated will simply be the strongest face of the rotor.
11-22-09, 09:09 PM
#20
When I checked mine I took the shrader valve outta my dad's snap-on tester when I tested the current motor in my 7. Don't remember what it read but it gave me a general idea of the health of my seals. I just look for good or bad when using a piston tester.
11-22-09, 09:53 PM
#22
i've tested tons of motors with piston testers you don't need to know the exact compression numbers to know if you engine is good or not..a side seal went out on my turboII checked it with a piston tester it showed around 37 on two faces and zero on the other this is how i knew it was a side seal. three even pulses on a piston tester and your good to go unless its showing very low compression on each face.
11-23-09, 06:37 AM
#25
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Proper compression test procedure using standard tester. HERE
Having the valve open will tell you if you have even pulses on each rotor face.
Having the valve closed will tell you the compression itself.
How is this not better than listening with your ear?
Get a brain morans!
Having the valve open will tell you if you have even pulses on each rotor face.
Having the valve closed will tell you the compression itself.
How is this not better than listening with your ear?
Get a brain morans!
Originally Posted by Banzai Racing
Note: if you do not remove the Schrader (relief) valve, you can also hold the valve down during the test and watch the needle bounce for each rotor face. However, you will not see actual compression readings. Once you have confirmed three even bounces, you can repeat the test without depressing the relief valve to ascertain the compression reading.
Reading the whole text of a link is good.
And why is that? From my understanding with the release valve held in it becomes just like any other pressure tester. The only difference is that it lets the pressure escape through the valve so the readings must be taken quickly. The reading is probably lower since the valve is open allowing some pressure to escape but still closer and more useful from a diagnostics standpoint than listening to the pulses...Last time the test on my engine I got 105psi for every face which is normal.
1.) Reading will be artificially low due to pressure bleeding off.
2.) Reading must be taken while needle is bouncing around.
A peak and hold gauge might be helpful, however, rotary specific testers are so cheap that anyone can buy one. I own one. It was approx $250 plus shipping.
Contact TwistedRotors on here for one...
http://www.twistedrotors.com/
Or swing by my house with an acceptable form of payment a spark plug socket, and a ratchet... Acceptable payment can be any one of the following:
-US$20
-One case of Yuengling (You may partake as well.) or any microbrew so long as it's not an IPA.
-Two 2/3lb burgers from Five Guys or Fuddruckers... (One with Jalapeno cheese, lettuce, tomato, pickles, onions, shrooms, BBQ sauce, a shot of Ketchup, mustard, and mayo on it... The other one gets whatever you want on it. You eat it.)
-Extra Large Pizza (Preferably Hawaiian, but whatever works, so long as there's no Anchovies.)
Payments may change based on how hungry I am or how much time I have to kick around.
In addition, the use of it does not take two days. It takes about half an hour... Including time to polish off a beer and bullshit around.
When did a conventional compression tester ever become an unacceptable method? Its been used by thousands for a long while now. I think the problem lies in the fact that there's a procedure to follow and when people don't follow it they get incorrect readings so they blow the whole thing off as wildly inaccurate.
-The data you get from it is not 100% accurate.
-It requires modification of the tester.
-The procedure must be strictly adhered to.
In addition, there is a variable.
What if I press my schrader valve harder than you press yours...
My readings will be lower and drop faster than yours...
Up until I actually press hard enough to cover the schrader valve completely with my thumb, then we go back to my values not dropping as fast or at all if the engine is bad enough.
Compression results also vary based on RPM... A bad bearing, thick oil, or an old battery, battery cables, or starter can throw the results off a bit.
Collecting your RPM numbers along with the test results is helpful.
+1
Last edited by Pele; 11-23-09 at 06:42 AM.