you've seen the pictures? if the bridge is made too thin it can crack. its really not a big deal, just dont go nuts on the bridge.

also if you port into the water jacket, then you're removing the engines water seal in that spot, it gets siliconed but it has a tendancy to start leaking a little overnight

on the legality issue, federally, the 20b was never in an epa certified car, so its illegal to have in a street car.

the state usually doesnt care, as long as you PAY the registration and PAY the smogs, and its not too loud etc etc

if you want to stay legal, you're kinda screwed into turboing the rx8 motor, which seems to be more costly and complex than doing the 3 rotor swap...

 

I'm sure I can get away with basic mods. The problem with that is that you can spend 5k or more upgrading your tranny, clutch/flywheel, diff, getting an intake, exhaust, losing the cat and A/C, getting an ECU, and getting light wheels, and if your really, really lucky, you might break 220whp. The upside? The car handles really well.


I'll do some more digging into bridge ports. But on the legality problem, it's almost California around here. This state cares about everything EXCEPT sound really. What they told me, is that "everything has to be OEM or else you have to go to court and they can take your car". Which apparently includes exhaust, and OBD system, which would be a bit of a problem.

No thx.

In any case the legality is a non-issue because now I have a solution - racecar registration. Exempt from everything. And I can drive it on the road to and from car events, which can be as little as taking it to an 8club meet. As for other transportation, a nice quick little Yamaha R1 will do the job nicely

As far as turboing goes, you'll have 300whp for a while, and 500 miles later your engine will die. Compared to a 20B it would be infinitely LESS complicated. With this swap I have to replace the entire drivetrain and all of the engine's supporting hardware. With a turbo its the airflow and ECU really. But that's just not the kind of car I have in mind.

I haven't even begun to think about how I would maintain some decent handling. 200 extra pounds in the front...200 extra pounds at ALL. I shouldn't even be considering this right now, I need to figure out the engine configuration first. This won't be happening for another 2 years at least.

I want to know more about lubrication. Consider a 9kRPM 400HP N/A 20B. How much oil does it need how fast, and how does that amount of oil get there that fast?

 

oh yeah 20b might add that much weight to the rx8. its only about 60lbs more than the FC turbo engine though, not a huge deal

oiling:

the sport kit 20b runs dry sump lubrication, should be around 100psi of oil pressure. other details are a little hazy, as i dont have one, just the parts catalog.

the usual tricks for the 13b apply to a 20b. basically the stock oiling system is all sharp corners and sharp edges. with some loop lines, you double the oiling to the bearings. oil pressure is raised etc etc

 

So basically:

-Dry sump
-Loop lines for each bearing (which bearings? Just e-shaft? what about seals?)
-100PSI total

That about right?

 

yep, if you do a search for loop lines, you get plenty of hits.

stock seals are good to 8500rpm, they will live higher, but dont seal as well as a carbon or ceramic seal, which are both lighter than iron.

 

Do people only use the mazda dry sump or is there another good option? Are they kits or customs?

In one of the links earlier in this thread, there is a clause that says "PPs are streetable with the right engine management.". Can anyone clarify that?

How much weight can be lost by removing the TT setup? How much weight can be lost outside the turbos?

 

Also tell me about compression. This is an N/A motor, so I want higher compression rotors, right?

 

the full peripheral port engines are full race engines, they were never really meant to be driven on the street, or even really to have mufflers.

the PP engine is like having a giant cam, with a carb, they are kind of nasty, but like a piston efi tames them a lot. go look at some youtube video of the 787b, it literally starts like and runs like an FC/FD

the 20b turbos complete, are in the 60-80lbs range

 

the simple answer is this;

the cosmo 20b comes with 9:1 rotors stock, as its a turbo, the 9.7 rotors from the 89-91 non turbo are the same balance weight and thus go right in.

complex answer;

mazda has done some testing, and there are some charts in the 'rotary engine' book, although we're still looking from something newer. anyways, compression ratio ends up being a compromise. to raise compression the combustion recess has to get smaller, and theres a point where it gets too small.

mazda's graph shows that being about 10:1, which is what the 787b ran, and what the rx8 runs.

it'll be interesting to see what gordons motor does

 

So really, when I buy the 20B all I'm really buying is the E-shaft and center iron, correct? Everything else, including the rotors, would be replaced.

I'm going to go with either the 9.7s or the 10.2s. 10.2s are sounding really nice right now but the 9.7s leave room for a turbo if it was ever needed. Us REN owners are kind of stuck with 10:1 SC, thats why you don't see any 400whp RX-8s out there.

