# Mazda Rotary Engine

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#### Urquiola

##### Well-Known Member
Renesis did not make more torque with the side ports, they used higher static compression and intake plenum controls to do that.
Thanks. You may like having a look at SAE Technical Papers:
Turner, J., Turner, M., Vorraro, G., and Thomas, T., "Initial Investigations into the Benefits and Challenges of Eliminating Port Overlap in Wankel Rotary Engines," SAE Int. J. Adv. & Curr. Prac. in Mobility 2(4):1800-1817, 2020, SAE MOBILUS.
Turner, J., Turner, M., Islam, R., Shen, X. et al., "Further Investigations into the Benefits and Challenges of Eliminating Port Overlap in Wankel Rotary Engines," SAE Technical Paper 2021-01-0638, 2021, SAE MOBILUS.

and 2004-01-1790 Ohkubo, M., Tashima, S., Shimizu, R., Fuse, S. et al., "Developed Technologies of the New R Rotary Engine (RENESIS)"
$33 to download from SAE.org Membership not needed. Mazda preferred the side intake ports because it provided more stable idle and better low rpm, low load functioning, good for street cars, but all experimental data indicate Peripheral Intake Port is better from performace point of view, this is the Aircraft Engine field. The Renesis has several side intake ports, this provides more intake area, but a bended path in mix flow impairs MEP. Renesis exhaust ports are also on side, eliminating overlap, loss of fresh mix into exhaust, recirculation of exhauts gases into intake time. Blessings + #### dwalker ##### Well-Known Member HBA Supporter Thanks. You may like having a look at SAE Technical Papers: Turner, J., Turner, M., Vorraro, G., and Thomas, T., "Initial Investigations into the Benefits and Challenges of Eliminating Port Overlap in Wankel Rotary Engines," SAE Int. J. Adv. & Curr. Prac. in Mobility 2(4):1800-1817, 2020, SAE MOBILUS. Turner, J., Turner, M., Islam, R., Shen, X. et al., "Further Investigations into the Benefits and Challenges of Eliminating Port Overlap in Wankel Rotary Engines," SAE Technical Paper 2021-01-0638, 2021, SAE MOBILUS. and 2004-01-1790 Ohkubo, M., Tashima, S., Shimizu, R., Fuse, S. et al., "Developed Technologies of the New R Rotary Engine (RENESIS)"View attachment 117156$33 to download from SAE.org Membership not needed. Mazda preferred the side intake ports because it provided more stable idle and better low rpm, low load functioning, good for street cars, but all experimental data indicate Peripheral Intake Port is better from performace point of view, this is the Aircraft Engine field.

The Renesis has several side intake ports, this provides more intake area, but a bended path in mix flow impairs MEP. Renesis exhaust ports are also on side, eliminating overlap, loss of fresh mix into exhaust, recirculation of exhauts gases into intake time.
Blessings +View attachment 117157
You seem to be confusing intake and exhaust ports.

#### rv7charlie

##### Well-Known Member
Don,
Both the images he attached are clearly referring to intake methods, and the papers referenced can easily be inferred to reference the Renesis, since they refer to eliminating overlap. Hover your mouse pointer over the 2nd image to see the file name.

Ignoring the leakage/reliability issue for the moment, I think a case could be made for the p-port intake to obtain more hp at *lower* rpm,
[edit: to be more clear, I'm trying to say that the smaller P-port intake improves 6000 rpm power vs the side intake port]
without the added weight/complexity of a turbo. In another thread, billrsv4 posted a link to Steve Beckham's more recent effort (still a 13B; not a Renesis) using a significantly smaller dia p-port to keep flow velocity up at lower rpm. Video of it running IIRC, they're talking about around 180 HP @ 6000 rpm, which as you know is the sweet spot in rpm for bearing/gear loads inside the rotary, and pretty close to the 'universal' peak BSFC rpm of 5252. As a side benefit, the intake manifold can be a lot simpler and a bit lighter.

I'd be very happy with 180 HP @ 6k rpm; near perfect match for most of the faster 2 seat homebuilts including my RV7.

