N/A 20b build

[aaron_bc]

So I've been emailing back and forth with Adam from RX7Specialites in Calgary, AB about a 20b N/A build. It seems like he wants me to do a ton of extra things that I don't know if I need or not. Basically, I'm going to be building a fun street car that I will take to HPDE once in a while. What I want is a large streetported 9.7:1, balanced to 9000RPM engine. He wants me to go with new housings and says new rotors are a necessity. Do I really need all of this for a 300whp N/A build?

He suggested the following in an email... New 13B housings, new S5 rotors, 20b hardened gears, Lighten, clearance and balance rotating assy (which I will do) Oil mods incl HP race oil reg. Bridge porting 20b (pri and sec) $1117.50 (incl std intake port and polish, exhaust porting and bridge work).


I figured a standard 9.7:1 build with S5 rotors, a LARGE street port and balancing would be good. Should I be doing oil mods? Race bearings? Scalping the rotors? He suggested a bridge port... not sure if I want to go that extreme.

I know he knows what he's talking about and I'm sure it would be a KILLER engine. But... it's all about dollars and cents.

What do I need to build a 350whp ITB'd street ported 20b?

I'm going to be runnign a Microtech, have some equal length headers built by a friend who is a fab king and most likely use the Hinson subframe with their bumpsteer kit.



Any input would be appreciated. :D

Thanks...


Aaron from Canada

[project86]

You dont need Bridgeport. and it you want as a street car dont. im going to be doing damn near the exact same build as you soon. my goal is the 350whp area as well. my mods to start are.... 20B engine/large street port/Rx8 10.0:1 compression rotors/balance rotating assembly/cryo treatment/ and stocke 20B UIM to start with. Eventually switching to a single 90mm TB which will free up some ponies and then if im still feelin froggy ill do ITBS. With all the mods i just listed (which sound very similar to what you want) 350ish whp is attainable. Ive talked to alot of people and done the research. But if anyone has something else to add lmk.

[RETed]

So I've been emailing back and forth with Adam from RX7Specialites in Calgary, AB about a 20b N/A build. It seems like he wants me to do a ton of extra things that I don't know if I need or not. Basically, I'm going to be building a fun street car that I will take to HPDE once in a while. What I want is a large streetported 9.7:1, balanced to 9000RPM engine. He wants me to go with new housings and says new rotors are a necessity. Do I really need all of this for a 300whp N/A build?
No.


I figured a standard 9.7:1 build with S5 rotors, a LARGE street port and balancing would be good. Should I be doing oil mods? Race bearings? Scalping the rotors? He suggested a bridge port... not sure if I want to go that extreme.
The stock bearings in the 20B (and 13B-RE Cosmo) already run better bearings.
The only upgrade would be to go FD bearings.
Not necessary if redline is set at 9k RPM's.

It is debatable about balancing the oil pick-up and districution system, since the engine is so long...
I'd go at least with an upgrade OPR and call it a day - if you're paranoid, run the FD or 100+ psi OPR, and you should be fine.

"Race bearings" are unnecessary unless you're planning to go over 9k RPM's...

Scalping rotors?
Sounds like they are trying to rip you off be charging you for expensive / unnecessary mods.

Bridge port is not really necessary...
We were able to hit 230hp at the wheels on a DynoJet with the STOCK block, STOCK intake, and a too-small air filter:
http://fc3spro.com/PROJECTS/SKY/20B/20bna01.jpg

The car could've gotten close to 250 if the air filter wasn't too small.
The stock intake is not meant for normally aspirated applications.
300 at the wheels is a realistic goal...


What do I need to build a 350whp ITB'd street ported 20b?
Aggressive street port
Short intake system
Tuned header and exhaust system
All the proper safety mods to support those power levels



-Ted

[aaron_bc]

Thanks Ted

Sounds just like what I was thinking. I am kind of paranoid so race bearings might be nice or at least new OEM ones and a balance of internals. Oil pressure is important so this might be something to go for as well.

Who would you recommend to get this work done by?

-Aaron

[aaron_bc]

I wonder what I could even get out of fully stock block with ITB's?

Hrmmm... maybe I should to that FIRST to get the car up and running, set up the way I want then get it built for more power?

[RETed]

Mazda Competition (now Mazdaspeed) used to sell "race bearings"...
Guess what they were?
Stock Cosmo bearings...which your 20B already has.
These are the "3 window race bearings" that you see.
I believe Racing Beat sells them as such also?

The only better bearings are the stock FD ones which are "9 hole" bearings and, I believe, deeper groove?

Sorry, I can't recommend anyone for your 20B build.
I do all the work myself. :)


-Ted

[project86]

Mazda Competition (now Mazdaspeed) used to sell "race bearings"...
Guess what they were?
Stock Cosmo bearings...which your 20B already has.
These are the "3 window race bearings" that you see.
I believe Racing Beat sells them as such also?

The only better bearings are the stock FD ones which are "9 hole" bearings and, I believe, deeper groove?

Sorry, I can't recommend anyone for your 20B build.
I do all the work myself. :)


-Ted



I think the reason they were talking about race bearings is because they were gonna build a 3 rotor istead of using a 20B block to start with. Just FYI:icon_tup::icon_tup:


sending you a PM btw

[aaron_bc]

Ah... like building a 20b out of 13b parts with a 20b e-shaft...

Hrmm...

Still doing re-seach. I may just find a good block and throw it in the car, get it running on stock comp ratio rotors and stock ports then once the car is running and all the parts fabbed up get the engine sent out.

