Mark_Huntsman

Hi all,
Finally I made an account, even though I don't have RX8 yet.
I would like to ask if anyone here can tell me the size/flow difference betwen intake ports on end and center irons? Figured as much that 4 port version of renesis engine will be closer to each other than 6 port, but I would still like to know how much bigger are the ports on end irons compared to center one.

The thing is, for past few months I have been playing with the idea of building a 26b using renesis engines instead of older 13Bs due to availability of parts and cost of used engines in central Europe. In next few months I will get one engine just to measure things and do all the engineering/Cad work. On a quick note, I work as a CNC machinist so I have the skills and machines to make almost any part from scratch.

Thanks for any info regarding port sizes/flow rates.

Edit: sorry if I should have posted in another topic, also did not find any results about port Flow rates using Google search within this forum

CaymanRotary

It's not worth it to use the Renesis motor as a base for a 4 rotor. I get that you are a machinist and could probably get it working, but it wont be a practical engine. Better off using the RX7 irons rather than the Renesis. You are going to have major and difficult issues vs having a relatively easy time with the RX7 parts.

Basically, even though parts are cheaper for Renesis, you will need to spend a lot more time to get it to work properly. Which means, go with the tried and true.

Brettus

iTrader: (2)

If you get hold of a center iron from a Renesis and look at the siamese exhaust port , it will be obvious to you why a 4 rotor Renesis will be a terrible engine.

Mark_Huntsman

Thanks for your answers, if I understand correctly what you are saying is that the engine will be restricted mainly by exhaust ports, not intake?
My goal was anything above 350hp N/A (compared to 192hp 4 port engine). Is even that unrealistic?
I know I can get close to that with FI, but if I consider that I want to have it pass inspection for street use, FI is a definite fail, while 4 rotor is sort of grey area, since the engine block will still say 13B.

So far I have some plans and ideas to make 4 rotor e-shaft quite cheaper than what they are sold by kiwi-re(?), using 5 piece design, which may not be as strong as 3 piece e-shaft, but according to my calculations so far for quarter of the cost, not including shipping. Another bonus, machine time could even be free for me.

Brettus

iTrader: (2)

Yeah..... the exhaust ports on the middle iron are terrible for flow . So you will have the two outer rotors making good power and the middle ones being strangled. It would probably make 350 ...but it will be a very heavy engine for that power.

Mark_Huntsman

So no way to equalize the flow of 1&4 vs 2&3 rotors? Only by restricting 1&4 even more? How would it behave if the middle rotors had small peripheral exhaust ports added, to even out the flow? Most likely it will be a nightmare to tune properly...

I was inclined to renesis engine parts due to them being dirt cheap, we are talking 300€ for whole engine from poland. So I would most likely get 2 whole engines and one extra center iron, or third engine, depending on availability. So parts and e-shaft will be around 1500-2000 plus new seals/gaskets...

Brettus

iTrader: (2)

That might work . if you could tune each individual rotor .

Mark_Huntsman

Right now I am working on having my new apartment finished, then I will buy one engine anyway, does not matter what condition it will be in, just to get all measurements I need and do some CAD work, run some simulations and see how bad the flow really is.

While I have you on the line, how much power can stock 6spd transmission and rear end take? So I can plan in advance.

Anyway I hope I did not make myself a newbie talking about building a 4 rotor without knowing anything about thede engines.

And again, your answers are really appreciated. Thank you

Brettus

iTrader: (2)

The 6 speed box will take that kind of power .....so long as you don't abuse it . Doing skids over rough terrain would kill it instantly though. The 5 speed gearbox is a bit stronger . I've run it successfully for years (without abusing it)on my 400whp turbo Renesis. Same story for rear end.

TeamRX8

iTrader: (25)

Well even after several years and several 100,000 dollars, if you did eventually get it to work it’s still a Renesis engine with all it’s flaws. Just so you can impress somebody on RX8Club?

