Meola

I am trying to swap a 20B into a 1990 miata. I have solved the issue of mounting the engine in the bay and what to use as a tranny and diff. My biggest concern is being able to get the donor engine to work in this car. I plan on leaving the engine stock with the sequential twin turbos on it so I can easily run the factory ECU. I am not looking to make the car a huge power dragster or anything, in the future I wouldnt mind doing work to it but in the end its just going to be a SCCA track car/ weekend warrior toy. Before I jump head first into the shallow end of the pool I would just like to know how many people have gotten there donor engines to fire up off the stock equipment. I do plan on removing the A/T to replace it with a 5speed from an FD so that will get rid of any issues in that sense. I can get the engine with all the stock components I am just wondering if its possible to get it into the engine bay firing and running properly or would I want to murder baby jesus before I got it to fire?

t-von

iTrader: (8)

Your biggest issue is the added weight of the 20b in that engine bay while trying to retain the twins. I know that some people put v8's in Miata's but with that combination, you will easily be double the weight of the all aluminum 4 banger that came with the car. Your weight balance will be completely not ideal for what you eventually want to use it for. Your better of going NA and buying an standalone ecu to control the engine. If properly built NA 20b will easily make 300+ rwhp and closer to 400rwhp it you get extravogent with the intake and porting set-up. That's more than enough HP in the light little 2,200-2,500lb car to conquer what you want.

now

iTrader: (1)

what you want to do has only been done a couple or three times that I know of.
I was one of the first to get the 20b to run outside of its factory car, all I can say
is unless you are very able in the wiring department do not try.
I have been busy with life so page updates have not happened for some time:
http://www.agt.net/public/nowback/rx7club/20b/
if you manage to get it to run outside of the car you will find that it will not run
under boost without a few resistors added in a couple places.

Matt

dimjo

I put a stock 20b/tranny into a 'vert, and ran it for 2 1/2 years. Stock wiring, coils, ECU,everything. I had to get a translator for the wiring diagram. It was great in straight line acceleration. Ran hot-(turbos in Florida).
Then the rear water gasket died, (hot in Fla) and I rebuilt the engine, but removed the turbos, and auto tranny, and went with a manual tranny, got a Microtech, and had headers made at the local muffler shop. Now I love to drive the car. Handles better, comes out of curves better, (manual tranny helps): What I am trying to say is: I thought I was going better, and cheaper by staying stock. I was VERY wrong. The stock 20b/twins/tranny are designed for a much heavier luxury cruiser, the Cosmo. After all the work to make the stock wiring work to run the car , hooking up the Microtech wiring was a walk in the park! Seriously! However, IF you see it as a personal challenge to use the stock ECU, than have fun, go with it.
I just think that a Miata would be more fun with a N/A 20b. Just like a Ford V8 in a miata is fun because of more torque coming out of a corner. The stock 20b with stock twins has turbo lag, and fuel lag (stock computer waits for boost), and I don't think you would like this in a Miata, coming out of a corner.

Meola

T-von the bottom end on a miata engine is actually cast iron they are pretty heavy little buggers thats why the all aluminum LSx series and the ford 302 drops in with no hassle but screw those american engines!

I would just love to toss in some high CR rotors and make the 20B an N/A engine but I was hoping to get away without purchasing a standalone thats why I was hoping to get it working on the stock ECU but from what I have read in the last three days it would be easier to put humpty dumpty back together. Its not just the ECU factor either I have no clue where to start looking to have a intake manifold made up. I have never done custom engine swaps like this so its kinda like jumping head first into the shallow end of the pool!

Is it possible to get the engine to run off something like a Weber down draft carb like a 48IDA? Or is it going to have problems feeding the engine, I know the 48IDA works wonders on a 12A and 13B upto bridge porting. Its reccomended to use a 51IDA on any 13B with bridge or more extensive porting.

My goal is basically to have the 3rotor in the car making 300ish HP I would prefer an N/A engine just because they take less abuse and have instant access to power but is the fabrication of an intake manifold as scary as it seems to me?

I know my questions are very noobish but I have never owned a rotary before and I dont want to jump into this and screw it all up. I am glad to get the feedback I have from you guys. Most of the stuff I have come across on the net is people spewing crap or talking big about stuff they really dont know anything about! Any advice on this project is grateful as I dont plan on putting it down there will be a rotary in my miata I just dont want to cheap out and use a 13B I wanna go big or go home!

t-von

iTrader: (8)

Oops my bad. I've been thinking 3rd gen block which is aluminum, not the 1st and 2nd gens.

