RX7withNitrous

i was wondering what the difference there was between a 20b and a 13B-RE 90-95 Cosmo if there is any at all. Is one easier to install ( less costly ).

Jesuscookies

iTrader: (1)

I am guessing you are aware of the obivious differences. E.G. the 20b has 3 rotors and 13b RE has 2 rotors? That would surely have a bearing on dropping it in your car.

I have no practical experience with the 20b, but when I was trying to figure out which motor I was going to use in my conversion, by my best guess, it was going to cost me an additional 5k for the 20b conversion, as opposed to the 13b conversion.

Hope this helps.

David

RX7withNitrous

So the 13b re is just a FD engine? Would an FD engine fit into a second gen? Could i use the Fd tranny? How hard would it be?

Rota_Motor

13B-RE from a JC model cosmo is pretty much a revised FD engine, slightly different port configuration, and also a different inlet manifold. a 20B is pretty much a 13B-RE with an extra half the motor added on again. which makes it alot longer.

FD engine into 2nd gen isnt the easiest thing, as the FC uses engine mounts which bolt to the intermediate plate, and the JC/FD engine doesnt have the studs or bolt holes to mount there. although I have heard of FD engines rebuilt using FC intermediate plates to get the mounting holes back, but not sure whats involved exactly.

WAR

The JC 13B-rew & FD 13B-rew are slightly different.

The intake manifolds are different, the JC engine gets a HT-12 + HT-15 turbo set up where the FD engine gets 2x HT-12 turbo's

The porting is slightly changed too, the JC to suit mid range & the FD to suit top end.

The JC 20B engine is the same except add an extra rotor

protlewski

Also you would have to convert the JC engine to manual since almost all JC's were automatic trans.
The 13B-RE has about 20 less HP and no it is not a revised FD 13B-rew because the 13B-re came before the FD. (the JC cosmo was built from '90-94) and that was the base engine. So in theory the FD engine was a revision of the 13B-RE.

From what I have gathered is they have a different intake manifold and intermeadate hosings with different port timing. Also im told the waterpump is different. I think the rotors are heavyer than the 13B-rew.

the turbos are the same as the 20bs. I think.

rxrotary2_7

WAR--- is your name Kris?

DMRH

Sorry dude, just to clear up a couple of points where you are wrong.

The JC Cosmo was built from Feb-90 till Sep-95

No JC Cosmo was ever a manual from the factory meaning .... ALL AUTO. However a manual box will bolt straight on with the exception of 1 bell housing bolt near the auto starter motor position.

The JC 13B was reffered to as a 13B-REW before & just like the FD 13B-REW. As both were "twin turbo"

Read the original post from WAR above as to the differences.

The rotors are exactly the same for FD & JC, 13B & 20B

Stay cool people............

rx7tt95

Ok let's assume a few things just for debate's sake. Let's assume one has an engine which is getting a bit weak and is looking to purchase either a)a Mazda reman or b) a used, low mileage Cosmo motor. Both have warranties that the compression is good just to equal things out a bit. There wasn't money for a full-on rebuild with all the goodies, ceramic seals, monster street port, cooling mods, extra pins, etc...not just yet anyway. The rest of the engine package equation is full mods including front mount, full exhaust, and a large single turbo like a T78.

Here's what I'm thinking and please, give me a bit of feedback if I'm going in the wrong direction....(and this would be for an FD)

I'd rather go with the Cosmo. First, it's a factory -built engine and thus the tolerances and clearances will be better than a reman.

Second, the induction side (intake manifold uppper/lower and intake ports) is more efficient on the Cosmo, ie. they're quite a bit bigger.

On the downside, some have suggested that it won't bolt right in and that as stated above, one bolt near the starter mount won't line up on the bellhousing.

Additionally, the exhaust ports are smaller. Now spool-up with a stock motor on a T78 isn't exactly resonsive below 4K rpm :-) Would the smaller exhaust port size further increase lag due to restriction or are the smaller port shaped better for more velocity and thus would spool the turbo faster?

It was also mentioned above that the sleeves could be removed and replaced with REW sleeves. Can this be done WITHOUT taking the motor apart?

I've done a search and there seems to be lots of conflicting info on whether this would work or not. The local rotary specialist has an RE coming in within a week. Some say it uses a different crank sensor but one could swap the FD parts on without much effort correct?

Additionally, if I remember correctly, SR Motorsport's project car (the red 93) used a Cosmo motor instead of the original REW.