Im back.

I built an fd3s engine (my first but my 4th in the car) in 4 years.

I didnt need to use new main bearings but they looked ace.

On teardown things i noticed.

The front rotor had scraped on the front housing and this is were the tips went. (poorly balanced rotating assembly?)

The front nut on the e shaft was not as tight as it should have been. but still pretty tight.

the counterweights front and rear were from different engines i believe. auto rear (unknown front)

The rev limiter didnt kick in at 8200rpm. revved to 8500

so either.

1) the e shaft bent or is bent
2) the front rotor needed clearancing (which i didnt pick up)
3) rotating assembly was out of balance which caused the front rotor to hit the front housing
4) rotor bearings new

good afr 10.1 at top rpm, so not det.

Anyways im rebuilding it and trying to match the rotor weights to the front and rear counterweight. If i give the rotor weights can you tell me how much the front and rear counterweights should weigh.???? i have my money on this being the cause. i have the auto rotors , rear weight and about 4 front weights knocking around the shed. one of these is the one i need.

 

8500 is not excessive. If you had some bad balancing issues or something was bent, you would have noticed it, I would guess you would have had side iron damage as well.
Were you physically looking at the AFR at 8500 rpm, was it logged? Did the apex seals break? Which ones?
What is your fuel and engine setup?

 

the only way the rotors can touch the rotor housings is if the engine twists(excessively, enough to break dowels/dowel pin bosses) or if the bearings/e-shaft are so excessively worn that the rotor can flop around in the housing.

 

Ok cheers,

set up as follows

standard oem seals,
pineapple racing template medium port
t04r with .81hotside hks boosting .75 bar
1600 bosh in the 2nds.
my own map. 10 - 12 split and 9 degrees of advance in boost and to the limiter
The housings are also ported at the exhaust exit for an extra 2mm of intake/exhaust overlap

1) Dowels are spot on, engine was tourqued to 31 lbs (thru bolts)
2) Yes i was looking at my afr, its in the middle of my tacho (no log though)
3) damage was a scraping look accross the corner seals (about 2cm from the top) front rotor (front of only) which had the effect of sealing the corner seals in thier holes. the apexes have sheared/broken from this/ areas by the looks
4) the 3 apex seals went (chain reaction (side housings look ok still)
5) I have a new main bearing i can get a .076 mm between the new bearing and e shaft. is this ok
6) the engine seemed to run very smoothly past 2k (solid engine mounts)

i dont have a 000s micrometer just a 00s. New bearings are on thier way and i was going to get a few 000 taken of the front of the front rotor for safety. Advice on this?

to aid reliability Ill use another e shaft and i have put put a larger 1.30 hotside on the turbo as maybe the heat/pressure generated by the .81 was too much? the car seemed very fast at half throttle but seemed to bog down a higher up the rpm or with wot more throttle ( i assumed it was the hotside being restrictive. )

Any more ideas for reliabilty considering i have to get this rebuilt in week from now in my spare time.

I have all my front counterweights in front of me and they all look very similar.

Any additional advice would be appreciated. i can get photos of the damage.

 

one more thing i thought might be worth mentioning was i had the engine mounts chopped by 10/15mm so the engine sits lower. I take it this wont effect the rotating assembly balance or put pressure on the front of the engine?

 

pics? what were the symptoms that made you tear it down? Did it run on one rotor?

 

I hit 8500rpm then i heard the seals go while overtaking a bmw m3 who was giving it some. one rotor 0 compression on all faces. the car pulled hard through peak tourque and power areas of the map. then at what seemed to be the very top rpm the seals went. i noticed when i let off the gas i got the wavey vacuum on the boost gauge (a familiar sight) but as i say pulled hard until then.

 

Actually on close inspection it looks like part of a seal (very small) got down the sides possibly and scratched the rotor. maybe the rotos didnt hit the sides. what do you think. something touched the sides though.

 

Hmm im stumped now...low boost high rpm apex seal fail..good afrs

 

holy destruction. I don't think I've seen it let go that bad before.

 

yeah. its a bad one. ive increased my split and took back a few degrees in the 9 bottom right cells of my map too.

 

Your boost, timing, and split are conservative.

It looks like apex seal failure.

How about some pictures of your housing at the exhaust port and spark plug areas.

Barry

 

When you built this engine did you clearance the hard seals?

 

More pics to follow.

Hard seals? Sorry. This is a new term to me. had the feeler gauges and a straight edge over everything i could. and used a micrometer on the housings

 

The apex seals in their grooves were as mazda intended the .007" feeler wouldnt fit and the grooves were clean and consistant

 

"Hard Seals" = Apex, Side and Corner seals.
New side seals need to be clearanced to the corner seals. Did you use new hard seal springs?

