tuj

Does anyone know the real difficulties in creating 4 rotor engines? It looks like just sticking 13b pieces together basically. I know that a custom eccentric shaft would have to be machined. But what are the other challenges?

Oil lubrication could be via dry sump. Coolant routing doesn't seem like it would be a problem. No need for turbos. A normal 13b performance clutch/flywheel could be used. What about ECU's?

I've searched the forum and the net and seen a number of these engines, but the only page that had any real detail on the construction was Granny's Speed Shop.

Apparently an engine like this will fit in a FD.
http://www.autotechmotorsports.com/projects-23afd.htm

Yes, I know anything can be done with enough cash, but how realistic is this? Besides the eccentric shaft and the motor mounts, it doesn't seem like anything else would need to be machined.

twint78

Here's a list of what you need:

1.This is the most important. A finger to click your mouse on the search function key.

Dear god learn how to use it.

T88NosRx7

iTrader: (1)

It looks like he already did some research, and didn't ask for your smart-*** comment.

This may help answers some questions
https://www.rx7club.com/forum/showth...ighlight=scoot

tuj

Right. Everyone says that its not as easy as just putting 13b or 20b parts together. Well, I'm asking, why not?

Granny Speed Shop did it with 2 13b's with their eccentric shafts joined. That seems to be a bad idea to me. You end up with a 3 piece shaft and your 2 13b's in phase with each other, rather than a nice 90 degree offset between each of the 4 rotors. So it seems that a custom-machined eccentric shaft is called for.

I don't read Japanese, so besides trying to infer things from pictures, I haven't been able to get much info on the Scoot showcar. I've seen the 4 rotor BWM, but again, nothing about the build-up. Same for Jim Downing's 4 rotor prototype racers.

I'm not all that intimate with the 13b, so before I start really thinking about this project, I'm trying to figure out if I'm overlooking something obvious that would greatly complicate the thing.

t-von

iTrader: (8)

There is a guy flooting around this forum who lives in new Zealand. He should have the info you need. I forget is name. He may chime in. Apparently they have the resources to build these 4 rotor engines fairly cheap ($6,000-$7,000).
A 13b version would be a little longer than the 12a (scoot) version. Also check the "The Hitman" web page. He has a custom made 3 rotor which uses a custom made center plate that is thinner than the standard 20b center plate. I think those guys in NZ helped him make it. Now as far as cost, regardless of what Rx7 your putting it in, you would probably have to locate the engine back a few inches to really help out with the balance of the car(4 rotors are heavy). That means custom crank shaft,sub-fram,& shift linkage(if you want the shitfer in the stock location). Those 3 mods alone are expensive. Then you will need a custom LIM & UIM. Mazda does not sell these. $$$$$ Then there is the ecu problem. I don't know of a single ecu that will operate a 4 rotor properly. Thererfore 2 will be needed. $$$$$$ Then there's the tranny problem. A 4 rotor would twist a stock Rx7 tranny into peices. Now you could save some money by running it na. I would! A na 4 rotor should have all the power you will ever need and be reliable. Plus it would run alot cooler. Hope that helps.

Evil Aviator

Downing Atlanta uses a Motec M800 to run their 4-rotor engine, but just about any EMS that can run an 8-cylinder engine should be able to run a 4-rotor engine.

The custom parts required would be entirely too expensive in the US, so you would probably want to try and source them from NZ, Australia, or Japan.

Jeff20B

iTrader: (13)

I agree that phasing the rotors 90º apart is a good idea. Jeff Bruce is the guy who makes custom eccentric shafts. Do a search on his name (you may get lucky).

rotaspec

Here's a text with some details on the New Zealand company:
Precision Engineering Multirotor kits:

This is a general list of parts available to convert Mazda 13B type
engines to 3 or 4 rotor variants. Only the modified parts are listed,
as most others are Mazda items or are easily fabricated by a
competent engine builder.
All prices are in NZ$ and are ex factory, so no allowances for shipping,
etc have been made.
NZ customers should note that GST is charged on top of these prices.

