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crack rotor housing

Old 09-10-13, 05:40 PM
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crack rotor housing

hi guys I would like to know what would cause a crack on the rotor housing right on top of the trailing plug and in the trailing plug area.thanks
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Old 09-10-13, 06:00 PM
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too hot a trailing plug from the outset
.. curiously the issue is far less common in australia
where i have dealt with a lot of housings and always looked out for the issue , and have only seen it a couple of times and only in the N326 housings
( which has same leading spark location as the US s4 NA and US only s4 T housings )

the hotter the plug , the less it can radiate heat away from the tips and out through the threads
i would suspect it is the higher resulting temperature differential between the plug surface area and the threads that is causing distortion

Last edited by bumpstart; 09-10-13 at 06:03 PM.
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Old 09-10-13, 06:45 PM
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the housing its a s4 turbo housing, im using 10.5 plugs.i will post a pic of the housing tomorrow when I take engine apart.
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Old 09-10-13, 07:09 PM
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a crack on the outside of the housing? a broken stat gear would cause it... prepare for carnage if that is the case.
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Old 09-10-13, 07:29 PM
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yes the housing its crack outside
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Old 09-11-13, 04:56 PM
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Old 09-11-13, 04:57 PM
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its crack in and out
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Old 09-11-13, 05:11 PM
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is there also a hairline crack on the leading plug hole?
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Old 09-11-13, 06:09 PM
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no that's the wrinkle paint that make it look like that.
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Old 09-11-13, 08:35 PM
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Turbo+Nitrous?
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Old 09-11-13, 08:54 PM
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turbo and fuel its e85
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Old 09-12-13, 04:36 PM
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i don't know, that looks like a strange failure and probably related to detonation issues that the studs didn't remedy(if you used any).
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Old 09-12-13, 05:07 PM
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it is strange, 1st time that this happen to me,where the rotor run its not damage all the damage its in the plug and outside area.
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Old 09-12-13, 06:01 PM
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i would check the dowels/tension bolts for warpage, that would probably point you in the right direction.
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Old 09-12-13, 07:40 PM
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im going to re-inspect everything but everything else look good, new tension bolts are on the way and put everything back.
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Old 09-12-13, 08:07 PM
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this might be a stupid question, but it didn't freeze did it?

Front or rear rotor?

Check engine mounts. Often if there is a dowel issue on the rear rotor (pretty much all dowel issues are on the rear rotor anyway) you will find that the engine mounts are damaged, as there is more stress on the dowels if all the torque is being transferred through the block instead of the mounts. Usually dowel problems result from high temperatures + knock. I have never before seen a case where the rotor housing failed before the iron though. What power level is this running? Maybe it is more a result of super high cylinder pressures without knock since you are running E85?

Can you see any casting flaws or anything that may have weakened that area? If it were my engine I would break it the rest of the way apart and try to see if there are any material defects and/or any signs of fatigue cracking.
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Old 09-12-13, 08:51 PM
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the issue was on the rear rotor only,irons are good everything seen good no sings of knock on plugs, egt was on 1300f the car made 397 [email protected] psi when I increase the boost to 21 psi the housing explode.the engine its all apart for a total inspection its everything look good put it back together.
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Old 09-13-13, 01:16 PM
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doubt it was freeze related since it hasn't been that cold, yet and after his reply it rules that out.

simply sounds like engine twist due to too much timing, but this is a rather rare failure mode result.

check the rotor and housing for any scuff/witness marks of contact, they may be very minor but that is all it takes.
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Old 09-13-13, 01:24 PM
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its weird it broke on the outside and not the inside...
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Old 09-13-13, 02:00 PM
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yep, the only other time i have seen anything similar was when a rotor tried to escape the engine...



but i could envision the rotor tapping the trochoid surface could put enough pressure on the housing to crack it while not causing such extensive damage. or there simply was so much pressure from a detonation cycle that the housing deformed before the rotor/seals gave up(weak aluminum casting or flawed/dirty aluminum mix).

Last edited by RotaryEvolution; 09-13-13 at 02:08 PM.
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Old 09-13-13, 02:51 PM
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You said u turned the boost up.
Detonation. Not enough fuel or too much timing.
Not enough octane

I've done away with trailing ignition all together to avoid this type of problem.

What is you timing under boost ?
What's was ur a/f under boost?
What fuel pump and regulator are u using?
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Old 09-13-13, 04:59 PM
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Originally Posted by RotaryEvolution View Post
yep, the only other time i have seen anything similar was when a rotor tried to escape the engine....
yeah me too!

http://www.fc3spro.com/TECH/HOF/K2RD/k2rdhof01.html
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Old 09-13-13, 06:08 PM
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i saw that page... scares the hell out of me when i think of what could happen with a stock flywheel when it happens.

luckily these sort of failures are extremely rare.

the damage of yours looks a little less extensive but on the FD engine i got in, the key managed to hold back the stock flywheel and only sheared it half way through(likely because there was no load on the engine when it let go).

Last edited by RotaryEvolution; 09-13-13 at 06:11 PM.
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Old 09-13-13, 07:17 PM
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Originally Posted by RotaryEvolution View Post
i saw that page... scares the hell out of me when i think of what could happen with a stock flywheel when it happens.

luckily these sort of failures are extremely rare.

the damage of yours looks a little less extensive but on the FD engine i got in, the key managed to hold back the stock flywheel and only sheared it half way through(likely because there was no load on the engine when it let go).
so that one let go at the rev limiter in 3rd, and the flywheel was just sitting in the bellhousing, trans and clutch were totally ok
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Old 09-13-13, 07:38 PM
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Originally Posted by ghost1000 View Post
You said u turned the boost up.
Detonation. Not enough fuel or too much timing.
Not enough octane

I've done away with trailing ignition all together to avoid this type of problem.

What is you timing under boost ?
What's was ur a/f under boost?
What fuel pump and regulator are u using?
a/f low 11
12 deg on timing and 10 split
2 bosch 044 and a aeromotive regulator
egt 1300 deg.
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