20b FAQ and Links - RX7Club.com - Mazda RX7 Forum

20b FAQ and Links

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Old 11-21-04, 09:28 PM
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20b FAQ and Links

Please send me PM if you have any suggestions for changes or additions.

I would like to attach forum members' screen names to their websites. Please let me know if you would like your name added to your website, or if you would like it removed.

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Old 11-21-04, 09:29 PM
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Frequently Asked Questions

Q: What is a 20B engine?
A: A 20B engine is a 3-rotor engine based on the 13B series engines.

Q: Which production cars came with a 20B engine?
A: Only the 1990-1995 JC Cosmo luxury car with an automatic transmission, which was only sold in Japan. See "JC Cosmo" in the Links page below.

Q: Are there different kinds of 20B engines?
A: Yes, there is the JC Cosmo's 20B-REW engine with two turbochargers, and there is the 20B Race non-turbo peripheral-port engine made by Mazdaspeed Motorsports Development. See "About 3-Rotor Engines" in the Links page below.

Q: What was the performance rating of the stock JC Cosmo 20B-REW?
A: 280ps @ 6500rpm, 41.0kg-m @ 3000rpm (276bhp @ 6500rpm, 296 ft-lbs @ 3000rpm).

Q: Is the 20B the only engine covered in this forum?
A: No, any rotary engine with 3 or more rotors is discussed here.

Q: Can I make my own 3 or 4-rotor engine?
A: Yes, but it is rather difficult, and only the top rotary engine shops have succeeded in this.

Q: How much does it cost to install a 3-rotor engine in my RX-7?
A: In the US, it costs about $10,000 to do it yourself, and about $35,000 for a professional conversion. Prices are lower in countries with lower labor costs and better access to Japanese engines, such as AUS, NZ, and Japan. See "3-Rotor Conversion Planning Websites" in the Links page below.

Q: Where can I buy a 20B engine?
A: New parts are available from Mazdaspeed Motorsports Development, and for used engines see "Where to Buy Used 20B Engines" in the Links page below.

Q: Can I use the stock JC Cosmo ECU to run a 20B engine in my RX-7?
A: Yes, but it takes a lot of work, and it would not stack up to the higher power levels available from aftermarket ECU's.

Q: Does the 20B engine attach to the stock RX-7 transmission?
A: Yes.

Q: Will the 20B engine attach to the stock RX-7 engine mounts?
A: No, custom mounts are required.

Q: Can 13B rotors and rotor housings fit on the 20B engine?
A: Yes.

Q: Will a 20B conversion ruin the "perfect" weight distribution of my RX-7?
A: The static weight distribution can remain 50/50 if you plan your project accordingly. A 20B conversion is a custom procedure, and how you go about it is your own choice.

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Old 11-21-04, 09:36 PM
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Links

Link Guidelines:
1) The moderator(s) and administrator(s) of this forum will determine which links are appropriate for this list.
2) While we will generally try to exclude links from dubious sources, the external links listed are not necessarily screened for viruses, adware, or good business practices. Visit these sites at your own risk.

Key:
Web Links with associated Forum Members in (boldface) type.
Internal forum links shown in orange.


JC Cosmo:
Club Cosmo (Japanese)
Cosmic Creation - Autospeed Article
David Morris Rotary Historian (DMRH)
Eunos Cosmo Aftermarket Parts
Eunos Cosmo Owner's Page (Japanese w/English Titles)

All About Engines:
Cosmo Engine Identification (DMRH)
A Tribute to Mazda The Past, The Present & The Future
Der Wankelmotor (German)

Custom/Modified/Race Engines:
Autotech Motorsports Custom 4-Rotor Engine "23A"
CLR Motorsports 20B Engines (GT1-20b)

3-Rotor Conversion Planning Websites:
20B FC Pages
20B VERT.com
FC3S Pro (RETed)

