AznPhoenix

im wondering which i should go for. Wat are the capabilities of a 20b compared to a 13b? I also have a question regarding exhaust modifications. Will a dp, hfc or mp, and catbak made for a 13b still fit and work just as well on a 20b?

Evil Aviator

If you are asking these types of questions, you should stick with the 13B. The 20B is really more for people with a lot of skill, a lot of money, and a passion for things that are totally impractical.

Everything else being equal (which is never is, lol), the 20B will produce 50% more torque at any given rpm.

I don't know about fitment, but exhausts are pretty much based on horsepower, so as long as the horsepower is the same, the exhaust will work just fine. For example, a 300hp 13B exhaust will be sized just right for a 300hp 20B, assuming peak horsepower is your reference. However, the resonance will be different, but most people don't bother with advanced things like that.

RotorMotor

iTrader: (5)

how do you tune a muffler for resonance?? so you saying something like a RB catback should sound funny? i was thikning about this earlier evil... but decided not to worry about it because i have so much other stuff to worry about .... i finally have everything stripped from the donor car... i mean everything! the wheels are still there though hehe. hopefully going into the paint shop very soon (once i decide on a color) to paint the bay...then the fun starts (whoops i totally just hijacked this thread.

back to the thread topic.... what do you mean you dont know which to go with?? you say that as if your buying chedder or swiss at the supermarket. doesnt your car already have a motor in it?

Sponge Bob Square Pants

Stick with the 13B, unless you are looking for MORE than 500 whp, and have lots of money for the 20B conversion($10,000 and skills/shop to do it yourself, or $35,000 to have it done for you).

And if you are looking for over 500 whp and have the money, are you sure it's the right project to jump into? Fairly extensive knowledge of rotary engines (and cars and mechanics in general) is needed to properly pull it off, not to mention the experience of driving such a powerfull car. (maybe you have both of these, i don't know?)

johnisenglish

Peak power is always the goal. I'm not looking for even 500whp with my 20B setup, but in my mind its still the best possible route for me to go and keep a rotary engine. Why? Because I want a broad powerband of the sort that the 13b just can't offer. If I just wanted to make a ton of power with a peaky powerband for drag racing for bragging rights I would have kept the 13B, slapped on a giant turbo and called it a day.

As far as the money part goes, you're dead right. My tally right now is almost $12,000, and thats not counting tools or the incredible amount of time I'm putting into this. However, when all is said and done, I'm still going to have less then the cost of a new S2000 invested in my FD, including the cost of the chassis. Not a bad deal, if you ask me

Sponge Bob Square Pants

The 500 whp number I through out there is a VERY loose guidline, due to the other variables as you pointed out.
Good points about the power curve, torque, type of racing, etc.

Evil Aviator

http://www.thevettedoctors.com/archi...5_products.htm

LOL, a goal of peak horsepower means that you are only concerned about producing the highest horsepower number possible, regardless of the powerband, driveability, or other factors. In other words, in the extreme case, you would be looking for a "dyno queen" or a "bragging rights" engine. It sounds to me like you are mostly interested in a flat powerband.

johnisenglish

Heck yeah I'm looking for a broad, flat powerband (assuming you were talking to me). That's why in my opinion a stock WRX is more fun to drive around town then a modified S2000. THe S2000 might make more peak power but who wants to hang out at 9000rpms just to get anywhere?

I'm building this car first as a street car (though not a daily driver, that would be silly), second as a track car but mostly just something that I'm going to enjoy. Going after huge numbers on a street car just causes more things to break and ultimately leaves you unhappy with the fact that driving a 700whp car between stoplights SUCKS. Hell, my 427whp Integra was more then a handful (ofcourse front wheel drive didn't help). Save that sort of power for race cars.

Wargasm

Well to be honest, at anything 400 rwhp or less, there is no doubt that the 13B is a way better pick. It's just WAY easier and WAY cheaper and still very driveable.

Doing a 20B is a nice project if you have a LOT of time and a LOT of skill at figuring stuff out/fabbing stuff and a LOT of patience and a pretty nice pile of money to spend on it.

I'm thinking of doing a 20B swap into a FD or maybe FC chassis.... but I'm not to the point of where I'm buying parts yet because there is so much work that goes into it. This isn't like when I built my current car (single turbo FD). For this car, I just bought a bunch of stuff, bolted it together and tuned it. There really wasn't much hard stuff to do!

johnisenglish

Well, when you get down to it its really just a matter of personal goals, time, skill and money. It'll vary with everyone. One guy might want a stock FC, another wants an FD with an LS1, and another wants a Chrysler Minivan. There's no right or wrong, no better or worse. Just cars that people like.

Drag'nGT

This was actually very informative to me. I want to put a 20B into a FC and was contemplating the thought of a 13B. I want a sole track car. Sure I wanna drive it around town every once in a while but I'm really building this for 1/4 mile times. Hmmmmm.... decisions.

Sponge Bob Square Pants

How fast do you want to go in the 1/4 mile?
Street Class cars (which are generally streetable enough) have done low 9's using the 13B.

604Ryder

is everyone saying that to have car outfitted with a 20b that the car would become less driveable as a daily driver? cause i too am intrested and pretty serious now about doing the conversion. not so much for the raw unmatched power as for the prestige of owning a very rare engine in a very unique car

Sponge Bob Square Pants

No no quite the opposite.
If you compare 13B to 20B with equal peak power numbers, than the 20B will be miles ahead of the 13B in terms of reliability AND streetability. Hands down.

Think of it this way: a Cavalier engine making 400hp or a stock Corvette engine making 400hp. the bigger displacement is generally more streetable/reliable.

johnisenglish

Yeap. You may be making equal or more peak power, but you're meaking less power per rotor and as a result straining the engine less.

rotaryforlife

I had a 20b fc which I totaled at the track 3 weeks ago.
I drove it everyday, it cruised like a stock car, but with much more torque. The only down side was that it comsumed a lot fuel. I'm planning to installed the engine in an fb so the I can tub it and installed a four l link rear suspension for better traction at the track .

604Ryder

how did you end up totaling your FC? maybe you have a different type of track then the one i go too ... at the place i go too there really isnt anything too hit so unless u flip your car we are pretty safe

Sponge Bob Square Pants

604Ryder, you might want to consider stopping by Staff's Auto. Those guys know what they are doing with rotaries including 20B's and do good work.

604Ryder

thanx for the info sponge, Im planning on doing most of the work myself with maybe some help from frenz (thats what they are for haha) but its nice to know there is a shop that does work on rotaries