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New member here. I am contemplating building a short crank 3 rotor renesis. I have my ideas on how to do it and my reasons for doing it.
i see its been done befor in the UK. But little information about it can be found on the net.
Has anyone gone down this route befor?
would love to here of any builds that have been done or are in the process of being done.
Because it sucks and is not worth the trouble. The center rotor only has the two small siamese exhaust ports and only four intake ports, which essentially chokes it off and kills power. You also lose the highly developed intake manifold which destroys the wide power range. Which they use the low power 4-port engine for this any way.
So it’s a double if not triple whammy; it can’t make high rpm power and the low-end is dead. Then there’s the overall Renesis longevity issue. In the end you have an expensive engine with potentially more reliability issues making less torque and power overall than a proper 6-port Renesis 2-rotor.
Try to understand that some shops are willing to sell anything a customer wants to make a buck, even if they know it will end bad. You wanted it; you got it.
It’s a bad idea particularly for what converting and fitting a 3-rotor into the RX8 engine bay requires, but that doesn’t stop some people people ... if you want a 3-rotor you will be better served to build a proper 20B type.
Because it sucks and is not worth the trouble. The center rotor only has the two small siamese exhaust ports and only four intake ports, which essentially chokes it off and kills power. You also lose the highly developed intake manifold which destroys the wide power range. Which they use the low power 4-port engine for this any way.
So it’s a double if not triple whammy; it can’t make high rpm power and the low-end is dead. Then there’s the overall Renesis longevity issue. In the end you have an expensive engine with potentially more reliability issues making less torque and power overall than a proper 6-port Renesis 2-rotor.
Try to understand that some shops are willing to sell anything a customer wants to make a buck, even if they know it will end bad. You wanted it; you got it.
It’s a bad idea particularly for what converting and fitting a 3-rotor into the RX8 engine bay requires, but that doesn’t stop some people people ... if you want a 3-rotor you will be better served to build a proper 20B type.
my new favorite meme for these type of situations
.
jusf curious to why it woulf suck? Can you please elaborate? Also why its not worth the trouble? Have you built this type of engine, or know of someone who has?.
I was planning to use the 4 port irons.
why cant it make high end power? also what revs are we talking about that you consider high?
why is low end power dead? It has an extra rotor so surely it would be more powerfull than a normal renesis?
as for longevity issues. As long as it lasts 50000 ks im happy. Thats more than a lifetime of driving for me.
are you saying it would be more unreliable than a normal 2 rotor? Why do you say this ?
why would an engine with an extra rotor make less power and torque than its 2 rotor counterpart?
Thanks for your time answering my questions.
i understand its not a common conversion.
Because it sucks and is not worth the trouble. The center rotor only has the two small siamese exhaust ports and only four intake ports, which essentially chokes it off and kills power. You also lose the highly developed intake manifold which destroys the wide power range. Which they use the low power 4-port engine for this any way.
So it’s a double if not triple whammy; it can’t make high rpm power and the low-end is dead. Then there’s the overall Renesis longevity issue. In the end you have an expensive engine with potentially more reliability issues making less torque and power overall than a proper 6-port Renesis 2-rotor.
Try to understand that some shops are willing to sell anything a customer wants to make a buck, even if they know it will end bad. You wanted it; you got it.
It’s a bad idea particularly for what converting and fitting a 3-rotor into the RX8 engine bay requires, but that doesn’t stop some people people ... if you want a 3-rotor you will be better served to build a proper 20B type.
my new favorite meme for these type of situations
.
hi can you please explain why it sux and not worth the trouble? Are you referring to it not being worth your trouble or my trouble?
if a 4 port rene is making 180 odd hp why wouldn't adding another rotor give it 50% more power?
what do you mean in regards to reliability issues or longetivity issues?
Im trying to reply to the guy above who says my idea is not worth it etc etc
he says it will make less power, less reliable etc.
please elaborate?
3 rotor Renesis isnt worth pursuing. There is nothing to be gained over stock due to the architecture of the porting. If you are looking to make more power than stock doing an engine swap, you are best off just swapping in a 2 rotor RX7 13b-REW engine and turbo it. You can then tune it to make far more power than a 3 rotor Renesis ever could. Would be roughly the same cost and be a better, more reliable engine.
Im trying to reply to the guy above who says my idea is not worth it etc etc
he says it will make less power, less reliable etc.
please elaborate?
It's not too hard to understand.
There has never been a production 20B-MSP(Renesis). That means you are on your own to figure everything out.
