Drewstein

I posted my feelings about this on the other thread.

On topic: Companies can produce the supercarger easily, but the necessary mounting hardware will need developement. I believe there are guys trying roots applications so all you would need is their hardware and a twin screw to slap on in the roots blowers place.

IKnowNot'ing

You sir know nothing about supercharger integration. I'm ready to cede my username to you if you wish...

WTF no turbo

Talked to smokin joe today.Im a little hazy on what he told me though.In one sentence he told me the SC was 90% done.Then about 3 mins into the conversation he told me he may scrap the entire thing.It seems they dont believe this engine can take any kind of boost for a extensive amout of time while keeping some kind of reliability.Not the news i wanted to hear since it seems others are droping projects as well.While i believe the greddy kit is done for j-spec we may never see it here.

IKnowNot'ing

Compression ratio must be reduced, and that requires some rotor machining on a rotary (i.l.o. a thicker head gasket on a piston engine).

Hymee

iTrader: (1)

That is probly gunna be the case for some serious boost. I wonder what the reliable limit would be for people who are chasing a "bolt-on" install?

The advice given to me is that the apex seals are the most at-risk components internally. The rotors and eccentrics can take heaps of power, but detonation is the killer.

Cheers,
Hymee.

IKnowNot'ing

Even for medium levels of boost a reduction in compression ratio would be a must to recover some durability.

Although I have no practical experience of rotaries, I do also believe that the problem is located on the apex seals, both due to detonation and peak combustion pressure.

Without any change in internales, I'd would not consider anything more than 15 to 20% increase in air flow at medium to high engine speeds. And maybe up to 25 -30% at lower revs.
And on MY PRIVATE OWNED CAR, I'd go for a controlled boost that rises up to +0.3 bar max at low revs and goes rapidly down to +0.15 bar and die at +0.1 bar at peak power engine speed.

That was the basis for some calculation I made a couple of years ago when I was thinking about supercharging my 2.6l V6 Audi. The good thing is that most of the calculations are valid for the 1.3l rotary!

Japan8

I dunno about your 2.6l calculations being that valid for a rotary. Rotarygod has gone over it before, but at the moment I am trying to hash through an explanation of rotary engines and the Renesis in a magazine given by Seiji Tashima... head rotary engine engineer on not only the Renesis, but also 13B-REW and prior ones as well. Of course it's all in Japanese and I'm reading only on the train when commuting... so it'll be awhile.

Anyway I have seen the 2.6l reciprocal engine calculation by both rotarygod and in the article, but the whole situation seems to be much more complicated than that.

ALSO far as boost goes, why reduce the compression ratio? What rotarygod has said does make sense... what the engine "sees" is the effective compression ratio and as such higher compression for off boost power isn't a bad thought...

Hymee

iTrader: (1)

The 13B rotary engine has the same theoretical displacement as a 2.6L 4-stroke piston engine, that is it displaces 1.3 litres of air per engine revolution.

The Renesis however, appears to have a higer volumeteric efficiency than a typical N/A piston engine, in the range of 85 - 100+ %. See my practical mass air-flow tests on my other thread https://www.rx8club.com/showthread.p...threadid=33370 to see what the actual mass air flow is through the rev range of a Renesis at WOT.

Displacement is not black magic. These engines (piston and rotary) are mearly positive displacement air pumps that flow a certain volume of air for every crank/eccentric shaft revolution.

Cheers,
Hymee.

Japan8

Hymee, no one was talking about displacement. Did you ever see that word in my post? I was refering to the overal operation, engine cycle and internal pressures... not to mention anything else of interest that I gleen from the article. Don't jump the gun. I may be posting in a week that in the end that it looks like the Renesis would have to be rebuilt to take boost. I'm still reading. I just said that at this point it looks like there is more to the situation than simply comparing engine displacements.

We have a blow-by cut-off seal in the Renesis, but not in the 13B-REW. All the seals are as thick or thicker than in the 13B-REW. Material is the same or better (?) There's all kinds of good info to come...

