roflcopter

iTrader: (2)

Now I've done some searching and everything I find seems to be old and more geared towards older 13B's, not the RENESIS. Now I know that it's not ideal, and from what I read some shops weren't too keen on it back when it was first being attempted, but we are currently rebuilding a motor and the compression issue seems to be due to the apex seal grooves wallowing out and leaving wayyy too much clearance(and uneven) between the side of the seal and the groove(think .008in+ gap in places). I know it is very common practice to mill the rotors out to 3mm to fit older seals in the RX7's, but I can't find anywhere that does that for the 8, or even any info on what exactly the problem with doing it on the 8 is.

Now I understand that the casting is thinner on the RENESIS rotors than previous, and that milling out to 3mm can easily end in cutting through into the oil cavity, but has anyone successfully milled a set out? We have a full machine shop at our disposal with people who know what they're doing running the machines, and from my reading it seems that most apex groove widening is done on an EDM wire cutting machine, not a mill. So it wouldn't be hard to get them machined, but we need to know what we're working with before we do it. First of all, I know that the seals in it now are 2mm, and we will be going to 3mm, but does that mean that the actual width of the seal is 3mm, or that the groove is 3mm, or is the clearance made up by having a slightly less than 3mm seal with a slightly larger than 3mm groove? Would it be possible to just cut the groove slightly narrower, maybe in the 2.96mm range and then just clearance the seals down to that, you sometimes have to sand them down to make an even fit anyways, to avoid cutting it close with the thin casting on the rotors?

Thanks in advance, and I know this is not something that should be tackled by 'non-professionals', but at this point there's nothing to lose since the rotors are shot anyways, and I have faith in the shop that would be doing the work.

Brettus

iTrader: (2)

I have gone with deeper (rx7) seals and that was no problem . The 3mm seal might be deeper again which could be why there have been reports of cutting through the casting ... not sure on that though.

roflcopter

iTrader: (2)

Hmmmm, what was the reasoning for going with deeper seals? Just more durable for boosted applications? I assume they'd provide slightly better sealing properties too, especially at higher RPM.

Brettus

iTrader: (2)

just for the extra strength under boost if there is a detonation .

roflcopter

iTrader: (2)

Righteous.

Now if someone who has tried to mill out a set of renesis rotors and has a few pointers we'll be in business. The only other question left is what to do about apex seal springs, since the older 3mm seals will have originally used the single spring setup, should we put single springs in it, or just put the double renesis ones in even though it won't have the second step to house the smaller one?

dannobre

iTrader: (3)

The problem was the depth combined with the extra width. They sometimes encroach into the rotor interior at the bottom endges of the cuts

nycgps

iTrader: (1)

Taller seals last longer and handles boost better.

thicker seal (2mm stock vs 3mm milled) can handle boost even better, but not sealing as good as 2mm

if I go boosting 1 day, I go with 3mm FD height seals no questions asked.

there are companies that does that kind of modification with EDM, even on MSP (Renesis), for couple hundred bux

roflcopter

iTrader: (2)

Cool, so the main issue will be in the bottom corners, which should be able to be avoided by staying on the bottom end of the width and then just sanding the seals a tad to get them clearanced right? This is an N/A motor and we're not worried about strength, just trying to avoid buying two new rotors for it if that's possible. What companies offer that for the renesis? I really couldn't find any.

Karack

for a better alternative if the engine isn't going to see boost is to use the oversize goopy apex seals.

RIWWP

iTrader: (2)

For an N/A normal rebuild, why aren't you just going with OEM seals, and then clearancing them properly?

There isn't much reason to go oversized for a basic N/A rebuild.


Edit: The problem with seals for most factory and remans are simply that they aren't clearanced close enough. You CAN clearance them properly if you do it by hand. You don't have to go to larger seals to accomplish this.

Brettus

iTrader: (2)

There is such a thing ? how much wider than stock are they ?

Karack

i haven't asked jon about them for the renesis as the engines usually don't need them, yet.

but i'm sure he could get the ball rolling in no time if he hasn't already. the issue is the rotor seal slots wear into a "v" shape and the clearances can't be met, even with new seals. he does make stock size seals currently but they're not listed for the renesis(generic 13B listing, but they carry all series of seals). i'd actually be surprised if he doesn't have them sitting on the shelf already. you would also need to run the oversize corner seals to match.

