13B Semi-Blowup Problem
11-28-05, 08:54 PM
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13B Semi-Blowup Problem
I have a single seat, mid-engined hillclimb car with a modified peripheral port 13B in it. While doing some testing the other day we noted a puff of smoke out the exhaust followed by a bloom of smoke over the car. The engine did not tighten or seize, and I only became aware of what happened (during a test run on an airstrip) after I stopped. There was oil all over, and the filler cap was gone.
Subsequent checking revealed that 1.5 quarts of oil had blown out. Compression testing (using a conventional guage , bottom plug), showed 50 front, 55 rear. The engine cranked normally. BUT oil was blown out of the rear plug holes while cranking the compression check on the front rotor. I am very new to working on Wankels and would very much appreciate diagnosis comments from you experienced guys. My non-educated guess is that an oil pressure line has opened up to the rear combustion chamber, allowing combustion pressure to get into the crankcase, which blows out the oil. The rear plugs were quite fouled, compared to the fronts.
The engine was bridgeported, and runs extreme RPMs (11,500) for short duration hillclimbs of 3 minutes or less.
KieftBandit
Subsequent checking revealed that 1.5 quarts of oil had blown out. Compression testing (using a conventional guage , bottom plug), showed 50 front, 55 rear. The engine cranked normally. BUT oil was blown out of the rear plug holes while cranking the compression check on the front rotor. I am very new to working on Wankels and would very much appreciate diagnosis comments from you experienced guys. My non-educated guess is that an oil pressure line has opened up to the rear combustion chamber, allowing combustion pressure to get into the crankcase, which blows out the oil. The rear plugs were quite fouled, compared to the fronts.
The engine was bridgeported, and runs extreme RPMs (11,500) for short duration hillclimbs of 3 minutes or less.
KieftBandit
11-29-05, 06:04 PM
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I'm not arguing, but wouldn't a seal or rotor hole problem greatly reduce the compression in that sector compared to the other one? They are within 10% of each other on the compression check, with the "bad" one the higher of the two.
The engine is not supercharged or turbo'd in any way; strictly atmospheric. In my forum reading so far I'm impressed by the much lower revs many very impressive engines are getting their power at, compared to my 11,000 plus.
The engine suffered a rotor hole many years back at the Giants Despair Hillclimb in Wilkes-Barre, PA. Thanks to all who have responded to my thread. I need all the help I can get!
The engine is not supercharged or turbo'd in any way; strictly atmospheric. In my forum reading so far I'm impressed by the much lower revs many very impressive engines are getting their power at, compared to my 11,000 plus.
The engine suffered a rotor hole many years back at the Giants Despair Hillclimb in Wilkes-Barre, PA. Thanks to all who have responded to my thread. I need all the help I can get!
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11-30-05, 04:12 PM
#8
a "normal" compression tester is not going to tell you if you have a bad apex seal because it will still show compression on the one "good" face of the rotor. What you need to do if it is possible with your compression tester is to remove the shrader valve found in the fitting that threads into your spark plug hole. doing this will allow the gauge to move freely up and down while the different faces of the rotor sweep by.... you should see a bump-bump-bump on the needle... if you only see a bump-...-... then more then likely you have a bad apex seal. If it is smoking and your compression test is ok, then you may have a crank case ventilation issue. Is your vent line on the oil fill tube plugged off?? Or under any kind of pressure. If it is blocked of you could be building pressure at which time the only place for it to go is in the motor via the oil control rings. If the vent is not plugged, but rather being vented into the intake then you will need to add a catch bottle like most racers use
best of luck
best of luck
11-30-05, 06:28 PM
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I will test again per Bastard and report back, and post pics also. The manifold is a pair of 2" tubes from the engine sides; they turn up 90 degrees to a Weber 51 two barrel carburetor. Thanks to all for your interest. Now must go get the books and bone up on "Wankelese".
12-07-05, 07:53 PM
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I re-did the compression check today, with a free-flowing guage as advised by Bastard. The front chamber showed 1 strong bumps, then 2 weaker bumps, with the needle tending towards 50# max, a bit less for the weaker bumps.
The rear chamber (very oily) showed somewhat higher guage readings and a combination of 1 weak bump, 2 strong bumps! It may be that the oil in the cylinder is not only affecting the pressure, but the "bump type" incidence, too? Because the needle is moving back and forth very fast it is hard to be awfully definite as to pressure numbers, and maybe bump types, too. Does this information confirm the opinion that an oil seal failed?
At any rate the starter sounded very normal and I have high hopes that nothing really bad has occurred. All 4 plug holes were tried, with that chamber's other plug in place, but no plugs in the other chamber. No particular difference was noted between the leading and trailing holes. As it is nontheless clear that something internal has given way the engine will come apart in my quivering hands after the first of the year, at which time I shall probably be bleating for advice once again!
