Node

iTrader: (1)

https://www.rx7club.com/forum/showth...threadid=63033
I had no idea what he was talking about, and neither did a couple other people. Finally it makes sense.

now

iTrader: (1)

Differences between 20B versions A thru F
### to 1999
and
A001 to A999 as far as I know was the first series.
B up were the 2nd series I didn't know that there were
any over C's but I am starting to think they might have gone as far as F .
as far as I know there is no differences in the e shaft
its all in the side / iron housings where the strength was
added, if you look you can see the difference between
the two motors, if you look on either side of where it
says 20b and mazda on the rotor housing on early
motor the cast iron part is almost flush with the top
of the rotor housing and the later ones the iron part
is clearly above the hight of the rotor housing.
I find out today that the early motors 001 all the way
to the late c motors have the dowel pins that have the
step, and in the later ones the stopped using the step
dowels and went back to using all the same pins.
cant imagine what the idea was to use a pin with a step
on it.

matt

Evil Aviator

Mine also has grindings on the housings. Since I can see no other reason for this, my guess is that it is a Japanese method to mark engines which are no longer supposed to be used on their roadways.

BTW, my engine is a "B" version (sorry, I forgot the number) Series I engine.

now

iTrader: (1)

I can just see it now, everyone is going to be running
out the the hardware store and buying number stamp
sets so they can stamp their motor to make it stronger!
Btw if there is anyone in canada who wants a 20b i will
have one for sale in the spring and can rebuild it to your
specs the number on it will be, lets say D454

matt

j9fd3s

iTrader: (3)

i just stamped a z on mine, it now makes 70000hp

mike

Jeff20B

iTrader: (13)

I've got four 13B rotor housings and some 12A side housings I could put in the appropriate places to make a correct length fake 20B. Then I could stamp a Z on them and it would start running!

Evil Aviator

B235

RX-Heven

iTrader: (1)

Talked to Pineapple Racing today and was told my number, B721 . He may have just stamped the B on there to get me to shut up so he wouldn't have to add extra dowells. It is almost done, just waiting on the sump plate. Guess that means I need to pay for it soon

Jeff20B

iTrader: (13)

Sump plate? Is it just a flat piece of metal kinda like a dry sump system? I'm still debating whether to run a dry sump or simply mod the oil pan.

rxeng

Ok guys here's the number deal as far as i know.
Mazda built the 20B's in batches of 1000.
The first batch didn't have a letter stamped in front of the number.
These were the engines with the square edged cranks that they had all the problems with,most of these engines were the first to turn up in Australia and New Zealand as they were all removed from Cosmo's in Japan,returned to mazda & then sold off to various wrecking yards in Japan.These engines were the ones that were pounced on by the importers who then sent them straight overseas.Supposedly the dealerships weren't allowed to dismantle these engines.They were to be returned to Mazda complete & in return Mazda would send a brand new one back to the dealer.
They then followed with A,B,C & D series.All of these came out from the factory in Cosmo's.The last series you may see are the E's.These engine's were complete Mazda crate engines that were only available from Mazda spare parts division.None of them came out in a car from the factory.I have a friend who has 2 of the last 20 or so Cosmo's made & both cars have engines with D stamps.
I have also seen a few engines arrive here in australia with the numbers ground off.If they were done in Japan they will still have the number stamped on the front plate under the alternator(cant get the grinder in there to get that one!!).Most of these engine's have been rebuilt for test purposes by the factory by using bits & pieces from various engines,hence the grinding off of the conflicting numbers.
Hope this sheds some light on some of the myseries surrounding the 20B's.
RE gards
Jon
RX Engineering
Newcastle Australia
www.rxengineering.com

inboost

How about firing order? I've heard of some 20B's running 1-3-2 instead of the normal 1-2-3. I was looking at an e-shaft @ Daryl Drummond's the other day I don't see how this could work unless there were two different versions. I think the last time I spoke with Roger Mandeville he reported seeing them both ways? Regardless, I'm sold on 1-2-3 until proven otherwise. It's curious that a myth like this could exist, perhaps there were some experimentals that leaked out of Mazda?

