In about a year i want to start putting together my first 20B for a 2nd Gen, 1986 actually. I have everything in order besides the engine aspect. I wanted some opinions on N/A and Turbo setups on the 20B and what would be easier to live with? Any stories with these? thanks in advance

 

i disagree, turbo is much better

 

Out of curiosity how many n/a 3 rotors have you driven?

 

 

i had a stock turbo 3 rotor in my FC from 2001-2004. the car had about 8 aftermarket parts on it. radiator, e11v2, walbro fuel pump, RB exhaust and the k2rd suspension. i even ran a cat!

i used it as a daily driver for about a year of that, mileage is hard cause i put a canadian gauge cluster in it halfway thru, should be about 8-10k miles. two trips to sevenstock, one appearance in the japanese rx7 magazine etc etc.

what it was... stock engine stock turbos = smooth and quiet! boost varied but most of the time it was just on the wg actuator, which gives you about 6psi in the midrange. gas mileage was 19.9 on the freeway, 15ish in mixed driving.

power is effortless, its got much more low end power than a 2 rotor. so it fits the FC chassis really well, its quiet and smooth, effortless power was a good fit. think BMW 6 series or something.

it made a good street car, in the hills cooling was a problem.

i always wanted to just ditch the turbos, in addition to weighing 100lbs and generating a staggering amount of heat (think FD + 50%!), ReTeD's NA dyno was only 15hp down on my friends stock 20b stock ecu truck. (my friend bought a cosmo clip, got it running and put it into a b2600, its stock ecu, stock turbos, stock boost, and one of the funniest pieces of transportation ive ever been in).

so if i had to do it again, it go NA, just cause its simpler, my current GXL is 2840lbs, the 20b car was 2860, so i'd be happy to add 100rwhp and 20lbs.

and MOST IMPORTANTLY in an NA setup you can make it sound cool. turbo is QUIET

 

OMG but turbos are teh sexay and U no you gotta have BOOOST otherwise it's not a real RX7


they should of made the 20B a triple turbo!

(why no, I have not much in the way of anything constructive to add, other than noting that 20B + turbo + cramped RX-7 engine bay seems to be the ultimate cooling nightmare. But since I just drove 8 hours in my N/A RX-7, my head feels like it was hammered flat, turbos are sounding like a good idea just for the muffling, and will someone PLEASE answer the phone the ringing ringing ringing is driving me NUTS)

 

When the Grammar/Spelling **** starts going all OMG u no wut I mean LOL! !!! then it's sure to be snark. (Plus look at the signature: I have swapped a 13BT into my car, minus that pesky turbocharger....)

I'm almost anti turbo. Almost, but considering it for my new VW (Audi), since it's so incredibly heavy and VW didn't really make any common engines big enough to fit in there that don't require lots of fabbing. They shoved the engine over to the right, so they could put the radiator way over on the left, and stuck a motor mount on the FRONT of the engine, and all that would have to be changed for a V8.

And for what it'd cost to do a turbo engine right (fancy EFI since tiny German distributor + 5cyl turbo = crossfire and blown engines) it would actually be about as expensive to buy a 20B and run any generic aftermarket EFI in six-cylinder mode. (I don't believe in timing split anymore) I wouldn't doubt if the adapter plate existed already, as the FWD version of the trans is used in a lot of GT40-clone kit cars...

 

I have to say that I have owned a few 13b turbo motors that were in the 300+ rwhp range @ 12-15 psi and my tired unopened stock converted to NA 20b pulls just as hard as those motors did...

I could only imaging what it will pull like when i rebuild it with hi compression rotors, balanced and ported... I will also work on some sort of custom intake manifold...

My 20b is a pre letter series version... so I am hesitant to put a hair drier on it.... however if i do decide to pump air thru it, I assure you it will be a twin-screw supercharger setup and not a turbo ( I have my reasons which I am not going to argue about)

either way you decide to go... the engine short block would cost about the same... but the additional turbo accessories will end up adding at least 60-70% more to the bill... or more if you opt for top shelf products

 

I don't see how you could have done that without knowing the engine type.

What is the purpose of the car? What does "easier to live with" mean? It is easier to live with a stock non-turbo 13B.

I disagree somewhat. Short blocks are nearly impossible to find in good shape. The cheapest and least labor-intensive way to go is to keep the stock twin-turbo configuration and slap on a cheap intercooler. While a custom single-turbo setup is rather expensive, a well-built NA with ITBs, manifold, custom headers, porting, and high-rpm mods isn't exactly cheap either.

