HeX

Just wondering why some would go the 20b route when a custom 3-rotor 13b is more accessible. What would the price differences be? I'm saving for a possible 20b converstion sometime next year. Just want a little feedback. I'm doing a little research on both. What would be the pros and cons of each? Gurus?

rynberg

A 3-rotor 13B would BE a 20B engine. I don't understand your post.

Are you asking whether or not it would be cheaper/easier to convert a 13B to a 20B than to just get a 20B? The answer to that would probably be no or not much.

Also, if you were serious about a 20B, you wouldn't be worried about small price differences......

kyle@insight

A 20B is going to cost you some serious cheddar no matter how you do it. Do it right the way mazda build it, order one. Trying to add another rotor and housing on there would probably work with enough effort put into it, but then you'd have to source an intake manifold and so on.... after that, it would have been a lot easier to just order the motor and got the same results.

No matter how you do it, it's still a 20B, not worth that extra effort in my opinion.

HeX

Just wondering since i've seen some custom 3-rotor 13bs. I heard the custom eccentric shaft was the most troublesome part of the conversion. I need to do a little more homework. Thanks for the input guys.

paw140

20B's are actually pretty cheap. I've seen some in the $3 to $4K range. Its the conversion costs that are really expensive.

911GT2

I agree. The motor itself is not expensive, it's the getting it into the car that'll cost you. I've seen estimates in the $20k range for the whole thing if you do all the labor yourself!

RotorMotor

iTrader: (5)

well if you do the work yourself it will be much cheaper but there are lots of things that need to be addressed. new subframe ($2K for pettits), flywheel (since all 20b's are autos) and engine balancing, porting (because 20b's dont make 500HP out of the box), and IC and radiator upgrade. i think those are the main ones if youre sticking with the stock turbos and stock ECU etc). oh yeah and a strong *** clutch . if youre going to be doing the work yourself i think a front clip would be a good choice.

Herblenny

iTrader: (13)

I'm not doing a conversion.. but a friend of mine is.. and doing it cheap, you could get a o.k. set up at 12K.. I think you could use stock flywheel and porting is not necessary unless you are going to pull huge numbers in the future.. But I heard only few people could really tune 20B's..

DMRH

The 20B sounds ok for now, but not much longer as parts are already hard to find. Shaft & centre bearing plate is expensive & sought after through out the world. Mazda will eventually give up on supplying these unique 20B parts.

Under Japanese law, they only have to supply parts for 7 years after the cease of production. That means 2002 people.

The 3-rotor 13B is a better option if you are going to customise all manifolds. The shaft is shorter making the engine shorter meaning it fits in the FD engine bay even better. The shaft material is stronger than the production 20B shaft, being shorter makes it stronger again.

The centre bearing plate is your normal 13B centre plate modified with stationary gears & centre bearing etc.. Bust one up, & you need only to supply a readliy available 13B centre plate for re-manufacture.

There is a guy in NZ selling a 4-rotor 13B kit for AUS $3500 right now if any body is game.

I suspect "Kit" means...............

Shaft - 2 or 3 centre bearing plates - through bolts.

You just need to add rotor housings, rotors etc to complete the engine

SpiritR

maybe he is saying a 13B 3 rotor because the original 20B wasnt made with 13B parts.

BoostedRex

I would have to agree with DMRH on this one. The 20B sourced from 13B parts is going to be stronger and fit better in an FD. FC's aren't as bad to put a factory 20B in, but they have soooo much more room under the hood. Just some food for thought.

Zach

HeX

Thank you, I knew someone would set me straight. Thanks dude. I figured a 3-rotor 20b would be a better alternative to a 20b. So how much would a 3-rotor 13b cost then. Seems to me like it should fit right in Thus avoiding most of the subframe work. Right?

BoostedRex

Careful with your wording Hex. All 20B's are 3 rotor engines. However a 20B sourced from a 13B is what you're looking for. And check with the Australians first. They really have their shyte together when it comes to 3 and 4 rotor engines! I don't know how soon you plan on doing this, but a friend of mine source the E shaft for his 4 rotor project from Australia without much problem. Too bad that project had to get scrapped due to lack of funds!! Laterz.

Zach

SomeGuy_sg

MMmmm... 4 rotor kit huh ...interesting ..gotta link for it ?

BoostedRex

Hex,

I also forgot to comment on your question of the 20B made from 13B parts fitting in and avoiding the subframe work. Wrong! You'll still have to have a different subframe dropped in. There's no way around the expensive stuff like that. It just has to be done. You're looking at $12K to $15K if you do ALL of the labor yourself. It's an expensive task to take on. I can promise you that. I'm looking at doing the same thing. I already have the motor sourced and now am looking around to find a machine shop that will custom make a subframe for me. If I stumble onto a good deal, I'll keep you posted. Laterz.

Zach

DMRH

Here is the easiest terminology to go by. Its how we "talk" about this in Oz & NZ

20B..... production 3-rotor
13G..... Factory race 3-rotor
26B..... Factory race 4-rotor

3-rotor 13B... custom 3-rotor using 13B parts such as centre plate making shaft & engine shorter than the Mazda produced version

4-rotor 13B... custom 4-rotor using 13B parts such as centre plate making shaft & engine shorter than the Mazda produced version

The guy selling the 4-rotor kit was BTCHN7 from NZ. He uses the same handle at various rotary forums. I think I spotted his 4-sale post at AUSROTARY forum

If not there, then at some other one. Alec Bell from Kiwi-RE knows how to get 3-rotor & 4-rotor 13B engines made up too.