And you have to understand that the side exhaust port design is not done for power, rather it's for emissions. Renesis doesn't have the same level of power potential as a 13B-REW when it comes to turbocharging. Renesis made good power NA because of its optimized intake system. It will take an immense amount of engineering to make a good one for NA 20B-MSP. For an NA engine, the intake design is critical since there is nothing else helping the engine shove air in other than atmospheric pressure.
Then there is the cost. I don't know about the UK, but a 20B-REW can set you back 6 to 7 thousand US dollars(Mazmart used as a reference). For a 20B-MSP, the parts will be custom. I hope you have a deep pocket. A very, very deep one.
i did explain, which perhaps another reason you shouldn’t is because you lack the technical understanding basics.
in that linked thread they talked a lot, but never provided anything to back it up. The 4-port peaks around 7200 rpm because it lacks the 2 additional APV ports to help it breath at high rpm, but they claimed it “pulled strong” to 8500 despite the center rotor only have two small siamesed exhaust ports. Some people think the 6-port pulls strong to 9500+ rpm too ... until they put it on a dyno and then see it was all downhill after 8500 rpm.
yes, they did have a free flowing intake system, but intake flow isn’t the issue on the Renesis. Exhaust flow is the issue. That intake manifold loses the factory SSV valve system, so all four intake ports are open all the time. That means it loses torque below 3800 rpm. Of course it was a drift engine and lowend didn’t matter. So from 4000 rpm up it’s ok and the 4-port motor makes more torque than the 6-port from there to around 5500 rpm. After that it starts falling off. Now maybe porting might help some, but I really question if it made more power that a good 6-port. Porting just doesn’t add much on this engine which is well established.
In that thread they claimed 250 bhp (flywheel) at 6000 rpm, but there were “dyno problems” that prevented going to higher rpms. What can we tell from that? Not much, maybe it did ok or maybe the dyno problems mean it’s not generating accurate information. My recent 6-port engine has roughly 210 bhp at 6000 rpm (250 bhp @ 6800, 268 bhp @ 8500). So it’s not that much more, but that’s where the 6-port starts out-pulling the 4-port, especially when the other two APV ports open around 6500 rpm.
All that was 6 or more years ago, the company is out of business, and nobody ever really proved much other than they did manage to do it. Even if they made those numbers, they kind of suck compared to what a 3-rotor pre-Renesis rotary can make. The cost and effort isn’t really different. Neither engine will be emissions compliant. There’s no support parts for a 3-rotor Renesis, but there are for the earlier engines. It just doesn’t make any sense to go Renesis, but somebody will do it anyway (see previously posted meme).
Thanks for the indepth replies. I will look more into the intake design. I wasn't aware it played such an important role. I could still duplicate what mazda did with the intake with my own design also.
I should mention im not building it for all out power. Its more just to do something different and i like the sound of a 3rotor.
I have zero interest in a turbo. I would go for a bridgeported na engine first. But my first choice is a 3 rotor.
My simple mathematical theory is if a 4port makes 190hp standard then a 3 rotor version should make at least 280hp.
and sound way cooler
It's not so simple though. You have to worry about a lot more than if you just choose a factory engine to work from. If you cant get enough excitement out of a 13b-REW swap I dunno what to tell you. The Renesis might make more power in a well thought out 3 rotor design but is it worth the weight and the space? Probably not.
I think there's a difference between whether someone should build a 3-rotor Renny and whether you should do it. It's not easy (see the points made above), and as a result, it's not cheap. I'm sure you can bolt a bunch of housings together, but building a custom intake, running a new ECU and wiring for all the extra injectors and valves you've added and timing the whole thing...AND tuning it for maximum performance... it's going to take a while and may blow up once or thrice. And it has to fit in the car after, which is itself a project.
But I think someone should do it and share the recipe. We've pretty much established the limits of a boosted 2-rotor Renny.
The Furai apparently had Racing Beat's attempt at a 3 rotor Renny, good for about 450hp (Mazda/Racing Beat claims). I imagine with boost.
That's Racing Beat working with Mazda on a prototype car, with Lemans runners as the starting point. So... that's what you're up against.
You know I take that back. It was in the marketing material somewhere, but according to RB now its a PP 20B. So, there you go. Even Mazda wasn't so keen on the whole 20B Renny idea
My simple mathematical theory is if a 4port makes 190hp standard then a 3 rotor version should make at least 280hp.
and sound way cooler
because you don’t understand the technical details
a lot of 6-ports don’t make that even, you won’t do anything but waste time and money, that’s what people who have no idea what they’re talking about do. That’s simply the truth, not condescending.
the Furai was 450 hp/278 ft-lb output on E98 though claimed any way, never saw a dyno graph, but no reason to doubt it
I was under the impression 6 ports put out 250 ish hp and 4 ports 180ish. Thats what mazda has claimed and ive also seen dyno results.