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#### Lendo

##### Well-Known Member
In reference to dwalker's comment on 6,000 rpm. The Rotaries internals are turning at only 2,000 rom when the crank is turning at 6,000 rpm, so stress on the motor is quite low as a matter of fact lower than any other RPM, I would compare it to a long stroke reciprocating motor at 2,000 rpm. The biggest issue is the Idle RPM at perhaps 1,000 rpm, which I think can be easily controlled - one way or another.
In his reference to welding in P-ports - all too TRUE!!
Nothing beats the original Mazda integral PP housings. If O'rings were able to be changed out easily I see it as only a maintenance issue, and I would see that as much less complexity than a Turbo installation.
These comments are only my own personal opinion and don't in any way malign any comments of others.
George

#### dwalker

##### Well-Known Member
HBA Supporter
Don,
Both the images he attached are clearly referring to intake methods, and the papers referenced can easily be inferred to reference the Renesis, since they refer to eliminating overlap. Hover your mouse pointer over the 2nd image to see the file name.

Ignoring the leakage/reliability issue for the moment, I think a case could be made for the p-port intake to obtain more hp at *lower* rpm, without the added weight/complexity of a turbo. In another thread, billrsv4 posted a link to Steve Beckham's more recent effort (still a 13B; not a Renesis) using a significantly smaller dia p-port to keep flow velocity up at lower rpm. Video of it running IIRC, they're talking about around 180 HP @ 6000 rpm, which as you know is the sweet spot in rpm for bearing/gear loads inside the rotary, and pretty close to the 'universal' peak BSFC rpm of 5252. As a side benefit, the intake manifold can be a lot simpler and a bit lighter.

I'd be very happy with 180 HP @ 6k rpm; near perfect match for most of the faster 2 seat homebuilts including my RV7.
There is simply no way the peripheral port intake make more lower anything, except lower power at low to medium engine speeds.

The peripheral port I'm advocating is the exhaust port, and the cheif objection to the Renesis side exhaust port is the lack of power and how it makes it.

I could get into a lot of personal theory and observations as to why my Renesis RX8 made more power than others due to the exhaust system we developed, and how many people who think they have a 200hp renny are shocked on the dyno to barely see 170, which is about normal, and the effort it takes to actually see an honest 180hp out of a Renesis.

Regardless of all that, the fact remains that accuracy in power production, reliability, and the path to that power is paramount. The reality is that because of the "180hp" rotary motor not delivering the claimed power in situ, the perception becomes that the motor has issues, is weak, unreliable, etc. when it's simply that the information they are basing those buikds and projects on are flawed.

I have a friend currently putting an Renesis motor on his RV6, because the 13B 4 port motor on the plane is weak and delivers poor performance. Ib think he will get an improvement out of the Renesis because my guess is the 13b 4port is maybe making 140hp, if that. The renesis will probably make 150ish, and make the power earlier with the higher compression. I'll have to swing over to see him in the next week or so and see hows it's going.

#### Lendo

##### Well-Known Member
rv7charlie, when you say significantly smaller p-port, I assume you mean smaller than Paul Lamar's 50mm (2"), if so I must agree, but it could be smoother with a smaller inlet again, which suggests to me some variable intake geometry - of some design. There are people working on that issue for some time now, so hopefully in the near future we may have an answer. However in that video it wasn't too bad at all at about 1200/ 1500 rpm.
George

#### Urquiola

##### Well-Known Member
rv7charlie, when you say significantly smaller p-port, I assume you mean smaller than Paul Lamar's 50mm (2"), if so I must agree, but it could be smoother with a smaller inlet again, which suggests to me some variable intake geometry - of some design. There are people working on that issue for some time now, so hopefully in the near future we may have an answer. However in that video it wasn't too bad at all at about 1200/ 1500 rpm.
George
You can look at this eBay ad https://www.ebay.com/itm/-/392865991631 the double peak RV allows for an independent closing of pass in the section closing earlier respect to the section closer to plug.
Dimensions of RV should not be as big as in a 2-Stroke, intake time lasts 270º of shaft turn in a Wankel, thus, mix flow is much slower, I don't want making Bernouilli calculations, but looks not difficult.
The 'all ports in side plates' of Renesis has an added difficulty, if something is dettached inside working chamber, it has no way to escape, will end damaging engine, but a Peripheral Intake port would provide some room to store for a while the broken pieces.
Blessings +

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#### Urquiola

##### Well-Known Member
This is connected too.
Blessings +

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#### Urquiola

##### Well-Known Member
For an street vehicle, a 33 cm long intake duct seems better, for aviation use, a shorter duct gives more power, this was tested in Taiwan with a 340 cc per chamber Wankel model, SAE paper 2013-32-9161: 'The Intake and exhaust pipe effect on Rotary Engine performance'
Dun-Zen Jeng, Ming-June Hsieh, Chih-Chuan Lee, Yu Han. From: CSIST, National Chung Hsing Univ.
Data published in 'Wankel News', magazine from 'Hercules Wankel IG', indicate a longer exhaust tube in the Suzuki RE-5 engine increases light load, low rpm performance in an impressive way.