Meola

The NC should have come with a rotary, Mazda needs to bone up and start producing the miata with a 13B option or something!! But ya this is going into a first gen miata so the block is pretty heavy. But I think if I strip all the turbos, ac compressor, ps pump and all the other junk I might be able to shave down the 150lbs difference. Although I dont think it would hurt the car too much.

stickmantijuana

iTrader: (1)

why not just stick 13btt on it? or 20b NA if that hasn't been said already.

Meola

My buddy has a 91 miata with a 13B-REW in it with the turbos removed, lightened rotors and balanced Eshaft. Bridgeported with a weber 48IDA feeding it and its a nice machine but in order for him to see power he has to rev it beyond 7K which is damn sexy to listen to but just too high revving for my blood I would end up blowing apex seals I could imagine. Thats why I was looking at the 20b and the more I reasearch it the swap would be about the same difficulty provided I can find a source on a Weber 46 IDA 3c1 carb to feed the bad boy. I am currently in the hunt for one of these carbs and if I can find it I will do the N/A 20B with maybe a street port but webers are tricky to hunt down especially the 3 barrel ones! If all else fails I will just build up a nice NA 13B and drop it in there, but as my buddy commented the 20B is just pure baller status

ghiaracer

go look at the porsche forums for a 3 barrel weber...

Meola

I just got a quote on the Weber carb that replaces the old 46 IDA 3c1 carb and they want $2000 just for the carb

t-von

iTrader: (8)

For that price, you could go with a haltech e11 v2 and run the stock 20b upper an lower intake manifolds NA. This will be a better option for you since it will allow for easier future upgrading. Stock manifolds will easily make 300+rwhp NA.

setupfc3s

iTrader: (1)

My friend dan ( eyecandy) and I, are in the process of installing a S5 TII 13b engine/ trans/ diff into my NA miata. so i know just about all the problems you would run into.

my car:











PM me and i will give some info

RETed

Seriously...start learning about standalone EMS'.
If you don't want to or can't...get enough money to pay someone else to do it.
The stock ECU has serious limitations.
Going carb / distributor is a step backwards.
If you're going to tackle such a swap, it's a shame to not go standalone.


-Ted

patman

iTrader: (3)

AFAIK, the stock 20B ECU will not run the engine without the auto tranny attached unless you do a lot of wiring modifications.

I'm with everyone else, if youre going to spend the $ for a 20B, man up and spend a little more for a proper ECU, you won't regret it in the long run.

Also if you do that, toss the stock twins and run a medium size single (62:1 or similar if youre being cheap about it) Running a rotary NA is just throwing away power and fuel economy. With a moderate turbo you should easily make 400whp, which is more than enough for a miata.

I'll be interested to see what you do, Ive often thought of putting my engine in my miata, or even more often thought of putting my old 400hp 13bt in it. Wish I had the time...

t-von

iTrader: (8)

Damn that is one clean Miata.

setupfc3s

iTrader: (1)

thanks!

if dan (eyecandy) ends up getting the 20b he wants, he will be test fitting it into the roadster!

ya, i would so have a NA PP 20b! but the cost of it.... one day it will happen

diabolical1

iTrader: (3)

i think Ted's post says just about all i'd say to you about it because yes, the Cosmo's EMS will not run the motor without "seeing" it's tranny and i'd imagine any efforts put into getting around that issue will be no less complex than wiring up and tuning an aftermarket EMS. you can always run it without the turbos until you can rebuild it for more N/A power (porting, higher compression, etc.)

Meola

Ya I have since scrapped the 20B plan the build cost started going sky high and the streetablity of the car went to crap. The odds of it successfully passing aircare were worse then getting hit by lightning. I plan on just doing a simple single turbo 13BT from a TII I got a quote on a rebuilt race ready with 500HP for $5000 from one of our speed shops, it pays to work in the automotive industry. I love the look of the pic posted of the 13BT in the red NA cause that is exactly what my car will look like in the end right down to the colour. If you have any information about how your turbo fitment and plumbing went I would be happy to hear.

Jobro

iTrader: (2)

Custom IDA style 20B Throttle Bodies


$1338.18AUD when we are trading at about 0.70 is about $950USD, but then you need to factor your manifold. That would have been a decent option if you hadn't already decided to go 13B

http://www.tweakit.net/shop/product_info.php?cPath
=326_27_176&products_id=118

M Skinner

Hello setupfc3s, Im really impressed with your install. If you wouldnt mine mailing me any info and pictures of your build I would greatly appreciate it. I am starting a near identical build to yours next year, so would be great to see what problems you came accross and how you resolved them.

Many thanks,
Martin

martin_skinner@tiscali.co.uk

M Skinner

Thank you setupfc3s, couldnt PM you back as my post count is too low. Im looking forward to making a start on mine now