Goopy Performance Apex Seals
http://www.goopyperformance.com/html...ner_seals.html

is it cheaper than replacing the rotors or milling them and still needing to replace hardware? yes, it is.

if interested i can check on it on monday.

roflcopter

iTrader: (2)

Exactly what Karack said, the grooves in the rotor are worn out, think about the lips being splayed outwards, and the problem is there being too big of a gap between the rotor and the side of the seal, there's no way to fix that without either running a wider seal or milling the rotor to accept significantly wider seals.

nycgps

iTrader: (1)

it's common for them to "weed" out

TeamRX8

iTrader: (25)

If you are building an NA race motor with ceramic seals then going to the deeper 13B apex seal and machining the rotor and corner seals is the preferred technique if the class rules permit it.

OE rotors with any significant mileage on them almost always have too much apex groove clearance and should be replaced rather than reused. This has all been discussed many years ago, though some still refuse to measure them properly or just ignore sound advice entirely and throw them back in ...

3mm seals have been done, but it can be hit or miss on whether there is sufficient material left after machining. The lifespan is considerably less as a result too. Regardless, you should always start with a new rotor even if machining the apex groove out.

roflcopter

iTrader: (2)

Well that's not exactly the news we wanted to hear. This isn't for a race motor, just a daily driven rx8. How often have you seem this be the issue that causes a motor to lose compression to the point of not starting? We tore it down and we're expecting something more significant, but the grooves being splayed a bit seems to be the only thing out of spec.

Brettus

iTrader: (2)

Did you actually do a compression test ?

Karack

why would you buy new rotors to mill them? the seal slots are hardened and once cut they are no longer hardened regardless if they are new or used rotors. the only reason to replace them would be if any of the other rotor clearances were out of spec with new hardware.

TeamRX8

iTrader: (25)

The recommendation is to make them deeper, not wider.

Ask yourself then, if they're treated so well then why do they wallow out so easily? In the past discussion, the example is two fence posts, with one 50% deeper in the ground than the other. Otherwise all else being equal, if you rock them both back and forth with equal force which one do you think will wallow out more/sooner? Sometimes the answer isn't as obvious as you perceive it to be.

roflcopter

iTrader: (2)

Yes, the motor was definitely having compression issues.

And are you recommending that milling the slots deeper and using taller seals would remedy the issues we're having? Or could be a preventive measure to keep this issue from happening? I don't see how going deeper would solve the issue of the groove now being too wide.

Karack

more mass on a MSP housing is a bad recipe in my book. the housings already look like junk at 100k with the shallower, lighter seals. part of this is due to inadequate oil injection IMO.

TeamRX8

iTrader: (25)

Rotor housings with any significant mileage should be replaced too.

My comments are more relevant for race purposes, just that the wider/deeper seal topic applies more to a high end street performance or race application than your run of the mill street application. A daily driver street engine should stay OE, but rebuilding a high mileage Renesis properly is not a cheap endeavor. There are a bunch of people here who don't really understand this and are short hanging longevity by reusing parts that should have been replaced.

Karack

yes, and i don't see where the OP asked about building an engine solely for track use. the renesis does wallow out the channel faster due to the short seal design but i have never run into an issue with the resizing the channel and excessive wear but i also referred to marginally oversizing the seals. building an engine with all new parts gets very costly very quickly. why not replace the irons, they are going to be through the nitriding at 100k as well and will soon be out of spec and begin to wear more rapidly.

new housings, new rotors, new bearings, new seals, new irons= new engine, $5k+. we're talking about the renesis, which doesn't exactly have the best of track records to be dropping money on all new parts and still questioning reliability.

skc

When I rebuild I will be specifying new rotors, housings,side plates ground and re nitrated. when it comes to apex seals if it is a NA car then stock is probably the best. My car is supercharged so I will have to look into something stronger and perhaps lighter.

I think it is false economy to reuse existing rotors and irons unless there is very little wear. In the case of the OP it is best to get new rotors and stay with new OEM seals.

roflcopter

iTrader: (2)

While I understand it would be ideal to replace rotors, housings, refinish irons, and all the seals, this would push the cost well into the range of making buying a reman the better option.

What seals are you referring to when you talk about the oversized ones that could slim down the clearances? From my understanding the goopy seals are the taller ones and would still require machine work to be done.