The RX8 being dirt cheap is what brings most people here now. It doesn’t fare well that you have such expensive ideas, but maybe you’re building an apartment on the penthouse floor of the most expensive building in Dubai and $500,000 is is chump change play money over the weekend.

TeamRX8

iTrader: (25)

on a 4-rotor???

do you even understand how long a 4-rotor is? You need to sit in the rear seat to shift it. The entire drivetrain has to be revised and the firewall and tunnel seriously chopped just to get an aftermarket solution in there.

Brettus

iTrader: (2)

Adding to your idea .....
6 port outer irons
6 port middle irons
small PP exhaust on middle housings
bridgeports on the both intake ports feeding the middle rotors
Three o2 sensors ...one on each outer ex port .... one on siamese port in middle of engine
Ability to tune 2 separate gangs of injectors .
Done!

Brettus

iTrader: (2)

Power wise though ...how would it be different to a two rotor turbo . Similar torque and power ?

Mark_Huntsman

I am not sure what you mean by expensive ideas. So far all I said was asking details about these engines, wanted to do some engineering/cad work - free, machine work - almost free...
Machining center irons and stationary gears to mount in there would take about 4 hours total, so even if I have to pay for my own work it will be still only about 100eur. Machining e-shaft as I have it laid out so far would take something about 300, again if I had to pay for my own work. If you can tell me why I should not even try to make this engine, I would appreciate it, but please don't say because its expensive. I will most likely find out myself, that some steps in the process will be expensive, like ECU and tuning, but I can make mechanical things work without spending 30k for ready built engine.

Sorry if what I said came out mean or ignorant, English is not my first language and sometimes I am not sure I said what I wanted the way it was meant.

Mark_Huntsman

I am sorry, but no, I don't know yet the exact length of 4 rotor, also I don't know how much space there is in the engine bay, I have only seen 2JZ swapped rx8s without modified firewalls and that engine is almost as long as a Smart. I was thinking about leaving everything from gearbox back as it is and moving around stuff in front of the engine.

Brettus

iTrader: (2)

On second thoughts ....... it will be too difficult to set up and control the aux ports for the 6 port outers and leaving them open is not good either.
A more balanced tuneable engine would be:
*all 4port irons
*small PP exhaust on all the housings
*bridgeports on all intake ports

Outer rotors would still flow better but the small pps would definitely even things out.

Mark_Huntsman

Additional exhaust PP could also be different sizes to match the flow rate as close as possible, for example all of them rounded rectangles of the same height to have the same timing across all rotors, but middle ones being wider than those on outer housings to compensate for smaller side ports.

TeamRX8

iTrader: (25)

Not trying to beat you up or down, but your lack of understanding leaves you in the dark about how little you grasp regarding the subject details and complexities involved. The people doing this didn’t do it for a 1-off engine but for commercial reasons, were well versed in the subject, had access to actual rare parts to work from, made their share of costly mistakes, and so on. Even if you do eventually manage to build something that holds together and functions properly for any length of time, the chassis fitment is just a deep of hole to climb into. The engine swap you mentioned is only 2/3 as long as a 4-rotor. If you leave the drivetrain where it is the front of the engine will be up near the hood opening. The Renesis is probably the least durable of the bunch. Basing it on that is like striking a match in a gas filled tunnel. As far as the engine goes you’ll be way ahead to instead go buy an assembled motor from the people who already paid their dues and learned the hard way. They have standard intake port versions. There was an RX8 that had a 4-rotor fit into it that seems to have disappeared. I bet they had at least $200k into it, but the engine was cut way back into the dash.

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Mark_Huntsman

Thanks for your write up with explanations. To be honest, I got pretty interested in the idea of building 4 rotor of my own after I stumbled upon a thread on rx7club ( https://www.rx7club.com/build-thread...-build-974831/ ).

About the length of the theoretical engine, IIRC MSP intermediate iron is 50mm thick and rotor housings are 80mm, which means it would be 260mm longer than normal MSP. From what I have seen so far I thought there was more space in front of the engine, but I am most likely wrong.

