Somebody...damned if I can remember who...posted I think in the Canzoomer forum that he switched a MAF that was reading extremely lean to a car that appeared "normal" and the problem followed the car, not the MAF. I should go hunt that post down, I'm not sure if there was any follow-up, but that certainly adds a wrinkle if verified.

jds

 

What? So using a different MAF may cause the engine to run lean? Damn, and I was thinking about swapping for a larger Mustang Cobra MAF. Was it a similar sized MAF, or was it larger?

 

MazdaManiac........any news on the impedance differences that you found between he MAF and the PCM??

 

This would definitely raise additional suspicions that there may be more to the horsepower variability than the previous "catch-all" mentality of the MAFS inconsistencies.

 

one of the things i am trying to get answers about is wether the mafs variance is caused by the mafs itself or perhaps lost voltage in the wiring harnesses/ connectors.

 

I wouldn't read this as additional evidence for some mechanical issue causing lost power. If I remember correctly, the test was more scientific than that...I think he was actually measuring MAF voltage before and after the swap. So, the idea of MAF variability is valid, it just may not be the MAF itself but something else in the surrounding circuitry.

jds

 

thats what i am saying it could be bad harneses or conncectors.

 

Thanks Google.com.

I found a pdf file regarding MAF troubles. It also doubles as an advertisement, so clear your heads of bias before reading.

http://www.wellsmfgcorp.com/counterp...erpoint3_2.pdf

 

I dont think you understand, the fact that the ports are ported 30% twards the opening side means you drop the leading edge of the side seal, this will then impact the "bridge" between the secondaries and auxe and the closing edge of the aux port. I might also venture to to guess that the trailing edge of the side seal, which in previous 6-port motors was unsuported when crossing the primary and secondary ports, but at the bridge between the secondary and aux became supported supported over the aux port to facilitate the abrupt closing of the aux port without seal damage, may also be droped. The opening edge is the edge that causes you to drop side seals,.. the trailing edge goes first when porting out, and is generally protected buy a gradually closing, and tapered port (insted of exactly at 80, it will sweep closed from oil seal to opening side to not damage the trailing edge). Dropeing the leading edge is next and oly happens on large ports,.. and is protected by a very gradual polished radius on the closing edge.


Mr. port and polish,.. can you tell us which seals are not housing supported over what ports?

Also Do you have any experience with the renn and that one thing ms7 tried that one time and didnt like leading him to his current motor?

 

That would seem to make more sense.

 

Actually now that I've thought about it overnight and stared at some housings, I'm not sure that it does make sense. Hopefully I can get some answers at sevenstock.

 

Take a side seal and move it up a port,.. the leadingedge of side seal travels uppast the and then twards the oil seal track. If you go out to far out on porting, the leading edge will impact the top closing edge of the port before it is supported by the housing again. The leading edge of the side seal is the edge that is pointing straight up at TDC of the non cumbustion side of the motor.

To visualize the trailing,, move a side seal into a position just before it closes the port, now imagine the port moved outward enough to drop the tip of the side seal,.. the edge closest to the intake runner side of the motor. If the seal is dropped and the port closes abruptly like the 6-port motors do it will put alot of stress on the seal and tend to round this tip off. Stock the older 6 ports had the trailing edge suported across the aux port. The trailing edge faces straigh down at tdc on the non cumbustuion side of the motor

 

i find it impossible to believe that the engineers at mazda would not have discussed, measured and understood every minute aspect of the seal-port interaction. to say there is so gross a problem with the design is to say that mazda is intentionally manufacturing this defect. but anyway, very interesting discussion!

james

 

Perhaps the design was sound in simulation, but since we're pretty much long-term testing the engine characteristics everyday, Mazda can't help but stand back and let it happen. However, Mazda, as well as us can come up with ways of improving the rotary engine design so that this doesn't happen. Also, Mr. Port & Polish mentioned it happened only to him. Therefore, the problem may not be universal. However, I believe there is evidence of a flaw Mazda might have made when designing their ports and how the seals interact. It is quite an interesting conversation. Hopefully those who attended SevenStock may get some information.

Does Mazda machine the ports initially before they assembled the engine? If so, what kind of machining technique do they use, i.e. chamfering, radiusing, etc.? Also, what about the side and corner seal material? I believe the side seals are metallic, but I can't remember. If they are, how about using ceramics, or a composite material with ceramic and bits of metal alloys. From what I know, ceramics offer excellent wear resistance, but I don't really know about how well it can be lubricated.

 

Well, according to Rob (?) at Pineapple Racing, there was an engine mount in the RX-7s that went through the oil pan. The seal on the mount eventually broke due to torquing under throttle and oil would leak. So, point in case, we can't assume Mazda is a a bunch of Gods. Sometimes things get overlooked or shortcuts are taken. I'm not saying anything is wrong with the Renesis at all. Just that if something did turn up, I wouldn't be surprised because people make cars and people are fallible.

 

So it turns out that the sideseal catching Mr. P&P mentioned is entirely possible, especially under FI circumstances. Let me explain, and then of course, we have the proof.

Sunday we went to the headquarters of racing beat in anaheim california. Inside, they had several torn down blown motors, one of which happenned to be a renesis. We noticed a few things about this renesis right away. First, the housing was all torn up where the engine had obviously pinged and dragged the seal. Second, the side housing was nicked right at the corner of the primary intake port where the side seal had obviously been catching. Now racingbeat admitted that they were supercharging that engine when they blew it, but in studying and especially feeling the edges of these ports, you can tell that a taper would GREATLY improve the reliability and wear on the side seals. I don't exactly understand why mazda would leave this without a taper, but they have their reasons.