3-Rotor and 4-Rotor Custom & Race Cars:
20B AE86 Video < Added 26MAR05
20B FD Page
20B FD
4-Rotor.com 4-Rotor 92 RX-7
Aero Management - Paul Carey's Blown 3-Rotor Drag 1Gen RX-7
Alamo Rotary - Tito's and Derrick's 20B 3-Gen RX-7's
Autotech Motorsports 20B Single Turbo FD
Blown 3-Rotor.com
Can-Saf 20B RX-7 (20B-3Rotor)
Chito's 20B FC - Craig's Rotary Page
City Performance Centre 3-Rotor Drag and GT Cars
Evil7.com
FC3S Dragger (Japanese)
Granny's Homebuilt 4-rotor
The Hitman's 3-Rotor 1Gen RX-7 (The_HITman)
HME 20B Convertible
Ibrahim Brothers BMW M4 4-Rotor
Mazda 3-Rotor 2Gen RX-7 Prototype (see bottom of webpage)
Mazfix 20B Drag Car
Mazfix 20B Series 2 RX-7
Mariah 20B 10AE
Mike's 20B TII
Norwegian 20B 1Gen RX-7
Now's 20B 10AE (now)
Pettit Banzai
Pettit Banzai - Turbo & High-Tech Performance Article
Pettit Banzai R1 - Matt Smith - Road & Track Article < Added 26MAR05
PFS - 20B 94 RX-7 Car & Driver Article
PFS - Ed Taylor's 20B 93 RX-7
RE Amemiya Asparadrink GT300 RX-7 < Added 26MAR05
RXX-7 20B Convertible (Attila the Fun)
Team Spencer Motorsports
Trini2DMax 20B 1Gen RX-7
Jose Valentin's 20B 1Gen (rotaryforlife)

Where to Buy Used 20B Engines:
Atkins Rotary
CorkSport
eBay Motors
FC3S.org
japanesenginesautoparts.com
Nippon Motors

Comparisons:
20B Throttle Body vs. FD Throttle Body

Engine Management Systems - Nearly every EMS that can run a 6-cylinder engine can also run a 3-rotor engine by firing the leading and trailing spark plugs at the same time, as used on non-turbo 3-rotor race engines. The following products are reported to allow for a leading/trailing timing split as used by Mazda on street car rotary engines.
AEM Plug&Play (3Gen RX-7 Only, Requires Factory Configuration for 3-Rotor Engines)
Electromotive TEC3r
Haltech E11v2
Microtech LTX-12 & LTX-12S (Requires Factory Configuration for 3-Rotor Engines)
MoTeC M600, M800 & M880
Wolf 3D Version 4 Plus
Also see our EMS forum for more information.

Tachometer Conversion:
Grannys Recalibration Procedure
Dakota Digital SGI-8 Tach Signal Interface

Last edited by Evil Aviator; 03-26-05 at 06:27 PM.
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Old 10-29-05, 02:23 AM
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Can't pm you, so I will tell you here. There are a lot of broken links in the 20B FAQ that need to be deleted or updated.
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Old 11-04-05, 09:40 AM
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thanks a lot
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Old 11-13-05, 11:47 AM
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Originally Posted by Rotary20B
Can't pm you, so I will tell you here. There are a lot of broken links in the 20B FAQ that need to be deleted or updated.
I no longer moderate this forum, so I can't edit the FAQ. I thought I changed the "Please send me PM" to "Please send the moderator of this forum PM" before I left, but I guess not. Sorry about that. Hmm, I also thought I locked the thread. Anyway, please send any PM about this FAQ to the current moderator of the 20B forum. It would help if you specify the required updates. I'm not sure the current moderators want to spend the time on the FAQ that I did, but I think it's still worth bringing it to their attention.
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Old 01-10-06, 10:28 PM
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MY 13bre cosmo needs help.
what do i do>i want to run the FD complete pulley setup because i didnt get the stock cosmo parts when i got this motor.
i dont even have the main crank pulley.
does this even work, to use the fd waterpump, bracket with the powersteering pump and a/c. people say it wont work. please call 510-773-4594 dennis.
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Old 03-15-06, 01:42 PM
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does anyone know where i can get a factory workshop manual for the JC Cosmo? if not, anything that outlines a 20B rebuild ...

thanks
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Old 03-18-06, 05:19 PM
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well, i've spent some time trying to track down answers to my question ...

i don't know if this was common knowledge, but i'll share it in case it's not.

i spoke with DMRH (a Mazda Cosmo and 20B expert - and very nice chap to boot ) and he informed me of the following:

1. the Cosmo workshop manual covers everything but the engines. Mazda did not want their dealers rebuilding neither the 13B-RE nor the 20B. they wanted them replaced. period!

2. for any people out there that build their own engines, and never got to touch a 20B, but are ready to do their first - if you ever hear about a New Zealand engine builder that made a DIY DVD/video for a 20B build think twice. he did not say straight out NOT to buy the DVD, but he made it VERY clear to PROCEED AT YOUR OWN RISK! there is a lot about this individual/company at www.ausrotary.com - you're welcome to research and decide for yourself.

