Why did my rebuild fail?
11-22-12, 09:21 PM
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Why did my rebuild fail?
So i rebuilt my first rotary with the help of the mazda trix dvd. I re used rotor housings and side housings. There was no flaking on my housings and minimal wear on my side plates. I replaced all the seals and my motor started up without a hitch.
I broke in the motor for about 2000 miles, when a drift event came up and i couldnt help myself. I went and drove even though i knew i probable should have waited.
Car never seemed to pull the correct vac always around 12, and the compression was around a 100psi. Summer was over so i put the 7 away for the winter.
So summer is finally here, I put in 4 quarts of royal purple, and start it up...... damn this thing seems to be smoking a bunch...hmm? Well after a day of driving it was still smoking. I checked the oil and it seemed really full. **** i could have sworn i drained the oil for winter, well i didnt it had 8 quarts of oil running wtf what an idiot.
I drove it for the majority of the summer even though my vac numbers were suspect thinking it must be a vac leak somewhere but i could never find one. I did another compression test and sure enough it was around 90psi on a couple faces. So i figured i better tear it down.
I ended up finding ridges on the side housings, major grooving on the rotor housings, and a pretty hefty burr on the one side of the apex seal.
Can someone tell me where i went wrong with my build or what may have caused this premature wear?
I broke in the motor for about 2000 miles, when a drift event came up and i couldnt help myself. I went and drove even though i knew i probable should have waited.
Car never seemed to pull the correct vac always around 12, and the compression was around a 100psi. Summer was over so i put the 7 away for the winter.
So summer is finally here, I put in 4 quarts of royal purple, and start it up...... damn this thing seems to be smoking a bunch...hmm? Well after a day of driving it was still smoking. I checked the oil and it seemed really full. **** i could have sworn i drained the oil for winter, well i didnt it had 8 quarts of oil running wtf what an idiot.
I drove it for the majority of the summer even though my vac numbers were suspect thinking it must be a vac leak somewhere but i could never find one. I did another compression test and sure enough it was around 90psi on a couple faces. So i figured i better tear it down.
I ended up finding ridges on the side housings, major grooving on the rotor housings, and a pretty hefty burr on the one side of the apex seal.
Can someone tell me where i went wrong with my build or what may have caused this premature wear?
11-23-12, 11:03 AM
#6
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12 inches of vacuum is pretty poor for a fresh rebuild. Also, a vacuum leak will cause your idle to raise which will actually give 'better' vacuum, not worse.
Sounds like anything could have gone wrong, I agree it's possible the clearances were not correct among other things.
There is a big difference between properly building a rotary engine and just assembling it. I've broken down more than one DIY rebuilds that failed after minimal use and found all sorts of parts inside that should have never been used in the first place.
Sounds like anything could have gone wrong, I agree it's possible the clearances were not correct among other things.
There is a big difference between properly building a rotary engine and just assembling it. I've broken down more than one DIY rebuilds that failed after minimal use and found all sorts of parts inside that should have never been used in the first place.
11-23-12, 07:06 PM
#7
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12 inches of vacuum is pretty poor for a fresh rebuild. Also, a vacuum leak will cause your idle to raise which will actually give 'better' vacuum, not worse.
Sounds like anything could have gone wrong, I agree it's possible the clearances were not correct among other things.
There is a big difference between properly building a rotary engine and just assembling it. I've broken down more than one DIY rebuilds that failed after minimal use and found all sorts of parts inside that should have never been used in the first place.
Sounds like anything could have gone wrong, I agree it's possible the clearances were not correct among other things.
There is a big difference between properly building a rotary engine and just assembling it. I've broken down more than one DIY rebuilds that failed after minimal use and found all sorts of parts inside that should have never been used in the first place.
^
This.
How many times on this forum have we seen a similar story? Not bashing anyone at all, but it is pretty apparent that a rotary engine rebuild is NOT as forgiving as a piston engine. Shoot, I've taken piston engines that were seized up after years of not running, got them broke loose and just replaced rings and ran a cylinder hone thru the bores and had the engine run GREAT! No WAY I'd be that cavalier about a rotary rebuild.