About Reed-Valves, in 2-Strokes, a short lenght stiff material is good for fast turning engines, while long, soft petals are good for slowly turning engines.
Tipically, in 2-Strokes, a metal petal of RV lasts 15'000 km; in carbon fibre 8'000 km, but imagine what could happen if a metal reed detach and enter working chamber.
Carbon fibre petals are less harmful. You can always consider adding a basket, or a grid, to stop dettached parts from going into working chamber, this adds drag to the incoming mix flow, and could dettach also.
Blessings +

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#### dwalker

##### Well-Known Member
HBA Supporter
I like theoretical as much as the next guy, but I'm talking about what you can do now, today, with parts you can buy that are proven to work.

You prove out my point-

For an rotary flight engine you want side intake ports and peripheral exhaust ports.
And boost if you need over 150hp, because NA is going to struggle to get there.

#### Lendo

##### Well-Known Member
If I can mention something not previously mentioned (unless I missed it, if I did I apologize) eliminating overlap which is in Most engines unless running Hydrogen, the overlap lets fresh air in to helps evacuate (flush-out) the exhaust. A problem arises is when that fresh air also contains fuel, which burns in the exhaust, helping to perpetuate the theory that the Rotary is a HOT engine. As Tracy discovered a delayed fuel charge helps eliminate that (as does Fuel Injection), although not entirely as the unburned fuel in the squish areas of the Rotor are flung out the Peripheral Exhaust Port by the Apex seals - this is eliminated mostly in the RX8 with side exhaust ports and any fuel is carried into the next combustion event.
Side Intake and exhaust ports are restrictive in their natural state and can be improved with Port and polishing but they still have a square edge - thus turbulence restricting flow. Peripheral Ports are straight-in and Straight-out
Nothing it seems is perfect, but selecting the better option is still the debate.
Hope that helps those unfamiliar with the different configurations.
George

#### dwalker

##### Well-Known Member
HBA Supporter
If I can mention something not previously mentioned (unless I missed it, if I did I apologize) eliminating overlap which is in Most engines unless running Hydrogen, the overlap lets fresh air in to helps evacuate (flush-out) the exhaust. A problem arises is when that fresh air also contains fuel, which burns in the exhaust, helping to perpetuate the theory that the Rotary is a HOT engine. As Tracy discovered a delayed fuel charge helps eliminate that (as does Fuel Injection), although not entirely as the unburned fuel in the squish areas of the Rotor are flung out the Peripheral Exhaust Port by the Apex seals - this is eliminated mostly in the RX8 with side exhaust ports and any fuel is carried into the next combustion event.
Side Intake and exhaust ports are restrictive in their natural state and can be improved with Port and polishing but they still have a square edge - thus turbulence restricting flow. Peripheral Ports are straight-in and Straight-out
Nothing it seems is perfect, but selecting the better option is still the debate.
Hope that helps those unfamiliar with the different configurations.
George
That is all correct. It is exacerbated by the fact so many people insist on running the rotary pig rich with no timing.

#### Cardmarc

##### Well-Known Member
Most aircraft using the rotary install an oxygen sensor (or several) and fine tune their fuel injection/ign ECUs using that for mixture control. No need to run ‘rich’. Also runs well lean of peak and lowers EGT temps as well to keep the turbo happy.

#### dwalker

##### Well-Known Member
HBA Supporter
Most aircraft using the rotary install an oxygen sensor (or several) and fine tune their fuel injection/ign ECUs using that for mixture control. No need to run ‘rich’. Also runs well lean of peak and lowers EGT temps as well to keep the turbo happy.

Ahh... thats not how that works. O2 sensors do indeed give an AFR reading, however they are simply a measurement and only IF the tuner decides to use them in an auto-tune or trim role do they matter to the running of the engine.

The tuner decides the AFR they want to run at a given engine rpm and load. MOST and by most I mean the vast majority, of rotary tuners run the engines stink rich. Like so rich your eyes water behind them from the fuel in the air.
Not sure the term "lean of peak" can be applied when dealing with an EFI rotary, it simply does not follow the rules the way a piston engine does. Maybe with a carb, but even then... What we are looking for is as lean as we can run the thing based on specific engine load and actual AFR.