Anyway, I would really like to get an RX8 as my next car even if I will not be able to build "26B-MSP". And with my plan to get one bare engine anyway, I can rebuild it and have it ready to be put in the car if anything happens.

That comment about proving something to rx7club members got me thinking why would I even attempt to do something like this. Most likely just to prove to myself that I have the skills to do the CAD work at this scale and to have something that will keep me occupied in my free time. So far I have made my own recurve bow riser (will post pics later) with geometry optimized for rigidity and reduced internal stress in material while maintaining reasonable weight, computer water cooling blocks, and some parts for formula student electric when I was in Uni.

CaymanRotary

Something to do in your free time? How do you have such an abundance to build a Renesis 4 rotor. I don’t think it’s ever been accomplished before. I could be wrong but when you can just use 13b-REW parts why even bother?

TeamRX8

iTrader: (25)

Well it’s true that you could build a shorter engine that way; assuming you can fabricate the multi-piece e-shaft properly and actually be able to assemble it that way, but again the end result is a more complex & stressed version of the most durability-suspect engine of the bunch. Seems like a rather high risk investment strategy.

Further, adding a peripheral exhaust port to a rotor housing isn’t anything the same as the peripheral intake port. It’s an entirely different set of design conditions and stresses as well. Even if you use std. 13B exhaust port housings you’re can’t just block the side ports. So piping all those ports for all those rotors is again both excessively complex and excessive in flow. So again, you come around full circle to just building a standard 26B, except now companies l, or at least one, offers billet plates with standard side ports that will be less finicky at low rpm.

all things are possible, but the questions are how much will it cost, how long will it last, and will there actually be any advantages that justify doing it the hard way vs. the easy way. I do some crazy stuff too. I also had this same idea a long time ago too. Knowing what I know today, I wouldn’t do it that way now. That’s just for the short block assembly. You still have to do all the peripheral support components and get it *all* to fit and drive properly.

Cutting off the front and caging it along with the rest of the car is one thing, but within the OE structure is tough. I’m well familiar with the reference thread. Go look at the beginning at how it fits into the FD3 engine bay. It isn’t going to be that simple or easy in the SE3P engine bay because the 10 year later design task difference was to get a 2-rotor in as far back and as low as possible. So the subframe, steering/suspension, side rails, etc are all designed with that in mind. The hood dives down low in front, and so on.

All possible with enough resources, but by yourself ... that’s a dedicated job taking who knows how many years. I see some pretty impressive stuff get built out your way though. If you tackle it then don’t take my words wrong; I’ll be rooting for you, but the odds are not stacked in your favor for a better let alone equal end result imo.

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Mark_Huntsman

I should again say, main goal was to have it legal for street use in Europe, since you can't legally swap or even turbo charge your car, if you don't want to pay about 15-30k eur just to have it inspected and certified for road use, many people do turbo builds or even swaps, but they do risk having their car impounded. As I said before, this would fall into gray area of legislation, since the engine block will still have the stock ID stamped on it.

Would be the stresses on e-shaft be that high even in N/A application with stock, or even lower rpm range? Or it depends mostly on balancing of rotating assembly?

I think the 4rotor rx8 you were referring to was built by BMI.

CaymanRotary

That car doesnt use a Renesis 4 rotor though. I am unaware of any successful Renesis based 4 rotors. I do know a 3 rotor is possible using Renesis parts however. It would be far more practical than a 4 rotor version. I do know they sell the kit to adapt the 3 rotor Renesis engine into the RX8 for $15k.

Rkesh88

ive read about the 3 rotor Renny. Any news on it? Was it made with 4 or 6 port plates? And any power numbers from it?

CaymanRotary

Dont have technical specs but this is the original thread. Im not crazy enough to even try to attempt something like this haha. 3 rotor Renesis drifting vid in UK - AusRotary