jaggermouth

iTrader: (1)

I'm buying a 20b eshaft and center iron in hopes to get a head start on my next engine setup. Those two parts are coming at a good deal.
I am wanting to build an NA 20b and a huge power goal is not my main objective. I am looking for response, curve, simplicity, and maybe even some fuel mileage. I would be doing stock porting or possibly a street port.
I have a variety of 13B-REW parts but also have access to NA 13B's. Would I be better off using all S5 NA parts or would REW irons and housings paired with NA rotors be sufficient?
I've done a few quick searches but they usually are turn into "why not turbo a 20 rotor and make a billion hp?" threads.
Any professional insight would be very much appreciated.

Thanks, Jordan.

Uwan

iTrader: (4)

I have your same views and goals but I'm unable to help. Im still new to the 20b scene. Wish someone would shed some light on this question tho.

BeenJaminJames

I too am looking for this information. I don't need turbos and aggressive porting and all that jazz. Just an all-motor streetport 20b that can run on lowgrade gas and would be docile enough to be comfortable in city traffic in the rain. I can do all the porting and fab work on my own, and i have tons of 13b parts, I just need to know what are the differences with the construction of the engine, since I've never seen a 20b opened up in person.

I can say that I probably would stay away from the 6 port S5 N/A irons since the 20b thick iron doesn't have provision for the secondary intake port. I'll probably wind up running S4 or S5 turbo 4 port irons/housings/rotors. The front iron will have to be drilled for the short tension rods to bolt into the thick iron from the front, probably a few other modifications as well. I am concerned about whether there would be any issue with differences in the end play spacer/torrington bearings/thrust plate, considering that it's a 2 piece e-shaft.

There seems to be very precious little info around about this, and I am considering just purchasing a low mile long block just to be sure that I won't end up needing some unforseen doo-dad. In either case, I'll probably take the time to post up a good build thread including advice or comments along the way for anyone else going this route. If I get the long block I'll try to show as much comparison as possible for the folks that want to use 13b stuff.

Better yet!... If Jeff20b or any other knowledgable folks out there could share some advice, please? Lots of things I just dont know and can't seem to find, lots of little things, like what should I torque the front tension rods considering they're half as long? Still 28 ft/lbs? Can the FD oil pressure regulators work in a N/A streetport setup, or would the 20b require a beefier oil pump? The only pictures I've seen of inside the front cover of a 20b showed a large gear driven oil pump, instead of the chain driven style. Lots of good questions, I know there are some nice kindred folks on this site that have the answers

Akagis_white_comet

iTrader: (4)

Okay, here's the skinny on building a 20B shortblock from the Eccentric Shaft and Thick Center Iron with middle stationary gear.

The rear iron is the same as the 13B-RE in the Cosmo (N390-10-C50x). The front and normal middle iron are listed as NF01 parts according to Mazdatrix.

I am not sure about the rotor housings as Mazdatrix lists a different part number for 20B housings than 13B-RE housings (NF01 and N390 respectively)

Front Cover is shared with 13B-RE (NF01-10-500). Very late S5T2's came with this one too

You'll need the 20B's front and rear counterweights and a 20B oil pan.

BeenJaminJames

Considering the rotors are interchangeable and the stationary gear is the same diameter, the housings should be similar as far as I can imagine. I'm assuming the part numbers are different as that's where the "13B" or "20B" engine code is located. At any rate, any 86+ 13b 4 port irons should theoretically be interchangeable assuming the ports aren't mismatched, no? Counterweights are a given, as well as of course the oil pan and manifolds. What about the oil pump, would it be advisable to run a 13b oil pump with fd regulator? What about torque specs on the short tension rods? Anything else to watch out for that I might've missed?

lastphaseofthis

iTrader: (8)

Which means they are specific to the 20b-only parts list, correct?

anyone made a 3 rotor with 4 bearings, or 4 rotor with 5 yet? I will one day.... one day. all needle bearings like the nz stuff.

