T-von

U want a 3 rotor Renesis, simply duplicate the center plate from the a regular 20b and engineer some more stock 20b e-shafts. You would need the wider 20b's center plate for several reasons. For 1 the wider plate would allow for the engineering of the 6th ports and the correct exhaust area ratio. You can't have this if you used another center primary port plate. It's too thin and won't allow for the correct matching port area. Now as far as the tension bolts, either engineer some really longs ones with butt loads of dowel pinning or fabricate another front plate to accept tension bolts from the front like the 20b does. There's your new 20b Renesis short block.

mike1324a

I think if you did that you would have issues making sure the same amount of air was getting into each of the rotors. Honestly you are going to have to make custom center plates to make sure the center rotor is running the same way the outer 2 rotors are. I like the idea of the 4 port per rotor mentioned earlier. It looks like a very good design. If you produce a 4 port per rotor, 3 rotor renesis, id be interested. that looks and sounds like a fantastic idea!

T-von

I know what your talking about. The stock 20B LIM is unbalanced because of the width of the center plate however, it is still capable of allowing the engine to make a tremendous amount of power reliably. If your going to bring up air flow issues, you might as well talk about how the center rotor always runs leaner in a 20b. The extra heat it gets from both sides of the engine naturally makes the center rotor run leaner. In the end, either of these flow imbalances can be tuned out. I mean we're talking a NA set-up here so it's really not that big a deal. A 9 port 20b is going to make the best power and be more emissions friendly in this application. 2 ports per rotor needs too much port area to match up with the flow of the aux ports. In a rotary more port area with 2 ports per housing usually means more over lap and lower velocity in the lower rpm's therefore killing any bottom end torque and less clean emissions.

Curious do you really understand how a 20b is put together? You would only be duplicating the stock center plate to allow for machining of the side exhaust and aux port. Racing beat currently has special aluminum side plates for the older 13b's to substitute the older heavier cast iron plates. Re-engineering the old 20b plate for side exhaust wouldn't be that big of a issue. Lastly the plate don't dictate the phasing of the rotors to make sure they run the same way, the e-shaft does. 13b is 180 degrees, 20b is 120 degrees and the 4 rotor in the 787b was phased at 90 degrees. Peace!

rx8wannahave

Any updates?

Thanks for the education lesson folks, while I'll probably forget most of it...lol

rotarygod

It wouldn't be too hard to get all the plates to flow equally. You just need to flow test them on a bench. The ports that have the least amount of flow need to be chacekd to see if any more can be freed up. If you can get them equal in flow to the rest, fantastic. You're done. If not you'll need to (gasp) decrease the flow potential of the other ports to match. This is actually a good thing though. Not too hard to overcome.

I personally think Racing Beat should modify the castings of their aluminum housings to include a side exhaust port but retain the 13B 4 port intake configuration. That would rock!

drivelikejehu

mazda recently discontinued the 20B centre bearing plate, and they arent doing another production run. theres a guy on the rx7 forums that got the last one in austrailia.

the center plate thats already in the renesis isnt wide wnough to put 4 ports on it. making that plate wider means a whole new e-shaft, which means two more things you need to replace to get a 3 rotor, and two more things that dont exist.

from hear say (not my personal experience) aluminum plates wear down REALLY fast because of the rubber seals on the rotors spinning against them. thats why the plates are cast iron and the housings are steel "plated" ... sort of.

this involves either a complete japanese 20B, or all new 13B parts. both we are trying to avoid. we wanna use all renesis stuff, because we know its going to be around. the last 13B was made 11 years ago in the US, its only a matter of time before mazda discontinues those parts. plus you can use existing parts from your renesis, rather than getting an ENTIRE new engine.

we also want this car to be daily driven... and a bridge port basically throws that out the window. once we have a "stock" renesis 20B that works and get some numbers from that, THEN we will tear it down and REALLY see what it can do.

yes its being worked on currently. yesterday we found a 1990 FC N/A 13B that we are tearing down. you ask why? because the intake ports on that are very similar to those of the renesis... imagine that. we can use this for measurements, as well as the renesis center plate (for exhaust ports) and 20B centre bearing plate (for width) we are trying to obtain. once we finish measuring and CADing, we can mock up an aluminum plate to be molded, so they can be casted, then machined. once everything is measured and designed, its pie from there.

sorry for the delay on the update. oh yeah, the "displacement on demand" idea has pretty much been killed by some things we forgot about.
- it will basically be miss firing when its not in use since they are phased at 120 degrees rather than 90. we dont know what this will result in, but thats enough to scrap the idea. we arent trying to re-invent the wheel.
- the oil thats put into the housing for the apex seals wont be burned.
- avoiding compression when not in use.
- some others i cant remember off hand

T-von

I know that. I'm talking using the stock 20b center plate as a basis to fabricate a new one for the Renesis like Racing beat did with their aluminum side plates. Using that plate would allow you to reuse a stock 20b e-shaft.

