Does anybody know if the 20B rear housing plate from a Cosmo is identical to the 13B-RE Cosmo rear housing plate? If so, does anyone have a trashed one for sale or one removed that they could take detailed pictures of? I could use a trashed one for fitment issues with transmissions and motor mounts.

Thanks,
Tim McCreary

 

The housings are all identical between the 13B and 20B versions with the exception of the front/center 20B housing and the "20B" castings on the rotor housings.&nbsp Yes, all the "big" tuners use the Cosmo 13B engine cores for 20B parts.



-Ted

 

The 20B rear has a few differences compared to older 13Bs. But the important bolt holes are the same.

 

Thanks for the info. My gameplan was to try and see if I can put a JC Cosmo (1990-96) 13B-RE into a 3rd generation RX7 instead of the 13BT-REW. My goal is to try and find a rear housing to see if I can drill and tap motor mount holes in the rear housing. I am curious if anyone else has tried this. My car is an Automatic and I was hoping to be able to modify the Cosmo motor enough to fit in an almost "Bolt In" fashion. It appears that Cosmo motors are more abundant, cost less, and available as compared to the RX7 engines.

My next concern is the intake bolt pattern. My understanding is that it is different. Can anyone confirm this.

Ideally, I would be using my intake and exhaust along with my original computer. If this does not seem possible, I can get a wiring harness and computer with the Cosmo motor to match.

Thanks,
Tim

 

Sounds like a lot of work! The REW is a much better engine. Why step backwards? I am sure the cost of the transplant would be quickly offset by a sturdy rebuild of your current engine. Any reason you want to abandon you block other than the low cost of RE's? Not to mention the much lower output of the RE vs. REW. Even if you used the stock computer, the maps would be completely skewed by the drastically different porting of the engine, and I am sure quite a few members will share their opinions about installing a different computer into the car.
Switch to a 5spd with your REW, and you will be very happy!

 

I am looking for a low cost solution for the engine. Assuming that the intake/exhaust manifold could bolt up (even with an adapter), I think there will be a performance increase based on the 20% larger intake ports. My understanding is the intakes are about the same as a street ported intake on a 13BT-REW motor. I understand that the Lower output HP difference is due to the fact that the factory Cosmo Turbos are smaller (Hitachi 10's instead of Hitachi 12's), not because of the engine design. They are smaller for the Automatic Transmissions since they were all Autos and they spool up faster. Since my car is an Automatic, It could not hurt much. I am assuming that the complete front end of the engine is interchangeable since the bolt pattern and face of the engines are the same. I think that the timing ring and pickup would easily replace the CAS from the Cosmo. and the oil pan should be able to switch also.

In other words, I would be attempting to convert the short block motor over to a 13BT-REW replacement.

I can get a Cosmo engine with a 1 year warranty for the cost of a cheap rebuild of my engine.

Unlike most owners of the 3rd generation RX7's, I don't have the extra cash floating around to waste on the car. (35 years old, married with two kids). I do have extensive knowledge and tools to work on the car. I have a very good understanding of the workings of the cars. I have had several other RX7's and the 3rd gen is my dream car. I finally got one at the right price with a blown engine and I am just hoping to get it back on the road quickly and cheaply.

I see the conversion to a 13B-RE as a possible increase in HP with a decrease in the overall costs involved if it can be done right. If I cannot do it right, I will not attempt it. I have talked to a Japanese tuner who said they do convert them over in Japan, but it is not straight forward. For a car with a 5-speed, it most likely would not be advantageous, but with a car with an Automatic, you have 1/2 the battle already won.

Thanks for the input.

PS I can easily change my mind if someone can direct me to a reasonable J-spec 13BT-REW or good used engine for an Auto car. It seems that every where I check, the engine they are advertising is the 13B-RE or they don't have the REW in stock or they cannot get them.

Thanks,
Tim

 

I either heard or read somewhere that SR Motorsport's project RX7 (red one) used the Cosmo 13B due to the better intake ports. He's making GREAT hp with his setup, about 20hp up on what I made with an REW and almost identical mods at a slightly lower boost level.
Michel

 

if you have an automatic the bolt patterns are the same. the intake from an fd wil also bolt onto an fd block, or vice versa. we have a cosmo 13b with a port matched fd intake gasket. you would need to bolt the fd front cover on the cosmo motor, the cosmo front cover has no way to mount the fd cas. the motor mounts actualy kinda look like they end up in the same place, bu to make it exact would be the hard part. the fd twins will also bolt right on to the cosmo, i would use those as they are easier to come by, and they fit your car car too.
mike

 

Mike and Michel,
Thanks for the information. The motor mounts on the Cosmo are very similar or the same as the 2nd generation, mounting to the side of the middle plate. The 3rd generation mounts are bolted on the bottom to the rear plate. I know this for a fact from pictures.

I would like to find a trashed rear housing to see if I can drill and tap the motor mount holes. I am just afraid I might drill through some type of oil or water jacket in the process. This is my only major concern with the swap.

Anybody have any other information on the Cosmo specifics or a rear plate separated from the car, that would be greatly appreciated.

I figure someone out there probably took a Cosmo 20B and mounted the Manual rear plate on the back end of the engine leaving a spare Cosmo rear plate for the Auto. I prefer to find one that is bad or damaged, but any more information would be very helpful.

Tim

 

Tim,

I admire your ambition! Only one line of your reply caught my attention:

Meaning the total project cost would be much higher with the RE since block price is equal, and you would require more hardware to install it. Think of the time that could be spent with your family instead of fighting the RE to install it. I have a child myself. Repair that REW and take the kids for a ride!! Kids LOVE rotaries, and they LOVE turbos!
FYI - a manual rear housing can be notched to clear the auto starter without removing it from the engine -- just in case you find a 5spd jspec REW that you wouldl like to use with your auto. I would rebuild your current block before gambling on an engine of unknown history though!
I must be getting old.... I would never talk someone out of a project before. Heck, do it in the name of science and tell us your results. I digress...

 

Remember that the 13b-re's have more restrictive exh ports though. It sounds like you just want to get a "short block" and bolt your FD stuff on it. I'm not sure the larger intake ports would be much of a advantage with the more restrictive exh ports still in there. Now if you were to take the -re ports out and put in the -rew's then you might have something there. Any one agree?

I bought a 13b-re because it was cheeper than the rew and people said it had "way bigger ports" later when I took off the turbos at my home I saw those ugly exh sleves... Funny how I never herd anything on the smaller exh ports. Just something to consider.