Japan8

Basically I'm saying that a 2.6l recip. engine isn't a 1.3l rotary even if displacement is the same. The combustion chanber is obviously different... t&l spark plugs, lack of valves, different seals, different pressures... a lot of differences. combustion still works the same, but the conditions under which it takes place are quite important as we all know.

Hymee

iTrader: (1)

Japan8,

It is cool. I wasn't flaming you or arguing with you.

Yes, there are many differences. In essence the thing flows a certain mass of air per revolution. That mass of air has an energy/power associated with it.

Cheers,
Hymee.

Japan8

Hymee, no prob then. Just sometimes you post something here and then the whole world wants to flame you.

Hymee

iTrader: (1)

It is true that is is hard to read emotions into posts. Emoticons help. If I was disagreeing, I would state it.

Lots of self proclaimed experts get on here and seem to have a point to proove. If I think I know something I am game enough to state it. If I don't know, I try to ask and learn. This should be a place for sharing and leaning. Inevitabley, people will disagree, but it should be kept honorable.

Cheers,
Hymee.

Japan8

I agree 100% with you Hymee. After some reading I might have some brilliant breakthorough, or maybe a setbac, but either way I'll know more than I do now.

Richard Paul

iTrader: (5)

Man I havn't visited this thread in awile. The heat is still here. pun intended. I must start with my opinion of the effective displacment of the Rx8. It seems to my virgin eyes that it is the equivalent to a 3.9 liter 6 cyd engine.
Is there something I don't see?? It has 1.3 l. disp. and rotates three times per output shaft rev. Since it is still an Otto cycle engine of four strokes then presto every two revs there are six firings, right?

Now here comes the biggie, everyone on the site is going to rag on me for this. It is less efficiant than the equivlant six cld with poppet valves. Why do I say this? because a 3.9 L of standard design would have no problem making 300 hp in street tune.
Not that the rotory doesn't have things going for it, it's just that there is only one small company working half heartedly developing it.
If it were a four valve hi po engine it would make 100 hp per liter. In Hondas case more. Or dare I say the word Ferrari. What is the current output of their 3.6 L V-8? dare I say over 400. NA. Weighs more then the Rx8 and is a 12 sec. car that can do 190 mph. The big difference is the $135,000 extra. You get what you pay for. Lucky for you there are deminishing returns. So you get one hell of a car for really little scratch with the Rx8.

I can say that because I've had at least one Ferrari in my garage for the last 35 years. Along with one of everything else at one time or another. So when I think that the Rx8 fits in my garage there's gotta be some reason.

So together we shall overcome. I will get you an FI system that you don't have to defend roots or screw. There will be a new kid on the block.

I've lost my way, I think I was going to offfer some different opinions from some posts but I forget. You probably didn't want to hear what I had to say anyhow.

Richard

Hymee

iTrader: (1)

Richard,

In displacement terms it is equivalent to a 2.6 litre 4-stroke. The rotors only turn at 1/3 shaft speed. Although it is a otto-cycle, the firings are more like a 2 stroke. But we don't need to get into an argument there.

For each turn of the crank (eccentric shaft) 2 of the rotars would have gone through 1/3 of their cycle (i.e. one chamber)

To summarise, the theoretical displacement is 1.3 litres per engine revolution.

At 9,000 RPM I measured the actual mass air flow at 225 grams/second at WOT and full load.

Cheers,
Hymee.

rotarygod

Yep that's it. A typical 4 stroke engine completes all of it's cylinder firing within 2 revolutions. It takes the rotary 3 revolutions to complete all 6 chambers.

Richard Paul

iTrader: (5)

Well I guess I read that one wrong. I can count that high I'm sure. I will go over it again, not that I disbelive you it's just that I want to see how I could have not understood.

We can all agree that it must be whoever wrote the explaiation that is at fault here. Otherwise this will be two mistakes in one week. And the joke is thats all that is public. If you only knew what I've done in the shop.