 

Did you check to make sure your front end play bearings didn't get pinched by your spacer?

 

New side seal to corner clearances CHECK (how would this cause the motor to pop

New hard seal springs CHECK, new apex and corner seals

End play CHECK (i used a DTI)

im running 9s in the L and T. going to upgrade to 10.5s

 

Pictures?

 

That's fine but it's highly unlikely the plugs had anything to do with it. What brand of apex, corner, and side seals did you use?

 

Not positive this contributed to the engine failure, but sounds like the seals weren't properly clearanced. This is the difference between 'assembling' and 'building' an engine IMO.

 

Why would your assembly be out of balance? All the counterweights will look the same. The only difference is the drill holes to match whatever rotors they were balanced for. They should never be just swapped around. If your putting together an engine with used parts, you need to know exactly what your getting. Also your rotor hitting the housing isn't surprising with a newly built engine with brand new apex seals. Anytime your apex seals go, the shrapnel jams the rotor hard against the bearings. You will almost certainly see a high level of copper on once side of the main bearings on the side of the engine that blew (front or rear). Newer apex seals are harder and thicker so the rotor is likely to move more when they get jammed between the housing.

You need to go back to what you did with your build from the very beginning because to me it seems you are having issues that you never got fixed in the 1st place. To properly diagnose any problem, you must 1st have to figure out the cause of failure. You've had way too many failures over the past 4 years for even most rotary vets to be able to properly help you figure out your problem. Threads like this here is one of the main reasons rotarys get the bad rep they do because you will have ill informed readers see your reoccurring problems and blame the engine and it's design as the fault when the reality is 9 times out of 10 it's always the ignorant owners doing stuff and not having any knowledge of what their doing. Now don't get me wrong, I'm not saying you are the IGNORANT one because **** does happen but, that will be the perception to the experts here. I hope you get everything figured out.

 

maybe i misread it but it sounded like you said the rotors hit the rotor housings, now i gather than you mean they rubbed on the irons. with all the debris floating around this isn't uncommon when seals let go. the rotors also rub on the irons when the rotor bearings get sloppy enough and the oil seal tract wear on the irons becomes excessive.

i see it happen alot on engines when just the apex seals let go, i wouldn't worry about it as a cause for your failure. redo the setup and figure out where your engine setup/tuning errors lie. IMO, i would put my money that your tune wasn't done properly or you have an issue with fuel(imbalance in fuel from front to rear or sudden drop in pressure variances during runs).

 

Karack, the the rotors hitting the side housings was ruled out on closer inspection.

T-Von, I am not having issues i never dealt with in the first place (you are wrong) this is a new failure. before this blew my last engine had water seal failure. the one before i put down to voltage drop of the fuel pump, the one before that was on a top speed run on a cold night and i overboosted.

This new failure is the only mysterious engine failure ive had hence the post. no copper showing on the bearings either. My new engine is a mix of parts in that i have a light flywheel with a counterweight now and a different rotor. most threads say you dont need to balance unless your going over 8500 rpm. hard seals had been clearanced. and the bearings were good.

Im not ill informed or ignorant i have been reading about rotarys for 5 years. I hope thats not the impression your trying to put accross. This post is here because the failure happened in MYSTERIOUS CIRCUMSTANCES unlike the other pops.

I dont need the generic patronising rant about "idiots giving rotaries a bad name". heard and seen it posted too many times and now its directed towards me. But hey cheers

I have been unlucky but im going to pick myself up and give it another go.

goodfella. im going to pay extra special attention to the clearances on the next build which im doing tomorrow through saturday

 

Good with the failures you had in the past, it is helpful to us to know what killed the earlier engines. You have to understand we don't know what you did on the earlier rebuilds. All we know is this"I built an fd3s engine (my first but my 4th in the car) in 4 years". Now you on here with your latest failure and don't know what happened?

I'll be honest, the 1st thing that went through my mind was "this guy doesn't know what the hell he's doing. To give you the benefit of the doubt, that's why I posted the comments I did to get you to give more info.

Knowing this in the very beginning is helpful to those who are trying to help you.

For starters, the engine wont just go out of balance unless you've swapped the wrong parts. I asked you before why you think the engine is out of balance. Is the front counter weight not the original? If not, you need to get ahold of the front counter weight that came with rotating assembly to begin with. As I said before, there all gonna look the same but the only difference will be the drill holes. What weight rotors did you originally have? You could have a MAJOR balancing problem with the wrong counterweight.

Example:
If you have "A" "B" rotors and a counter weight from "E" "F" you will be way off. The counterweights don't have stamps on them to let you know what rotors they were balanced for so your in a crap shoot. Getting counterweights confused is something you never want to happen.


You ever get your injectors cleaned and flow tested? A perfect tune can never compensate for improper fuel flow.