3. for anyone that thought it might be cool to get the Cosmo manual ayways (as memorabilia) it's written in Japanese ...
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Old 12-08-07, 01:56 AM
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Ok, I apologize for the Rotary newbness. I'm not going to bullshit, I have always been a very serious Honda lover. I've owned probably 9 in the last 7 or so years. My latest was an 07 AP2. I want something different and would love to get into an FD. My question is though I hear alot of people doubting the reliability of the 13b. Is the 20b any better or are all the rumours just that, rumours of people who can't tune or work on a car.
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Old 03-10-08, 09:19 AM
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Hi mate,

It's VERY true that rotaries have a reputation of being unreliable and prone to going south with little warning. It's also true that if you take care of your 13B (NA or Turbo) and/or 20B that they can be very reliable indeed. Common killers are overheating, pre-detonation from incorrect/ bad fuel or bad computer fuel mapping, over-revving, over-boosting and incorrect oil choice. If you cover those basics and don't overtax your engine without taking reasonable precautions, then your biggest concern should only be fuel consumption

The precautions vary on your application, and more so expected power delivery. But a good guide on your road car is the use an oil cooler (larger the better) and an aluminum core radiator with a couple of electric fans. Set a rev limit that's logical (say 6.75 to 7 in a 13BT or 6.5 in a 20B) and keep the boost logical in both psi and turbo size, and of course a decent computer and water injection will save you from pre-detonation for the most part.

I have a 12a that I blew apart through ignorance several years ago. After the rebuild and a steep learning curve I've done over 40000k's of hard driving without an issue. More K's on the 13BT with no ill effects as I added a decent computer and took every measure to keep it cool. My BT pulls 290 odd rwhp which is marginally more than a standard 20B and still enough to light up 225 rubber with a limo.

I'm also building a high powered (500+ rwhp) 20B currently and at every step I'm adding additional cooling of oil (including better flow than the standard config - which was known to restrict flow to the rear rotar under high load), water and compressed air - with of course water injection. I'm also adding a simple system that will lower the boost if high oil or water temps are reached. It's nothing special, just a failsafe to the engine going south. I'll also be running a 1:150 2-stroke oil premix as I do in my 13BT as well as the OMP.

If you can it's always a good idea to do a soft rebuild of your rotary 13 or 20B. If you can't, then have it dyno'd with a safe (rich) tune and minimal boost and water injection if you can manage it. It won't be the most economical car to run, but it will still perform extremely well (astounding well in the case of the 20B if you remove the standard twin turbo and replace it with a single medium to hi-flow unit.)

The bottom line is yes, rotary engines are prone to going south if pushed. But take the precautions and you can get a mile of power out of them with reliability to match. I also don't think anyone will argue that the 20B isn't actually more reliable than the 13B as it develops more power easier. But if you want miles of gut wrenching power, then definately look at a 20B - but look really closely as the costs of the engine and correct setup are not for the faint hearted. A 13BT setup done correctly can still be a brutally quick ride and have reliability to match, but clearly said, it'll be nothing to a 20B.

Good luck!

Last edited by TDIT; 03-10-08 at 09:28 AM. Reason: missed information
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Old 09-21-08, 11:05 PM
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This Write Up is just what i was looking for! Thank you very much op!
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Old 10-14-08, 07:59 AM
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there are still some broken or not working links eg 4-Rotor.com 4-Rotor 92 RX-7
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Old 11-19-08, 10:29 AM
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Is it worth it to run a 20B without turbos?
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Old 11-20-08, 01:19 AM
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Originally Posted by CookAuto View Post
Is it worth it to run a 20B without turbos?
Definately!!

To explain why is simple. A 13B develops minimal torque pre boost without significant porting and carbi jetting. Sure it can be done (heck I've done it.) But even so, the design of the rotary engine leands it to high rpm and high power delivery; they just arn;t designed to provide good power at low to medium rpm. SO getting off the mark quickly means you need to clutch slip a little.

So how is a 20B different?

Well first of all, that extra rotar doesn't just add a 50% boost to your capacity. It adds greater manifold valcum sooner, which is all important to getting torque out of an engine sooner.

There are several these 20B NA engines around and making significant power. Some use tripple dcoe webers or tripple ida's. When I say signicant power, it doesn't compare to boosted projects, but they last longer because they don;t work as hard. Some street cars can't have a 20B turbo in them (in Australia anyway but leaving them NA makes them legal.

So the advantages of a 20B NA verses a boosted job are simple:

Better fuel economy (for those who it's imnportant to).
Better engine life as it's not running as hard under load.
Less componet failure/ wear from the clutch through to the entire drive train.

