An engine conversion involves a lot more than just putting a standard motor in, take for example the 'standard' Stage 1 13BT conversion available from RotorWorx which can be found here: http://rotorworx.com.au/engine_packages.html
Power is quoted at 180kw at the wheels, which would be somewhere around 230+ at the engine, which a lot more than the standard S4/5 13BT made from factory, and this still retains the standard turbo.
This conversion costs around $7500

A 20B engine alone will be at least $4000 if you can find one

13BT's make either 138kw or 153kw @ 6500rpm standard if you go for either the series IV or series V type which seems to be most peoples choice. a standard 20BT makes 208kw @6500. if your not worried about the price i think going for a 20b would be awesome aswell as probly smarted becasue the way i see it is you can either have a worked 13b making 200kw or you can have a standard 20b making 200kw, the 20b being standard making it way more reliable not to mention nice rough 20b sound that cant be mistaken for anything but a 20b. also the 20b has almost double the torque of a standard 13b so for these reasons i think the 20b would be a great choice however like was mentioned before you have no chance in hell of getting it road registered. with strengthening it up you would want to do this which ever way you go so thats not really an issue. my make has a ca in his 1600 (makes 215rwkw) and this played havoc with the body of it so obviously it would be in your best intrest to seam weld it at least but yeah if your not worried about not being able to road register it or about the coast i recon go with it and good luck

Nice job, nice looking rotary 1200 Datto. Just watch out , that motor, that weight, on those tires...... make sure no beer is around...you might forget about the tires, and ...please, add some substance to that car, it is excelent, aside from the tires, it is a safety issue, not just looks.
Cheers.
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Also if anyone is interested in hearing/seeing some 20B powered cars in action, check out the 'Videos' page on www.mazdarotary.net where there are a few videos available to download of 20B-powered cars.

Yes traction would be quite an issue!

I have a 13B in mine, with a GT35/40 roller bearing turbo, it currently makes around 220kws at the wheels (no intercooler, water injection is used instead) and as you would imagine, the 175s on it don't grip for too long once it comes on boost





One thing you can't beat however is the sound of an angry 20B, they are awesome!!!

Here are some more pics of my car...

http://mazdarotary.alphalink.com.au/datsun/

yea would be awsome with that much power in a little twelve hundred. mite need to mini tub it tho or you would never get anywere, too much tyre frying

You would have to enlarge the tunnel , or you might sneak in with a shell that was a factory auto. (bigger tunnel)

you won't have to touch the firewall at all.

but yeas, you will need lots of rubber for traction!

If you were posessed enough to do it you would have to modify the fire wall, seam weld the body, fully cage out the car. It would need big tubs to fit tyres anything like big enough to put the power on the ground.
Its not impossible , but unless you are rich I wouldnt try it.

the 20B is the size of a 6gal drum, so making it fit is as easy as pie. it's actually not much longer than an A15 block - but the mounting points are all wrong. you should run with a 12A style timing cover, and use modified RX3/7 mounts to mount it over your swaybar as per most of Mazda's arrangements.

a ported NA 20B would see you filling up at every servo on the way to your destination. and of course, there's the rebuild cost.
you could make it carby, but then, you'd need to make all new manifolds to suit and then get the carbies on top of that.
the 20B has one of the best flowing inlet manifolds around, so why ditch it? hook up an LTX12 microtech onto all the std manifolds and injectors for $AU1395 and SAVE yourself money by going EFI.

the 20B doesn't need to be revved as hard to make the same power as a 13B, hence why they have the tag of being more reliable. but don't be fooled, the very early engines are known for eccentric shaft failure and rear rotor shifting. this problem was quickly rectified though, i think the problem engines were 1991 and early 92.

you could use a std FC3S RX7 5 speed behind a 20B with no turbos, with a good 13B clutch and flywheel and the 20B counterweight.

the sump might need mods though, although if it does foul, use a 180B / stanza crossmember and be done with it.

it's certainly a conversion i was considering, but trying to get a "4.0L" engine (mazda quotes it at 1998cc - so double that) engineered into a 1200 would see you on a mission from god.

but if it's not going to be street legal, then take it away. it's certainly not an overly complicated conversion.

good luck