A question for Mr. Port-and-Polish or rotarygod or whoever wants to answer: Mr. PnP's motor made 240 rwhp, most of it apparently a big surge in the upper-RPM band. Looking at the ports firsthand, do you think it will be possible to increase midrange power a little too, or is the motor just inherently peaky, or how does that work?

Also I think it was RG (?) who said something about the siamesed center exhaust ports being a restriction and making real gains with a header difficult...is this still going to be a limiting factor or...? Sorry, I'm going off memory here, I know this is a separate issue than the internal ports.

And speaking of emissions testing...does it cover the full RPM range? I've never actually sat there and watched them do it.

Finally, did Racing Beat mention anything about releasing some sort of ECU fix?

 

Racingbeat DID mention releasing an ECU flash for the car.

 

I think its safe to asume that our engines are in NA form should be fine. While Mazda can't predict everything, I know they put quite a few engines on a chasis dyno, ran them for 120K+ miles then torn them down to see what the effects were. Mazda's rotary "skunk works" had years to work on a redesigned rotary, and there is no way they could have gotten the design approved if they couldn't prove that the engine had durability. Mazda was bitten so hard by the RX7 reliability issues, they would't make that mistake again....hell I'm sure Ford put them through the ringer on reliability. Sure, anything is possible, Mazda R&D cold be full of idiots, but I doubt it. I'm feel pretty confident Mazda just figured polishing the intake ports was not necessary due to R&D testing and finally cost.

Mazda does have to care about reliability well past warranty. The FD's reputation really hurt Mazda's brand name and set rotary PR back a decade.

Please someone correct me if I'm wrong here, but NA we should be fine. Now, as for FI, things look to get more interesting. I guess we won't really know until Mazda releases its MS 8 with its SC kit and someone tears the engine down.

 

RB (Racing Beat) not RP (Richard Paul or Rotary Performance) were the ones who said it was a problem under forced induction. I don't know why this would matter though. Nothing was disclosed as far as how much boost pressure was run or how fuel/ignition were controlled. The only things that were mentioned were that at least 2 different types of superchargers were tested. They didn't tell us what kinds though. Nothing as far as turbocharging ever came up. 2 Renesis engines that have blown up under forced induction have exibited side seal impacts. None of the naturally aspirated engines have. Why, I have no idea. This is not to say that it can not happen though. It also doesn't say that it is a problem for everyone. After seeign and touching the ports firsthand I can tell you that it wouldn't be a hard issue to resolve. You just have to open the engine up. Not a good idea though for warranty reasons.

I really don't think that the side seal issue is anything that was done on purpose so others couldn't supercharge it. How would anyone even think that could happen only in forced induction scenarios and not others? There is no way to tell. Even after I've seen it, I'm not sure I understand how it is possible.

My guess is that if this really is an issue with everyone's engine's, Mazda isn't going to admit it. What is more likely is that they will quietly fix the problem at the factory and then ship all later engines corrected. This is pure speculation on my part though but about the only way it could be done without negative publicity.

FWIW I met and spoke with "Koby". I asked him why the side seal clearances were so great compared to the older engines and he didn't know! He told me to talk to a Mazda tech. Actually he hasn't been project manager for years now so he shouldn't be expected to. It was still an honor just to meet and shake the guys hand.

 

Sorry to go OT, RG, did you happen to ask "Koby's" opinion on the use of synthetics in the Renesis?

And I think your right on with how Mazda would just fix future engines.

 

The peakiness of an engine can be determined by many things. The esiest of which to change is the intake manifold length. It is just the way it is designed. There are ways to affect it.

The siamese center ports exibit a problem due to not being able to tune the distance at which the different rotor exhaust pulses collect. In the intermediate housing they collect before they ever get out of the block. Racing Beat has built 2 that I have seen and held, prototypes of headers. The first one was 3 even length pipes that collect at one common point. The other was a 4 runner setup that kept the center port divided in two. It had an insert that joined the center dividing wall and kept the pulses apart and no longer siamesed. Supposedly neither of these headers produced more than about 3-5 peak horsepower improvement over stock. zoom44 has some good pictures of each of these headers that he can post.

