Clearance of the tip from wall to wall. Hold the rotor in front of you at eye level. Look through the apex seal slot along it's length (looking in from the side, as if looking at the corner seal). Focus real well for a second and you'll probably notice the groove widens near the top, like a V (not as eggagerated, though) instead of a set of parallel lines like ||. This is an opened up apex seal groove clearance, it lets the seal rock back and forth as the engine rotates...each time you accelerate and decelerate (shift) or shutdown and startup the engine, the "tilt" of these seals changes from one end to the other. A slight bit of clearance is normal, but if you can move the thing around much at all, then that flex is what will cause the seal to beak along it's length like yours did...the lower half of the seal is in a tight groove, the upper half is in a looser one so you develop a stress point there.

 

kinda on the subject of rebuilds... Does anyone have pics of a good and bad rotor housing. I blew 2 stock apex seals and pulled the motor. I havent ripped it apart yet, cuz im scared. I wanna know what to expect. So as long as the rotor tip is in good condition, i should be fine using it? thanx

 

apex damage, takes a rotor and housing with it:

 

Sweet mother! After looking at that I feel really damn lucky.

Sure is a shame to see destroyed components....do they make new rotors anymore?

Thanks for clearing up my question Kevin!

James

 

James, they still make the replacement rotors, whether or not you can get them in the states though I have no idea. (think you can though) the big thing is the cost, just like the rotor houseings they are costly. still if you are rebuilding with new houseings, going with anything less than a absoulutely good rotor is a risk IMHO, and one not worth taking. obvisouly as seen in other photos your seals didn't go as bad as some others. there are many debates on which seal is better, I am not going to bother to dignify any of the arguments with an answer aobut which i feel is better, just remember that a properly tuned ecu (timing/fuel) is your best bet against this problem. 3mm seals can resist a little more, but they are no substitute for a properly sorted out ecu.

check with some of the computer whizzs here on the forum, and they will tell you the same. 2mm, 3mm, who cares, the ecu tuning is much more important.

good luck
kenn

 

Sounds like it's running at around 250 to 270 at the wheels with my estimate.

Can you give me any numbers?

What is that chart did you post?
Can you tell us what the chart represents?
I see 4 columns - 4 different sessions?


-Ted

 

I don't know if I'm reading that chart right, but it looks like you tuned it to a 14.6 AFR. If thats the case, then that would be your cause of detonation right there.

-Joe

 

i have a very limited knowledge of metallurgy too,.. but to mee it looks not like they are soft,.. (soft would deform insted of chunking out like that) but that they are made of some kind of sintered metal like the side seals,.. this would make them break like that i think...

 

Landers is the man

Wankel7, sounds like you could have used larger secondaries as well - 12psi on the larger turbo is gonna be pushing more air than 12 psi on the stock turbo and it sounds like you were running stock 550's on just a walbro. You've got an SAFC which is good, but when you run out of injector you run out of injector.

 

Thats my motor *cries*.

Hahaha, yeah that was bad......

 

Yeah, I just felt like jacking your photos, since they were already uploaded to the forum as attatchments, and were easy to paste in as IMG's here. And they illustrate the point very well too.

 

Feel free to use them. I have no idea what I am going to do with this motor. The front rotor and housing are trashed. The rear housing has 3-4 little scratches I can feel with my fingernail so I should not use it.
I might just sell whats good on it and use the money to afford a jspec, I have to get my car back on the road asap.

 

How are the irons? If it's just the housings and rotors you can find housings on ebay all the time, or various people on the forum. Rotors might be a tad harder to get ahold of (used) but I see them on ebay frequently and have been watching for them.

 

Reted/Overdriven - The run that blew the engine was the first wide open in third gear I had done since I did work to it (RB exhaust, EGT, ported the WG). So, I was more focused on what the boost was after the porting. Should have got the 60MM gauge eh

On that chart that is four seperate runs all from the same night. Where the AFR dips down that is when I got on it. It was from 4000rpm floored thru 7000ish.

I would normally see 12.5 und richer under WOT.

DRAG086 - That is intresting what you say about the seals. I am going to email the picture of the failed seal to Aktins and see if they can offer any insight to the failure.

jon88se - My fuel setup was the walboro, rewired with some thick wire to the battery, SAFC, Wideband, 550CC primaries,720 CC secondaires.

Now with the BNR3 I am not sure on the setup. I am thinking 4 720CC or 720CC X2 and 1600CC X2. Since I am going with an EMS I suppose that would acceptable.

James

 

On the irons I had to leave town to so I was not able to check for warpage on the irons. There are no cuts on them at all. However, you can feel rises and stuff on them. I guess that is from the side/corner/oil seals wearing on it.

I was considering sending them off to RB for the their lapping service.

On the rotor I better start hunting.

I am going to go with new rotor housings though.

James

 

Never again!!!!!

 

Santiago has told me about using S4 rotors to help lower compression and that might be a safer route to go. It makes sense and all. Since you can't cool engine compression but you can cool boost.

The only things I dont like about it is I have find two rotors not just one. Also, would I not need a new counterweight upfront. Also, running an aftermarket flywheel don't i need a s4 flywheel counter weight.

 

Lapping is always a good idea on rebuilds in my opinion. Unless your irons are in really good shape and within specs, but usually lapping is a good idea either way.

On the note of the s4 rotors, sure you can get lower compression rotors and it'll be "safer" but if you're going standalone you really don't have to worry about it as much as you should be properly tuning your car anyways. A properly tuned car wont have to worry about going between s4 and s5 TII rotors, the difference isn't very major. If you swapped rotors you'd need a front and rear counterweight for an s4, I have a front counterweight for s4's if you're interested But I'd suggest just using s5 rotors still.

 

You know...I think your right on that man. Esp after Kenn Chan said it really doesnt mater what seals you use...it is all about the tuning to make sure it is safe. You and his comments make sense...thanks!

 

all of atkins turbo motors come with 3rd gen corner seal springs.


damn, if you think he has that much at the wheels, how much hp do i have to get me down the track in 13.467 @105.44??

the only problems i had with my atkins motor was the trailing edge of the exhaust port wasn't beveled. after 8k miles, the apex seals wore until it lost too much compression to run. oh, and i ordered it with a stage 2 (i think) streetport, but the port shapes were hardly changed, rather smoothed. runners in the irons looked nicely ported tho. i rebuilt the motor using the RA seals and redid all the ports and have about 12k miles on it now. haven't checked compression yet, but it runs great.

 

So what did you do with your ports when you put her back together. Did you fix the exhaust port? I need to look at my exhaust port!

James

 

If you're not registered at nopistons.com yet, register and read up on JudgeITO's exhaust porting tips thread.

Essentially factory housings have a 2mm bevel around the port to keep the apex seals from catching or wearing prematurly. Lots of shops and builders seem to not do this, unfortunately, but they should. Thread:

http://www.nopistons.com/forums/inde...pic=31895&st=0

 

Man, now I can't wait to go home and check my exhaust ports to see what was done/not done. Thanks for that link!

James

 

i thought your broken apex seal looked rather odd, it seems to have broken off exactly where the exhaust port passes across. maybe it had some wear on the apex seal from the non-beveled exhaust port causing a point of weakness at each end of the worn section of the seal. the transition from worn section to non worn section will cause a stress point where cracks are prone to start.

 

That's a good point. If the exhaust port did indeed have a sharp edge then that could've been the cause of all this.