HeX

Cool, thanks everyone. Keep me posted BoostedRex. Anyone know the price of that 13g? Anyone put one into their FDs?

inis

but then again, WHY THE **** WOULD YOU WANT A 20B. youve got a perfectly capable engine. you can get any hp number you want pretty much. they are cheap to replace, THE BALANCE THE CAR WELL.

HeX

I agree with INIS. My basic concern is making upward of 500+ hp reliably. 500hp with a 13b-rew is pushing its reliability envelope from what I understand. A 20b could produce the same numbers whilst running the engine a little more conservatively. Doesn't anyone wanna keep with the Enzo? HA!

fastcarfreak

for the cost of a 20b conversion, you can mod the hell out of your engine, and then replace it with a new one like 4 times. and thats without you doing the labor!!! I understand being unique, and wanting a cool show car, but if you think that 20b isnt going to break, your dead wrong and it is going to be costly!!!

Red-Rx7

The 20B / 3rotor done correctly is expensive. Many people have already indicated this. Most all front engine component parts have to be reworked some-way or another.

The 20B block itself can be cheap. But keep this in mind: when you purchase a 20B block, you are not purchasing a new or REMAN engine. Rather, you are purchasing mostly an "UNKNOWN" milage engine from a WRECKED / PARTED out COSMO from Japan.

So, say you get a "good" deal and pick up a 20B block for 2500.00. Next, you need to roll the dice. Is your engine health? Slightly used? Rebuildable? Good parts / Bad parts?

Now, figure the cost to rebuild your 20B engine. Some people do not do this. Me, for example, think it is silly to spend that much money for an engine and conversion without going the *FULL MILE*. A stock 20B engine mated to a good single setup @ 15 psi would most likely yield good power (500rwhp), but would fall off quickly due to the restricted exhaust sleaves.

So, you dump in the rebuild (depending on the builder... 5,000 - 8,000 for new parts), and now you have roughly a 8,000 - 12,000 engine.

Start adding up the little stuff...

- subframe & spindles (ie pettit) ... or some other shop's go at it: 2500
- Custom intercooler: 2000.00 (big range here, but most are custom made for off-shelf components aren't the best when going full custom and tight-fit design. Room here for change)
- Custom Radiator & fans: 670.00
- Custom little pieces (water pump, intake elbows, LIM, etc): 1500.00
- EMS system: 1500.00
- Wireloom, 3Bar Mapsensor, Coils, Ignitors, Sparkplugs, etc: 1800.00
- Intercooler piping: 230.00
- Single turbo (Again, another large range to work with): 1950.00
- Turbo manifold: 1000.00
- Downpipe and exhaust fab's: 1000.00
- 20B flywheel & Counter weight: 650.0
- Tripple disk clutch: 600.00
- Upgraded transmission? Yeah, stock will work if you never floor it in 1st or 2nd gear and ease into it in 3rd.. but why? You spent all that money for it, use the damn thing.): 4000.00 (ie a guru) or 3200 (richmond + the fab to make it fit ++ 1200)..
- Differential to support the rear power: 780 (Kaaz)
- Axles to support the power: 780 (chromoly)
- New rear bushings to remove the 4w steering so the torque doesn't throw the car sideways and puts you into a wall: 400.00
- New suspension to manage the power: 1850.00
- Larger front brakes to support the power (not a real nessesary item, but a smart one, yes?): 2100.00
- Intake filter, hoses, piping clamps, little things: 500.00
- Fuel upgrades: Injectors, fuel pumps, sump, AN lines, etc: 1700.00
- Pulley kit for the engine: 480.00
- Anything not listed here that you will need and the things you don't expect and will bite you in the *** because you thought you were smart and had it all figured out which in reality you were stupid for not allowing a safety margine in your budget costs: 3000.00.

Someone add that up for me. I am sure I missed some things, outside of the last item I listed..

Mike

SpiritR

All depends on where you buy your parts and engines from....

psi4psi3

how many times will you need to buy a shaft or how often do you break one...as long as mazda sells 13B rotors and housing ppl with 20Bs will be ok.

500hp 13B and 500hp 20B are 2 different animals. Low end torque is the key word my friend. 20B also has enough exhaust for a good sized turbo like T-66 to spool up much quicker than it would in a 13B.

Evil Aviator

The 13G was replaced by the "20B Race" in 1988. The 20B Race engine debuted at about $42,000, so I would imagine that the 13G sold for close to this amount before going out of production. I don't think that you can get fully-assembled 20B Race engines any more, but you could check with Mazdaspeed to find out.
http://www.mazdamotorsports.com

13G and 20B engines:
http://members.rogers.com/sofronov/C...otary/13G.html
http://members.rogers.com/sofronov/C...otary/20B.html

UntameD

hey, HeX...

sorry this isnt related to the topic of the thread - but where in LA do you live? im at Glendale and i actually grew up in N. Hollywood. im all over LA all the time - i havn't noticed your 7 around. there are a few i've seen but non of them seem to have any major mods done to it... and non of them had you're body kit on. (assuming the 7 in your avitar is yours)

i'd REALLY like to check out you're rx i'm about to buy me an rx7 also and itd be pretty cool to see one up close instead of just reading **** all over the net lol

btw - i was about to post this same question. you just beat me to it

take care,
UntameD