1. 3 rotor crank assembly $2100
2. 4 rotor crank assembly (including rear c/weight) $3200
3. Centre housing modification for 3 or 4 rotor kits $ 600 (2 required for 4 rotor)
4. Through-bolt set for 3 rotor $ 175
5. Through-bolt set for 4 rotor $ 195
6. Dowel set for 3 rotor $ 110
7. Dowel set for 4 rotor $ 130
8. Direct oil feed for 3 or 4 rotor kit centre housing $ 250 (2 required for 4 rotor)

Other services:
1. 13B 2-piece crank and centre bearing kit $1800 (fitted to customer’s housing)
2. 13B dowel set and machining $ 700
3. Mill 2mm slotted rotor for 3mm apex seals $ 30 (per rotor)
4. Surface grind iron housings $ 100 (per surface)

Note that the multirotor centre housing modification cost is only for the modification.
It does not include the cost of a standard front gear or housing. These item, especially
the housings, vary greatly in price depending on the year and type. They can be priced
on submission of Mazda’s part number.

Notes on the 3 rotor eccentric shaft:
The shaft is very similar to the 20B one, and is held together by the front bolt.
It is a 2 piece construction made from billet. The front lobe slides off, and is
indexed by a key and held by a taper.

Contact: Jeff Bruce
Precision Engineering Ltd.
9B Airborne Road
Albany
Auckland.

Phone 09-415-3264
====================
Gary

mmaragos

When I checked with Rob at Pineapple, he said that he would build a custom 4 rotor for about $7000-$8000 with a 13B core.

Scalliwag

I don't have the links offhand but check out articles on the 4 rotor Mazda LeMans car that won in '91. I believe it used a 3 piece shaft as well. It also had slide throttle bodies and other wild ****.

Grizzly

http://www.mymazdarotary.com/mazda_r...paper_html.htm

www.4rotor.com

I am in the Prosses of building a 13b Triple, the Main thing you must know is if you use the Custom center plates (With Staitionary gears fitted) it will only lend itself to being a Periphral port.

Basicly becouse the Primary ports on a 13b-rew plate cant be made big enough to flow as much as a Stock Secondry, so this leaves you with a problem where even if you do make them big enough you cant extend them.

This is why i have spent the last 6 months trying to get my P/P running properly with a Turbo fitted.

I would say the easyest way of making a Quad is to get hold of 2 20b center plates,20b end plates and a custom E-shaft and Bolts, then your on your way to making a Roadable Quad.

Chris

Jeff20B

iTrader: (13)

That's why the HITman used CD Cosmo/RX-5 4 port 13B side plates in his. They all have the same size ports whether primary or secondary. That's a good rule of thumb. If it's a 1st gen or older engine, you can use side ports. If it's a 2nd gen or newer engine, it'll need P ports.

Grizzly

Did'nt Hitman use 12A Plates?

I did Ask when i started Building mine but was Put off as i could'nt run the Size of side ports i wanted (Bigger that a 20b) i felt it was not worth the agro making sumps and Inlets if i was going to see less power.

So thats why i have a P/P Triple how well it runs on the Road is a diffrent matter but i am trying to building it for a Good comprimise in Low end Torque and Mid/High end power (With a bit of luck).

Chris

tuj

Due to the issues involved with getting the center two rotors to breath properly, maybe sticking two 13b's together isn't such a bad idea afterall?

Granny's Speed Shop did this, basically joining the two e-shafts. They kept the engine orientation the same and said it worked ok. Seems like ideally, the second engine would have to be 90 degrees offset, but with the odd mounting issues that would create, probably woudn't be worth it.

Using the two 13b's in a configuration like that would let you stick with stock manifolds too, right? Cooling could be stock as well. Sump would still be custom. Thoughts?

Jeff20B

iTrader: (13)

Two 13Bs together would be really long though.

The HITman probably did use 12A side plates (for the nitriding).