[aaron_bc]

Mazda Competition (now Mazdaspeed) used to sell "race bearings"...
Guess what they were?
Stock Cosmo bearings...which your 20B already has.
These are the "3 window race bearings" that you see.
I believe Racing Beat sells them as such also?

The only better bearings are the stock FD ones which are "9 hole" bearings and, I believe, deeper groove?

Sorry, I can't recommend anyone for your 20B build.
I do all the work myself. :)


-Ted


You interested in building mine? :D

[project86]

Ah... like building a 20b out of 13b parts with a 20b e-shaft...

Hrmm...

Still doing re-seach. I may just find a good block and throw it in the car, get it running on stock comp ratio rotors and stock ports then once the car is running and all the parts fabbed up get the engine sent out.

ya thats what i thought you and your builder in canada were talking about doing cause you said something about using 13b housings in that first post you made.

[aaron_bc]

He said to get new 13b housings, because 1) they're new and 2) they already have the FD exhaust insert.

[Prodigy]

if you are going to be spending that kind of money to build a motor, even more so a 20B its not a bad idea... then you know you have a completely fresh pallet to start with.. not wondering if the second hand housing, or irons were abused, or overheated, or whatever...


Adam @ 7 specialties knows his stuff.. but I also know quite a few guys from the Calgary area that will not let him touch their cars...

everything I "know" about that place is all second hand info, so I wont post any of it..

but I will say that he is one of the most knowledgeable people in Alberta when it comes to Rotaries... he does like to make high dollar builds though...


I'm hoping in the near, or distance future to do a build very similar to this one... maybe even 26B, if the funds are there when I go to build it...

but either way... looking forward to the running log...


where are you located BTW... if you are somewhere close I would offer my help if you ever needed it..

currently I live/work in fort mac.. but that might be changing soon

cheers

J.

[aaron_bc]

That's the thing... I DON'T really want to spend that kind of money. I just want a solid, reliable 300whp N/A engine. Simple.

I'll do some oil mods from which I've read help with high revs for the center bearing but nothing else other than balancing I really think I need?

[aaron_bc]

I'm in Vancouver BTW.

[RETed]

You interested in building mine? :D

Interested?
Sure. :)

You do know I'm from Hawaii, right? :)


-Ted

[aaron_bc]

Oh... N/M then. Lol...

[project86]

i wish i was from Hawaii

[aaron_bc]

Vancouver's better anyway :leaving:

[Prodigy]

I'll throw my vote vans way... As it's 'local' compared to the islands...


I'm hoping to make it out this fall for a couple days... Enjoy the city and such...

Maybe take a quick dip into the Seattle... See if their are any meets, on either side of the border....


J.

[gmonsen]

Sounds like a good general plan to me. I would suggest you go with a 90mm throttle body instead of ITB's with a large street port. The street port runs out of steam at around 7500 rpm. You are totally constrained by the stock throttle body. There are plenty of 90mm throttle bodies you can mate to the intake. You should be able to make close to 350 with that. If you want to go higher, you really want to go pport (or semi pport)and ITB's.

Gordon

[GtoRx7]

Late to the thread, but figured I would throw in some info. I have been doing 20b n/a R+D for over 6 years, and over the past 6 months its really coming together. This is mostly to put a bunch of facts on the board. And to produce some of the most powerful n/a 20b's in the world for my customers (Christopher is a big one that comes to mind!)

Proven 313 rwhp 20b spec sheet-

20b with our circuit port on intake and exhaust
USED not new 9.7:1 rotors
Balanced assembly
Stock 20b stationary gears and bearings (identical to fd bearings)
110psi regulator
new stock oil pump
Our stainless 20b equal length header
Stock intake manifold, shortened stock lower manifold
Standalone of your choice
3" exhaust from header back
8000rpm
Stock apex seals
stock used rotor housings

Thats it, good to go. If you want 350rwhp+ we have done this as well, and I can help guide you in the right direction from facts and actual results.

[NoDOHC]

I believe the above, as I did 216 WHp (Mustang) with 8.2:1 polished s4 turbo rotors, stock s4 rotating assembly (not balanced), stock intake manifold and very mild porting. An equivalently built 20B should make 320ish WHp.

[GtoRx7]

Nice work, can you link me to the dyno chart?

[NoDOHC]

http://i594.photobucket.com/albums/tt25/NoDOHC/WithAFRandNoHeader.jpg

I fixed the rich spot later, but I had the AFR trace off for the next run that I got a picture of.

Although the curves do not line up, the rich spot made the dip in the torque curve. I wish I had a picture of the afr on a run with a 13.3 afr throughout, but once it was good, I was fooling with trailing split and had the afr trace turned off.

Edit:

I should also post here that target AFR was 13.3:1 (optimal power). Ignition timing was fixed at 38degrees BTDC above 3000 rpm.

I was initially running from 3000 rpm, but I had to wait too long between runs for engine cooldown, so I started at 5000 instead to minimize the engine heating. I revved to 9,000 once (182 WHp at 9,0000 rpm) I think I was ignition limited, as my peak VE was reached at 7,700 rpm and my power had long since started to fall off at that point.

BSFC was right around 0.42 lb/Hp.hr until 6,800 rpm, where it started to increase to 0.54 lb/Hp.hr at 9,000 rpm (which also indicates an ignition problem).

Interestingly enough, this engine only barely eaked above 100% VE (I saw 102% at 7,700). Rotary engines have a lot of potential.