That all depends on what's used on the side plate surface. The stock iron side plates have a nitrided coating on the chrome surface to reduce the wear. A newly engineered aluminum side plate can be engineered the same way. Look at the aluminum rotor housings, those housings have a chrome ring on the compression surface.

drivelikejehu

oh ok, i wasnt clear on what you were saying. we are defiantely using a stock 20B plate for a basis for the renesis plate, so we can use the stock 20B e-shaft like you said.

as for using aluminum and other metals. coating and layering im sure could be used for this application, but i think that casting and machining is the most accurate and cost effective for us right now. its also what we know how to do without a doubt. once this thing runs im sure we will look into other metals like you said.

T-von

Cool anyone with some photo shop skills wanna modifiy this drawing showing how this new center plate may look with Renesis side exhaust and aux ports? Here is a pic of a new 20b center plate to get someone started.

rx8wannahave

drivelikjehu...thanks for the update, I'm glad this is past the "initial idea" stage and actual work already started.

Per fellow rx8club members, they have said that the 4port (from the automatic RX8) Renesis would make a 3-rotor Renesis alot simpler. Have you thought about exploring this idea also? I know we all would want the 6port since it could develop more power but if the 4port could give us 300whp and still rev to 9K...while being cheaper and simpler...then maybe this is an idea worth exploring.

Again…thanks for the effort to build a 3-rotor Renesis!

drivelikejehu

if the intake ports on the renesis are the same diameter as on the engine we have in the shop (they are very close, but maybe not exact) then 4 ports wont fit on the existing center plate, which means it would also have to be widened.

this creates two problems.

1) there wont be an existing e-shaft that will have the correct spacing between the lobes for the rotors and their housings.

2) an entire new center plate, as well as the intermediate will have to be designed and made, not including the new e-shaft. thats 3 entirely new parts that will have to be designed and made. so the price is going to be even more outrageous.

if the ports are SMALLER on the renesis then on this 6 port engine we have, then it might actually work. but i dont think this is the case. if someone has the end plate of a renesis so they can measure the diameter of the intake port inlets, it would be very useful.

making the inlets small enough to fit with the width of the existing center plate would restrict it more than keeping the slotted design.

rotarygod

The ports on a 6 port Renesis are much larger than those of the 6 port 13B. Most of this diference is on the intake opening side. The intake runners are also very different. They are farther out on the Renesis which means that the air doesn't have to turn as sharp to enter the engine. The secondary intake runners are slightly larger on the Renesis and the auxiliary port runners are much larger as the auxiliary port valve actuation system is not done the same as the older engines. The 6 port 13B probably isn't the best model to be using. You really need to have a Renesis housing.

drivelikejehu

oh were not using this engine for measureements by any means, really just looking at the plates for casting purposes, since they are the closest to the renesis plate, and free.

rx8wannahave

It's been 4 days...is the 3-rotor Renesis built yet?

LOL

Honestly because of the cost involved for a 3-rotor and the poor bang for your buck NA mod's for the RX8, my love of NA power is getting more and more strained...I hope one day something comes along...

Greddyturbo1

Hey Rotarygod, where did you get this info that the Renesis intakes are much bigger than the 13B.. The reason I 'am asking is, if this is true than maybe that explains why the boost falls on the FI systems. On my thread on New intakes, maybe its not the intake on the Renesis that's making the boost fall , but maybe the Turbo isn't big enough when the all the auxilaries kick in..

If that's the case , I wonder if twin seq. turbos would be a good idea for the Renesis...By the way I would love to put in a 3 Rotor Renesis in my 8, But try to keep the pricing reasonably...

rotarygod

All you have to do to find out that the intake area is larger is to look at one and compare it to a 13B. I've plyed with a few of them and compared them to the 13B. They are definitely larger. The port runners in the primary ports are the same size but the ports themselves open earlier which gives you more port area. The secondary and auxiliary runners are larger and again the ports open earlier which is more port area.

When it comes to boost falling off, it is all about turbo size. It's definitely not the intake's fault. The turbos used are just too small on the compressor side to make the needed power up high. This is the most likely explanation. There is one other possibility though.

The exhaust ports on the Renesis are terrible. I've seen them and played with them. When it comes to flow they are laughable yet the engine makes alot more power than the naturally aspirated 13B. There may be considerable pumping losses in these stock exhaust ports. Basically they could be a big restriction. Think of the difference in power between using a cat and not having one at all on a turbo car. It's huge. Now just build that restriction into your exhaust ports. A restriction gets worse and worse the faster the air has to travel through it. We might just be reaching an area of diminishing returns. It wouldn't be too hard to improve the flow of these ports but that requires opening the engine up and having some fun with a die grinder. We've got nice large intake ports but small poorly flowing exhaust ports. When it comes to making more power from forced induction, you need good exhaust flow. All you'll do with an exhaust restriction is to crank up the boost for little gain but more importantly you'll really increase your engine temperatures and the stresses on it. This is a possible explanation and at some point this is true. Where that point is I don't know. Since a few people have already crossed the 350 hp mark, I would start with the turbo size first. Porting definitely won't hurt it though.