When you worry about emissions, it is an all or nothing affair.

Racing Beat did mention the ecu. Jim Mederer showed us their ecu bench. Interesting device. It doesn't do what you would think it does. Instead of being an ecu set up to controll an engine and tune from, it is an ecu that responds to signals that are given to it. There is no Renesis attached to it. There is an electric motor taht spins over and is hooked up to the tach. They have resistors atached to fool some things. There are switches that change voltages to the ecu. There is a degree wheel hooked up so we can see the timing advance. We did not see any timing split differences. When Jim revved up the engine (motor) you could see what timing was run. Then he could reach over and give the maf a different voltage level and you could see how the timing changed. The same thing applied to the temperature. The setup is to learn what the ecu does in certain conditions. It does not help tune an engine in a car or on a stand. The RX-8 is found to run about 5% rich most of the time. The RX-8 ecu has several different maps. The leading ignition has it's own map. The trailing ignition has it's own map. The fuel has different maps for accelerating and decelerating. Within these it has a few different one's. On deceleration either only one or 2 or more injectors may be shut off. Weird huh? It's a complex machine. I'm definitely leaving some info out. Jim did say taht he will eventually release their own tuning for the car. It will also take into account emissions legality so remember that.

 

Koby was in a hurry. The event was over and I was walking the same direction as him. He slowed down just to answer my question or at least try to. He was also in a hurry. I was honored just to talk to him and shake his hand. I wasn't going to take up all of his time. I didn't remember that anyways. I will tell you that Racing Beat endorses Royal Purple though.

 

I saw that side plate too, makes me not want to use renn side plates for some projects i have planned for them,.. i wish they would have kept the side seal supported on the plate,.. a taper will greatly help but it will still lose a little compression, anyhow i wouldnt really call this a huge long term reliability proble, the motor will just loose compression over time... i still dont understand why they didnt keep the seal on the plate,.. the ports would have just been a tiny bit smaller...

 

so over time, would the damage be to the side seal or the housing? I imagine the side seal would be elss expensive to replace

 

The damage to the housing is not significant, and eventually will actually help out not damaging the side seal as it will get worn down in that area. The corner on the leading edge of the side seal will get rounded off however, leading to lower-then-when-new compression. this can be 98% eliminated with a simple beveling and polishing of this area, something mazda should look into.

Looking at that pic it looks like all seals are supported over the aux port so the whole problem lies in the secondary port, and possibly the primaries, though i havnt seen a used center plate yet.

On a side note, can anyone fiigure out why all the renny pots have that odd projection into the port on the opening side?,.. even the exhaust ports have them,.. was mazda trying to help out the side seal a little by supporting it? and if so why even have that little notch out at the top thats causing all the problems,.. i want to see a renny plate with the side seal arc scribed,..

 

That little notch where the problem occurs isn't even functional. If you looked really close at the port, the actual casting behind that opening isn't the same shape. Air doesn't even flow through that little spot. If they just filled it in, the port would still have the same effective timing but no possibility for damage. They should either round off the top lip or they should adjust the machining so that little notch isn't there. Either way the engine's performance won't be affected at all.

 

For those of us who simply don't understand the implications of all this very interesting but confusing technical talk, can someone please tell us what this all boils down to?

It sounds like it basically will result in eventually having lower than normal compression. How long will it take for this to happen? Will we even notice it? Will it cause the engine to quit working prematurely? Can I still expect to get 150,000-200,000 miles out of this engine? How does this affect owners in a real world, practical sense?

Thanks to all for your help and for the interesting discussion.

 

The problem is that it is causing excessive wear to the side seals. These are very very small clearances so over time the side seal wears down more and more. As a stock motor this just means the motor looses a little bit of compression which will cause a small power loss overtime, however in boosted applications you are looking at the possibility of accelerating the wear greatly and ruining your motor (possibly because the excessive heat caused by forced induction causing the seal to expand more). This can possibly be solved by tapering and smoothing out the areas around the ports however I am not sure if anyone has done this yet. Frankly as long as you plan on just driving your RX-8 and not boosting it I wouldn't be worried about it.