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11-23-12, 11:47 PM
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Thanks for all the replies, For sure it obviously is not an easy task to do a good rebuild. I will post some pics up when i get a chance but its pretty much just grooving. I was kinda thinking that the rotor housings might have been narrow causing the rotor to be to tight of a tolerance i never did check that, speaking of that i should go measure them and see if they were narrow, i don't have mics but i have some good calipers. I used stock 2 piece apex seals but i did not tamper or sand anything on them. GoodfellaFD3S I used all new seals, but i think the irons and housings were just on there way out or fair. I will have to check my side seals for any burs. thewird, no premix and i was kinda thinking maybe the oil metering pump was malfunctioning or something of the sort. I appreciate you guys not bashing me to hard, I dont really have a rotary expert around and i just wanted to learn how to do it myself. I think its taking lessons learned that turns you into a good builder or have someone that knows what the hell they are doing.
11-24-12, 06:36 AM
#10
Constant threat
My hat is off to you for doing your own work. I am sure there aren't too many resources in your area to refer to or get help from.
I hope some of the expert builders on here can help you, maybe you could send the irons to one of them for a look-see?
What are your plans in the mean time, to get your car going again?
Good luck!
I hope some of the expert builders on here can help you, maybe you could send the irons to one of them for a look-see?
What are your plans in the mean time, to get your car going again?
Good luck!
11-24-12, 10:47 PM
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Well at this point the bad economy, is kinda put things on hold. I am thinking about selling my rm250 for the cash to rebuild but its a tough thing to do. I just wonder what the hell obamas next big bull **** thing is going to be. I am just trying to plan my attack for the next build so i don't have a repeat.
11-24-12, 10:57 PM
#12
did the low vacuum occur after the rebuild or after the drift event? a good timeline of events and how the engine was running may help diagnose your problem.
but it sounds to me like a lack of combustion chamber lubrication.
FYI, all rebuilds take approximately 500 miles before the OMP system primes and begins lubricating the combustion chamber components and could be a partial reason for the failure. usually i give customers a quart of 2 stroke oil which is about how long it takes to prime (30 gallons of fuel).
but it sounds to me like a lack of combustion chamber lubrication.
FYI, all rebuilds take approximately 500 miles before the OMP system primes and begins lubricating the combustion chamber components and could be a partial reason for the failure. usually i give customers a quart of 2 stroke oil which is about how long it takes to prime (30 gallons of fuel).
11-25-12, 06:06 AM
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Have you had a good look at the Rotor bearings? i saw a rebuild a while back that had used new Rotor bearings, what had happened is the guy fitting the new bearings had damaged them, this causing them to start to fail very quickly after Assembly. When the engine was taken apart the rotor had made contact with the Plate making the Corner seal stick in its hole. The knock on effect was sticking Apex seal and scoring to the plates.
The Rotor bearings where obviously well out of spec when taken apart, but there was traces of metal filings in the oil pan and the e-shaft had signs of blueing on the sides of the Lobes.
The Rotor bearings where obviously well out of spec when taken apart, but there was traces of metal filings in the oil pan and the e-shaft had signs of blueing on the sides of the Lobes.
11-25-12, 11:53 AM
#15
porting will also drop vacuum, a moderate street port will usually dip down to about 15-18"Hg from the previous figures.
13"Hg on a stock port engine is bad, and i'm somehow figuring either the compression was lower than claimed or there is a large vacuum leak somewhere. even at 90psi of cranking compression the engine should be pulling more vacuum than that.
Last edited by RotaryEvolution; 11-25-12 at 11:56 AM.
11-25-12, 01:12 PM
#18
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When you built it, what did you use to seal the front cover......around the OMP oil feed hole
I get a crappier Idle and alot lower vacuum when my airpump isn't running I think I was getting -14ish without it and 16-18 with it. at 730rpm idle
on my rebuilt small streetport engine its at about 750miles so far its still only getting around -12 vacuum with the airpump not running. Im hoping it will raise soon, the car runs and starts awesome I lost one of the primary injector diffuser, I ended up just using the tops of some S5 TII ones with the actual diffuser part cut off to fill the gap so that might be part of my problem. I just wanted to get it broke in before winter
did you fit all the seals and check the clearance and free play?
