RX7 13b and 20b engines

[Jordan Clarkson]

I'm a lover of all things Japanese, especially Twin Turbo Supras, Skylines and Silvias. Recently I am really into FD Mazda RX-7's as well, and was wondering what are the differences between the 13b and 20b engines? Just curious to know, have searched RX7 forums but want a simple clear explanation. Cheers!

[dern]

Hadn't heard of a 20b (have a 13b in my kit car) but wikipedia says it's a 3 rotor engine whereas a 13b is a 2 rotor engine.

[Kaiser Damz]

as above the 20b is a 3 rotor engine, 13b was 2 rotor. The 20b was fitted to the mazda/eunos cosmos, some people have fitted 20b's into rx7's as stock they made easily around 300 bhp but tuned it can go much higher than 13b.

[probedb]

It's also expensive to fit into an FD

You can get quad rotors too....

[cocopop]

13b:


20b:


‘26b’:


As above, fitting a 20b to an FD is pricey, fitting a quad rotor is silly money. Various companies sell quad rotor engines off the shelf, Scoot in Japan for one, but you would need very deep pockets.

[Ali_T]

20B motors are ultra rare as a factory unit. There are plenty of people willing to butcher a 13B to create one though so watch out. IIRC it was only ever available commercially in the slow selling Eunos Cosmos. Beyond that, only the endurance cars used them. You'd only go for a 20B if you want crazy horsepower though. The 13B is more than tuneable enough!

[gareth_r]

Cosmos




Cosmo

[groupcracer]

The 20b is a popular race engine. I have one built by the renowned race engine builder CLR Racing in Florida and as a triple rotor naturally aspirated engine it pushes out 530 hp. That is progressive power, not peaky turbo type power which is great for putting you in a ditch. I was going to use it for a race car project but would sell it as I have gone in another direction and am racing Group C cars now. It would work in a road car as it runs smoothly without the turbo. Noise would need tamed though as it sounds like an F1 engine doing 18000 rpm. It is zero hours and is technically a two litre engine, hence good for racing.

[rossw46]

I watched a pretty good video on YouTube last night, search for "What its like owning a 3 rotor 20B RX7".

Sound warning, its bloody good !

[Jordan Clarkson]

Cheers for the all the infomation guys! Now have a better idea of the differences between these engines. And Rossw46 Yeah I watched that video yesterday was looking through a couple of Rob Dahms videos one of the best car guys on youtube in my opinion. Thanks everyone for your input

[BrettMRC]

For road use there is little point in going for a 3 rotor over a two rotor, unless you need more low end torque. (Hence why it was fitted to the larger Cosmo)

The tripples make excellent power when running a peripheral port and N/A - plus they sound like nothing else!
http://youtu.be/_ieBKyaVHO0

Really, it depends on how deep your pockets are

[Rotorheid]

That was a RX7 FC N/A 13Bpp engine on the road and different sound from 20Bpp
enjoy it..

[probedb]

I love this video for the sound, the car is secondary I believe the Furai had a 20B in it?

http://www.youtube.com/watch?v=oEOHn7rspsk