Cracked rear iron... I think
 

So I just finished having a little bit of fun in the vert... datalogging and such. Saw a little bit of smoke, wondered if it was mine, so I went home.

Oil leak on the drivers side of the engine... sprayed it down with brake cleaner, started the engine. Nice stream coming from the coolant temp sensor that feeds the dash gauge. Obviously isnt coolant, so I'm guessing I cracked the iron.

Ben - I'm directing this at you (kinda). I googled the leak and up came a thread from the other forum where this happened. You replied saying you've never seen it. Now you have, twice!

I suppose when I get to CA I'll pull the engine and figure out whats going on.

Maybe more likely a blown dowel o-ring.

must have found an older thread, i've got a stack of cracked FC rear irons and even 20B irons with the old thin castings that cracked.

is this Junito?

if it is the iron did you feel any hesitations? it takes quite a bit more work to break the pinned engines but it is still possible. on the stock pins you can crack one without even feeling a hesitation.

Nope. My name over there was midnfauciusn. Its coming from between the iron and plate about 1/2 inch above the coolant temp sender.

No hesitations... actually runs as well as it ever has... just spews oil now. Probably about a pint per minute.

ah ok, well i would clean off the dowel area just forward of the oil filter and just above the coolant temp sender. shine on the rounded part of the casting with a flashlight and look for hairline cracks.

with the amount of oil it's pumping out it sounds like a crack at the dowel pin, sorry.

consider a stud kit, the iron will also have to obviously be replaced. it can be salvaged either by studding the engine and welding the iron or running external oil feeds to the front and rear iron and blocking the upper pin oil passage but that's only really worth it on drag racing engines or on track racing builds.

the drift guys have been going through irons like a fat kid in a candy store so i'm going to have to push more real fixes on them instead of throwing them together on budgets and hoping for the best. just had a early B code 20B that cracked the front iron, center thick iron at the front AND the rear of it, studding the front worked but i only noticed the crack at the rear of the thick plate after the engine was running again, the superficial fix only last half a run around the track but the front held up fine(replaced the broken front iron with a reworked 13B-REW iron matched to cosmo 20B spec, repaired the cracked thick iron by welding it and reinforcing the front housing with tight tolerance 1/2" studs, the back half of the engine was not reinforced because we did not have time before the event after we found the crack at the rear section).

being that the 20B thick iron is NLA we have to work around it or he has to source a C-D code short block. external oiling would save the block from the scrapper, as i'm not sure even studding the engine with a cracked iron will keep it from failing again down the road.

at least that gives you an idea of options if you never want to deal with it again and it winds up being a faulty iron.

i will be making a titanium stud kit for the 13B in the near future, but the price will be slightly steeper than some other kits at about $400 for 6 full length studs(to fit an unmodified block or 1/2" which is more suitable for high HP applications and requires block reaming/rethreading, priced higher because titanium still isn't exactly cheap). titanium may not be as strong as some other alloys but it does have good corrosion resistance as well as tensile strength, in the conditions it has to survive in corrosion can weaken other alloys over time.

OP - are you absolutely sure its coming from the coolant temp sensor area and not somewhere above it? Reason I point this out is if the O-rings under the oil pedestal blow out, it will flow down, make a mess and possibly look like its coming from the area the coolant sensor bolts into the rear iron.

Positive. I'm pretty familiar with the engine. Its clean as it is, but when I sprayed it down with brake cleaner, I had no doubt where it was coming from. Definitely not the pedestal. You can actually watch the oil flow out.

and a leaky dowel seal or oil pedestal o-ring wouldn't leak that much without any prior notice. a loose filter that spun off some might but it would probably be worse.

o-rings don't just "blow out", they can leak and slowly ramp up but not an immediate "there one minute" problem.

I'll shoot a video for you guys and throw it on youtube.

sure you dont want to pull it and rebuild it before you leave Jax? we could make it happen with a quickness..

I'd love to... but the move comes first... financially and otherwise. I just bought 3 major appliances this week for the new house. That didn't help.

So, this thread is on pause for a couple months... until I do the teardown. Lots of pics will follow.

i take it you did find a cracked dowel casting?

you can replace the iron without disassembling the whole engine but unless the engine was putting out over 350whp you should look into why it failed otherwise even if it is fixed it will fail again or other parts will fail along with it. for example, if the tune or pump is bad which caused the detonation that took out the iron and you stud the engine the seals will be next to go.

i'm also looking to moving the shop down to central florida, but on the west side near clearwater/tampa. but that is about a year from now.

the iron cracked for sure, either because of too much timing or a lean spot in the fuel map, possibly an injector going bad or even a clogged fuel filter.. find what caused the problem or it will crack again.. good luck with the move !

The cause was prolly Big turbo on stock jdm import swap. Chances are it could use a rebuild even without the crack..

probably would have been a good idea, the 3 piece 2mm cast iron seals just look for a reason to take out a rotor and housing so this may actually be cheaper than the alternative.

BUT

without reinforcing the block i find that they break irons with less trouble after having been rebuilt recently. the mating surfaces are usually etched together and more difficult to twist on older engines.

Haven't found anything yet... won't tear the engine down until I get to monterey.

My afrs we're at 11.x all the way to the whopping 13 lbs of boost I'm running... I can attach a log I took after it happened... before I realized anything was wrong.

Not really a big turbo... just a bnr stage 2.

here is a sample datalog, and the ignition and fuel maps I've been using.

Using 550/720 injectors, all freshly rebuilt. walbro 255 fuel pump... haven't had any fuel issues to date.

