Stupid question...
 

Why not build up a 20B? It creates more displacement than a 13B.

Are they not available? Harder to build because of the three rotor? Too expensive?

Or is it just not worth the extra 654cc's of displacement?

Im new to the RX-7 world so i don't know what the deal is with all the different engines, but im learning.

Thanks!

Displacement is always worth it! "There's no substitute for cubic inches"

However 20Bs were only sold in one car, in the top-line model, so I'd imagine they're not very common (and frankly I want to know how everybody seems to be getting 20Bs now!) and they cost about $4k for a used engine... that's a good chunk of change. And it's a good chunk of work trying to fit them in to other vehicles, too...

That's what I was thinking. Hmm.

You say they only came in the top of the line model. Do you mean
RX-7? What is the size difference between a 20B and a 13B? The chambers width are the same 80mm between both of them.

The extra rotor might make the difference I guess. Would it be hard to put a 20B into a 3rd gen? Thanks for your reply!

Top line Cosmo.

As I understand it's a real PITA to put the 20B in an FD, you either have to relocate the steering rack which makes handling scary from bumpsteer, or you have to hack the firewall/floorpan and mount the engine rearward, which requires lots of other work as well. (shortened PPF and driveshaft/relocate shifter/custom metalwork/etc.) Supposed to fit real nice an an FC though :)

If you look at an FC, (atleast in mine S5) there are suttle notes that it could support a 20B. Even the smallest observation like the number of sparkplug wires the brackets can hold (3 for each coil)...makes ya wonder...

not only the 20B is so hard to find, it's will increase the weight too. Not to mention the money you need to put it to install it.

Yes, it will give the car a lot of power. But so does a single turbo kit and some fine tuning to the car.

I think the weight increase wouldn't be too great, making it a very attractive option. Then, you can add a turbo on top of that. I hear about people spending 20 grand on a transplant. Can't see where it would cost half of that. Motor mounts are cheap to make. So is a drive shaft and exhaust. Electronics is the most expensive necessity other than the engine.

Anything else that would push the price up???????

Comso's 20B already is a TT engine. :D

www.FC3s.org has them as j-spec engines. Tach won't work afterward. Fr-Rr weight ration will be affected slightly, torque increase is supposed to be amazing. You need custom mounts to put them in, k2rd.com has them fro $450 I think.... I believe a custom hood is needed too. And they will really only fit in an FC easily. Check out FC3's january car of the month, it has a 20B vert featured. He's selling it for something like $49,000 to give you a hint of what it would cost for a conversion.
Sean Cathcart
anyone else find that price a little high?

How in the KCUF can motor mounts cost $450????

$49,000 for a 20B vert? gotta be a joke.

"There's no replacement for Displacement":D

"Technology Over Cubic Inches" :D

Yes there is...its called a HUGE turbo =P

I read in this mag that petit racing did a conversion costing nearly 35000 for parts and labor. I don't think it's worth it. It's 02' now guys, technology has made that "there is no replacement for displacement" a thing of the past.

More displacement = more weight

more weight = bad power/ weight ratio (making all that extra HP useless)

bad power/ weight ratio = slow acceleration, most of all..bad handling

slow acceleration + bad handling = piece of shit car ;D

Hell yeah! $450 for motor mounts??? Jeez does that come with the vaseline too? Granny's Speed Shop will sell you a whole V8 conversion kit including subframes and mounts for that much. Motor mount brackets are stupid easy to fabricate if you have the inclination, the cutting tools (cutting disc on a die grinder worked great for me the past 6 years) and a way to weld it together. Now some people will say, blah blah you need a TIG and TIG setups are extremely expensive. Total BS. A MIG welder should be more than good enough - I know someone who did an IFS conversion on his old Chevy pickup several years ago, lots of welding involved, and he used an ARC WELDER. That scares me a little but it'd held up great and he doesn't really baby the truck either! So a MIG should be plenty. (I paid $250 for my MIG setup not including the argon tank, and a professional-grade unit shouldn't run very deep, if at all, into 4 figures)

As for tach re-calibration... again, just go to grannysspeedshop.com and they detail EXACTLY how to recalibrate for a V6 or V8 conversion! It looks like a real no-brainer, too.

I agree most of the cost would be in the software, plus the stock twins need the stock ECU to control them, so most people just put a big single on - adds lots of $$$ to the price (although two T3s with large exhaust housings are prolly enough) and anyway, who says you need a turbo anyway? Most of the people buying up 20Bs are aircraft enthusiasts, and they get more than enough power without turbos at all.

BTW - GotLag - there is no replacement for displacement, period. What that means is, there isn't nothing you can do to a small engine that you can't also do to a large one. High RPM? Sure! Forced induction? Sure! The only problem is there's not much use for a 6000hp engine :)