now

iTrader: (1)

where exactly on the eshaft " crank" do you see the
"square edges" ?
I have looked at my 2 and cant see any difference
between my 454 motor and the b991.

matt

j9fd3s

iTrader: (3)

i dont think that is correct, i have a non-a (#246) engine and it came with, the ignition coils (which are mounted on the car) the afm, airbox and bits of the dash harness. it also has never been apart and runs fine =). i will grant you it is possible that it sat in a junkyard for 10 years (the wires are date coded 1991); i also will grant you they improved the later engines, but there are 2 things that bug me.
1. why would they change the whole engine assembly (manifolds and turbos), when it cheaper to change the block only?
2. why would a lot of harnesses be cut at the firewall?
i'm not saying your wrong, but i dont think we have the full picture either.

mike

Evil Aviator

All of the Motec diagrams appear to show a 1-3-2 firing order, assuming that the software is firing the outputs 1-2-3.
http://www.motec.com.au/drawings/m16.pdf
http://www.motec.com.au/drawings/m41.pdf

These 13G and S2 20B cut-aways look like 1-2-3.
http://www.fortunecity.com/silversto...3G/EWK2_8B.JPG
http://www.fortunecity.com/silversto...B/EWK3_16B.JPG

As with any engine, I think it's best just to turn it over by hand to determine the firing order, as well as to troubleshoot other problems, prior to firing it up.

j9fd3s

iTrader: (3)

for what its worth mine fires 1-2-3.

mike

inboost

Evil,

I'm familiar with the diagrams but hadn't seen the press pics. Thanks for posting those! I definately agree with you on the before-start discovery, firing the wrong way on any engine is bad news. I just though I'd throw that out to see how it affected the engine origin / series questions.

rxeng

the engines that came with a square edged crank had a square shoulder where the front half of the crank slides over the main shaft.the later models have a radiused shoulder there

RETed

That's weird that MoTeC states that.
My motor fires 1-2-3 too.


-Ted

rotor

The person you need to speak to is David Morris of www.dmrh.com.au he knows everything there is to know about the 20B and the Cosmo.

This pic. attached is from a later 20B engine, note the taper (top shaft shown) which was introduced to increase strength. As the original 20B shaft was very similar to that of a 13B - just extended, the tapered section provides much more strength:




If you have lots of money, you can get yourself a Short-Crank 3rotor (Mazda called is a 13G) like Allistair of www.evil7.com has had made. Pic. here: Note that he is using 13B housings (Series 6 or FD RX-7 housings).

I'll send this URL Thread to David and see what info. he can provide us with.

setzep

All this talk about 20b #'s got me thinking about my 13B-RE. I went out to the garage and took down every number/letter I could see.
On the front plate under the alt it has a "E084025" stamped
Both of the rotor housings have a "R" stamped almost on the top of them (a little more twards the spark plug side)
The front rotor housing has a "6" stamped near the oil injector nozel, the rear housing has a "5" stamped in the same location.
On the front rotor housing there is a "Z" stamped near the "6".
There are no numbers/letters stamped near the "13B" casting on the rotor housings like your 20b's.
My center plate also has the same (NF (screw casting) 01) as this pic, leads me to believe the 20b's and the 13B-RE's use the same center plate.


Can anyone give me any information on these numbers/letters?

Thanks

-Cam

j9fd3s

iTrader: (3)

the E084025 is the engine number it corresponds to the car somehow (it doesnt match the car).
the nf01 casting is the "casting number" the fd has n3a1, the 74-75 13b's are 1757 etc it tells you what the engine is. yours should have nf01, or n390 on the other housings somewhere. the r on your housings means rear, the usa fd for example has f (front) and r (rear), the only difference is the air injection passages

mike

setzep

So you're saying I have two rear housings on my engine? Hmm... guess it's been rebuilt.

usfdr

Mine says B661 whatever that means. All I know is its a 3 rotor Twin Turbo, and thats all I care about.

HyperRex

There's another, kind of more obvious reason why the serial numbers might have been ground off the block.

The engine might have been stolen in Japan.

HyperRex

Hmmm. Is it possible the original "problem" engines fired 1-2-3, and later versions were changed to fire 1-3-2?