Hi,

As you can see i'm new to this site (its like starting school or over again) and i've been doing/getting as much research done as possible for the above title. Yes two 13b rew's strapped together.

Yes i must be insane, yes i will see it through and yes the cash flow (still living with parents - how sad) for this isnt that bad but i want to keep it how can you say "affordable" still. I'm not going to go buy some fantastic expensive part if i can get something that does exactly the same job but cheaper.

The reason for this post is here your views on what certain systems etc to use.

I have a welder/fabricator (actually two of them thinking about it)
Majority of tools to carry out the operation (Engine crane etc) + mechanic. The only thing i do need is a pit or a set of ramp lifts but i might be able to borrow my mates workshop for that.
The Will (i you aint got it, you will never get the project finished)


So anyway, i'm looking at starting with buying to complete rx8 engines (the higher bhp model) as these are very cheap from salvage yards around here and still in good condition.

Before buying these, i'm looking into the eccentric shaft. So i have contacted someone who makes the eccentrial shaft and are awaiting an email.

All of what i buy/ custom make (except engines) are going to hopefully be made in 5's. What i'm wanting to do is to have 6 engines in total (1 being mine) to sell off at a slash price to what all these performance companies want to charge you.

I may sell as parts - i may sell as complete engines or kit engines - i'm not sure yet as its still early days.

SO custom engine management i was thinking Motec? I hear there the best

Custom fuel rail/injection - not sure yet - thinking of combining injection systems off each engine.

Exhaust - going to have to be custom of course

Fuel pump/s?

Gearbox? RX8 one to keep i assume but may/wil need uprated flywheel and perhaps different bell housing.

Anyways i am just throwing it out there to you guys as i know alot of you have already done it or have a greater knowledge of it than me. (though some peoples knowledge will be NO - dont do it. lol)

Look forward to hearing from all you fanatics

Oh yeah - this is a na project

Thanks

Mav248

 

I honestly don't know where to begin...

4 rotor shafts need to be three piece in order to make it actually possible to assemble the engine. A skilled machinist, for a few thousand dollars, could make such a shaft using several 13B shafts. At the very least you would need one center bearing to keep shaft flex under control but if the engine is designed for high RPM, you will want a 4 piece shaft with a bearing in each middle iron.

Everything will need to be custom. Mounts, intake manifold, dry sump system, fuel system, cooling, etc.

Best bet is to start with a kit. KiwiRE and Precision engineering both make 4 rotor kits of parts that have the hard stuff (shaft, irons) in them. Looking at about $8,000.

 

It was actually Kiwi i've contacted, just awaiting the reply.

I found this pic when searching the sites - would this break down into 4 pieces - i always assumed that were one piece?

 

N/A? 13B-REW? I don't understand why you would do a n/a build with a low compression motor. Throw some S5 N/A rotors in there. And Don't use the RX-8 tranny. You'll be replacing it REAL quick. Get the Turbo-II drivetrain.

I do hope you know what your getting yourself into...

 

hi there thanks for the info. kinda do and dont know what i'm gettin into but i know once i've done it will be an accomplishment.

still researching, hence the post on the site.

I'm looking at N/A because of the sound that the rx7 scoot makes. cant get enough of it.

i thought of using rx8 tranny and renesis engine as i would have thought they were far superior (sounds like the wrong assumption now maybe?)

Would you suggest just going for normal 13b motors then rather than the ones from the rx8?

look forward to your reply

 

Aaron Cake
you said "shafts need to be three piece in order to make it actually possible to assemble the engine" why is that?

 

13BREW and the 13BMSP-RE (Renisis motor) are two different engines.

Then you are talking about 13B NA motors as well?

You would need to figure out what base parts you are using. Two MSP-RE engines would be fine for non turbo and lighty turboed applications.

And you would probably want to use a 87-91 R type tranny as found in the 87-91 Turbo RX-7, Ford F150 and a couple of other cars. It will be stronger than the Asian built 6 speed in the RX-8.

 

Im pretty sure the scoot rx7 uses two 12a motors. not sure how much that would change the sound. im sure there porting is a big factor in sound as well.

 

ahh i see. So the engine that i'm actually looking at creating has a code name of 26bmsp-re i suppose? sorry chaps

Alec at Kiwi got back to me. Luckily i didnt use the engine code and just told him it was two rx8 engines.

I'm a bit worried mainly at finding an engine management system? any ideas?

 

It would seem you would want a very good engine management system for this, Motec would likely be the way to go, if you could find someone to tune it for you.

One of the reasons the scoot 4-rotor sounds like it does is the Independent Throttle Bodies and being a Peripheral Port engine, not ONLY because it's a 4 rotor.

 

There is no engine code for the handful of 24a or 26b engines out there.

