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hey i have a 1994 rx-7 twin turbo.. my engine just blew for the first time but i have heard that after they go bad, they just get worse. i was thinking about putting a sr20det engine into my baby. how much do you think this project might set me back? and what exactaly am i gonna have to do? because the sr20 weighs a little less but is slightly a bigger engine..

posted by  Guns_10

Yeah i know a guy that went through 3 wankels. DO NOT DROP IN AN SR20!! You can get SO much more power per liter from a rotary. You can import a special i think 2.0 liter rotary from japan that comes in some minivan there or something. Its what the hard core rx7 owners do. I suggest you look into that

posted by  TurboLag

Go to rx7club asap.

posted by  importluva

I have seen an SR20 engine swap before and they work quite well but as turbo said there's no real point in swaping out the rotary for the SR. If money is no problem then how about a 20B (triple rotary) engine swap? Many of the fastest rotary drag cars use this engine.

posted by  GreekWarrior

Shoot for anm LS1, you gain zero weight and have a nice stock 305-350hp.

posted by  thunderbird1100

If hes going to do that, he should just drop in a 390, or 302.

But my first choice would be to put another rotary engine into it.

posted by  FordFromHell351

i think the one from japan is called the 3rotor or the 20b, thats the one u should put in

posted by  j3ff

Ok, just so you know it is called the 20b and it was put into two different cars the HB cosmo:
and the JC cosmo:

Now, for Guns10:

How did your engine blow? Apex seals? Over boost?

Either way, don't waste your money on a SR20DET, just get a new 13b. You can find one for around $800-$1000. Plus it will be a straight swap, no moving engine mounts are weird wiring.

posted by  Zalight

i love SR20's, but dont u think it doesnt seem right to have a Silvia motor(NISSAN) put into a RX-7(MAZDA)...if i were u, i would only put stuff that belongs to my car's manufacturer.

posted by  nissanTFsx

Thats the one i was talking about

posted by  TurboLag

Some company makes a complete kit for a LS1 swap into an FD Rx-7. That's why I recommended it.

Here... I found it. Hinson Supercars makes a LS1 kit and LT1 kit. Hmmm. for the price I'd just go to a junkyard and pickup a 94-97 LT1.


posted by  thunderbird1100

The 20B is a nice, fun and rare engine. My girlfriend drives a 20B powered 94 RX7. It's loads of fun, but then again a LT1 or LS1 swap will yield much more hp/$ in the end.

posted by  thunderbird1100

Yeah, the LS1 swap is pretty cool, but for me it goes against the soul of the car. Its like putting a gorilla in a suit. The gorillas powerful, and the suit is really nice. But they just don''t go together.

posted by  Zalight

Props on the analogy Zalight, or whatever you would call whatever you just said. I totally agree

posted by  TurboLag

I'm a fan of keeping the FD Rotary powered too. But your options in that are keep throwing in 13b's or really spend a ton of money for a 20b. An LS1 or LT1 swap is just so much more of an economical decision.

posted by  thunderbird1100

if i throw a 20b 3 rotar motor in there, would i still have to replace all the electronics and stuff? or would i have to go through any of the othe complications of engine swaps like replacing the engine harness and what not?
would it be easyer to buy another 13b and put another lower milage engine in?

posted by  Guns_10

The 20b swap into my girlfriends car was not easy. (Assuming you can find someone who CAN actually swap one in)The swap will run you in the $5k-$6k range. It's not cheap and pretty complicated.

posted by  thunderbird1100

Honestly, the easiest swap for you would just be a lower mileage 13b. Both the cosmo and the LS1/LT1 would take a lot of work.

posted by  Zalight

im a real big fan of the ls1 swap, if i did that, would it throw the cars 50/50 balance off? im gonna be doing it myself with a few buddys help, how much am i lookin to spend? and what exactaly am i gonna have to do, will i have to replace the transmission as well?

posted by  Guns_10

The Rx-7's biggest advantage is it's light weight and balance, why would you want to ruin that by putting an LS1 in it?

posted by  GreekWarrior

It doesnt ruin the balance at all. In fact the LS1 is lighter from what I've read than a 13b-rew.


All the info there.

posted by  thunderbird1100


It doesnt ruin the balance or lightweight at all...

Take a trip to hinsonsupercars.com and read the FAQ's.

posted by  thunderbird1100

*sigh* gone over this many many times. it does NOT change teh weight balance negatively. In some cases it actually improves slightly to 49/51 f/r 9a slight rearward bias is actually better for handling."

As i've asked on other boards... The Sport model weighs 2600 lbs stock. the GXL wiighs 2780 lbs stock. the TII weighs 2850 lbs stock. Sice they are all same from the firewall back, which version, exactly has a 50/50 weight distribution?

In fact, the TII has more weight on the nose than the LT1/LS1/Ford 302 swap.

Remember, due to the design of the chassis, any engine except the 20B actually sits behind teh front wheel centerline, so they add weight (when they add it) to both ends of the car. My personal Ford 302 swap ended up weiging 2720 lbs woithout any effort to lighten it. Since it weighs LESS than a TII, and is the same from the firewall back, where did the TII have more weight?

My personal swap cost me les than $2500 to get a daily driver engine that had close to 400 hp. the LS1 costs more, but has more power in completely stock form. Unstressed. Reliable. And retains all the handling the RX7 was known for. Seriously.

