drivelikejehu

im trying to decide which route to go with modifications, keep in mind im NOT a power junkie and id be more than happy with 300 at the wheels. Id also prefer to spend more money to do things safely and correctly, rather than double my power for half the cost. NOW with that out of the way... what do you guys think.

Are the mods required to get my stock 13B twins to 300rwhp going to throw reliability (i know thats a curse word on these forums, but my rex IS my DD) out the window?

OR

Go with a ported N/A 20B (and necessary bolt ons) for a much simpler engine, with some more power, and as much reliablity is my car is stock? or will there be more or less? im also a machinist so many of the parts required for this project can be made myself. and i also have two local friends who rebuild 13B's all day long. im sure a 20B isnt too far of a reach for them.

i love everything about the 20B and basically im just looking for a much simpler engine, with a little bit more power, that doesnt require me to stare at a boost gauge or rebuild every 6 months. and would also allow for expansion if i decide to in the future.

am I looking in the right direction with a 3 rotor? remember, i dont mind spending the extra money for less power if it means its doen correctly and SAFELY (i dont want to blow up my motor)

im looking for opinions, so dont be afriad to put your 2 cents in. unless you say V8... there will forever be rotors in my car...

fcfanatic

Talk to Damian on the boards. He daily drives his MB fd and I believe he has over 300whp reliably. www.myrx7.com

GUITARJUNKIE28

the 3-rotor is gonna run you a bundle. 300+whp can be achieved reliably on a 2-rotor for a lot less money.

jerd_hambone

300 on a 20b is like getting 200 on an n/a 13b

its possible if you do it the right way.

although 200 is about as much as you can get out of an n/a 13b, with a 20b, i think you could more than 300

but gas mileage is gonna be baddddddd

drivelikejehu

very true and i actually thought about this alot since my 7 s my daily driver. but sacrifices must be made, and this is one im willing to give up its worth the growl of the 20B


this is also part of my question. but really how reliable is this route in comparison to a N/A 20B? im not an expert, but to me it would seem increasing boost (and engine complexity) will shorten the life of my engine reguardless of how safely it was preformed or a perfect tune.

i also realize that every car and every engine is different, and what one person does to their car may not yield the same results on every car. for instance, one person may DD their 400hp rex with stock twins for 10 years without a problem, but id rather base my decision on the 50 people who tried the same thing and had to rebuild in less than a year.

Rocking Rotary

iTrader: (14)

Wow Here is what you need to dicied

Spend 35k plus on a 20b

or

5k in good parts and a reliable FD if everything is done right.

Personally install a down pipe, cat back exhaust, intake, and some hard pipes and see how you like it. I think you will see a diffrent beast. Any mods will cut your life expectancy on your engine put these aren't to hard on it. Do a search and you will find what your looking for.

GUITARJUNKIE28

$35k?
are you planning on a gold plated engine?

try $8-10k on the cheap side, and the sky's the limit.

drivelikejehu

plus im working for a machinist and MANY parts can be made, including the e-shaft. money isnt really my issue honestly.... although a 24k gold rotary would be pretty sweet...

vspecpgt

Any tuned N/A rotary will be very very reliable, and probably outlast many piston engines. there are many less moving parts, and apex seal wear on an N/A isn't really a concern.

you could just do a few simple mods and make 300 to the wheels on your turbo motor though, there are lots of people running 400+ reliably, 300 shouldn't be that bad at all.

remember though, even if your car is tuned perfectly and you never "blow" your motor, the motors in the FD have been known to fail just based on the fact that they make so much heat, they eventually ruin the water seals. if you've never had a rebuild, you will eventually need one. but if you do it right, with the right parts, you will be fine.

if money really isn't the problem, than i would suggest a 20b. it would be cool, it sounds cool, and you have a very very reliable motor (as long as you use reliable parts).

i beleive gtorx7 made over 300 whp on his 3rotor, with just ported side ports, he's currently rebuilding it, but i think something was wrong with his motor in the first place.

js3324

Excuse my blasphemy but if you want reliablity, great gas mileage, and 300whp(hell lets say 400whp with PLENTY of room to play with) get an LS1. All of which are EXTREMELY important to a daily driver. It will probably be cheaper to swap than the 20B and will be lighter(oh yes I said it) than the iron blocked 20B.

Seems like your attatched to arbitrary things like sound(granted it does sound sweet) and "soul" though so I guess you wont be come to the smarter dark side.

Of course you can do it with your 13B and do it the cheapest(rebuild on twins, exhaust/dp, tune, fuel(dont know if thats necessary or not) should do it

GUITARJUNKIE28

i'm sure if he were down for a piston swap he would have mentioned it.

i like ls1's. i like triangles. can't we all just get along?

DocMazda

Well, i dont think he deserves a bashing. piston motors are great! but--i would just say he's pissing into the wind simply due to the fact that the above post stated he doesnt want a piston engine. its not an offensive thing by any means...its simply what he WANTS to do with HIS car. personally--if i had the money i would do a piston swap in one 7 and a 20b in the other. it would be nice to have--but im not made of money...yet.