Sometimes when I use the old parts to check on the rotors they will fit fine and move freely, but when I start fitting all the new seals some will bind or fit really tight, so I will have to go back and clean them up a bit an check the free height when seated
I get a crappier Idle and alot lower vacuum when my airpump isn't running I think I was getting -14ish without it and 16-18 with it. at 730rpm idle
on my rebuilt small streetport engine its at about 750miles so far its still only getting around -12 vacuum with the airpump not running. Im hoping it will raise soon, the car runs and starts awesome I lost one of the primary injector diffuser, I ended up just using the tops of some S5 TII ones with the actual diffuser part cut off to fill the gap so that might be part of my problem. I just wanted to get it broke in before winter
did you fit all the seals and check the clearance and free play?
Sometimes when I use the old parts to check on the rotors they will fit fine and move freely, but when I start fitting all the new seals some will bind or fit really tight, so I will have to go back and clean them up a bit an check the free height when seated
11-25-12, 05:45 PM
#19
altitude plays a role, higher the altitude the lower your vacuum figures will be. at sea level for example a healthy engine should be pulling about 18-21"Hg. figure about a 1"Hg drop per 2k feet.
porting will also drop vacuum, a moderate street port will usually dip down to about 15-18"Hg from the previous figures.
13"Hg on a stock port engine is bad, and i'm somehow figuring either the compression was lower than claimed or there is a large vacuum leak somewhere. even at 90psi of cranking compression the engine should be pulling more vacuum than that.
porting will also drop vacuum, a moderate street port will usually dip down to about 15-18"Hg from the previous figures.
13"Hg on a stock port engine is bad, and i'm somehow figuring either the compression was lower than claimed or there is a large vacuum leak somewhere. even at 90psi of cranking compression the engine should be pulling more vacuum than that.
My dad's non sequential car runs 0"Hg on stock porting, freshly rebuilt engine, 360rwhp, 20,000km since rebuild, with Knighsport twins..
11-25-12, 06:29 PM
#20
Seems odd. Mine pulls 15-18" Hg at sea level, and compression checked out fine last time we tested it, on original factory engine only just covered 100,000km.
My dad's non sequential car runs 0"Hg on stock porting, freshly rebuilt engine, 360rwhp, 20,000km since rebuild, with Knighsport twins..
My dad's non sequential car runs 0"Hg on stock porting, freshly rebuilt engine, 360rwhp, 20,000km since rebuild, with Knighsport twins..
thewird
11-25-12, 08:48 PM
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I speced my side seals to the factory specs grinding them down as needed. I guess i should have been running 2 stroke oil. I think the vac numbers were about the same after the drift event. My numbers were more like 10hg at 1000rpm and i did use the pineapple street port templates, and no air pump either. This still doesn't make sense seeing how badly grooved it was i will take some pics tonight.
11-25-12, 09:06 PM
#24
Clearance between corner and side is- .05mm -.15mm ( .002"-.00059")
Protrusiong is .5mm (.020")
Some like tighter, some run zero tolerance(pretty slick)
Between grooves in the side plates, your side seals and corner seals were not sealing properly plus possible warped apex's your vacum and compression will be down.Put the apex seals crown to crown and see if you can see light between them, if you can.
Protrusiong is .5mm (.020")
Some like tighter, some run zero tolerance(pretty slick)
Between grooves in the side plates, your side seals and corner seals were not sealing properly plus possible warped apex's your vacum and compression will be down.Put the apex seals crown to crown and see if you can see light between them, if you can.
11-25-12, 10:56 PM
#25
but it sounds to me like a lack of combustion chamber lubrication.
FYI, all rebuilds take approximately 500 miles before the OMP system primes and begins lubricating the combustion chamber components and could be a partial reason for the failure. usually i give customers a quart of 2 stroke oil which is about how long it takes to prime (30 gallons of fuel).
FYI, all rebuilds take approximately 500 miles before the OMP system primes and begins lubricating the combustion chamber components and could be a partial reason for the failure. usually i give customers a quart of 2 stroke oil which is about how long it takes to prime (30 gallons of fuel).
OP stated there was 100psi compression immediately after rebuild but after only a few hundred miles and one "season" compression dropped 10psi. This all screams of insufficient internal lubrication likely compounding a problem with sticking seals from sitting idle for an extended period of time. Without oil those internals rust VERY quickly and will result in recalcitrant seals and subsequent loss of compression.
My 2 cents...regards,
Crispy