 

I wasn't talking about buying a long block vs short block... but rather rebuilding a short block... regardless of accessories (i.e manifolds etc...) that came with the engine

... porting, hi rpm mods, etc are all things that would be done to any 20b whether it is turbo or not...

also when you start pushing air thu the motor the fuel and ignition system will need upgrading


as far as ITB+manifold=nice turbo+W/G+exhaust manifold... a nice turbo can run excess of 2500 bucks, turbo manifold 1500+, w/g 300-500+... then you still have all the intake side of a turbo setup to get(intercooler,piping, BOV, boost control...)

however this can all be argued until blue in the face... there are endless possibilites on various setups

 

Agreed. My point is simply that the engine usually comes already turbocharged, so keeping it that way is the cheapest and easiest way to go if everything is in working order. Your post made it sound like extra parts were needed.

 

What i mean is: i know what to do suspension wise when it comes to either motor setup, i know its easier to live with a stock 13b n/a but which is easier to live with as a strong street/strip car but in not over doing it. All i really want is to know, from you guys that have had single turbo or n/a 20b's, is how the car drove normaly, while "playing" around, and which would be more cost effective for the enjoyment

 

here are the engine choices in order of easiness

1. stock NA. if you go from 20b to stock NA you'll be so bored you'll be waxing brake pads, or maybe take driving lessons, so when you go to the track the spec miata guys dont pass you in the turns

2. stockish 13BT. a mild setup runs well, and is almost as boring as an NA, from a tinkering point of view. you still get to open the hood now and then, you can always post long debate threads over which brand of intercooler is better....

3. 20B. HUGE learning curve. since you cannot run stock ignition or ecu's you get to learn those too. header tuning on a 3 rotor is a rather esoteric subject. its hot and thirsty (FD guys have nothing on a twin turbo 3 rotor, that can heat the whole house, not just the garage).

basically the 20B swap has a large R&D component to it. you can just drive the NA

 

OK, just as long as you realize that the fuel system, cooling system, and possibly the driveline, braking, and lubrication system may also be different. There may also be different safety requirements if you plan on racing the car.

Best: Buy somebody else's completed 20B project. Given the average time and expense of a conversion vs. the average price of a 20B car on this forum, this will save you about 2 years and about $20,000, maybe more. As an example, here is one of the nicer 20B cars for sale at a bargain price:
https://www.rx7club.com/2nd-generation-rx-7-1986-1992-vehicles-108/fs-20b-powered-convertible-767071/

Second Best: Start with a completely stock 20B-REW, get the car running without any cooling or other problems, and then see how you like it. You can then convert it to a really nice NA or single-turbo configuration later when you have more time and money. The best thing about this process is that you can slowly upgrade (fuel pump, fuel injectors, radiator, brakes, etc.) while still driving the car. Trust me, it sucks to have your car down for several years while building the "perfect" 20B RX-7.

 

I really appreciate everyone's input on this, i wanted to get a bone stock 20b and just leave it as is like evil aviator said. I know when jumping to a 20b its not going to be easy or cheap but thats the fun part. but having the car down for months or even a year does suck but im used to that. Im looking for parts in Illinois while my car is stuck in Michigan. Trying to look for a job in the performance aspect of rx7's but there is only one shop here mainly and he has no openings. I cant wait to get my car down here and start actually planning everything out. Does anyone know of more shops in illinois that does this? Or someone that does this as a side job and needs help? I really want to get my hands dirty now !

 

13B... the car i had after the 20b/13bt one was a S5 na, nice to drive, but man nothing to work on!

 

well while i'm not here to join the "turbo vs. na" conversation, however, i would like to add that before comparing the two projected engine builds.. set some sort of scope first. define the parameters then ask for opinions..

now with that unbiased thought out of the way, here is my biased thought!!
depending on the ecu in the turbo car, i'd rather be in it. there are lots of strategies to keep the boost up between shifts and also for launch control & traction control (which could be useful in both FI & NA).

...so, just saying... given some other parameters - the turbo engine might be my selection (i'm not talking a road & track GT55r setup, just properly sized).

 

I have had a GT35R turbo setup with a .86 hotside that had the best throttle response of any 13b turbo setup. N/A has nothing to do with it. Turbo lag gives poor throttle response from restriction. GT35R with a small hotside (.84) boosts fully at 2700 rpms.
http://www.youtube.com/watch?v=Ty85qzSQKcE

If you want to drag your car, a Garret GT45 will suit you well. If you want to have a quick spooling 20b and put down 550 HP, a GT37 or GT40 with a smaller hotside would be good. A 0.89 hotside (turbine) on a GT37 would have really quick spooling characteristics, but extremely high EGTs, also have a boost drop near redline. A GT45 with a 1.44 hotside will lag, but when the turbo is spooled, hold on to your seat.

If you're drag racing, get a big GT45 turbo. If you are auto crossing, get a GT37 with a small hotside. If you are daily driving it, a GT40 will do nicely.

http://www.turbobygarrett.com/turbob...ochargers.html