As I said, most tuners will tune the rotary excessively rich for "safety", because it is believed, and in fact a simple search will lead you to believe it is FACT that the rotary must be run rich to prevent "blowing an apex seal" or whatever. This is false. Rotaries in practice will follow very much the same desired AFR as any other engine. Most tuners are running the rotary richer than 11AFR and I have personally seen closer to 9.5 AFR in many, many engines. These engines obviously use a lot of fuel and actually make far less power than is practical. I tend to want to see 11.5AFR under constant boost- say 13-14psi at 35 or 40 lb/min. Higher boost and airflow and I might add fuel to around 11AFR. Never really richer than that, with the exception of transition into and out of boost, where going into boostwe might see slightly under 11- around 10.8, and coming out of boost leaner than 12. under no boost and light rpm I want to see 14.5 to 15.5AFR, and idling around taxi or light load cruise I like to see as lean as possible with no stumbling, lean pop, or other bad habits.

Now here is where, when discussing this with rotary car folks I would go into how running it stink rich almost guarantees melting engine components at some point, as the still burning fuel inevitably causes pre-ignition which WILL break apex, side, and corner seals. This event is almost ALWAYS put down to something else, because a very large percentage of rotary engine specialists have never considered the idea of pre-ignition and typically simply blame the failure on running lean, too much boost, or too much timing causing "knock". They never consider the fact that whatever unburned superheated fuel that is not swept out of the exhaust port continues its ride and as the intake port is opened the rotor gets a large dose of fresh air fuel and of course, it lights off, at the exact wrong time. I am personally not convinced this actually breaks the seals. I think the heat from the slow-burning fuel softens the seal material, and when the fresh air from the intake hits it the rapid cooling causes the seal material to crystalize and eventually fracture. I have looked at a lot of broken apex and corner seals and the very fine grain texture and fracture pattern seems to indicate a pattern of heating and shock cooling that develops microfractures that lead to overall failure. We have also noted in recent years as apex seal material has advanced, that the failure point has moved to the rotor face. The failure here is the rotor face is "dented" or sagged in, much like they are melted from a torch.

Now all that said, these days with almost any ecu the tooner simply maps out his desired AFR and Timing and the ECU auto-tuned to those numbers. But you still have to put the right numbers in.

#### Cardmarc

##### Well-Known Member
Are you familiar with Tracy Crooks EFI/IGN rotary airplane ECU? Someone on here must have one; they can explain how to ‘trim’ the mixture and timing.

#### rv7charlie

##### Well-Known Member
I think that you'll find a quite different 'tuning world' when you get familiar with the guys flying rotaries. I don't know of anyone running a NA rotary richer than stoichiometric, and most I know are running *waaay* to the lean side in cruise.

#### dwalker

##### Well-Known Member
HBA Supporter
Are you familiar with Tracy Crooks EFI/IGN rotary airplane ECU? Someone on here must have one; they can explain how to ‘trim’ the mixture and timing.
There is simply no way I would ever use Tracys ECU. He is a great engineer but t is 20 years out of date. When it was built it was a decade behind in technology. I have a friend flying one now and he has expressed an interest in replacing it more than once.

EDIT-

I am going to add here than ALL decent ECUs are able to control timing and mixture on a rotary or linear pot as an overall trim. With a modern ECU there is really no need, as you simply input the desired AFR for a given RPM and load and the O2 feedback dials it in. I am being very, very general here, as there are tables that can be set up to trim fuel or ignition based on almost any parameter you so desire.

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#### dwalker

##### Well-Known Member
HBA Supporter
I think that you'll find a quite different 'tuning world' when you get familiar with the guys flying rotaries. I don't know of anyone running a NA rotary richer than stoichiometric, and most I know are running *waaay* to the lean side in cruise.

Almost all of my comments are related to boosting the engine, in my case via turbocharging. However, since you mention it, Best power in an NA rotary under mid to high load should be around the same 11.5 AFR as measured on a calibrated and quality wideband. Maybe a tick leaner at around 12AFR. Once at cruise lean it until it breaks up, then richen it up a bit.

#### rv7charlie

##### Well-Known Member
Once at cruise lean it until it breaks up, then richen it up a bit.
People I know who are actually flying them (with well tuned ECUs) say that there is no 'breaking up'; you can lean with smooth running all the way down to the engine just quitting due to lack of fuel. And while it'll run well at extremely lean mixtures (unlike a Lyc on mags), there's a sweet spot in AFR (somewhat lean of peak) where BSFC is best in cruise. Info comes from, among others, an actual scientist flying a rotary, who's obsessed with accurate data.

#### Lendo

##### Well-Known Member
rv7charlie, I know your a busy man, but can you get any specifics from this scientist fellow.
George