Anyway, we took several pictures of the side housing itself and i have not altered or resized any of them. I'd like to show one here in it's totality and if you cant see it there, I know rotarygod will be posting his picture with Zoom44's pointer (knife) pointing to the exact location of the problem.

I think we learned more about the renesis in the few hours we were at RB than the entire time we've talked about it and studied it in other places. The motor has a lot of potential when it comes to porting, and I do mean a LOT.

Anyway, this shouldn't freak anyone out, I'm just saying it's POSSIBLE. RB was running a supercharger on this motor when it blew so it was obviously doing more than it was intended. They wouldn't say how much pressure they were putting into it or what kind of supercharger they were using.

Look at the pic. You'll see what i'm talking about if you look at the top edge of the primary intake port from the left side. Zoom in if you have to.

 

and btw.. if anyone is freaking out, i wouldn't reccommend it. Remember, this car was running FI. Mazda had a reason for leaving the ports like that, the trick now is to find out why.

 

OK I just got home from Cali. We learned alot out there and I am going to change my position on a couple of things. Since this thread is about the side seal issue I address it here.

Yes it is entirely possible for the side seal to catch. Earlier in the thread I was very adamant that this could not happen on a 6 port engine. 86rx7 pointed out that I may not in fact understand where this is happeneing. After seeing one first hand I agree with him. Kudo's to 86 for understanding what was being said. I was addressing the issue of the leading edge of the side seal hitting the closing edge of the auxillary port. I said this could not happen. If you look at this housing you can see that in fact I am right about it. It doesn't catch on the edge of the auxillary ports. However, it does catch on the top left (in this picture) corner of the secondary port though. As was pointed out this is due to the much earlier opening of this port. I looked at this housing really hard and compared to where the ports of a 13B open. The 13B opening point is just barely far enough in that the side seal never has an edge to cross in this part of the housing. The Renesis does and the score mark from the side seals was very obvious. I could catch my fingernail on it. This particular engine was blown up on the dyno with a supercharger.

RB has found that the Renesis engines that have been using forced induction suffer from this side seal issue. They have not found it to happen on a non forced inducted engine. At least they haven't yet. When I think about it I can't see why it would make a difference. Until they find a non forced inducted engine that has these issues, I wouldn't necessarily go out and assume that everyone's engines are bad. However if you are building a turbocharger kit, supercharger kit, or are using nitrous and you are using the stock engine, don't be surprised if something happens. This is not good news for the world of aftermarket forced induction.

Not many people want to open up an engine while their car is under warranty. This is a very easy issue to fix though if you do. The intake ports can be cleaned up a little but not enlarged much if any. It depends on which intake port we are talking about. The secondary can only be smoothened out not enlarged. The auxillary ports can be modified and I suspect the primaries can be too. Looking at the exhaust ports, I am amazed that that engine makes ANY power at all! Those exhaust ports are terrible. The good news is that this is very easily fixed with a die grinder. You can probably get at least 50% more exhaust area with a little work. Speaking to RB they still say you just can't get much out of the engine even with porting but then they also wouldn't elaborate to the extent which they have tried to port it. They did admit that they are really concerned with upgrades that would keep the car emissions legal so there probably is some more power to be had yet. When I look at the exhauts ports I have no doubt that there is more power to be had.

 

how much boost was RP running? Before we condemn all FI, it would be good to know at what point your going to have issues. 50-75WHP addition I would't think would be to hard on the engine. Now, 200WHP more? ok, at that level you should prolly pull the engine anyhow and do some work prior to running that kind of boost. Just curious.....good info though

 

Maybe Mazda did not fix this problem so others could not install FI. From what RG said the problem only seems to come up in FI engines. In another thread you can hear how they went after Judge Ito and how he feels that Mazda will try and stop him if he revealed what modificatione did to increase his engine's power. I would imagine that might be because Mazda has an FI (or power increasing) solution in the works, and they don't want to lose business. I am not saying that I believe this is true, just threw it in there as a possibility.

Good job those reporting, and good news about exhuast porting .

 

mazda definitely has something FI up their sleeve for this car. we saw that same car from laguna at SS7. Vaccuum gauge, intercooler and no turbine.

 

no turbine? you mean no turbo?

 

Ajax, you made a comment in RPs axial SC thread about the seals expanding with heat. That would easily explain some of the issues with FI. Did you pick up this info at Sevenstock or were you guessing? (damn good guess I might add)

 

we picked up the info about seals expanding at 7stock, and then it seemed very obvious why the clearances were off and why FI wouldnt work. Obviously, if the seals expand, with more heat they could expand more, but as Zoom44 stated at 7stock, they'd only expand so much further with the extra heat. Who knows if that's what we're seeing here is that little extra that mazda didnt account for when they built the engine. That's also why we say we dont see problems with this when we're running NA, only under boost or nitrous.

 

Excellent info!

So, if Mazda does come out with a FI version of the Renesis, is it safe to assume that it will have modified ports?

I wonder what kind of testing Pettit Racing has done with regards to the FI and durability issue, and what their findings were. We need someone from Pettit to leak the info here! :D