In reference to the requested pictures, they should be on the way in another 2-3 days, providing we can figure out how to send them to the form.
One other thing: I recently posted a thread about possible stalling of the water pump. If you care to, please post responses on that thread- and thank you all.
The rear chamber (very oily) showed somewhat higher guage readings and a combination of 1 weak bump, 2 strong bumps! It may be that the oil in the cylinder is not only affecting the pressure, but the "bump type" incidence, too? Because the needle is moving back and forth very fast it is hard to be awfully definite as to pressure numbers, and maybe bump types, too. Does this information confirm the opinion that an oil seal failed?
At any rate the starter sounded very normal and I have high hopes that nothing really bad has occurred. All 4 plug holes were tried, with that chamber's other plug in place, but no plugs in the other chamber. No particular difference was noted between the leading and trailing holes. As it is nontheless clear that something internal has given way the engine will come apart in my quivering hands after the first of the year, at which time I shall probably be bleating for advice once again!
In reference to the requested pictures, they should be on the way in another 2-3 days, providing we can figure out how to send them to the form.
One other thing: I recently posted a thread about possible stalling of the water pump. If you care to, please post responses on that thread- and thank you all.
12-08-05, 01:44 AM
#14
Originally Posted by KieftBandit
I re-did the compression check today, with a free-flowing guage as advised by Bastard. The front chamber showed 1 strong bumps, then 2 weaker bumps, with the needle tending towards 50# max, a bit less for the weaker bumps.
The rear chamber (very oily) showed somewhat higher guage readings and a combination of 1 weak bump, 2 strong bumps! It may be that the oil in the cylinder is not only affecting the pressure, but the "bump type" incidence, too? Because the needle is moving back and forth very fast it is hard to be awfully definite as to pressure numbers, and maybe bump types, too. Does this information confirm the opinion that an oil seal failed?
At any rate the starter sounded very normal and I have high hopes that nothing really bad has occurred. All 4 plug holes were tried, with that chamber's other plug in place, but no plugs in the other chamber. No particular difference was noted between the leading and trailing holes. As it is nontheless clear that something internal has given way the engine will come apart in my quivering hands after the first of the year, at which time I shall probably be bleating for advice once again!
In reference to the requested pictures, they should be on the way in another 2-3 days, providing we can figure out how to send them to the form.
One other thing: I recently posted a thread about possible stalling of the water pump. If you care to, please post responses on that thread- and thank you all.
The rear chamber (very oily) showed somewhat higher guage readings and a combination of 1 weak bump, 2 strong bumps! It may be that the oil in the cylinder is not only affecting the pressure, but the "bump type" incidence, too? Because the needle is moving back and forth very fast it is hard to be awfully definite as to pressure numbers, and maybe bump types, too. Does this information confirm the opinion that an oil seal failed?
At any rate the starter sounded very normal and I have high hopes that nothing really bad has occurred. All 4 plug holes were tried, with that chamber's other plug in place, but no plugs in the other chamber. No particular difference was noted between the leading and trailing holes. As it is nontheless clear that something internal has given way the engine will come apart in my quivering hands after the first of the year, at which time I shall probably be bleating for advice once again!
In reference to the requested pictures, they should be on the way in another 2-3 days, providing we can figure out how to send them to the form.
One other thing: I recently posted a thread about possible stalling of the water pump. If you care to, please post responses on that thread- and thank you all.
Also, the unevenness in compression pulses would likely be a symptom of some type of 'hard' seal failure...You'll more than likely have to tear-down the motor and rebuild.
12-11-05, 02:16 PM
#15
If it blew the oil fill cap off there was huge amounts of crankcase pressure, ie blow-by. Oil being sucked into the rotor housing shows a bad oil control seal. All of this combined with your other thread on over heating problems sounds like you've cooked an oil seal.
The two strong pulses with one weak pulse you describe sounds like a bad side seal on one rotor face which would lead to the blow-by.
And as ERIKSSEVEN says, 50psi is terrible.
Combine all of the above or take any one of them seperately and you're looking at a rebuild.
The two strong pulses with one weak pulse you describe sounds like a bad side seal on one rotor face which would lead to the blow-by.
And as ERIKSSEVEN says, 50psi is terrible.
Combine all of the above or take any one of them seperately and you're looking at a rebuild.
12-14-05, 07:43 AM
#16
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I agree 50 PSI is low, even for a ported engine.
Lower compression on two faces than the third points to a bad apex seal.
Compression on one face lower than the other two is a side seal failure symtom.
Also high blow-by is a side seal failure symtom.
This motor has served you well, but it's time for some TLC.
Lower compression on two faces than the third points to a bad apex seal.
Compression on one face lower than the other two is a side seal failure symtom.
Also high blow-by is a side seal failure symtom.
This motor has served you well, but it's time for some TLC.
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