 

At this point it doesn't appear that there is any problems with side seal impacts on non forced induction applications. This is only based on the information at this point. If this is true then it will have no long term affects. If there is a real issue, it will start to show up over time. So far only forced induction engines have had a problem but I don't know why it matters. Until we have more definitive proof that it is happening to other engines, we just don't entirely know for sure. All we know at this point is that it apparently is possible.

 

For those of us newbie-rotor-heads following this thread, these illustrations might help with some of the terms being discussed. I was personally having problems visualizing the side seal's path around the side housing, so this helped out:

http://www.rotaryengineillustrated.c...-shousing.html

(although unless I'm mistaken that is not a 6 port renesis side housing).

And where the various seals are on the rotor itself:
http://www.rotaryengineillustrated.c...nat-rotor.html

I would love to see the side housing illustration above with the seal paths superimposed on our 6 port Renesis housing.

 

I would have some pictures of the renesis ports for you except Kari recorded a video and used up all the memory on my digital camera instead.

 

hi Q. nice to see you posting. RG will be getting us some pics soon. and ajax has a couple of them too.

86rx7 that little "notch" was one of the things we looked at right away. as RG said it's not like that in the casting so doesnt need to be there. there were 2 theories tossed around about it. 1- they need it for the tool they use on the milling machine. 2. its a programmig error they thought they could live with. if that notch wasnt there i dont think the seal would drop and hit that edge. from talking with people there the major difference this makes between NA and FI is the extra heat that is directed at the seals with FI. since there was a Mazda Supercharged RX-8 at seven stock on display(in the ACd room off the Courtyard) i bet Mazda has already dealt with the issue sometime in production. it would depend on when they starting noticing it as to how many engines are affected. Tapering would help reduce the wear alot. that edge is really sharp although i understand now that they are always that sharp from the factory.

 

Anyone know how new the engines are that have been torn down and examined? It would be interesting to see a relatively recent tear-down and see if it has changed.

jds

 

Thanks, that helps. I have no plans to turbo- or super-charge the car, so I feel much better. It's great that this info is out for those who will be using FI.

 

For those that need more pictures, I have 7. I will not post them all on this thread because they're 1600x1200 and the one I posted is obscene enough. Some of them are kinda worthless too as i was so close that the camera couldnt focus properly. I need to learn how to use the manual focus on my digital camera one of these days.
Here's links to them all:
http://jedi.betterbox.net/images/rx8...keports-01.jpg
http://jedi.betterbox.net/images/rx8...keports-02.jpg
http://jedi.betterbox.net/images/rx8...keports-03.jpg
http://jedi.betterbox.net/images/rx8...keports-04.jpg
http://jedi.betterbox.net/images/rx8...keports-05.jpg
http://jedi.betterbox.net/images/rx8...keports-06.jpg
http://jedi.betterbox.net/images/rx8...keports-07.jpg

 

What about Pettit's Supercharged 8??? Is he going to have issues? He said he had 5,000 Miles on the car now, and it is running strong at 6PSI.

 

1st the ecu/timing issues, now the side seal issues, it seems that the possibility of fi on this car gets more and more difficult.(not impossible) Ive always said heat is goin to be a problem with this car in referance to fi and daily driving . One question please. Charles Hill has been running nos(55 shot currently) for a little while now. I wonder if adding the nos will also expose his engine to the side seal issues? I realize heat will not be as big a factor with the nos but I seem to remember he had some trouble(initially) with pinging with just the 55 shot.
thanks to all who have shared info here. It really helps us old muscle car farts that are trying to learn. Its a good thread

olddragger

 

While I agree there are issues, have this come out now is a good thing. Makes planning and designing a FI car much easier, now that we know whee the week points are. Better than installing a TC/SC and blowing the engine at 50K b/c you didn't know

 

There is nothing wrong with the Renesis and the side seals; I can't believe this thread is still alive...

 

Never mind.