Richard Paul

iTrader: (5)

I was just joking about whoever wrote the explaination but I just reread it and Mazda's explaination sucks. It doesn't sound anything like you guys explain it. They just basicly show a four cycle cycle. If that makes me clear. I mean their drawing says nothing about the ratio to the shaft. So I can see why I got it wrong. Exactly the ratio stated 2 to 3. 2.6 vs 3.9. I refuse responsability.

Just joking guys. You would think after all the years the thing has deen around I would have taken more interest. But Wankel had many other designs. One or more of them for air compressors. About 15 years ago Holley built some prototype superchargers of a wankle design. I had one but donated it to someone for his supercharger colection. Shouldn't have done that, I also gave him a multistage centrifugal I built around 1979. Shouln't have done that. Anyway the Holley thing had a vane and a slit tube. If anyone knows what that is called. I can't explain it, I can picture it but don't know what say about it.

Richard

IKnowNot'ing

Most of the questions left slightly unanswered would be levied if I could get that damn damn damn Yamamoto's book...

Japan8, what's the compression ratio of the RX7 engine? I guess it's lower than Renesis, is it not?

And in term of air consumption, the Renesis behaves a bit like a 2.6L piston engine, exactly for the reasons Hymee has exposed here.

So : who's got The Rotary Bible on his shelf?

Japan8

What does the compression ratio fo the ancient *** gen3 have to do with the new high tech Renesis? What about the seals and ports... they certainly weren't the same. The two engines sound REA comparable to me...

Reread above... I agreeed with Hymee in the end. in terms of air consumption the 13B is like a 2.6l 4.

IKnowNot'ing

Hi Japan8,

The only part of my post directed to you was the line about the compression ratio, not the rest.

Peak combustion pressure is related to compression ratio. The current CR of the Renesis corresponds to a given peak pressure that dictated some of the hardware dimensionning and materials. Boost will increase peak pressure and therefore might stretch the resistance of some parts beyond their designed limit. Detonation is also a big issue when peak pressure increase.

As it is turbocharged, I'm expecting the Gen3 rotary CR to be around 2 to 3 points lower than the Renesis CR.

Hymee

iTrader: (1)

2.6L in a single, twin, 3, 4, 5, 6, 7, 8, 9, 10, 12 cyl or whatever They all consume 1.3L of air per revolution like the 13B. Their firing intervals and torque fluctuations differ. Not trying to fight or argue, just extending the discussion.

IKN,

Just some more info to consider... The rotors and eccentric shaft in a 20B 1400HP 6.99s ET 201.5 MPH drag car can handle the forces, and they are "stock". And it doesn't get rebuilt in-between runs like a Top Fueler. The apex seals must be special though. This is going to be our downfall perhaps, in relation to their resistance to detonation. I guess we will have to waste and engine before we know the limits! All part of the process of determining what is reliable and what isn't. It is not going to be an overnight development!

I'll have to check my RX-8 book - it details the developments of the seals through the ages. I might be able to check that CR thing for you as well.

Cheers,
Hymee.

Japan8

Mazda had gone from the 6 port engine in the 13B 6PI to the 4 port engine in the FC because all JDM models were turbocharged. W‚ˆen turbocharged, intake timing is early and flow rate (velocity) is different.


Apex Seal
13B-REW
2mm thick/ 3 piece
material/ cast iron

Renesis
2mm thick/2 piece
material/ cast iron

Side Seal
0.7mm thick
perpendicular cross section
material/sintered iron

1.2mm thick
trapezoid cross section
material/sintered iron

Corner Seal
Rubber plug

Cast iron plug
DLC (Diamond-like Carbon) coating

Blow-by Cut-off Seal
N/A

material/ductile cast iron

wakeech

actually only 1 point: it was 9.0:1, just like every other turbo wankel motor Mazda's ever produced (AFAIK, someone might come up with a freak trivia answer and prove that wrong, but i doubt it).