BTW, if you haven't noticed this subject is a bit like a first year physics student attempting to rewrite the laws of relativity. To be blunt, your chances of success (and sufficient funding) are between slim and none. If you're very serious and have the funding, do a "simple" 20b install as a warmup and then consider the 4-rotor project.

 

90% percent of the folks hear run 2 rotors, the rest are rebuilt 3 rotors. jeff20b is the only person i know who's builing a 4 rotor and is not a custom shop/race team. hes just a guy with a **** load of parts lol, and its still not done because of funding(building it for some one else).

if your for real about doing this. get some non rx8 housings and irons and dont use a 6 port motor.just make sure the two motors you get are of the same type.ie if i rember right 12a irons can be used in older 13b's but not in 13b's from a fd if i remember right?.

the intake and exhaust ports will make the price higher to make this motor if you use rx8 parts.since not two many places sell a plate to make your own intake or exhaust. also 6 port motors cant be ported as much and dont know how they would run if you have all 6 intake ports open all the time.trying to ge the extra 2 ports(per rotor) to work right will add so much work to what you need to get done.

get a dizzy and see if jeff20b will mod it to work on a 4 rotoror maybe the rotary shack will do it for you. then buy two carb intake and your good to go. heck summit are selling a intake for 200,


cut them and mod them to work on you motor. youll save so much more money running it as a carb motor then trying to find a ecu to work and all the tunning time needed.


correct me if iam wroung on any thing i am talking out of my butt since i only really know about 12a's and some stuff i learned about rx8's since i got one.(sa's for life)

 

Kiwi buys the kit from Precision, so either one is a good place to start.

I'm sorry, I must have been on crack when I said four piece because I looked it up last night and it is a three piece. There is a center section with two lobes, and then two outer sections, each with one lobe.

True, but it is a huge task to take on as a first project. Few 4 rotors exist outside of Mazda because it is a formidable thing to do.

That's a nice noise, but once you've heard a real Mazda 4 rotor a few feet from your ear, Scoot's car sounds tame.

The RX-8 transmission is quite weak compared to the TII/FD transmission. No advantage in using a Renesis because you will need to cut peripheral ports in the housings anyway and block up the side plates. In fact a Renesis would be more of a pain due to the lack of factory peripheral exhaust ports.

This is a fairly basic thing though. The difference between the 13B and the Renesis is fundamental and makes the Renesis obviously unsuited for such a project. I am pointing this out because I believe that not knowing such basics could make the rest of this project very, very difficult.

Without hesitation. That's what I'm doing. I'm using irons and housings from the S4 NA because they are cheap, and S5 rotors because they are light and have the highest compression of all non-Renesis NA 13B rotors.

Physics. The maximum amount of rotors you can install on a single piece shaft is two. During engine assembly the shaft must be lifted up to slip the intermediate housing over the lobes. This can't be done if there is already another rotor and intermediate there.

Peripheral ports. And the 90 degree firing angle.

So what did he say about the prospect of using Renesis parts? Likely the same thing I just did?

Well, you will need to run 8 ignition channels. And the ECU needs to support trailing split across 4 channels if you intend to run trailings. The only one that comes to mind are the Motecs.

I will be running leadings only and using a Megasquirt.

You can add me to that list.





That's my 4 rotor test shaft. It won't be used in an engine, so I painted it up and hung it on the wall. I'm planning on using the Precision/Kiwi kit just so save me the trouble of re-engineering what they already have done.

 

Wow! What floods of information!! Thankyou. U dont ask, you dont get, even with all the searching you do!

So the run down at the moment is to run 13b motors from an S4 N/A and use S5 rotors using e shaft from Kiwi. Then forget the engine management and run the car on throttle bodies which will save a little money. Is there any downfall to using s5 motor?

Dont pp engines have less life expectancy? If this is true, does anyone know how much you slash life expectancy of the motor?

 

Jeez, you're starting to look like TTT with all the multi-quote replies and all!

Anyways, ever considered running 4 "waste spark" leading coils, and have each coil firing both leading and trailing of 1 rotor at a time, essentially running a zero split trailing and leading ignition with the Megasquirt?

Seems to me that many people have had success with zero split (not sure about idling...) especially with N/A PP's, and the second gen leading ignition is more than adequate to light the fire. Just a thought.

Throttlebodies have nothing to do with engine management. You can run carburetor setups, but you will still need some sort of engine management (or some crazy distributor) in order to control spark. Are you sure you know what you're getting into my friend?

Only reason Aaron is running S4 motors (pretty sure) is cost efficiency and availability, combined with the superior S5 N/A rotors (like he said, for lighter weight and higher comp. ratio)

Any full out race motor has a pretty low life expectancy. You're surely not going to be getting 150k+ out of a PP 4-rotor, you don't exactly build them for longevity.

