Track day shakedown / excessive blow by
08-14-22, 05:57 PM
#1
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Track day shakedown / excessive blow by
Hey guys, as the title states this was my first shake down with the fd. I have owned it for a few months now and doesn't get street driven, this was the first time ever driving it. I did about x4 30 minute sessions that day, after each session my catch can was full enough to start blowing the oil out of the can filter ( vented to atmosphere ). id say after the 4 sessions I collected about just under 1 quart of oil. I've read that cornering right can cause the oil to push up the filler neck ( this track does have a lot of long hard right corners) The car is single turbo, Both catch can lines are running to the two nipples on the filler neck. i don't know if having the catch can significantly lower the the filler nipples would make things worse or not. After the 4th session the oil that was collected smelt like gas. Previous to this shake down i was on the dyno and over boosted and shot oil out everywhere ( no catch can at the time) I'm curious if i got a bunch of gas mixed in causing a low viscosity now and slipping pass the seals. I know i know i should have changed the oil after dyno tuning. Im going to flush all the oil out a few times, let it air out and do a oil change, raise the location of the catch can and possibly try a baffled filler neck. Any other ideas what could be causing this?
08-14-22, 06:21 PM
#2
It will continue to be an issue till you drysump $3,000 or put in a trap door straight sided oil pan $600.
If you dont want to fix the issue the bandaid is to have the catch can drain back into the old 2ndary turbo oil drain on the rear side housing.
Also, if you dont have a drycell or gel cell battery you are sloshing its acid out too- btw.
If you dont want to fix the issue the bandaid is to have the catch can drain back into the old 2ndary turbo oil drain on the rear side housing.
Also, if you dont have a drycell or gel cell battery you are sloshing its acid out too- btw.
08-14-22, 06:27 PM
#3
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It will continue to be an issue till you drysump $3,000 or put in a trap door straight sided oil pan $600.
If you dont want to fix the issue the bandaid is to have the catch can drain back into the old 2ndary turbo oil drain on the rear side housing.
Also, if you dont have a drycell or gel cell battery you are sloshing its acid out too- btw.
If you dont want to fix the issue the bandaid is to have the catch can drain back into the old 2ndary turbo oil drain on the rear side housing.
Also, if you dont have a drycell or gel cell battery you are sloshing its acid out too- btw.
08-14-22, 06:29 PM
#4
Gas smell in oil is normal as at high temps the side housings distort from cool side and hot side and oil control rings cannot function well.
Its made worse with loose sideseal clearances and rich afrs which are just part of turbo rotary life.
Mazda's naturally aspirated endurance race strategy was to keep oil metering pump/oil injection so they didnt have to keep pitting to drain some oil out of the engine oil system as it became gas + oil.
2008ish? Mazda did a whole big study on the issue hoping to keep rotaries in production as emissions tighten. You can find the sae paper.
Its made worse with loose sideseal clearances and rich afrs which are just part of turbo rotary life.
Mazda's naturally aspirated endurance race strategy was to keep oil metering pump/oil injection so they didnt have to keep pitting to drain some oil out of the engine oil system as it became gas + oil.
2008ish? Mazda did a whole big study on the issue hoping to keep rotaries in production as emissions tighten. You can find the sae paper.
08-17-22, 08:01 AM
#5
Racing Rotary Since 1983
iTrader: (6)
"on the dyno and over boosted and shot oil out everywhere"
since there aren't a lot of curves on a dyno lateral forces are not the primary cause of your problems nor is your catch can arrangement.
there are two internal items that function as the lower ring on a piston engine: the steel oil control rings on the sides of the rotors and tight side seal to corner seal clearance.
oil control rings present an angular sharp scraper edge against the side iron. if too much is worn away they lose their ability to seal and the sump gets pressurized. the steel rings are pressured against the iron with a spring. it is possible the spring was not replaced during a rebuild. the steel rings seal against their groove with an O ring. it is possible the O rings were not replaced.
most likely is the oil rings are worn past factory spec.