GUITARJUNKIE28

id you've got the money, do the 20b and just run like 6psi. that'll be loads of fun and reliable.

if you fear the twins, hit up a gt40 with a small hot side, then just bump it up if you ever decide to turn up the boost.

drivelikejehu

i like this idea, and eventually i believe i would add a single turbo into the equation once a i had a 20B... but one step at a time.

js3324: i bet an ls1 is pretty nice, but personally i prefer my triangles

vspecpgt: about the rebuilding. i totally agree that i will need one either way in the future for one reason or another. but the way i see it, building a 20B would require me to "rebuild" the engine in the first place, so id pretty much be working with a fresh build, with a good base to expand from later.

im glad you mentioned gtorx7's car because i LOVE his setup. although i dont think i would go that crazy with some of the things he did like the completely custom intake manifold/ air box thing and throttle bodies.

overall, i still think i like the idea of going 20B better than modding the twins to reach 300 just for simplicity and longevity. if i go ported N/A 20B for now, i will still have lots of room to add a single turbo later, no need to rush into things. plus it will be a fun project. just out of curiosity, roughly, what does a mild port job on a 20B with intake and exhaust put to the ground? (basically what im looking to do)

oh yeah, i just picked up 2 FD rotor housings (one is in really good condition) and an FD Rotor... im on my way! haha.

RotaryX

If this is the case, then go all the way.... 4 rotor

RETed

Since I'm one of the very few that actually worked on a running 20B NA, I'd think I can offer some tips...

Sounds like you're starting out with an FD?
This makes a 20B swap more complex.
You do mention fabrication resources, so this might not be a big deal for you.

We managed to make 232 at the wheels from a stock block 20B with stock manifolds.
There's another member who managed to break 300hp at the wheels - custom intake manifold and ported motor.
So making 300 with an NA 20B is possible.
Be prepared to throw that stock intake manifold in the trash.

If you managed to get the 20B in and running, you'll immediately notice how much more torque you got all over the RPM range.
It's almost like driving another car!

The bad news?
These things run HOT.
If we're talking street car, you might not push it hard enough to notice it.
With an FD (front bumper), it already has problems keeping a moderately powered 13B-REW cool.
With a 20B under the hood, we're talking extensive cooling mods to keep it safe!
You might want to keep this in mind...even NA.
Going with a turbo 20B, I doubt you could keep it cool enough - get this beast on the track, and I bet you'll roast it in a couple laps.
This almost necessitates an aftermarket front bumper with significantly larger frontal openings for cooling.
Fanatic ducting is necessary!


-Ted

drivelikejehu

^thanks for that info!! i was hoping for some expirienced knowledge somewhere! and yes it is an FD.

the intake manifold i never thought i would have to fab up to reach 300, and the heat issue is definately a problem. besides huge radiators and other cooling parts, what other body solutions may work? as I have the resources for this as well.. man... arent I a lucky guy

has anyone tried venting into the wheel wells? the dummy brake vents? what about getting air from a scoop underneath the car? id like to minimize body work as much as possible, but if it has to be done, it has to be done.

also, how does the stock mazda turbo 20B cool itself? is this the reason they threw it out from production?

vspecpgt

with dual oil coolers, and decent airflow to a aluminum radiator i don't think you'll have any problems.

i have trouble getting my car "up" to operating temps with my setup now.

GUITARJUNKIE28

^ don't you have oil and coolant thermostats?

my car gets up to operating temp fas and it's got a big 2-pass radiator, and dual oil coolers.

GtoRx7

iTrader: (5)

A Ls1 is a great option if your not attached to the unique and badass rotary. However, I have shown over and over again, that a N/a 20B is in fact about 20lbs or so lighter than a Ls-1. Comparing a turbo 20B to a n/a Ls-1 wouldnt be fair. Gas mileage out of a 20b n/a? Not as bad as you'd expect, I average 15-19mpg with a very heavy foot. The good ol' soul attack is dumb, any mod you do to a car will technically change its "soul", so do whatever the hell you want. A n/a 20B has potential, and hopefully this season I will re-prove it more so than ever.

drivelikejehu

^ i was hoping you would find my thread!

id like to ask a few questions about your setup if you dont mind.

how do you go about cooling your 20B? and have you had any major problems with heat like RETed mentioned?

also, did you design and fab your throttle bodies and intake manifold yourself? as i see alot of your work is completely custom.

last, do you have any advice for someone building a potred N/A 20B?

GoodfellaFD3S

iTrader: (213)

Interesting thread.

I just spoke to a guy who claimed he had a half-bridge n/a 20B in an FD making ~315 rwhp with very rich AFRs and redlining at 9500 rpms, with some serious torque. Claimed it was a racing beat motor and had spun it as high as 10,500 rpms with no ill effects.

I must say I am intrigued.....

RETed

The Mazda Eunos Cosmo has a pretty good sized radiator, and it's a big luxury coupe with a good sized grill (opening) in front.
The stock HP rating was "only" 280ps at the flywheel, via printed JIS power limits on engines back in the day.
Owners of a Mazda Eunos Cosmo claimed it could easily do 300hp.

The stock 20B with turbos running at stock boost would typical make 240hp to 250hp at the wheels - this is the typical numbers I've seen posted.
We were able to make 232 at the wheels minus the stock twin turbo system.
That's within 8hp with no turbos!

I think the Mazda Eunos Cosmo was dropped due to insufficient demand from buyers.

Sorry I can't answer the questions about the cooling mods, as this is more FD specific than anything...


-Ted

vspecpgt

yea i've got thermostats... it just takes a long time getting up to temp, i run a pfc, a vmount utilzing a koyo radiator, and dual 25row mocal oil collers using an 85C mocal thermostat. i am running thick oil though, so thats probably part of the problem. 20w50, but i'm getting if for free too so...

drivelikejehu

this brings me to another question. what type of port would i need to go with to reach 300 (or get close), and still be able to drive the car everyday?

i was looking at different types of porting on mazdarotary.net and it seems an "extend" port is the farthest you can go without seeing too many problems with driveablity. is this correct? is there any other porting options to be considered?

and what about high compression rotors?