 

Searching for 4 rotor stuff is hard. Loads of people have talked about it, few are knowledgeable enough to discuss it intelligently, and even fewer are actually capable of executing it in the physical sense.

I picked S4 irons/housings because they are a dime a dozen. It really doesn't matter what your irons are as long as they are all the same. But 6 port NA irons are worth about scrap value and the porting configuration doesn't matter because they will be filled for peripheral ports. There are of course better choices in housings like the REW housings. They are available new from Mazda and the price isn't too bad at about $350 each. I may go that direction if I can't get a good used set of S4 housings.

S5 rotors are the lightest and highest compression of all RX-7 NA 13Bs, so they are I think the only choice in that sense. The Renesis rotors are superior but require machine work to make fit in a peripheral port engine and don't seem to make any more power over the older rotors.

The life expectancy of a peripheral port engine is exactly related to how much it is beat up. The myth of low life expectancy comes from the fact that peripheral port engines are often spun to over 10K as their powerband extends well past the stock redline. Without balancing, things don't last. A street driven 4 rotor peripheral port is a complete opposite story. Reasonable sized peripheral ports will make power below the typical race PP setup. Kept at 8-9K with occasional jaunts to a bit higher and engine life should be superb.

I've been multi quoting for 10+ years.

That's a possibility as well. Zero split seems to make good power under high loads at high revs. I guess it's probably a better choice then running leadings only under almost any circumstance.

And that's a big one right there. My brain seems to think that any engine firing at 90 degrees can lend it's distributor as long as the gear is matched to the engine so that it will actually rotate. But then the other side of my brain says there is something wrong with that. I'm sure someone will point it out of that plan is stupid. Then again, it is a stupid plan simply because it is a distributor. They have no place in cars when electronic ignition is available.

A custom intake manifold (100% custom) with ITBs is the way to go. Considerable fabrication, plus an airbox, etc.

 

Aaron having followed your other builds I am definitely looking forward to your 4 rotor build! and before long this thread is going to be archive ready for some basic 4 rotor info.

 

i use the ignition system jeff20b cam up for 2 rotor motors with the wasted spark. iam not sure how it would work for a 4 rotor but i can tell you about it for a 2 rotor. it made a night and day difference in my little 12a. i can be sitting parked and dump the clutch in 1st gear and my car wont stall it will creep around and it idles at 1k no lie.
i want to make a 4 rotor so bad you have no idea. but there big section i don't under stand. like why dry sump for one.

 

Tried to do some swatting last night (wikipedia) - I was trying to bring myself up to date with rotary tech talk etc. Notice the side port exhaust exits on the renesis.

Tried to find where the 13b rew engines come from (model etc). I believe they are from the Mazda RX7 FD3s twin turbo. Rotary engines seem to be easily sourced out of the uk which is a shame or perhaps i'm not looking in the right places. Getting out of uk which cost mountains in shipping which is pointless!

 

13B-REW is from the 3rd gen RX-7, FD3S
13B-RE is from a Cosmo
13BMSP-RE is from an RX-8

 

alrighty.

A) You would need a dry sump because with a stock oil pump you both not have the flow capacity to feed a 4-rotor engine, and the stock oil galleries would not flow enough to feed through the entire motor.

B)You can source basically any used rotary motor from the classified section in this forum, other forums, e-bay (but please stay away..) Or the forum vendor Japan2la, who gets good quality engines at seemingly good prices.

C) You do not really want to buy 2 full long-block engines and piece them together. You need to get all the parts and BUILD this. This means 4 rotor housings (of any series), both 1 front and 1 rear iron, and 3 intermediate irons. I'm not sure about the doweling, but there's a chance some machine work would be required there. Then you need to have the intake ports on all the irons filled smooth and machined. You need to have the Peripheral Intake ports pressed and welded in the ideal place (Read: understanding port timing and overlap in a rotary engine) in the rotor housings, and have the water jackets filled around them to seal them. And this is just a start. I really don't think you have any idea what you are getting into, and are only choosing an engine based on its sound, which is stupid.

Maybe you should consider building an N/A PP 13B first, or at the very least an N/A PP 20B, where the parts have at least been manufactured by OEM.

 

ok, thanks for the info about the irons and of course your entitled to your opinion. It's not just based on the sound but that is one of the main things. Its based on power and also the engineering behind it. Conventional piston engines have got boring for me so this seems the logical step to a rotary. Ok maybe not logical going straight to a four rotor but what the hell. There is enough info/enthuisasts on the internet willing to share mechanical information and experience. Of course some of them will say not to do it but that wont stop me lol.

 

Well then I wish you the best with it, I do hope you pull it off and definitely should post about it. The only last thing I could suggest is doing as much researching, reading and searching on this and other rotary forums as much as possible so that when you do have questions, they will be researched, educated questions, and people will be much more inclined to share information and help you out with it. Good luck!