Larry Oslund

HI all,
New to this Forum. I have a '93 3rd gen. It has a pretty nice engine in it right now - Rebuild by Pettit about 15000 miles ago. FP intercooler, and computer. But I'm in the mood for something even more unique! So, I just recently bough a 20B engine and want to put it in the car. I know Pettit and PF do these conversions, but I'd like to do as much as I can, plus I don't really have the $40K or so that they charge for the whole package anyway. Plus, kind of looking for a project to do with my teenage son!
I don't even know if this is the proper thread to post this question on, so if there is a better one, please let me know.
I'm looking for anyone who has actually done this conversion, or even knows someone who does. Also is there a way to tell what specific model of the 20B I have - if there are such things. The only distinguishing marks I can even find is the number #516 stamped on each of the rotar housings.
Other information. The 20B is very clean looking. I was told that it only has 11k miles on it. It has the seq. turbo's too. Should I start by rebuilding the whole thing, putting higher perf. parts in. Mayber switch to a single turbo?
Thanks in advance to all who respond.
Btw - I live in Raleigh, NC

rx7eaven

I have not done this however it is very interesting to me. There was a thread before, basically the same thing. Try browsing through and see if you can find it. Good luck.
94 rx7 blk r2

Barwick

Wish you were my dad.. mine's only interested in sports.. that's cool and all, I love sports, but I wish he'd be cool with cars too..

I'd suggest doing a search through all these forums, and then looking on the internet for the 3 rotor swap, there's bound to be something out there on it.

AARotary

20B engine is unique in itself. I know a couple of RX-7 owners who successsfully have a shop convert the 20B into their RX-7.
Here is the figure to do it right it will cost you 25k to 30k for the job that is with the engine. Let say you have the engine already so I would say somewhere in the neighborhood of 20k to 26k. That is with the 20B and using the stock twins well if you are going single that figure is going up. Recently, Dave at KDRotary if you know who he is have done this conversion using the stock twins and it cost the guy 25k. It is alot of work involved and the drivetrain have to push back to accomodate the 3 rotors. Why don't you try rotorsportsracing.com they lare ocated in North Carolina maybe they can help you. Personally if you are looking to swap that engine anyway do it right the first time and you will be happy. I am looking toward the 20B as my next project. If you are looking for a shop to do this conversion for you I would recommend you to KDRotary because he have done this conversion before and that is where I get my car done. Here is the website you can check it out and give him a call well he wouldn't be back til Oct.2, he can definitely help you with this. If you have any questions feel free email me at advant_wide_body@yahoo.com. Good luck!

www.kdrotary.com

Evil Aviator

Oh boy, that certainly IS a project! You can do a lot of the work yourself, although I recommend that you use the Pettit subframe unless you are a chassis design & welding guru. (Hehehe, we FC and FB types have it much easier).

Whether or not to rebuild the engine is a tough question. My engine is so clean that I'm going to forgo the rebuild, and just see how it runs as-is (after an ATF treatment). Be sure to keep the 20B water pump, as it flows at a higher rate than the 13B pump, and cooling is going to be your main problem with this engine. The 20B comes standard with a lot of parts that are considered "hi-performance" in the 13B world, so you may want to check with Mazda Comp before you order any upgrades. Once I decide to rebuild my 20B, I'm probably just going to give it a street port and Iannetti seals, and call it good.

The JC Cosmo (3-rotor) was made from 1990-1996. If the intake is natural aluminum color it is a Series I (1990-1992), and if the intake is black it is a Series II (1993-1995). Sorry, but I can't help you any more than that. You can probably get help on the serial number from the Anzacs on this forum, or by searching for links at www.3rotor.com .

I opted for the single-turbo setup. If I could do it over again, I would just run the stock turbos parallel, and save the single-turbo cost and labor for later on down the road when the smaller turbo burns up. Going "single-turbo" doesn't mean just installing the turbo, it also includes a custom manifold, custom exhaust, big wastegate, BOV, FMIC, fuel injectors, etc. I'm very happy with the quality of my single-turbo setup, but I wish that I could have initially gone the simpler route and driven the car sooner.