drivelikejehu

^ i completely agree with this.

although with the exhuast ports being on the side of the housing, you can port them just like you can the intakes. imagine if it were possible to do a full bridge port on the exhaust like you can on an intake. the tradition 13B has peripheral designed exhuast, so flow is increased, but at the same time effciency is decreased from unburned gases crossing over into the intake chamber. this is where the side exhuast port design shines.

once we build this engine in the 'stock' form and get some base numbers, then we will tear it down and rebuild a monster. porting everything pretty well (keeping it daily driveable), and stream-lining the intake and exhaust manifolds to let everything breath. get some numbers from that. then tear down and rebuild again using FC s5 rotors and scalloping those, then slapping a huge turbo on there and seeing what happens. this one is a looong time down the road though.

my guess is the port job and opening up the intake and exhaust on the N/A 3 rotor renesis will crush 350. but once you hit 400-450+, your looking at a whole different ball game. at that point, the entire driveline needs to be upgrading to keep from ripping your car apart or staying on the road.

the cool thing about having an N/A motor... is that you can still get a WHOLE lot more out if it if you want to spend the time and money. you can only go so far with FI. unless you dont care about rebuilding every six months or your car is for the track or weekends only, then go ahead and pump that boost up!

Detrich

i would either (a) get a c6 corvette or (b) wait for the new toyota supra or (c) wait and see if the kabura comes back as the rx-7 in explosive form. but, i'm really leaning towards the supra if push came to shove...

drivelikejehu

what about the new 2008 skyline GTR? first one ever to be sold in the US. that takes my vote.

and you could buy a new rx8, and (once we build this) do a 3 rotor conversion, and probably slap a huge turbo on there for less than a new c6, and you would CRUSH it. and youd have a completely unique car. i see about 5 c6's a day, and that number keeps getting larger.

....but to each his own.

p.s. that kabura thing is UUUUUGLY!

Greddyturbo1

Thanks for the info Rotarygod/guys.
Question, you did'nt answer if a twin seq. turbo like the 13b would be a route to go and if the exhaust seems to be more likely the case in the Greddy scenario, then would a new exhaust manifold be also beneficial or not.. So it looks like you saved me $ 1,599.00 thanks.

Also with regard to Detrich, Hey I was ---this close to ordering a C6, but after see one everywhere I realize how much more I really like my RX8 with all the changes I made, it just
looks much more unique then what I've seen out there so far...

DARKMAZ8

Do you feel that porting the exhaust ports would net anything in N/A form?

Renesis_8

If the exhaust ports are the biggest restrction for this motor to gain more power, perhaps Mazda should look into redesigning the ports for the next gen RX-8.
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EdvinRX8

I will do it. Iam talking with speed force right now to boost my 8 to 400whp for 12-15k. If you can get me a motor that has at least 100% 300whp all motor and later look into a turbo system iam very interested. If this is for real i would like to get into touch with you over the phone. And see what we could arrange.

rx8wannahave

Nice movement since I last posted...and yes, RG...if it's that bad then wouldn't that be a huge area to work on for NA power in our Renesis?

drivelikeajehu...not to distract you from the 3-rotor project, but has your company thought about maybe working on the 2-rotor Renesis and just getting as much whp you can out of it without hurting reliability or adding a Turbo?

rotarygod

I feel that the exhaust ports need the most attention in the engine. The intake ports can be cleaned up a little bit but I really wouldn't enlarge them at all. The exhaust port area is far less than the exhaust runner area. On top of this the transition from port to runner is horrible. The first thing that needs to be done is to address this issue. You can enlarge the exhaust ports a little bit and this would help to smooth out the transition into the exhaust runner. The ports wouldn't get alot larger but flow would increase. From there I would work on the exhaust runner on a flowbench and actually add material to the runners. I see no reason why you couldn't make the runners smaller and still have them flow just as much. That's the goal. You want as much flow through as little area as possible. Larger is not always better. If this can be accomplished then you could design a good header that had the same sized primaries in it. Now you can better take advantage of the velocity in the exhaust to help pull the charge out of the other rotor.

The stock exhaust ports are so bad right now that even though the stock exhaust manifold has a terrible shape to it, it is still better than the ports. Even replacing the cat, muffler, header, etc isn't going to do much if you aren't addressing the single biggest isue in the system. No one has yet. Once you fix that issue you'll see other mods do a bit more. Don't expect miracles though. The engine is quite easily capable of flowing enough air for 250 hp. The problem is the cost and effort of making it happen. You cn pretty much figure that if you increase the flow internally that the ecu will overcompensate for it and you won't get much out of it. It's always something. Naturally aspirated power is expensive.