Akagis_white_comet

iTrader: (4)

While you could THEORETICALLY use any 86+ rotor housings & irons, the 20B's thick middle iron will always have the largest ports & runners. They are even larger than the FD's 13B-REW intake ports, so you'll have to port everything to match. See Banzai Racing's post about the Xcessive 20B LIM and you'll see the difference.

To aid comprehension, I've put together a few short videos on youtube that explain Mazda's part numbering system here:
Part 1: Part 2: Part 3:
Engine parts ALWAYS follow the Electrical/Mechanical Prefix. In the case of the FD's oil pump, the prefix is NF01, meaning it was first used on the 20B Cosmo (ECU part# is NF01-18-881). If it was made specifically for the FD, it would have a N3A1 prefix.

The only exception to this that I am aware of are a few parts shared between the 13B Cosmo and 20B Cosmo because they were developed side-by-side
such as the 13B-RE's Air Bypass Valve (NF02-20-250) or the 20B's Throttle Body to Intake Elbow gasket (N390-13-W69)

The last digit of the prefix can vary a bit, depending on the part in question and how the vehicle was originally equipped. For example, a S4NA Starter is N326-18-400 for manual transmissions and N327-18-400. A North American FD's ECU is N3A1-18-881, while a Japanese model begins with N3A7. On bodywork-related parts, this can help determine original equipment such as a rear wiper. In Mazda lingo, this bodywork prefix comes from the first four digits of the MSC Code.

Using the North American S4 FC as an example, parts common to all versions have a FB01 prefix (F044 for Japanese models). Rear wiper parts use FB02 as the prefix. Sunroof parts start with FB03, Auto Adjusting Suspension are FB04, Power Windows are FB05, Power locks are FB06, Audio related upgrade parts such as the door subwoofers got FB07 & FB08 and so on.

Banzai-Racing

iTrader: (11)

You cannot theoritcally use FC irons in conjunction with the 20B thick center, the intake runners on FD and Cosmo irons sit around 2" higher on the side of the engine. The only way would be in a p-port application since the runners would not be used.

jaggermouth

iTrader: (1)

Yup sounds like ill be buying a long block instead of pieces then...

BeenJaminJames

Akagis, thanks for linking your vids on the part numbers, very informative!
I was expecting to street port all the irons to match each other, but if the intake runners are 2" higher on the fd/cosmo irons, that might make it a bit tricky to use cheap commonly available turbo2 irons. If I'm gonna pay for fd parts, I'd probably be better off just finding a good price on a low mile 20b long block. But at least I know what will and won't work...


Edit: As long as we're talking about the theoretical, you could theoretically make your own manifold that would work with the offset ports in the thick iron. I was originally planning to fab my own manifold if I went with the cheapo route of only buying the e-shaft and thick iron, but dealing with slightly unequal length runners would just be that much more trouble than I care to bother with. If I'm gonna spend $5k on a bunch of fd parts and custom made manifolds and oil pan and whatnot, seems more logical to just spend the 5k on an imported motor.

Banzai-Racing

iTrader: (11)

The intake manifold would need to be custom along with the fuel rails...and a ton of other stuff. Custom = $$$

Here is a TII intermediate next to an FD. Using FD parts does not really make sense since the intake runners are a lot smaller and require a lot of porting. It is far less expensive to just buy a complete long block 20B and rebuild it.

j9fd3s

iTrader: (3)

that is the best way to go.

you can use FD rotor housings, and any S5 or FD rotors (balancing is a good idea), but the irons are unique to the cosmo. the FD irons are similar, but different enough that it just makes sense to start with the cosmo parts, the irons aren't expensive new, except the thick one

jaggermouth

iTrader: (1)

Where would be a good start finding a C or D code block or even early blocks? Was gonna go with japan2la but have been reading some interesting bad feedback lately...I just sold my 13b so I'm now in the market for real.