I am nearing completion of my FC 20B conversion. I will be happy to share everything that I have learned about the engine swap, although I don't know much about the FD.

BTW, what did you have in mind for your 20B car?
(emissions, street legal, road race / drag race, show car, etc.)

Rx7aholic

iTrader: (22)

Hi i did not this mod con, but I thought this idea might help in sort way, It look like u planning not to tear the engine apart which means u will use the same injector's etc. Anyhow try this company out they have a compuer system that u can use to run the stock 20b engine setup.good luck. www.atkinsroatary.com

rx720bt

Hi Larry,

I did the work on my convertion with lots of help from my brother. My brother is just a genius - Auto-Deisel Mechanic (and self taught machinist) by profession.

If the engine has really 11K miles and the compression is good then maybe you should just not rebuild it. Otherwise it will cost you money.

For my case I've rebuild my 20b since it has 46K miles on it. I've replaced every thing that needs to be replaced. -- Ianetti ceramic seals, ported exhuast, competition seals and o-rings, lapped housings, etc).

You probably know this already -- there a couple of ways you can go with your convertion.

a) Cheaper and least work - buy a pettit subframe
and just drop the engine. You may need some mods on your spindles and sterring rack to fit the engine. I'm sure pettit or alamo rotary can help you on this one.

b) More expensive and more work - pushing the engine to mentain the cars' geometry. This envolve shorting the PPF, drive shalf, firewall mods- hammering, transmission shifter assemble mods, belly braces fabrication, custom subframe, custom lower intake manifold, custom injector rail and mounts.

Either way its your call.

On top of that you may want to ask your self "to go single or not go single." This will cost you money too. That means turbo plumbing, wastegate, exhuast manifold, oil lines, water lines and etc. custom down pipe.

Overall, I've spent betwen $15,000 and $20,000 on
this project. Just havent totaled all my reciepts yet. But again I went with the expensive route. If you go with a) you could probably do it for $12,000 considering you and your son do all the work.

Anyways, good luck on your project. Here below are pictures I've took of the project.

black99

also check out www.alamorotary.com

RX7-2JOCK

WoW.....Good **** rx720bt.....Whats your 1/4 mile time ?..........Nice 7 !!

Chimera

Hey, to the people who have done it or know how it's done:

Can the 20b conversion be done on a 12a engine?

If it can, where can I research for the parts I need and the actual procedure of doing it?

Larry Oslund

I'm pretty sure you can replace a 12a with a 20b. From the information that I have gathered, it seems to be easier in a 1st or 2nd gen 7 than the FD. Not sure why, except maybe more room in the earlier versions. Check out 3rotor.com, also hitman.com in Australia has some interesting information. (i.e. He has built a 3-rotor up from a 12b. I think the same thing can be done from a 12a. There is also this guy in NZ, Jeff Bruce, (precisin@ihug.co.nz) that custom build eccenstric shacft, housing, etc. for 3 and 4 rotor engines.

Good Luck

Also to respond to 'Evil Aviator', I would like to do so road racing, but would also like my car to be street legal.

Keep the information coming on 3-rotor conversions. Thanks to all

Node

iTrader: (1)

What about swapping into other cars that have the room for the bigger engine. You would need engine, turbos, ecu, piping and wiring. Custom engine mounts I'm assuming and what about tranny. Would it be relatively easy to mate a 20b to a non mazda tranny?

Evil Aviator

Sure, you can replace a 12A with a 20B as long as you figure out how to get the thing under the hood. I don't think that a 1Gen would be too difficult, but something small like an RX-3 is going to need some major mods. The FD 20B conversion is more complicated because of the car's unconventional frame design which requires a custom sub-frame for the engine.

That's exactly how I am building mine. Did you check out the build pics on my web site icon?

This site is the most comprehensive "what you need" 20B conversion site that I know of. Although it is geared more toward an FC conversion, you can still get the main idea for conversions of other makes and models.
http://www.se-rx7.com/20b/