360 degree support (contact with the side iron) is essential. the intake ports all have a ledge that is about an 1/8th of an inch that Mazda purposely cast to support the oil seal. this ledge is a direct impediment to charge flow. more than half of the 160 BREWs that i have rebuilt had been previously ported and the ledge had been removed to increase flow. really bad idea. maybe 3 hp by removing the ledge but loss of oil seal support and the end of a dry catch can. i turn the ledge into a 45 degree slope to ease the restriction but retain the supportive surface.
wide sideseal gap (to corner seal) is another culprit. sideseal gap should be .002 or less. FWIW, i now build only from new stock motors and i mic everything on them on dis-assembly. it is common (and by common i mean on almost all of them) to see a couple of sideseals at over .01... sometimes as much as .015. this is one of the few things Mazda can't automate. SS clearance is done by humans and...
my point is, most of these motors are not torn down and blueprinted but are just installed... and they generally run fine and don't fill up catch tanks. so, probably your sideseals would almost all need to be really really bad to be the cause. (possible)
another possibility could be a leaking fuel injector or injectors.
most likely, worn oil control rings
get it right and you won't see anything in your catch can. here is mine after over 250 500+ hp runs. fabbed in 2013. 'don't remember ever cleaning it.
since you will be doing what the FD was designed to do... carving up road courses, you will want to use the rear turbo oil drain port on the back iron as another vent into your catch can. if you vent from only one side of the motor (left/filler tube) when you are in a right hand corner the vent hole will be covered w oil so the sump will have no vent. adding the other side assures some venting. note the two fittings on my catch can. one for each side of the motor.
since there aren't a lot of curves on a dyno lateral forces are not the primary cause of your problems nor is your catch can arrangement.
there are two internal items that function as the lower ring on a piston engine: the steel oil control rings on the sides of the rotors and tight side seal to corner seal clearance.
oil control rings present an angular sharp scraper edge against the side iron. if too much is worn away they lose their ability to seal and the sump gets pressurized. the steel rings are pressured against the iron with a spring. it is possible the spring was not replaced during a rebuild. the steel rings seal against their groove with an O ring. it is possible the O rings were not replaced.
most likely is the oil rings are worn past factory spec.
360 degree support (contact with the side iron) is essential. the intake ports all have a ledge that is about an 1/8th of an inch that Mazda purposely cast to support the oil seal. this ledge is a direct impediment to charge flow. more than half of the 160 BREWs that i have rebuilt had been previously ported and the ledge had been removed to increase flow. really bad idea. maybe 3 hp by removing the ledge but loss of oil seal support and the end of a dry catch can. i turn the ledge into a 45 degree slope to ease the restriction but retain the supportive surface.
wide sideseal gap (to corner seal) is another culprit. sideseal gap should be .002 or less. FWIW, i now build only from new stock motors and i mic everything on them on dis-assembly. it is common (and by common i mean on almost all of them) to see a couple of sideseals at over .01... sometimes as much as .015. this is one of the few things Mazda can't automate. SS clearance is done by humans and...
my point is, most of these motors are not torn down and blueprinted but are just installed... and they generally run fine and don't fill up catch tanks. so, probably your sideseals would almost all need to be really really bad to be the cause. (possible)
another possibility could be a leaking fuel injector or injectors.
most likely, worn oil control rings
get it right and you won't see anything in your catch can. here is mine after over 250 500+ hp runs. fabbed in 2013. 'don't remember ever cleaning it.
since you will be doing what the FD was designed to do... carving up road courses, you will want to use the rear turbo oil drain port on the back iron as another vent into your catch can. if you vent from only one side of the motor (left/filler tube) when you are in a right hand corner the vent hole will be covered w oil so the sump will have no vent. adding the other side assures some venting. note the two fittings on my catch can. one for each side of the motor.
Last edited by Howard Coleman; 08-17-22 at 08:17 AM.
08-17-22, 11:51 AM
#6
bunch of good threads on oil catch cans if you want to search
here's one: https://www.rx7club.com/3rd-generati...ce-car-792344/
here's one: https://www.rx7club.com/3rd-generati...ce-car-792344/
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