I wonder, is it easier to buy a 20B from a cosmo or buy an E-shaft/parts and build it myself?

Also, what about weight? The TT system looks pretty hefty, so if I'm getting rid of that what will the engine weigh, and how much weight can I take off beyond the TT system?

 

in concept, yes, in reality the 20b plates are all different. you can machine 13b ones to work, but that would cost more than just buying new 20b stuff. mazda has all of the irons, and shaft. the thin irons are cheap, the shaft and thick iron is $$$$$

so far the tuner people have gotten more power from the 9.7 rotors, although its early in the renesis rotor/old engine game.

TT system complete with all the piping and solenoids and stuff is at least 80lbs

 

I'm curious though, if I buy a used Cosmo 20B, I'm just going to end up replacing the rotors and housings anyways. So why buy a cosmo 20B just to sell off the parts I'll be replacing anyways? Why not just start with an E-shaft and build outwards? Would that be more cost effective?

Also, wouldn't stock parts from mazda come already balanced and clearenced, due to them being OEM and new?

What do the stock rotors compress at?

 

Thanks for all the help.

I'm still missing how one fixes an imbalance. Take material off or add it...how do you do that to rotors without screwing up the shape of the combustion chamber/sealing? And the E-shaft?

If I were to buy a Cosmo 20B, with, say, 40,000 regular miles on it (by regular I mean those aren't race miles and it has been fairly well maintained) what parts can I expect to replace?

RPM is important to me. I am thinking a redline of 9k with power to 8k but the higher the better.

I assume that means peripheral port, which I've heard is expensive. About how expensive are we talking?

 

i pulled the stock turbo 3 rotor with front mount out of my FC, and dropped in a stock 13bt, and it only lost 60lbs.

 

shop around a bit, but mazdatrix sells the eshaft for $3700. you can buy the whole cosmo engine for that.

when an engine is built new, the parts are matched together, balance wise. when you buy a new rotor, it cant be. clearances are there, but stock clearances, if you're spinning to 9k, theres a couple changes.

stock cosmo 20b rotors, are the same as the 89-91 turbo rotors 9:1 compression.

 

theres a spot on the side of the rotor that gets machined, every rotor has some drilling there.

rpm is nice, but the 3 rotor has more low end, if you want to have power to 7k, and be able to hit 8 here and there, not much needs to be done, but to make power at 8+ without it coming apart, it needs a lot of work to stay together.

racing beat sells PP rotor housings for about $900, you need 3...

 

If I buy a Cosmo 20B how do I know that the E-shaft and center Iron will be in perfect shape? If they aren't won't I just have to replace them anyways?

 

EDIT: So when we say "PPs have no low end power"...how literally do we mean that? Can I build 100hp below 3k or will I actually not be able to move the car from idle?

And what is all this about partial throttle?

 

stock 3 rotor, stock turbos. no emissions (except a cat), no rats nest, all mazda parts, except the ecu/coils/suspension and exhaust.

the 13bt was stock/turbo/ecu/rats nest/emissions. same exhaust/clutch/radiator as the 20b

the front mount came out with the 3 rotor. sway bar went back in

and the car went from 2860lbs to 2800 (i wanna say 2820, i posted here when i did it, so you can search if you want) full tank of gas both times, same scale.

 

you dont really, ehshafts dont wear too much, and the plates live a long time too.

new thick center plate is about $3000 new, shaft is $3700.

 

the PP engine is a race engine, its like a piston engine with big ports and a really wild camshaft. its also developed for race cars, so they dont care about performance under 5000rpms.

the exception might be the 787b, which they used the production engineers on, and uses an o2 sensor and stuff, but anyways....

http://www.youtube.com/watch?v=nH-kr...eature=related

http://www.youtube.com/watch?v=uCwLU...eature=related

http://www.youtube.com/watch?v=9675TKafw3g

listen to how it runs when you're not accelerating. BTW when uncle koby is revving the 787, thats 1000rpm to 8000....

 

As long as it's not going to damage itself from idling or from constant throttle I'm fine with it. It's not like it would be street legal anyways, but it does have to get itself to and from the track and that has to be done under the speed limit.

 

its fine daily driving, you might not want to, though, its kind of intense for that

 

Perfect.

Can you link me to some PP housings? I can't find them.

 

Here are some porting pictures to help you out.

http://www.rotaryheads.com/porting/rx7-porting.html