My car:



An LT1 version:


posted by  ChrisV

Like was said, the FC is a light, balanced chassis regardless of engine. It's a GREAT looking car regardless of engine. It's a well built car regardless of engine. How come all teh rotards can see in the CAR is the effin' engine??????

I often find rotards that think the only good thing about an FC is the engine. Apparently they think the rest of the car is a POS that only exists to give the rotary something to move around.

That attitude completely ignores the fact that the FC is lighter, looks better, is better built, has better brakes, looks better, has better ergonomics, is smaller, looks better, has a better interior, better suspension, looks better, etc... the FC is numerous, cheap, easy to get, and unlike a lot of swaps, is dirt easy to do as the engine compartment accepts the V8 as though it was designed to be there. And the chassis carries the engine in such a way that it simply doesn't change the balance that the original car had, due to how far back it sits."

posted by  ChrisV

quick question here...why would anyone want to go back to pistons after experiencing rotary smoothness and simplicity?

posted by  importluva

hey, if money's no problem then go with a 20BTT, send it to PAC PERFORMANCE in melbourne or QLD and give them $20k to fool around with.... 450kw later....

posted by  HyundaGuy

Not everyone wants a rebuild every 100k miles.

posted by  fudge

Torque? Reliability at elevated power levels? Lower cost for the same hp levels?

Seriously, high power rotaries are fun. I've had many. I raced this car in rotary form for a year before it died. I've rebuilt rotaries on my kitchen table (don't do that if married or living with your parents... just a friendly head's up..)

I wanted something that 300+hp rotaries did not give back in '93: torque and daily driver reliability. Most guys doing the swaps have already rebuilt a number of high power rotaries and are tired of it. And, to be honest, as nice as a stock rotary sounds, I was rather tired of the way modified ones sounded. A high power rotary (especially an N/A one) sounds like a chainsaw right next to your head.

And back when my stock 145 hp N/A 13B died, it was going to cost over $2500 to rebuild it to stock 145 hp form, and making more than 200hp from the N/A one would make it very unreliable. The next option was a turbo 13B, which would have cost a minimum of $3000 to put in in stock form, and to get more than 200 hp would have cost almost double that. A 20B was going to be a minimum of $10k at the time (and the average to get a 20BT finished at the time was about $25k!!!!). So while I was looking at my empty engine bay, two things happened at the same time. I noticed how HUGE my empty engine bay was, and my buddy offered me his built up 302 from his race car, becasue he was going big block. An engine that had cost him $3000 to build for $1000, and I could pay him $100 a month for it. Sold!


I had HAD built-up rotaries. I had an R100, RX2, 2 RX3s, 2 first gen RX7s (one with a bridgeported early 13B) and this FC in rotary form. I had crewed for team running an IMSA RS RX3 and a rotary powered Formula Libre and helped a friend build his RX3 race car and an RX2 SCCA rallye car. I simply wanted something different and unique from this project.

So I built a more modern Cobra Daytona Coupe for about $2500 with almost 400 hp and similar levels of torque. And I had the car like that for the next 5 years on the street and on the track, without having to rebuild it.

posted by  ChrisV

The problem is if money's no problem you start with a different car. We use FCs because you can get a dead one for under $500. I already HAD mine, bought and paid for on a $7/hour job. Money was definitely an issue.

And you know, the 20B turbo does the one thing to the car that rotards think the V8 does: it puts more weight over the nose and upsets the balance of the car. So now you've spent $20k on the engine, and more to install it, and you end up with a car that has about the same power as a barely modded $3000 LS1, and you've actually made the balance worse than the LS1 conversion. Might as well that that $20k and light it on fire and watch the dollar bills burn.

Oh, and if you use it regularly, you'll probably have to rebuild the 20BTurbo annually.

posted by  ChrisV

i'm not gonna argue with that!! lol, i was just sayin' it to sound smart.. :smoke:

posted by  HyundaGuy

I just suggested th 20b because that's what the fastest (or one of the fastest) rotary drag car uses.

Here take a look, it's an MX6 with a 20b transplant that has run a 7.04 quarter mile time.

PAC MX6 (http://www.pacperformance.com.au/content/lang__en/tabID__3928/Team/mx6.asp x)

posted by  GreekWarrior

*drools*.. gotta love pac performance...

posted by  HyundaGuy

You can get a 1.3L rotary engine up to 700hp...not that you would need that much...well...maybe. Anyways, don't worry about getting a different type of engine, you can blow any of them up. Next time get a better radiator, turbo timer, or anything else you can find to keep the engine relatively cool. The rotary engine is great unless it overheats, then its done :ohcrap: .

posted by  WakeF2005

:laughing: we all know how i feel about the topic :thumbs:

actaully now that the TII is going good i am getting a 89 supra NA for a daily to replace the Jetta. But another 7 project will be up soon...

posted by  Low Impedance

well it depends on what you want to do with it!

Pro-Drag throw a nice 302 or 305.

Street 13bTt or Tri-rotor

casual every day 626 engine is perfect

if you decide to go rotor be prepared to be an on the spot mechanic and take care of the car like an infant. Means little to no drive and park driving mind you it is a converted airplane engine so it is built for the longer drives. I own an 85 RX-7 with the 13b in it and the previous owner tore it up now it is getting a complete overhaul. I cannot decide weither i sould throw a 305 or go for a jza80 or AE86. Dreams! :clap:

posted by  TDash

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