I just noticed that I had tooth #1 set to 5 deg BTDC, would that essentially advance my entire table by 5 degrees? Would that be enough to cause detonation given the ignition map I posted above?

you mean to the right mark on the pulley? that would be 5*ATDC so your figures would be 5* higher than actual

These were the settings at the time of the uh, mishap.

i have never messed with a megasquirt, so i would ask someone who has setup the trigger the proper setting. but i would also verify it by setting it to 0 and 5*ATDC if allowable and see where the timing mark goes on the hub(advances or retards).

DIYAutoTune's writeup says its supposed to be at 0 degrees.

well i say that because if the CAS is timed to the leading mark on the pulley and if the CAS trigger is advanced 10*(standard is 5ATDC/20ATDC for the markings on the engine) then your timing tables will be into the 22BTDC range under full load, which is rather aggressive for pump gas, a bit too aggressive if you ask me without a knock detection device.

but that assumes it is advanced 10 degrees with the correction factor you're using, if the CAS wasn't retimed to adjust for this correction. all this should be verified with a timing light.

well, I sourced another JDM S5 TII, and will be picking it up on Sunday. I'll make sure that the base timing is done properly this time. If that timing map is pretty solid, this should be really easy to pick up where I left off.

looks fine but that seam where the timing is halved is pretty rough, like someone overly concerned wrote it. all changes should merge into one another versus stepped like that.

same goes for fuel, don't just start dumping fuel once you see positive pressure.

That would be Aaroncake that made the timing map. The fuel one was tuned by VEAnalyzeLive (auto-tune based on desired AFRs).

Something that crossed my mind last night was the fuel cut... it was set to come on at 7400 RPM. I dont know why its set up like that... but shouldn't I be cutting spark? It SEEMS a little more safe...

Your fuel injectors are too small.
You only have enough fuel injector capacity to handle about 270 - 280hp, if everything was tuned nicely.
By your datalog, your tune is still all over the place.

Look at the max pulsewidth - 89.4%.
As a rule of thumb, you're not supposed to go past 85%.
Anything over 85% will possibly lock up the fuel injector - basically > 85% is the same as 90%...95%...100%.
You ran out of fuel capacity.
This could be one reason why the engine let go.

Don't bother with the older S4 (rear) irons.
I've broken them on a customer's FC @ 320hp on a Dynapack dyno.
Replaced with an S5 (rear) iron, and it's doing 400+ reliably daily driver.


-Ted

so this:
http://rx7.com/cgi-local/2ndgencalc.cgi

tells me that 720/720 is able to support 350 at 85% duty cycle...

If I keep my 720 injectors (currently secondaries), swap them over to the primary rail, and throw in some 1000's on the secondary, are there issues when the secondaries come online? The only real reason I'm asking is that the above mentioned calculator says so... but I can think of people running even 1600cc secondaries without issue.

Guess its all in the tune.

Anyway, getting the engine tomorrow... cant wait. Though it will be a while until I swap it in. Gonna throw in new front/rear main seals for the hell of it, order some new exhaust gaskets, and of course a pair of bigger injectors. standing by for recommendations on injector size. I'd like them to fit the stock secondary rail.

that calculator is bogus, the figures are too high for rotary engine applications. perhaps it was carried over from piston engine calculators.

stock 550's good for 262whp at 85% duty? i don't think so.. it also claims FD 550/850's would do 342whp at 85% duty? right.

and i'm not sure why i have to keep repeating this, a turbo S5 engine does not guarantee a thick cast rear iron. they are actually quite rare even on j-spec blocks. if you wind up being unlucky and get the thin cast i would suggest studding the engine or keeping the power levels reasonable(sub 300whp) until it needs to be rebuilt and then reinforce it.

I think I'll shoot for 720/1000s then to be safe. I dont see myself ever getting a bigger turbo, at least with this particular car anyway.

Ben... I believe you on the rear iron. I just happened to find an engine about 4 hours away. It'll provide me with spare engine parts if I ever end up REALLY blowing an engine and not just cracking an iron.

I'll check to see if it has the little gusset going from the iron to the oil pedestal - I think thats one of the telltale signs of the thicker dowel area, right?

nope, the extra rib does help but i have still broken those irons easily. the thick cast rear iron protrudes quite a bit outside the "L" edge of the rear rotor housing. look at the front iron versus the rear where it meets the rotor housing, the thick cast iron will be easy to spot. if they look the same F+R then it's the thin casting.

Thanks. Maybe after I get to Monterey and get this thing back up I'll take it down to Vegas and have you play with the tune (if you want to mess with a MS2). Dont pack up the shop yet! I imagine I'll be done sometime around July-August.

i'll be around, i won't be leaving here for at least another year. we may be looking at houses down there in the next few months though.

Picked up the engine... definitely has the thick dowel area. I don't like the front rotor pulses at the exhaust via the poor man's compression test, so ill be rebuilding.

The front rotor has a blown apex seal, with some rotor damage. Haven't seen the inside of the housing yet... but I'm sure it ain't pretty!

But the back is good! :cheers2:

pic of the front...

Tore the engine down today... the donor engine is near immaculate, with the exception of the front housing and rotor.

The front and rear irons both have the thick dowel area. From what I read, I thought it was just the rear.

Question number 1: God knows what this engine has been through, its a JDM s5. When I tore it down, I found 3 piece apex seals, but the funny part was that the corner seals had FD springs. Anyone know if the JDM engines came with these?

Should I keep the front iron too?

pics attached... somehow.

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