Weight Difference 20b NA and T-2 setup
 

I currently have an intercooled T-2 setup in my car. I am thinking of going to a 3 rotor NA. I just like the simplicity of the setup and want to try something different.

I imagine it would be lighter than the current setup turbo, manifold, intercooler added together.

Thanks

its close, actually. my FC with a stock turbo 3 rotor was 2860lbs. i pulled the 20b, and replaced it with a 13BT and it only dropped to 2820lbs. same radiator, same trans, same exhaust.

so give or take its 40-50lbs, but it is further forward

The 20B is 80 pounds more than an S5 T2. The thick intermediate plate is 36 pounds, rotor housing is 13 or 14, rotor is 9, extra length of shaft maybe 10, extra length of tension bolts maybe 8.

Intake manifold is heavier than a 13B because there's more aluminum. A header can be lighter than a stock S5 turbo.

Relocate the battery to free up 40 pounds from the front end, and you can say you've only added 40 pounds up front and 40 pounds in back.

you two guys should get together and wright a rotary info manual....

Ive actually been tossing that idea around for a while.
If I can get a 20B running N/A with the stock ECU,maybe some 460cc N/A injectors,Im betting itll pass smog.CA laws are strict,but also kinda vauge.There is no mention of N/A or turbo when engine swapping and most shops dont/cant tell the difference between a turbo/NA rotary or a 2 rotor/3 rotor, for that matter.If it looks stock and the numbers out the tailpipe jive,Ive already got the refferee certs to be running a 90's EFI engine.....
Expensive idea,but it could be fun. 20B's are still popping up for sale,I just need to get one some day and stash it away for a future project....or as an investment,they are only going to get rarer and they dont make some 20B parts anymore.

running the stock 20B ecu is a TON of work, its structurally like an FC, except bigger, so there is a LOT of wiring that goes thru the dash, and a lot of stuff that sits on the left inner fender (coils/relays etc), so its actually easier to get a front clip and get that to run with no codes than it is to try and wire it up yourself.

that being said once its up and running with no codes it'll pass out the tail pipe.

i do agree with going turbo-less too, those things are HEAVY and complex, and not very boosty either.... NA has the potential to sound wonderful too

20b
 

Thanks for all the responces. I think i am going to go forward and start looking for one. I am not after crazy HP, i just want the torque and instant throttle responce.

I have an MT LT 4 on my car presently, but plan on getting an LT 12. Hopefully i can find a used header somewhere. Also, as you all are aware,this can get expensive very quick. Can you get away with putting a header, injectors and standalone ECU on the motor. What kinda HP will it produce since it has somewhat of low comp rotors. I know this issue is all over the place on different post.

I will have a nice T-2 complete setup available in the near future for sale.

thanks

there is no such thing as a used header for a 3 rotor, you need to custom make it.

ReTed put his unopened 20B in an FC with an ECU/header and it did 232rwhp. my other friends stock ecu/stock sequential turbos 20B only did 247rwhp....

the turbo car made more low end torque

My 20B has been streetported. It kept the stock 9.0 rotors. It will also keep the stock 550cfm injectors.

For driveability I went with an RB light steel flywheel.

ECU is a MegaSquirt. I got it running a few years ago unopened, stock ports, but was completely untuned. The exhaust was just thrown together out of 2" components. Way too small above 4 or 5k, where it fell on its face.

The new exhaust will be 3" and will be tuned for a streetport. Just curious how loud it will be. I keep going back and forth whether to keep it NA or go turbo. I'll let the exhaust note and noise level dictate what I do.

I kinda hope I can keep it NA.

the 20B and you by jeff and mike?

.............:icon_tup:

That totally just reminded me of The Worst Show on Radio, on a local college radio station, hosted by Jeff and Mike. Maybe one of these days I'll upload some of my old tape recordings on youtube.

20 b
 

Thanks for all the info Jeff and Mike. The car presently has a 3 inch ex with racing beat muffler and silencer, so i think i am good on the ex. Also, have a light flywheel on the T2 tranny as well.

I was going to sell my car and do a Porsche 911 project, but decided not too. So i want the setup that i beleive bets fits the car, a 20b NA. Will keep you posted on the progress. I think i have located a motor that is somewhat local.

I guess I didn't mention the components in my 3" exhaust yet. It'll start with the RB/Mazdatrix 3 rotor flange, 2" thickwall RB tubing as either a header kit or some of their mandrel bent tubes. Three tubes cut at 30° to create a collector. Collecting to 2.5" then expanding to 3". RB 3" universal presilencer. 3" Magnaflow with a 4" core (this doesn't really do anything and probably leaks more noise than it surpresses). Then over the axle and into an RB universal 3" muffler. Lastly it has a down turned dumpy.

I've listened to this system on a 2 rotor. It was too loud for me. But Mike says 3 rotors might be quieter due to the 120° pulses. And back when I test ran the 20B, it was quieter than a 2 rotor on a 2" exhaust system with only one minor component change. By minor I mean I readded this component after the 2 rotor had been running for a while, and it barely made a difference. In my mind that means a 20B really does run quieter. But I've streetported and swapped in T2 sleeves since then.

i like that car! 20B will be perfect.

my 20B was quieter than the 13BT with the same exhaust, not by a lot. the 20B also sounds better...

This thread might help you out with some ideas. He made 245rwhp with stock intake.
Not to mention, torque like a mofo.
https://www.rx7club.com/showthread.p...ght=20B+Intake


By the way, he made 295 rwhp with a new intake.
https://www.rx7club.com/1st-generation-specific-1979-1985-18/20b-na-videos-295-rwhp-588489/

Those power numbers were on dyno dynamics dynos, so consider them to be 10-15%
higher numbers if on a regular dynojet.

Here's a REALLY GOOD thread on custom Intake/Exhaust for NA 20B.
https://www.rx7club.com/20b-forum-95/my-rx-7-done-cup-holders-3-rotor-semi-p-port-n-setup-stock-subframe-454580/

20 b NA
 

Directfreak, thanks for all the links, they are great. When I finish the latest mods, that I plan to do, your are welcomed to drive the car. I believe you are in Miami or Ft. Lauderdale from reading your other posts. You will be amazed how much down force that body kit produces. Also, looking forward to the torque from the 20B!!!!

So my plan is the following.

--- Remove entire T-2 setup.
--- 20B NA setup shooting for like 300-325 HP. Need to talk to my engine builder see what he thinks.
--- MT LT12
--- RE Speed Rack and Pinion kit.
--- Seal off all openings into cabin, dymat and insulate all interior.
--- The AC is in the car now I would like to hook it back up.

Kinda looking to model the car after a GT3 Porsche, big NA horsepower and great handling. Looking forward to the next phase of the build.

Thanks all for the assistance and comments, I am sure I will have more.

Sounds good. I sure as hell wouldn't mind.

Dude, I am practically across the street from you. I live in Countrywalk.

20b
 

U actually are, i live in Venetia Lakes a block from Countrywalk. Small world.

I usually drive the car in the weekend on occasions, it does not get much use. I just picked up that M-Coupe in August, i love it. Its one of the best driving cars I have ever owned.

Larry