Some people have to run NA, others choose to for cost reasons, and others still just want to by choice. Whicher the reason, I still think it's worth doing a 20B NA - especially if it's going into an RX =) It just feels right =)

Cheers to all!
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Old 12-24-08, 01:39 PM
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20b bottem end

I heard a 20b bottom end would fit on a 13bRe. Would it?
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Old 12-24-08, 03:00 PM
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Originally Posted by cosmo7 View Post
I heard a 20b bottom end would fit on a 13bRe. Would it?
rotors don't have "bottom ends"

what are u trying to ask exactly?
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Old 12-25-08, 08:56 PM
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I agree witrh Otto!
If you're asking if the housings or rotars are interchangeable, then the answer is yes and no - depending on what you're trying to put where... But a 'bottom end' they don't have. More details please =)
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Old 05-20-09, 10:56 PM
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I think the "Where to buy" part needs to be updated cuz most of those links are broken or they dont sell them anymore.
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Old 05-21-09, 11:24 PM
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Originally Posted by Evil Aviator View Post
Please send me PM if you have any suggestions for changes or additions.

I would like to attach forum members' screen names to their websites. Please let me know if you would like your name added to your website, or if you would like it removed.
just posting so i can posting ty
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Old 05-21-09, 11:24 PM
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any one flying a 20b ?
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Old 05-21-09, 11:27 PM
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9 to one

Originally Posted by TDIT View Post
Definately!!

To explain why is simple. A 13B develops minimal torque pre boost without significant porting and carbi jetting. Sure it can be done (heck I've done it.) But even so, the design of the rotary engine leands it to high rpm and high power delivery; they just arn;t designed to provide good power at low to medium rpm. SO getting off the mark quickly means you need to clutch slip a little.

So how is a 20B different?

Well first of all, that extra rotar doesn't just add a 50% boost to your capacity. It adds greater manifold valcum sooner, which is all important to getting torque out of an engine sooner.

There are several these 20B NA engines around and making significant power. Some use tripple dcoe webers or tripple ida's. When I say signicant power, it doesn't compare to boosted projects, but they last longer because they don;t work as hard. Some street cars can't have a 20B A in them (in Australia anyway but leaving them NA makes them legal.

So the advantages of a 20B NA verses a boosted job are simple:

Better fuel economy (for those who it's imnportant to).
Better engine life as it's not running as hard under load.
Less componet failure/ wear from the clutch through to the entire drive train.

Some people have to run NA, others choose to for cost reasons, and others still just want to by choice. Whicher the reason, I still think it's worth doing a 20B NA - especially if it's going into an RX =) It just feels right =)

Cheers to all!
noobie here, droped the turbos but are the same roters good ? or do i need the non-turbo'ed ones?
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Old 05-25-09, 09:10 PM
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Originally Posted by steve parkins View Post
noobie here, droped the turbos but are the same roters good ? or do i need the non-turbo'ed ones?
The stock rotors give you 9.0:1 compression. The S4 NA rotors will give you 9.4:1 and the S5 NA rotors will give you 9.7:1. If you think it will be worth it to swap them out then go for it. The stock 20B rotors will be fine NA.
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Old 09-04-09, 05:48 PM
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this is a very usefull thread thank you
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Old 09-30-09, 11:38 PM
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Originally Posted by TDIT View Post
Definately!!

To explain why is simple. A 13B develops minimal torque pre boost without significant porting and carbi jetting. Sure it can be done (heck I've done it.) But even so, the design of the rotary engine leands it to high rpm and high power delivery; they just arn;t designed to provide good power at low to medium rpm. SO getting off the mark quickly means you need to clutch slip a little.

So how is a 20B different?

Well first of all, that extra rotar doesn't just add a 50% boost to your capacity. It adds greater manifold valcum sooner, which is all important to getting torque out of an engine sooner.

There are several these 20B NA engines around and making significant power. Some use tripple dcoe webers or tripple ida's. When I say signicant power, it doesn't compare to boosted projects, but they last longer because they don;t work as hard. Some street cars can't have a 20B turbo in them (in Australia anyway but leaving them NA makes them legal.

So the advantages of a 20B NA verses a boosted job are simple:

Better fuel economy (for those who it's imnportant to).
Better engine life as it's not running as hard under load.
Less componet failure/ wear from the clutch through to the entire drive train.

Some people have to run NA, others choose to for cost reasons, and others still just want to by choice. Whicher the reason, I still think it's worth doing a 20B NA - especially if it's going into an RX =) It just feels right =)

Cheers to all!
N/A 20b FD - My plan for a reliable track car.
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