Technically between 180hp-210hp depending on the automatic and 238hp for the 6port manual. But this is on a factory spec new engine and at the crank, not the wheels. 6 speed manual will only do 200-210 stock on a dyno. The 3 rotor Renny won’t really be worth the effort to build for previous reasons. But also, the extra weight and space it takes in the engine bay will cause more problems than benefits. Why is it important to try to build such a thing when other options are far more viable and cost effective?
I do not want a turbo and want a little more power than a 13b will provide. A 20b in nz is very expensive and hard to find. Usually 15k for one needing a rebuild. The renesis housings and irons and rotors are plentiful and i can get as many engines in good condition for free. Only thing i will need to buy new is the e shaft, center bearing and seal kit and ecu. The rest looks straight forward. Im hoping to retain the original engine mountings also.
Extra weight and space it takes up is irrelevant. The weight is so minimal its like having 1/4 tank of gas verses 1/2 tank. Engine will be about 6" longer at the most.
What you still don’t get is that with a Renesis, the center rotor ends up with significantly smaller intake and exhaust ports than the two end rotors. There’s a difference between reading a few things vs. understanding how things work. Just like your output results comments. Even the other guy you’re talking to there still doesn’t have that right either.
It’s only X” longer, except that means it no longer fits where the 2-rotor is. Again, you talk and talk, but you don’t understand. The motor mounts won’t line up unless you move everything to the rear. More talking, no understanding. Not saying it can’t be done. It was already done, except in an FD3 which is an easier fitment than an RX8. It’s not being pursued for good reasons you still don’t get. There aren’t any simple solutions to the issues. The only solution to the Renesis issue is casting and machining new custom plates.
Otherwise you’ll spend the same absurd amount of money to have a subpar excuse of a 3-rotor engine than as if you’d built a proper 20B that will make 350 hp at the rear wheels. You’re not even straight on flywheel hp vs. wheel hp. Most of the 6 port engines on here would probably be under 180 wheel hp if they got on a dyno.
Q: Why are you even convinced to use a Renesis?
A: Because you’re reading a bunch hyped up stuff that doesn’t directly translate to reality.
They stopped making this car/engine 8 years ago. That was after an 8 year production run. Did you honestly expect to swagger in here and show everybody how it’s done? Like nobody else ever had the idea? There’s a lot of things that were done. You don’t see it plastered all over the forum because the results aren’t good. You already look silly talking on without understanding the basics. Most people on here can’t even afford to spend what a proper rebuild requires on a 2-rotor. You won’t be spending 1/3 more than that.
More like $25,000+ USD fully installed for a subpar dyno result. That’s called having more money than sense. You’ll have to rework the drivetrain, it will need a stronger transmission, bigger oil coolers/radiator, subframe/motor mount/steering modifications, a custom intake/exhaust system, custom oil pan, a custom oil pump but everybody used the 2-rotor one, a custom water pump but everybody used the 2-rotor one, an aftermarket ecu, a proper wiring harness/ignition.
I didn’t get into the actual custom engine build modifications, which again nobody supports a 20B Renesis so you’re on your own. The parts don’t just directly swap over, though some can be used with proper modifications if you understand what they are. Some people would say it needs stronger differential and axles, but you won’t have to worry about that because with a Renesis 20B the output level won’t be there.
but it’s been explained to you properly multiple times now. There are other dreamers on here who will be quite pleased to talk nonsense with you all day long though. Have at it.
you can start here on your adventure quest for reality though:
I do not want a turbo and want a little more power than a 13b will provide. A 20b in nz is very expensive and hard to find. Usually 15k for one needing a rebuild. The renesis housings and irons and rotors are plentiful and i can get as many engines in good condition for free. Only thing i will need to buy new is the e shaft, center bearing and seal kit and ecu. The rest looks straight forward. Im hoping to retain the original engine mountings also.
You need this picture...
As Team has emphasized, a car is more than an engine. Even the engine part, you are oversimplifing. How do you plan on controlling that engine? How do you plan on keeping the engine cool enough? How do you plan to not have the transmission grenade on you?
Unfortunately there isn't much more to squeeze out of Renesis in NA form. Turbocharging is the way to get more power, and it improves the low-end torque which NA rotaries desperately need.
Originally Posted by SmallPP
Extra weight and space it takes up is irrelevant. The weight is so minimal its like having 1/4 tank of gas verses 1/2 tank. Engine will be about 6" longer at the most.
Yeah, a new housing, rotor and plate are gonna be more than 15 kg...
Sometime even an inch or two make all the difference.
06-12-2020, 10:31 PM
claimed any way, never saw a dyno graph, but no reason to doubt it 